RE: [Repeater-Builder] Re: Rule on tampering with a FCC licensed transmiter

[Jeff DePolo]

There are some new laws (so I'm told) that have gone into effect since 9/11
that deal with terroristic acts as related to broadcast stations, antenna
structures, etc.  Sorry, I can't cite any rule, but I can tell you that both
local and federal authorities were involved in one such investigation
locally this year, but I won't go into any detail beyond that.

I can tell you from personal experience that the FBI will investigate crimes
related to tampering, trespassing, theft, etc. at broadcast stations/sites.
I've had broadcast sites broken into and the FBI did take reports,
fingerprint, etc.  In one case, the theives were caught about 4 years later,
attempting a simliar break-in at another transmitter site several states
away.

--- Jeff
 

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Jeff Kincaid
> Sent: Saturday, December 09, 2006 10:59 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Rule on tampering with a FCC 
> licensed transmiter
> 
> >From WWII onward it was a federal crime to tamper with a licensed
> radio station of any kind.  It was a matter of national security. 
> But, about 10 or 15 years ago someone noticed that the rule hadn't
> been used in decades and it was dropped.  The only remaining recourse
> is under local property laws; vandalism, willful destruction,
> trespassing, etc.
> 
> Jeff
> 
> --- In Repeater-Builder@yahoogroups.com, mch <[EMAIL PROTECTED]> wrote:
> >
> > They most certainly do license transmitters. It's only in 
> the Ham type
> > services the operators are licensed and can put 
> transmitters anywhere
> > (almost). That's why the commercial licenses have coordinates and
> > frequencies on them.
> > 
> > As for the rule, I know it exists, but I don't know exactly where
> > offhand. I think it's going to be in the 'lower CFR parts', 
> not in the
> > rules specific to any one service.
> > 
> > On the other hand, all the tower signs I've ever seen don't 
> reference
> > any specific rule - they just talk about the site being under the
> > "jurisdiction of the federal government". Nobody I know of quotes a
> > specific law.
> > 
> > Joe M.
> > 
> > Gary wrote:
> > > 
> > > Not sure what you mean John. The FCC does not license transmitters
> > > however they do license operators of transmitters and they approve
> > > transmitters depending upon they application in the U.S. 
> All the rules
> > > and regs can be viewed at the FCC's website. Go to the Wireless
> > > Telecommunications Bureau and click on the link to 'Rules and
> > > Regulations'.
> > > Gary
> > > 
> > > JOHN MACKEY wrote:
> > > 
> > > > Can anyone qoute me the rule abotu tampering with a federally
> > > > licensed
> > > > transmitter?
> >
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
> 
> -- 
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>  
> 

RE: [Repeater-Builder] spur from UHF MASTR II mobile - link radio

[Jeff DePolo]

> Nothing forgotten - the ICOM still gets 10 V, just not 10 V for the 
> oscillator.  There are two separate 10 V feeds to the RX: one 
> for the LO 
> oscillator & one for everything else.
> 
> Bob

Confused.  The ICOM *is* the oscillator, and it only has one 10V input pin.
Or are you saying that the multiplier chain is what gets turned on and off?

--- Jeff

RE: [Repeater-Builder] spur from UHF MASTR II mobile - link radio

[Jeff DePolo]

> Not quite, as 145 MHz will never make it through the UHF 
> helicals.  It's 
> just leaking out of the RX & case.  Neil's got the easiest 
> solution: order 
> a high-side LO xtal for your 447.575 RX.
> 
> Bob NO6B

But that will just move the problem somewhere else...up to 152.925 where you
might make even more enemies than on 145.460...

RE: [Repeater-Builder] spur from UHF MASTR II mobile - link radio

[Jeff DePolo]

> I forgot to mention: the reason you don't hear it on TX on an 
> unmodified 
> Mastr II is because the RX OSC 10V is cut off during TX, so 
> there's no RX 
> LO when TXing.
> 
> Bob NO6B

I don't have a manual in front of me, so I have to ask the question here.
If the 10V to the Rx oscillator board is cut off during Tx, how could you
put a 5C element in the Rx and an EC in the Tx and still have the Tx EC
element be compensated by the Rx 5C while transmitting?  The Rx 5C ICOM
would need the 10V in order to generate the compensation voltage.  Or am I
forgetting something?

--- Jeff

RE: [Repeater-Builder] spur from UHF MASTR II mobile - link radio

[Jeff DePolo]

> Hi guys,
> 
> Built a link radio out of a MASTR II mobile a while back.  
> 444.575 TX, 
> 447.575 RX.

It's the LO multiplier chain that you're hearing.  145.460 * 3 + 11.2 =
447.580 (447.575).  

> After having the link installed in my basement for a few days, I 
> realized that it's throwing a fairly strong dead carrier on VHF at 
> 145.460 or thereabouts, but ONLY when it's sitting idle in Receive. 
> When the radio is transmitting the carrier generated by the receiver 
> disappears.

You don't hear it when the radio is TXing because the T/R relay
disconnects the receiver from the antenna.

--- Jeff


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RE: [Repeater-Builder] Wanted: 1 5/8" N-type air hardline connector

['Jeff DePolo']

Need the brand and model of the line; there are differences.  I probably
have some used Andrew (for HJ7-50) and Cablewave (HCC158) in good
condition; I'll donate one if it will work for you.  Email direct.

--- Jeff

> -Original Message-
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] On Behalf Of dvickn4ome
> Sent: Sunday, November 26, 2006 7:18 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Wanted: 1 5/8" N-type air 
> hardline connector
> 
> 
> Recently our repeater site was burglarized and the connector
> along with 
> several feet of the 1 5/8" air hardline was stolen. (for the copper)  
> There were several other pieces of hardline also stolen.  I'm willing 
> to purchase a 1 5/8" N-type connector for air hardline.  I would 
> appreciate hearing if anyone has a connector or a source for one.
> 
> Thanks
> Darryl - N4OME
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
> 
> --
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> 

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RE: [Repeater-Builder] Anyone know what the windload numbers are for a gp-9 by comet

[Jeff DePolo]

> Anyone of the illustrious members of the group know what the wind load
> numbers are for a gp-9 by comet and also the wind load of the cx-333
> by comet

I don't think I've ever seen wind load specs published for Comet or
Diamond.  But you can get a pretty good estimate by using the following
formula:

W = (D1 + D2) * L / 36

W = windload in square feet
D1 = diameter at base in inches
D2 = diameter at tip in inches
L = length in ft.

I'm guessing here to make up an example, but something like a GP-9 is
around 1.5" at the base, 0.75" at the tip, and 18 feet long, so the
windload would be about 1.1 square feet.

In contrast, something like a SuperStationmaster is more like 2.5" at
the base, 1.25" at the tip, and 20 feet long, or about 2.1 square feet.

--- Jeff


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RE: [Repeater-Builder] New Dipole Antenna Line

[Jeff DePolo]

> It looks like Andrew has terminated either a large portion, or all of
the classic Decibel Products exposed dipole
> antenna series such as the DB-224E, DB-408, etc.  You can't even order
a replacement harness or dipole kits
> anymore.  They claimed there was no profit in that line.

Chris - where did you see that?  I've still been able to order DB408's
and DB420's, but not in the special ham-cut versions (they discontinued
the custom models January 2004 if memory serves).

> Bird/TXRX has come out with a new similar line (see link below).  They
are touting significantly better specs than 
> Decibel, such as one model that tunes continuously from 136-174 MHz
and another from 400-512 MHz without 
> adjustment or tuning.  They are also claiming industry low 3rd order
IM and noise.

I'll be ordering one (a 4-bay) as soon as my coordination application
gets approved, hopefully within the next month or so.  I haven't seen
any out at any sites in the field to date.

--- Jeff

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RE: [Repeater-Builder] Problem of repeater after lighting striked RX antenna

[Jeff DePolo]

Did you test/inspect the feedline?  Arc-over within the coax isn't uncommon,
and can leave resistive pathways between center and shield that translate
into high loss and/or high VSWR.  Center pins on connectors are often burned
or vaporized in a good strike.  

Is the new Rx antenna and exact replacement of the former?

--- Jeff
 

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of muahhh
> Sent: Thursday, June 01, 2006 10:25 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Problem of repeater after 
> lighting striked RX antenna
> 
> Hi..
> 
> Recently, the repeater i was maintaining was hit by lightining. The 
> whole antenna was gone, and our turbo fans were fried..
> 
> However, luckilky, all the radios are still on..
> 
> I've changed the RX antenna, the pre-amp and the lightning arrester. 
> However, when we tested, between two points, lets say A and B.. A is 
> nearer to the repeater and B is further.. when A calls B, B could 
> hear, but when they reply back A couldn't hear.. 
> 
> What could be the problem? I've changed the RX radio, but still the 
> situation is like this.. it seems that the coverage of the repeater 
> is smaller than before..
> 
> Is there any thing that i should check also or changed.. What should 
> i do when lightning strikes..?
> 
> Thanx
> 
> Fred
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> -- 
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> Date: 5/31/2006
>  
> 





 
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RE: [Repeater-Builder] Re: Double the gain or double the power?

['Jeff DePolo']

> I can't measure the reflected power.  I can measure SWR and 
> that is flat.

You said you had a wattmeter to measure your power output - why can't
you use it to measure the reflected power?

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RE: [Repeater-Builder] Re: Double the gain or double the power?

['Jeff DePolo']

> Yes I have to add a tee for the bottom half.  The entire 
> antenna is one complete unit 4-folded dipoles.  Maybe I 
> assumed and thought all the phasing harness's were already 
> there as I can see where the splits are on the coax.

What kind of antenna is it?

> I am measuring from out of the duplexers up the LMR-400 cable 
> and not at the top.

How long is the run of LMR400?


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RE: [Repeater-Builder] Re: Double the gain or double the power?

['Jeff DePolo']

> Yes, I was using the Top Half of a 4-element antenna.  I have 
> now added the 3-Way connector and now have the entire antenna 
> connected. 
> I have noticed it has cleaned up the receive on week stations 
> but, it seems to have dropped a little in the signal.
> 
> System was just re-tuned, duplexers and radios.  It's a 
> Motorola MSR-2000 Canadian 40 Watt version.  When I add the 
> duplexers and the top half of the antenna I get 25 Watts out. 
>  When I add the second half I get 10 Watts out.  Measuring 
> the wattage just after the duplexers.

This doesn't make sense.  The transmitter output shouldn't be changing.
It sounds to me like when the second set of bays was connected it wasn't
done with a proper matching/phasing harness, but rather just by "teeing"
the two halfs together.  This would throw the match off (a 2:1 VSWR
mismatch best-case), which results in a detuning effect at the duplexer
which makes its insertion loss go up, which is why you're seeing less
TPO.  Have you measured the reflected power at the antenna both before
and after adding the second set of bays (or if you can't measure at the
antenna, measure at the output of the duplexer and tell us what kind/how
long your feedline is and we can back-calculate from that).

Also, what band is this repeater on?

--- Jeff

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RE: [Repeater-Builder] Re: Micro Exciter, Low Output?

[Jeff DePolo]

> With the xmit channel element always running, I see a continous 
> measurable output from the exciter or the test set. No difference 
> whether the repeater is in xmit mode or idle. Just curious as to 
> what I should be seeing. I have a spare exciter board and aligned 
> both as per manual, both give the exact reading which is down from 
> what the manual gives as typical..Thanks...Don 

You should see a significant jump in output when the transmitter is keyed.
I don't have a manual in front of me, but from what I remember, the last two
(three?) multiplier stages get powered when the transmitter is keyed.  If
you're not seeing any change in reading, it's my guess that the exciter
isn't really being keyed, probably due to either a mis-configuration of
jumpers on the backplane or a card not installed or properly jumpered.  It
could be something as simple as the PL board isn't installed in the exciter,
or the jumper needs to be installed if the PL encoder isn't used.  I can
pull a manual later and give you the "most likely suspects" later if you
don't find it on your own.

If you have some pads (of known accuracy), you could attenuate the exciter
output sufficiently to feed it to the spectrum analyzer in your service
monitor and get a ballpark measurement of the output that way.

--- Jeff





 
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RE: [Repeater-Builder] Need source for RF RCA connectors

[Jeff DePolo]

Geez, lots of discussion, but nobody answered the question.

RF Connection (www.therfc.com) has RF-grade RCA males, standard solder-on
type (no strain relief or anything).  Short center pin, silver plated,
Teflon dielectric.  If you can't find them on the web site, call and ask for
Joel and tell him what you need, he'll know what you're talking about.

--- Jeff

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of 
> [EMAIL PROTECTED]
> Sent: Sunday, May 28, 2006 12:44 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Need source for RF RCA connectors
> 
> My stock of RF RCA connectors (the ones used for carrying RF 
> inside GE 
> MVPs, Mastr IIs etc.) has run dry, & I haven't seen any at 
> our local swap 
> meets.  Anyone know where I can find these?  Thanks.
> 
> Bob NO6B 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 





 
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RE: [Repeater-Builder] Sinclair Antennas

[Jeff DePolo]

> Has anyone lately been having quality issues with the Sinclair base
> station/coliinear antennas over the past 5 or 6 years? 

Can't comment on the whitesticks, but the yagis have gone downhill.  I had a
couple of 900 MHz Sinclair yagis that were built like the proverbial brick
outhouse.  They discontinued the model I had been buying, but they had a
replacement model which was slightly more expensive.  I ordered one and was
really disappointed.  The old ones had heavy solid-rod elements (3/8"
diameter I believe).  The new one had smaller 1/4" diameter tubing elements
which never would have held up to falling ice.  The mounting hardware was
cheesy compared to the old.

Their dipole arrays still seem to be built the same.

--- Jeff







 
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RE: [Repeater-Builder] Re: Mitrek Channel Elements Wanted

[Jeff DePolo]

> All said and done, I've not had a problem with temp drift 
> in re-rocked channel elements after the practical settle 
> time.  Once set F_center pretty must stays put over the 
> normal expected operating range. 

While I agree with most everything Skipp said, historically I've seen fairly
significant downward drift over the course of about the first year of
operation for most rocks.  I'll typically have to re-center the element two
or three times in the first year (on UHF, maybe once on VHF) to keep it
within 1 kHz of Fc.  After the first year or so, it may be two, three, four
years before I have to adjust again.

And like Skipp, I've re-rocked many elements, and continue to do so for
those that will be in a temperature-stable environment.  The original poster
didn't say what kind of environment his radio were in, but based on the
excessive drift he cited, I would tend to think it's not a stable
environment and a real recomp job is what he will need regardless of the
specified stability (5PPM or 2PPM) of the element he uses.  Either that or
he got some really bad rocks (like ones I've gotten from Jan ;-)


--- Jeff






 
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RE: [Repeater-Builder] Mitrek Channel Elements Wanted

[Jeff DePolo WN3A]

> I'm looking for some "high stability" Mitrek channel elements 
> to use in 
> several link and repeater transmitters we have. The part 
> number is KXN- 1095.
> 
> I can use about 15 of these channel elements.
> 
> The standard elements we are currently using are not very stable and 
> allow the transmitter to drift +/- 5 kHz as the transmitter heats up.
> 
> Any help in locating these would be much appreciated.  Feel free to 
> contact me off-list.  Thanks.
> 
> Rich, N6CIZ

Did you install the crystals in your existing channel elements yourself,
or did you send them to the crystal manufacturer to have them
compensated?  If you did it yourself, and you plan to do the same with
the high-stab elements, the results you get will likely be no better
than what you're experiencing now.  Unless the element is compensated to
the specific crystal that is installed, all bets are off.

--- Jeff


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RE: [Repeater-Builder] Anetenna Help

[Jeff DePolo]

Somebody, maybe Larsen or 
Antenna Specialists, used to make a "stiffener" for use with NMO mounts.  
It was basically an oversized brass fender washer with a 3/4" hole in the 
center.  It was thick enough that it stiffened the body near the mount, but 
flexible enough that it would take the shape of the concave contour of the roof 
when you tightened down the NMO.  I haven't seen them advertised in a 
while, not sure if they're still made.
 
I had a Diamond 
dual-bander act as a can-opener to the roof of one of my previous trucks (Chevy 
Tahoe).  It got snagged on a low-hanging ice-laden branch on the way up to 
a tower site.  The roof gave up before the antenna did.  I guess that 
says something about Diamond mobile antennas...?
 
    
--- Jeff
 
 

  
  
  From: Repeater-Builder@yahoogroups.com 
  [mailto:[EMAIL PROTECTED] On Behalf Of 
  [EMAIL PROTECTED]Sent: Thursday, April 20, 2006 3:46 
  PMTo: Repeater-Builder@yahoogroups.comSubject: Re: 
  [Repeater-Builder] Anetenna Help
  
  Just about any 5/8 wave antenna mounted on top of a Ford pickup truck. 
  The roof metal is so thin that frequent flexing from antenna sway, wind 
  resistance, low tree branch contact can cause metal fatigue on the cab 
  roof.  The antenna NMO mount was installed directly above the cab 
  interior light. Nice install but the metal finally cracked about 1/2 
  inch circumference further out from the outer edge of the NMO mount. 
  The singing problem was resolved by wrapping thin fishing line around the full 
  antenna length at about 1 turn per 1 1/2 inches for its full length. The 
  thinner the whip antenna the higher the audio frequency. Observe 
  automobile antennas and you will see many factory manufactured AM/FM antennas 
  wrapped as mentioned above. Go out and wiggle your mobile antenna. Look at the 
  automobile metal near the base. Watch it flex. The longer the antenna the more 
  flexing. I solved the problem by relocating the antenna using a homemade 
  bracket mounted between the front fender and hood near corner of 
  windshield.  
  Gary  K2UQ
   













  




  
  
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RE: [Repeater-Builder] Re: Dayton Hamvention

['Jeff DePolo WN3A']

> Avoiding it like the plague Sir!!

If you don't go, how are you going to earn any Dayton spending money?

WN3A's Las Vegas motto: "There's no such thing as a loser, just winners
that quit too early."

--- Jeff

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RE: [Repeater-Builder] Re: Dayton Hamvention

['Jeff DePolo']

> "See you at IWCE and Dayton... I'm the guy with the pen 
> in my shirt pocket... :-) "
> 

Anyone else going to NAB?

--- Jeff

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RE: [Repeater-Builder] High Power Mastr 2 Station

[Jeff DePolo]

> One other query to put out. Does anyone have a couple of those 
> resistors that are in the splitter/combiner panel of a high power 
> Mastr 2 station? I found a spare panel for my repeater that I would 
> like to get going for just in case. I have the panel and the cabling 
> but one resistor is missing and the other is now cooked, well 
> done. If 
> not any suppliers of them or a good replacement? Thanks
> 
> Andy KC2GOW

To save me a trip to storage, refresh my memory.  Are the Wilkinson
resistors soldered to the back of that little square perforated box, or do
they have a mounting flange and attach to the box and rack plate with
screws?

If the former, I'm not sure where to get them.  But they could probably be
replaced fairly easily with a flange mount type instead.

For flange mount types, try EMC thick-film resistors
(http://www.emct.com/microwavepassivecomponents-a40835.html).  I've used
them for building my own Wilkinsons for other projects.  They also make
terminators (one lead instead of two, with the flange being ground) which
are nice for building quadrature hybrids using "twisted wire" coax.  

I've used others from KDI/Triangle too in the past (now Aeroflex, who also
took over IFR).
http://www.aeroflex-kdi.com/resistor-products/pdfiles/PMS.pdf

If you Google some combination of the words stripline, RF, resistors,
flange, etc. you can probably find others.

If you totally strike out, I might be able to spare one of the flange mount
ones from my stock.

--- Jeff


Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] Dayton Hamvention Reply back (as requested)

[Jeff DePolo]

> Has anyone gotten thir Hamvention tickets yet (vendor space tickets
> and/or vendor admission tickets)? Getting no response to the 
> hamvention
> email (sending CCs to chair and achair today).

NOT ME!
 
> As I said before, they are trying their darndest to kill the 
> thing. :-\

Time to start faxing, emailing, and calling AGAIN just like last year...

Very frustrating.

--- Jeff





 
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RE: [Repeater-Builder] Andrew Antennas - Beware

[Jeff DePolo]

It's not an omni, it's a cardiod.  A DB-411 would be a comprable model.  I
don't want or need any higher gain or narrower beamwidth; the site is almost
2000' HAAT in the direction of interest.

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Paul Finch
> Sent: Monday, April 17, 2006 5:30 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Andrew Antennas - Beware
> 
> A DB-410 or newer DB-420, both omni directional at 9 dB.
> 
> Paul





 
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RE: [Repeater-Builder] Andrew Antennas - Beware

[Jeff DePolo]

> 
> Hello,
> 
> Is that a total of 8 loops or 4?  If only 4 loops that's not 
> much in the way
> of gain.
> 
> Paul

4 in-line bays, 9 dBd (11.1 dBi) gain in the forward direction.

It's not much gain compared to what?





 
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RE: [Repeater-Builder] Andrew Antennas - Beware

[Jeff DePolo]

> For what it's worth, TX RX Systems now offers exposed dipole arrays.
> 
> Chuck
> WB2EDV

I'm planning on ordering one of the TX-RX arrays this week (4-bay UHF).
Has anyone else used these?  They look pretty nice.  The company that
makes them is RFI in Australia.

--- Jeff



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RE: [Repeater-Builder] Re: Mastr 2 PA Matching Unit

[Jeff DePolo]

> As suggested in a post (I believe by WN3A) these actually are Z
> matchers, and should be tuned for best efficiency.  I tuned these
> things by slowly and carefully watching the current draw and power out
> simultaneously.  It takes some time, but there are combinations that
> will yield considerable reductions in current draw for the same PO. 

Yeah, that was probably me.

The GE method has an underlying flaw in that the voltage you are measuring
is supposed to be representative of the reflected power.  However, as the
forward power is reduced, it is possible/likely that the reflected power
will likewise appear lower at the test point.  So, as Andy found, it's very
easy to end up with the PA mistuned for something approaching "least power
output" rather than "least reflected power".

If you have a 200 watt station (100 watt driver feeding a pair of 100 watt
combined finals), my recommendation would be to tune the driver into a dummy
load first at about 75 watts output, then connect to the Wilkinson divider
feeding the finals.  This way it's at least pre-tuned in the ballpark.  Then
tune the finals for best efficiency (using the "upper" and "lower" ammeters
in the station panel) coincident with the power output level desired.
Finally touch up the tuning of the driver PA for best efficiency once you
have the finals happy.

Keep in mind that the tuning of the Z matchers will vary with power level.
Start out well below rated power (say, 100 watts total output at first),
make small adjustments to the matching, re-adjust the driver output pot,
repeat until you've reached rated power.

I have a few of the 200 watt UHF M2 stations, and as Laryn said, tuning with
this method results in 3 to 5 amps less current draw per "final" PA while
still maintaining full power output.


--- Jeff





 
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RE: [Repeater-Builder] Re: 220MHz Repeater Power Repair

[Jeff DePolo]

> > The RF power transistors are listed as "Factory Select".  
> > Do you know what the mfgr and part no. is or what would work?
> > Thanks
> > Gene
> > WA2IJE
> 
> Probably some Motorola MRF-xxx type equivalent. I'd probably use 
> a Motorola RF Transistor Data Book to look for a matching power 
> level and case style.  I'd also need to know how many stages 
> are in the amplifier...?  ... direct drive of 2 output transistors 
> or if there's a single or dual predriver stage before the 
> final sections. 

I have a new (well, it's been sitting on the shelf for a few years) TPL RXR
series 220 amp here.  It uses an MRF-646 driving a pair of MRF-648's.  This
is the same configuration as used in their UHF amps that take 8-15 watts in
for 70-100 watts out (though obviously with different component values and
microstrip Z/geometry).  Obviously, at the lower frequency, the gain is
higher - this one is labeled 5 in for 100 out.

    --- Jeff


Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] Sinclair MR356-2 Tune-up

[Jeff DePolo]

> 1.  Do the low side tuning rods (3 cavities) affect the high 
> side tuning 
> (3 cavities)?

Very little, if any.

> 2.  Since there is no way to use (or measure) just one cavity section 
> (they are hardwired together), how does the tuning of one rod 
> affect the 
> others?  Do you just start the adjustment from one cavity and 
> then move 
> to the next? 

Basically, yes.  Do you have sweep equipment (tracking generator/spectrum
analyzer) or network analyzer?  If so, the tuning will be very obvious.  If
not, you will at least a signal source (sig gen) and receiver (spectrum
analyzer, well-shielded receiver, etc.).  Keep in mind that even if the
duplexer says "Tx" and "Rx" on the ports that if you are using a
Northeastern inverted pair (i.e. Tx 446, Rx 441) that you will be using them
opposite of how they are labeled.

Generally speaking, here's a quick outline of the tuning.  Don't worry, it's
pretty hard to screw up tuning notch duplexers.  I'm giving you the simple
version - no patch cable swapping involved.

I'm going to assume that your Tx is 441 and Rx is 446.  You'll need to make
the appopriate changes if this is not the case.  Of course, all of the usual
caveats apply: use double-shielded test cables, a high return loss
termination, quality 6 or 10 dB pads on the sig gen and receiver for
isolation, etc.

1.  Hook up the sig gen to the port labeled "Tx" or "low pass".  Hook up the
receiver/detector to the "Rx" or "high pass" port.  Terminate the antenna
port with a good load.

2.  Generate a signal at the 441 Tx frequency (and likewise tune the
receiver for the same).  Tune the slugs on the "high pass" or "Rx" side of
the duplexer for minimum signal (maximum notch), increasing the signal
generator output as necessary for an on-scale reading if using a receiver
with an S-meter.  You will be screwing the slugs inward to go lower in
frequency from where the duplexer was originally tuned.  Since you're moving
> 20 MHz from where they were originally tuned, you'll be cranking in quite
a ways...

3.  Generate a signal at the 446 Rx frequency (and tune receiver for same).
Tune the slugs on the "low pass" or "Tx" side side for maximum notch.

4.  Repeat steps 2 and 3 one time for good measure.

You should have at least as much isolation as the specs call for.  If you're
very careful in your tuning, you should be able to significantly exceed the
spec's notch deptch.  Insertion loss should be right at spec, maybe 0.1 or
0.2 dB below if you're lucky.

> 3.  Can you mis-adjust the unit such that you seem to have a notch at 
> the right point, but in fact there is a better adjustment point?

Provided that the notch depth meets spec, the answer is no, it's not
possible if the duplexer is working right (i.e. hasn't been damaged).  There
is only one notch "dip" per resonator, unlike some pass/reject duplexers
which show a "dual notch" response (typical of many full-size cavity
resonators that have a single loop with a series reactance to ground).

> 4.  Can or how do you adjust or affect the 5 MHz split?  Or 
> is each side 
> (Low vs High) independently adjusted?

They're independent.

> Thanks for your time,
> Marc
> W1MBT  Trustee

If this is your first shot at tuning a duplexer, you probably couldn't pick
an easier one than a UHF notch-only flatpack, so consider yourself lucky!

---
Jeff

Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] Duplexer advice

[Jeff DePolo]

> We are going to be installing a UHF repeater on 443.475 atop 
> a downtown 
> building. On this same location are several commercial UHF repeaters, 
> the closest being only about 2.7 Mhz away. 

What kind of Tx and Rx are you using, are you using a preamp, and how far
away (physically and frequency) are the other UHF repeaters?

General comments, not knowing all of the details:

The Motorola T-1504 has a pretty good passband response compared to many
other pass/reject duplexers, so that's not a bad option.

While the T-1500 will have the best bandpass performance, it may not provide
enough Tx-Rx isolation for your repeater alone.  That is, the Tx to Rx
isolation may not be adequate, especially if you are running a preamp.

The Celwave 6-can is probably your best bet.  What I'd do is tune the last
cavity on the receive leg (i.e. the cavity closest to the receiver, NOT the
one closest to the antenna port) to reject the commercial transmitter's
frequency.  Even with just two cavities tuned to notch your own transmit
carrier, you should still have > 90 dB of carrier supression.  However, keep
in mind that you may still have desense issues related to transmitter noise
from the commercial-band transmitter, and that's something that you can't
filter on your end.

> We plan on using a preselector/preamp that is showing 40 dB of 
> isolation at that seperation. 

I'm rather leery of most of the preselector/preamp combos like the GLB's and
similar clones.  While they advertise a net gain of unity or better, they do
so at the expense of poor noise figure performance.  The preselector may
have 8 or 10 dB of loss, followed by a moderate-gain amplifier to make up
for that loss, with the resulting noise figure being something slightly
greater than the preselector loss, i.e. pretty poor.

A better approach is to use high-Q/low-loss filters (i.e. pass cavities,
window filter, etc.) and a low-noise preamp.  With a combination such as
this, the noise figure can be kept in the 1-2 dB range, as compared to 8dB
or worse with the former.  Since it sounds like you already have extra pass
cavities (part of the T-1500 duplexer), all you really need is a preamp to
go with them.  It will perform better, and cost less, than most of the
preselector/preamp combination units.

    --- Jeff


Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 








 
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RE: [Repeater-Builder] Re: Band-split units

[Jeff DePolo]

Yeah, I've opened the TX-RX units up before, out of curiosity.  I can open
one later and take a few pics and post them if you want.  I have a few TX-RX
on the shelf, both indoor and outdoor units, for VHF/UHF and UHF/800 splits.
I think I have a Telewave or two, but they are coated with a blue epoxy
paint and I'd rather not take them apart as it would ruin the
weatherproofing.  I also have a Relm, I think that one opens up with just a
few screws.  No EMR's on the shelf.  I think I have a couple of Diamond or
Comets too for comparison.

--- Jeff






 
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RE: [Repeater-Builder] Band-split units

[Jeff DePolo]

> Any recommendations on bandsplit units? (other than not to use them)
> I don't have antenna options, it's one dual band antenna, or move to 
> another non-existent site. 

In my opinion, TX-RX crossband couplers are the best out there.  I have many
in service and have never had a failure.

--- Jeff






 
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RE: [Repeater-Builder] Re: Looking for N connector jam nuts

[Jeff DePolo]

I didn't even think about Joel, and I just ordered a bunch of stuff from him
a couple of weeks ago.  Anyway, Robin K4IDC had the jam nuts in his stash
and is sending them - thanks for the replies though.

--- Jeff 

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Mike Perryman
> Sent: Friday, April 14, 2006 1:53 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Re: Looking for N connector jam nuts
> 
> I didn't hink about Joel over at RF-Connection.
> He is a good honest vendor..  -->just my opinion..
> I have no ties other than I order from him quite often.. and 
> have never been
> disappointed so far..
>  73
> Mike Perryman
> www.k5jmp.us
> 
> 
> 
> -Original Message-
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] Behalf Of msf5kguru
> Sent: Friday, April 14, 2006 1:32 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Looking for N connector jam nuts
> 
> 
> Don't know if you ever found any, but this place sells them for $0.25
> each (just ran across it today while looking for something else):
> 
> http://users.erols.com/rfc/uhf.htm
> 
> Bob M.
> ==
> --- In Repeater-Builder@yahoogroups.com, "Jeff DePolo WN3A"
> <[EMAIL PROTECTED]> wrote:
> >
> >
> > I'm trying to find about 40 hex jam nuts for bulkhead N
> connectors.  The
> > thread on N connectors is 5/8-24, and most of the jam nuts are 3/4"
> hex,
> > roughly 1/8" thick.  I'm trying to find stainless steel.  I've
> tried a
> > number of places on line, including McMaster-Carr and others, but
> came up
> > empty at all but one place, and they quoted me $10.50 EACH!???!?
> Anyone
> > have a favorite vendor that they could recommend?
> >
> > --- Jeff
> >
> > 
> > Jeff DePolo WN3A - [EMAIL PROTECTED]
> > Broadcast and Communications Consultant
> >
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> -- 
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> Checked by AVG Free Edition.
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[Repeater-Builder] Looking for N connector jam nuts

[Jeff DePolo WN3A]

I'm trying to find about 40 hex jam nuts for bulkhead N connectors.  The
thread on N connectors is 5/8-24, and most of the jam nuts are 3/4" hex,
roughly 1/8" thick.  I'm trying to find stainless steel.  I've tried a
number of places on line, including McMaster-Carr and others, but came up
empty at all but one place, and they quoted me $10.50 EACH!???!?  Anyone
have a favorite vendor that they could recommend?

--- Jeff

----
Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] Sinclair Q-201G duplexer

[Jeff DePolo]

The notch "generally" will track the pass as it's adjusted, but it's not a
fixed-offset kind of thing.  If you retune one of the cavities +1 MHz, the
notch may move +1.1 MHz, or +0.9 MHz, or ...you get the idea.  So, no, you
can't just re-tune the pass and assume the notch has followed exactly.

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Ken Arck
> Sent: Sunday, April 09, 2006 7:30 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Sinclair Q-201G duplexer
> 
> Hi folks
> 
> I know the "stock" answer, but I'm looking for the non-stock 
> one :-) (and
> yes, I've read the manual!).
> 
> But I was wondering (and checking my rationale here). in 
> many Bp/Br
> cavities, the notch tuning actually tunes to a certain freq 
> above or below
> the pass-tuned frequency. Therefore, if moving the duplexer a 
> meg or two
> but you maintain the same offset spacing, can you simply get away with
> retuning the pass freq and, all other things being equal 
> (port impedance,
> etc), is that all that is needed?
> 
> Manuals always seem to talk about tuning but rarely (if ever) 
> REtuning...
> 
> Ken
> --
> 
> President and CTO - Arcom Communications
> Makers of the world famous RC210 Repeater Controller and accessories.
> http://www.ah6le.net/arcom/index.html
> Authorized Dealers for Kenwood and Telewave and
> we offer complete repeater packages!
> AH6LE/R - IRLP Node 3000
> http://www.irlp.net
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> -- 
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Re: [Repeater-Builder] Favorite power swr bridge

[Jeff DePolo]

On Tue, 04 Apr 2006 13:26:45 -0500, Jay Urish wrote
> Right now I have a Bird 4410.
> 
> What does everybody think about the telewave units?
> --
> Jay Urish W5GM


Birds and the Telewaves are not SWR bridges, they're directional wattmeters.

With that said, I'm not fan of the Telewaves.  I have two of the 44A's, but 
I rarely use them.  The switch is a little flakey on one of the ones I have, 
even though it's only maybe 5 years old.  The other one is a little older, 
and it has someting intermittant internally that results in it giving 
different readings on sucessive key-ups.

I have several different flavors of Birds including 43's, 43P's, the digital 
4391A, etc.  Without fail, I always find myself grabbing one of the 43's 
(call me a stubborn OF, but they just work).

The digital 4391 is nice, but as you might imagine, the battery is always 
dead at the most inopportune time.  I have a Bird 4410 at one of my clients' 
locations, and like it for what little time I've used it.

I have Coaxial Dynamics wattmeters of various types at broadcast sites, but 
generally speaking, if I'm the one doing the buying, I buy Bird.

--- Jeff







 
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[Repeater-Builder] Looking for datasheet - SD1499-1

[Jeff DePolo]

Trying to find a datasheet for an RF power transistor - SD1499-1.  These
were made by Thomson/ST Micro.  Can't seem to find anything on-line, not
even a cross-reference.  Any help would be appreciated.  Thanks.
 
--- Jeff
 
 





 
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RE: [Repeater-Builder] Dayton Hamvention

[Jeff DePolo]

Kevin sed:
>I've been attending Dayton since 1974.  This year, I've had 
> two folks 
>contact me to see if I had gotten my tickets yet, as they have not 
>received any word. They need to be more prompt about 
> communications, or 
>they are going to
>piss a bunch of folks off.
>Scotty, did we get our tickets/spaces yet? (we hadn't the last time
>we
>conversed about it)

Has anyone received anything yet?

This will be my 17th year at Dayton.  For at least the last 10 years
we've always had the same fleamarket spaces.  Last year, we didn't get
our fleamarket tickets or entrance tickets.  I called, faxed, emailed,
probably ten times, and it wasn't until the Monday before the event that
I got a call-back saying that they were having problems getting tickets
out in time, and that I'd have to pick them up at the fest on Thursday
when I got there.

This year, I didn't even receive the usual sign-up package which usually
came in December in previous years.  I called, faxed, emailed, and never
heard back.  Finally I gave up and downloaded the forms from their web
site, filled them out, and faxed them in.  I still don't know whether or
not they received it or processed it.

Dayton is always a good time, even in the years with lousy weather, but
they need to make some improvements in the "customer service" side of
things...

--- Jeff

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[Repeater-Builder] Mouse-tr II chassis - free

[Jeff DePolo]

I have a Mastr II chassis that apparently a group of mice were living in
without permission and without paying rent (is there such a thing as a
mouse crack house?).  Anyway, if anyone wants it, let me know before
before 10 PM EST tonight else it goes out for the morning trash.  It's
just the chassis, backplane, door, harness, speaker, etc., no PA, no
cards in the shelf, no exciter, no receiver, no system board, no lid.
And it's anything but clean.

--- Jeff






 
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RE: [Repeater-Builder] Fiberglass antenna protective coating?

[Jeff DePolo]

> I have a Phelps-Dodge VHF antenna about 21'10" long.
> 
> Tell me about the three radials at the bottom.
> For the 2 meter band, what should the length be?
> 
> The NCG GP-6 antennas use about 19.5" long radials.
> 
> Should the radials be straight, like the GP-6, or angled down 
> some degree(s)?
> 
> What should the length of the radials be, for a UHF band antenna?

It depends on which model antenna you have.  From what I've seen, having
disassembled many, those that are comprised of coaxial half-wave elements
(VHF PD220, UHF PD1151, PD455, etc.) use radials sloping down at a 45 degree
angle for decoupling only.  The length of radials is nominally 1/4 wave, but
they are slightly shorter than that physically due to their width.  For
antennas that are non-coaxial elements, the radials are at a 90 degree angle
and serve more as a ground plane.  PD200 on VHF, PD400 on UHF have 90 degree
radials.  For these antennas, the radials are arguably more critical than
the models where they are used for decoupling only.

If your VHF antenna is in the 21' range, it could be either a PD220 or
PD200.  Does it still have a sticker on it?

--- Jeff

Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 


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RE: [Repeater-Builder] FW: [rc210] Power sensor

[Jeff DePolo]

Don't have any of the Motorola power sensors, but I have a surplus of
Telewave and Decibel for various bands if anyone is interested.  N male to N
female, with RCA jacks for forward and reflected.  I know the Decibels have
adjusable pots for the forward/reflected output sample voltage, I forget if
the Telewaves do.

http://www.telewave.com/pdf/TWDS-3010.pdf  (this only shows 118-512 MHz, but
I have the lowband ones too)

http://www.dbspectra.com/products/decibel/DB8880Sensors.pdf

--- Jeff



_ 
From:   Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED]  On Behalf Of Mike Perryman K5JMP
Sent:   Monday, March 20, 2006 11:10 PM
To: Repeater-Builder@yahoogroups.com
Subject:[Repeater-Builder] FW: [rc210] Power sensor

Figured I would post it over here as well...

Other folks looking for Moto thru-line adapters on the RC-210
group...  anybody got excess thru-line adapters?

73
Mike
K5JMP
www.k5jmp.us

 -Original Message-
From:   [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 
Sent:   Monday, March 20, 2006 11:03 PM
To: [EMAIL PROTECTED]
Subject:RE: [rc210] Power sensor

Mark,
Sorry...  Mike WA6ILQ has already asked for it.  Keep your eyes on
eBay...  they show up every once in a while.  Wish I had more of them to
share, but parts have been flying out of here pretty quick lately!! 

Could I interest anyone in a 1/4kW 6m PA of the GE variety? It will
be pick-up only in Stafford, VA. I may also have a 1/4 kW UHF /\/\oto
variety PA leaving if someone has something of interest to trade  I am
currently seeking 900 gear for a repeater.
73
Mike
K5JMP
www.k5jmp.us


-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf
Of
Mark Phillips
Sent: Monday, March 20, 2006 10:51 PM
To: [EMAIL PROTECTED]
Subject: Re: [rc210] Power sensor


How much for the HF one? I've a 6 mter machine I could use it on.

Mark

Mark, G7LTT/KC2ENI
Randolph, NJ
http://www.g7ltt.com


Mike Perryman K5JMP wrote:
> Paul,
>  
> I have 2 left...  one is 500-1000MHZ @ 50W (TRN5323A) currently
slated 
> for a 900 repeater, and one 25-100MHz @ 100W (no number on
low-band 
> unit).  I am willing to let go of the low-band unit, just sorry it

> doesn't fit your needs..  Keep an eye on the 'Bay..  they
generally go 
> pretty cheap. Sometimes you can find them in a rack panel
configuration 
> for around 70-100 bucks.  Then all you have to do is tap the
rotary 
> switch for the appropriate reading, and calibrate the RC-210
"meter face".
>  I guess I should have bid on the set (portable  meter and full 
> assortment of adapters) that I saw go past about 2 months ago.  I
recall 
> it went for less than 80 bucks for the whole shooting match.  You
might 
> also check on the repeater-builder list...  lots of
"/\/\oto-heads" over 
> there...
> Good luck,
> 
> 73
> Mike
> K5JMP
> www.k5jmp.us
> 


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RE: [Repeater-Builder] Re: Decible low band Dipole Array matching section value?

[Jeff DePolo]

> There are at least one or two other VB numbers. Anyone 
> have an idea what the other values are? 
> 
> cheers,
> skipp 

I've only ever seen VB-83 (35 ohm, similiar to RG-83) and VB-8 (50 ohm,
similar to RG-8).

I have RG-83 cable available if anyone is looking for some to rebuild
harnesses, but it's not cheap...

--- Jeff

----
Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 


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RE: [Repeater-Builder] Deltas as repeaters and Channel Guard thoughts.

[Jeff DePolo WN3A]

>Being new to repeaters, I've been doing a lot of research and 
> reading though the LBI's available in repeater-builder.com (thank you 
> to all who contributed, btw).  I have learned LOTS.  For my first 
> VHF "learning" repeater I plan to use a couple GE Deltas (an SX for 
> transmit and an S for receive due to the helical filters).  First 
> question: has anyone experienced issues with turning the PA on the 
> 110-Watt delta transmitter down to 50 to 60 Watts with a fan for full 
> duty cycle?  I'm concerned with spurs of course.  

The Delta-S's, both on highband and UHF, seem to be very stable at any power
level.  I've had issues with lowband Delta-S's programmed at the high end of
6m (52/53 MHz pairs) sometimes getting unstable at certain power levels.
However, even with the TPO turned down, there are still thermal issues.
You're better off with a low-power radio (or even better, putting a
low-power PA in a high-power chassis to take advantage of the bigger
heatsink).

> or advice to give?  I don't mind learning from my mistakes, but I'd 
> rather learn from others'.  :)

If you haven't already found it, go to
http://www.ka9fur.net/delta/delta.html for additional info beyond what is on
repeater-builder.com.  Some of it is specific to UHF, but there is a lot of
good general info there, including dissection of the EEPROM storage format.

>Secondly, more often than not I have read that people toss the 
> Channel Guard boards in these radios for HAM use.  Why is that?  

I don't know, I've never heard of anyone doing that.  The software decoder
in the Delta-S is very good.

> Anyone actually use the board for tone 
> squelch?  

Most definately.  

> You can I'm curious why someone would go with something like a TS-
> 64 when the CG board accomplishes the same task.

I don't know, the ComSpec PL boards aren't the greatest as far as decode
performance, and the encoders have higher THD than most other designs.

>   Incidentally, I am considering replacing the micro/prom in the 
> Delta with a micro of my own (I fancy the Atmel line, though any 
> would do.)  

While we haven't totally replaced the uP, Dave (KA9FUR) and I have come up
with some software mods to facilitate customization of radios for
non-standard uses such as locking to external frequency references (for
simulcasting) among other things.  Finding windowed (EPROM) parts (8749H) is
getting difficult though.

> As you can tell I'm loving these radios (and similarly, 
> the Phoenixes) so far...

They're great radios.  The Delta-S front end is very good, and is virtually
identical to the front end in GE Mastr III's.  Transmitters are extremely
clean with low phase/sideband noise.  I was told that the design criteria of
the Delta-S/SX series included the requirement that sideband noise was to be
less than current protection crystal-based transmitters (at the time, Mastr
II series), and from all indications, they have exceeded that specification.
Duplex operation on 2m seems to be comparable to the Mastr II PLL exciter,
which represents about a 22 dB reduction in noise over the standard
multiplier Mastr II exciter at 600 kHz T/R spacing.

--- Jeff


Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 



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RE: [Repeater-Builder] 4 Bay antenna

[Jeff DePolo WN3A]

Sounds like an old Cushcraft AFM-4DA array.  Bad news.

--- Jeff

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of 
> [EMAIL PROTECTED]
> Sent: Sunday, March 12, 2006 3:10 PM
> To: [EMAIL PROTECTED]; repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] 4 Bay antenna
> 
> I have a 4 bay vhf antenna, with each antenna straight and not 
> folded. The harness is old and cracked. Some one has used 
> electrical tape on some of the harness. There is no label or 
> markings anyplace to know what brand it might be. If I made a new 
> harness, can I use "T" connectors? Each antenna has a gama 
> match for tuning. and using mobile size coax; no markings on the 
> coax either.
> 
> Rod KC7VQR
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
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> Date: 3/10/2006
>  
> 

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RE: [Repeater-Builder] lightning arrestors

[Jeff DePolo]

> The commercial site where my 900 MHz repeater is, has
> a bunch of PolyPhasers, so I bought one too. For that
> band, it's only good for 50 watts, and I don't think
> they had one rated for more power. So I had to replace
> it with an Alpha Delta; I should have just bought that
> the first time.
> 
> Bob M.
> ==

The high-power (500+ watt) Polyphasers are usually advertised as being
"combiner protectors".  They are made for various bands.  In fact, if anyone
has a need, I have a surplus of the UHF ones rated for 500 watts.

--- Jeff





 
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RE: [Repeater-Builder] A sad story

[Jeff DePolo]

> Now the new cable is in place, and that power that was getting turned 
> into heat is getting delivered to the cans. But, something smells 
> funny, and the interconnect cables between the cans are noticably 
> warm.

How much power are you running into the cavities?

I can't think of anything inside the cans that would "smell funny" with
power applied unless there was really something very wrong with them (like a
shorted capacitor).  As a longshot, is there any chance that your PA is
going spurious, which could a) cause excessive heat/loss in the cabling to
the off-channel spurs creating high VSWR, and b) the "smell" could be a
component failing in the PA, which could either be a victim of the
oscillation, or the cause of the oscillation.

> These are Wacoms, I don't have the exact model number in front of me, 
> but if I remember right, they were rated for 150W or thereabouts. I 
> had tuned them before, and everything was looking good, but it 
> appears that when the adaptor chain wasn't in the picture sucking up 
> power, I crossed some threshold and damaged the cans.

Or, the difference in cable length between the old conglomeration and the
new patch cable has made the PA unhappy resulting in the spurious condition
(again, this is a bit of a longshot, but a plausible explanation).

--- Jeff





 
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RE: [Repeater-Builder] Looking for MRF648's

[Jeff DePolo]

No, not yet.  Several vendors still have them, but I thought maybe I'd find
someone with a surplus stash that would make a deal.   

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Bob Dengler
> Sent: Thursday, February 23, 2006 8:13 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Looking for MRF648's
> 
> At 2/23/2006 01:53 PM, you wrote:
> 
> >Anyone have a surplus of Motorola MRF648 UHF power 
> transistors that they'd
> >sell or trade?
> >
> > --- Jeff
> >
> >-
> 
> Uhh ohh, don't tell me they're getting hard to find.
> 
> Bob NO6B
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 





 
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[Repeater-Builder] Looking for MRF648's

[Jeff DePolo WN3A]

Anyone have a surplus of Motorola MRF648 UHF power transistors that they'd
sell or trade?

--- Jeff

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RE: [Repeater-Builder] Re: Best broadband VHF antenna

[Jeff DePolo WN3A]

> I would agree the Sinclair Antennas are well built and 
> very broadband, but I had a  horible time with a number 
> of 4 bay vhf broadband units installed (and removed) 
> in 2005.  We bought a large number of VHF SLR-235 
> units new. The part number has changed but the antenna 
> is the same current 4 dipole current model. 
> 
> The performance stank, with wild patterns and imd 
> generation from all the brand new antennas we bought 
> and installed at different locations. What a let down 
> vs the good performance of other Sinclair antennas we've 
> purchased in the past. 

Geez Skipp, that's pretty unusual.  I've never had anything but good luck
with Sinclair's dipole arrays, both on highband and UHF.  I'm not a big fan
of their whitesticks though.  As I'm sure you know, most of their antennas
are available in "low PIM" versions, though I've never had any IM problems
with even their older, standard models.
 
> I figured it might be something we did, so I had a number 
> of people check everything at least twice over. Yes 
> we checked the harness phasing, element spacing yadda, 
> yadda.  But the same problem with 6 brand new antennas 
> at 3 different locations?  

The only thing that comes to mind is maybe a "quality control" issue at the
factory that resulted in one or more of the dipoles being assembled
upside-down resulting in severe cancellation.  I know they usually mark one
side of each element with a band of red tape to ensure they are properly
phased, but somebody could have screwed this process up (or maybe they
marked them after assembly instead of before).  If you have nothing else to
do (hi), maybe you could do some tests to ascertain whether or not this is
the case, perhaps by transmitting a few hundred mW into the input and using
a scope to look at the relative phase between elements (i.e. check to see
that the upper side of the feedpoint is in-phase between each of the
elements).

--- Jeff

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RE: [Repeater-Builder] Best broadband VHF antenna

[Jeff DePolo WN3A]

> Have a question for the list.  Is there an antenna (VHF) that 
> will cover a 30mhz bandwith?  (Reasonably)  
> 
> There is a system in Georgia incompassing the entire state 
> using various tall towers.  On the towers will be antennas 
> that will be used for VHF Repeaters and VHF digital. (in the 
> ham band)  T
> 
> he NWS is hoping to use the same antennas on a "Mesonet". 
> (like this one http://www.mesonet.ou.edu/)  They are looking 
> at the government freq.s right now but thinks there may be 
> something in the 175mhz band.  

Sinclair wideband dipole arrays are probably our best bet (SD214-HL as an
example).  They cover 138-174 MHz, available with either 1/4 wave or 1/2
wave spacing from element to mast (go with half-wave if you want to get
close to omni, quarter-wave for a more unidirectional pattern).  Built like
a tank.  Telewave also has broadband dipole arrays, but personally I like
Sinclair's construction better.

--- Jeff


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RE: [Repeater-Builder] Co-Locating in an Elevator Room

[Jeff DePolo]

> I was told the following things:
> 
>  440 Mhz is "too high" of a frequency to be in an elevator room

Well, they've got you there.

>  NFPA and the "elevator code" says that nothing can be 
> stored inside
>  of an elevator room other than equipment directly 
> relating to the operation
>  of the elevator system

Although admittedly I know little about NFPA, I can tell you that on an
install I did in an elevator mechanical room that one of the requirements
was that we had to "isolate" the equipment location from the rest of the
elevator room by installing a chain-link fence encompassing the side of the
room containing elevator-exclusive hardware.  Perhaps there is something in
NFPA that requires the area in which the elevator equipment is located be
properly protected from access by anyone else?

>  Even if the unit is "just receiving", it is still building up
> "frequency" on the walls
>  of the room that will cause "bad things" to happen "eventually".

Obviously they know the laws of physics better than any of us.

> Any suggestions? Anyone know of a good "waterproof" cabinet that can
> go outside? Is that a good idea? Help.

Sure.  I like DDB's outdoor cabinets (www.ddbunlimited.com).

You might also ask if there is any other location, perhaps on the floor
below, where could relocate your cabinet too.  Like maybe some extra space
in a janitor's closet or telecom closet or something.

How bulletproof is your lease agreement?

--- Jeff





 
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RE: [Repeater-Builder] Micor PA woes---The Results!

[Jeff DePolo]

> I also noticed that one of the high output amps seems to have an 
> issue when feeding the circulator. The output through the circ. (loss 
> thru the circ is about 1.2 db) starts at 60 watts and then jumps to 
> 75 or so and the spectrum analyzer light up like a christmas tree. 
> Turn the power control all the way up, it's OK, turn it down some, 
> it's OK. I touched up the circ in the chassis and no change. 

About the only times I've seen Micor UHF PA's go spurious is due to one of
four reasons:

1.  One of the parasitic supressors is bad (the little miniature-domino
looking things that span from base to collector on all but the controlled
stage device).  Usually when they go bad, you'll see a crack where one of
the legs attaches to the substrate.  Next time you get it to go spurious,
wiggle on each of them with an insulated tool and see if you can change the
spurious response.

2.  A cracked board, often not at a point that affects one of the microstrip
lines on the top side of the board.  If cracked along an edge or near a
corner, it may "disconnect" the underside's groundplane from the rest of the
RF ground system.  Take an excacto knife or a sharp dentist's pick and
gently run it across the boards; sometimes the cracks are hard to see but
usually you can find them that way.

3.  A broken ground solder joint either between boards, or more often than
not, up along the top of the board where there are little tin straps that
tie the boards' RF ground to the DC ground bus bar.  Usually you can find
these by flexing on the board a little with an insulated tool in the area of
the tin straps.

4.  Insufficient drive from the LLA.  The spec for the LLA output is 1 to 2
watts.  Depending on whether or not you've retuned the helical filter on the
LLA output, it can sometimes behave a little squirrelly when connected to
the PA even though it shows normal/clean output when run into a dummy load.
Sometimes you can confirm or deny this is a problem by adding extending the
cable length a bit, such as with a couple of BNC elbows or male-male +
female-female adapters.  If it clears up by changing cable lengths, you need
to retune the filter.

Oh, there's one other possibility, but it's really a longshot.  On the
transmitter interconnect board there is a filter cap on the control line (I
think it's around 10 uF; it's visible from the front of the chassis, just a
little to the left of the power control board/chassis frame).  If that
opens, you can get oscillations on the control line, which in turn
translates into RF spurs.  I've only seen this happen once.

> Any comments on the funky amps would be appreciated.

Well, for the dead ones, first you have to figure out what stage it's dead.
You can sometimes get a rough idea by looking at current draw (i.e. if it's
only drawing maybe 8 amps, chances are it's not in the finals but somewhere
earlier).  If it's drawing a lot of current, the problem may be at the PA
output where the RG142 jumper meets the board.  The intra-stage coupling on
Micor UHF amps is all 50 ohms, which is nice, so you can open the circuit at
the appropriate point, tack-solder in a little jumper to go to a wattmeter,
and test the stage that way.  Look at the schematics to figure out where the
opportune points are to "jump in".  Likewise you can open the circuit, say,
before the finals, and transmit about 30 watts into the finals and see if
you get power out.  You get the idea.

Another common cause of no power output is one of the DC blocking caps had a
bad solder connection.  If memory serves, these are 56 pF ceramic chip caps,
and they are usually at the point where the semi-rigid coax ends (there is
one along the upper-left between the first two stages, and another along the
lower/mid-left between the pre-driver and driver stages).  Sorry I don't
have one here to look at it to give you more definitive locations, but I'm
sure you'll find them, especially if you have the schematics.

For the one that drops off in power, usually this is a sign of either an
intermittant solder connection (see 2 through 4 above), or a cap that is
going bad or has a poor solder joint.  This happens most often at the four
25.5 pF ceramic chip caps between collector and emitter, and emitter and
base, on each of the transistors.  Examine the edges of those caps with a
magnifying glass.  If you find any that look the solder didn't wet the face
of the capacitor and flow properly, or in severe cases, if it looks like the
metallized end of the cap has pulled away from the rest of the body of the
capacitor, replace it (don't try to re-solder them - replace with new).
Again, sometimes you can find these by poking at them laterally with an
insulated tool to make/break the connection, or you may even be able to see
them arc-n'-spark a little if you dim the lights in the room while wiggling.

Keep the power control voltage around 7-8 volts when testing; 12 is really
running the thing wide-open.

Do yourself a favor while you have i

RE: [Repeater-Builder] VHF Seperation

[Jeff DePolo]

The usual questions:

How much transmitter power?

What kind of transmitter and receiver?

What kind of antennas?

Are you using any other kind of external filtering, or trying to get by with
just split antennas?

What kind of feedline for each, and approximately how long?

--- Jeff

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
> Sent: Friday, February 17, 2006 5:25 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] VHF Seperation
> 
>  Could anyone give me some advice regarding antenna 
> seperation for a VHF Repeater...  Using TX of 152.000 and RX 
> of 159.000, what would the min. vertical and horizontal be?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> YAHOO! GROUPS LINKS 
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RE: [Repeater-Builder] UHF Micor Receivers WANTED

[Jeff DePolo]

Huh?  Micor receivers are Micor receivers, whether they're sitting in a
mobile, station, or SpectraTAC chassis.  Or in some cases, even in a
PURC/MSF5000 receiver chassis.

--- Jeff  

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of N9WYS
> Sent: Friday, February 17, 2006 2:45 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] UHF Micor Receivers WANTED
> 
> Only thing about using mobile receiver sections in a 
> SpectraTAC is that the mobile receivers do not have the 
> preselector on the board itself.  
> 
> Otherwise, it's plug and play.
> 
>  
> 
> Mark - N9WYS
> 
>  
> 
> 
> 
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of 
> [EMAIL PROTECTED]
> Sent: Friday, February 17, 2006 9:10 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] UHF Micor Receivers WANTED
> 
>  
> 
> Have you tried ebay? Just in the last few weeks, there was a 
> set of three - 406-420 MHZ range UHF MICOR mobiles that went 
> for $10 for the set of three.
> 
>  
> 
> Sometimes you have to go digging.
> 
>  
> 
> LJ
> 
> 
> -Original Message- 
> From: Steve Rubeck 
> Sent: Feb 16, 2006 10:22 PM 
> To: Repeater-Builder@yahoogroups.com 
> Cc: [EMAIL PROTECTED] 
> Subject: [Repeater-Builder] UHF Micor Receivers WANTED 
> 
>   Hello all, 
>   
>   I am still looking for a source of Motorola Micor Range 
> 1 receiver cards. 406-420 MHz. I'd like to use these for 
> repeater linking.
> 
>
> 
>   Or does anyone have a source for any power, low split 
> UHF 406-420 range Micor Repeater stations? 
>   
>   I had a few contacts however still looking. HELP!
> 
>
> 
>   Reply off list directly.
>   
>   Steve - KB9FMU
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> YAHOO! GROUPS LINKS 
> 
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>  " on the web.
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RE: Radio quality (was RE: [Repeater-Builder] UHF Power)

[Jeff DePolo]

> Ok, I'll bite-what's AIP? I have a G707, and don't remember seeing 
> anything labeled like that.

Kenwood's AIP = "Advanced Intercept Point".  It reduces the sensitivity of
the receiver which has the effect of reducing receiver-induced intermod by
lowering the TOIP/compression point.  Although I thought it might just be an
attenuator that is switched in, Bob said that what it's really doing is
reducing the gain of the first RF stage (I guess there's an RF amplifier
before the first mixer).

I didn't get a chance to re-measure my V7A with the AIP turned on yet.

> Course, intermod isn't what it used to be either. Through the 
> late 70's, 
> 80's, and early 90's, you couldn't drive through downtown Cleveland 
> without hearing intermod on 2M or UHF. With ANY radio. Not a MastrII, 
> not a Micor. NOTHING was immune to all those 1/3KW 
> IMTS/paging transmitters.

You'd think it should be getting BETTER with all of the VHF/UHF paging
activity having dropped off in many areas, IMTS being dead (or in some
cases, the channels re-used for other purposes), etc., but that doesn't seem
to be the case.  Go figure.

--- Jeff





 
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo WN3A]

> I have enjoyed this thread and hope that no one has taken 
> anything to be any kind of personal attack on how anyone runs their 
> repeater.

Of course not.  No matter how much I or anyone else nit-picks technical
details, it's still supposed to be a fun hobby.

> My point was "is it needed?"

I think you were debating the issue from the "functional" standpoint, while
I was looking at it from the "technical" standpoint.  All things being
equal, I guess I'm more comfortable comparing numbers than trying to
ascertain what users might perceive.

> Thank you to all.

Thank you for motivating me to go tinker with ham radio stuff for a change;
it was a nice diversion from what was otherwise a paperwork-laden
work-at-home weekend.

--- Jeff





 
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RE: Radio quality (was RE: [Repeater-Builder] UHF Power)

[Jeff DePolo WN3A]

> Did you try the V7A with AIP on?  

No, I didn't, but I'll do that later today if I get a chance.  The other ham
rig in my truck is the other Kenwood dual bander (TM-708?  getting old and
don't remember model #'s like I used to).  I'm not sure but I think that has
the AIP function too.  I never dug into it to see how it's designed - is the
AIP feature just a switchable attenuator or something else?

--- Jeff





 
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RE: [Repeater-Builder] Cheap "Tunnel" Heatsink

[Jeff DePolo WN3A]

I picked up an electronic load on Ebay a number of years ago, and have
gotten more use out of it than I ever thought I would.  Here's a well-done
article on building an electronic load.  The general design could be easily
expanded to handle higher current by using a beefier transistor and/or
multiple devices.

http://www.siliconchip.com.au/cms/A_30506/article.html



--- Jeff

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Tony King, W4ZT
> Sent: Sunday, February 12, 2006 9:06 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Cheap "Tunnel" Heatsink
> 
> 
> Here is my version of a 12 Volt dummy load: 
> 
> 
> And, for those of you that are like me and would like to load 
> test HIGH 
> VOLTAGE supplies, here's my high voltage dummy load: 
> 
> 
> Careful... either of them can burn you... BAD.  The high 
> voltage dummy 
> load can KILL you if you get into it.
> 
> 73, Tony W4ZT
> 
> 
> Mike Morris wrote:
> > Years ago I saw a homebrew version of that:
> > 
> > Twenty tungsten auto headlights in a metal box, with a switch
> > for each bulb, and a couple of heater blowers.  Bulbs were
> > 50 cents at the auto junkyard, as were the headlight switches. 
> > They were wired so that the parking light position (half-way out)
> > lit up the low beam, and the headlight position (all the way out)
> > lit up the high beam as well.
> > 
> > A regular wall thermostat was used along with a relay to run
> > the heater blowers (off of the 12v input).
> > 
> > Cheap to build and worked just fine
> > 
> > Mike WA6ILQ
> > 
> > 
> > At 10:46 PM 2/11/06, you wrote:
> > 
> >> Brett, I have a copy of a commercial "Load Bank" which is 
> nothing more 
> >> than
> >> a bunch of large resistors in a case controlled by switches.
> >> I'll dig it out and scan it for you
> >>  
> >> These people get $3,000.00 for this package !  I have the stuff to 
> >> build one
> >> and have about $75.00 invested so far.
> >>  
> >> 73 John VE3AMZ
> >>
> >> - Original Message -
> >> From: Brett 
> >> To: Repeater-Builder@yahoogroups.com
> >> 
> >> Sent: Saturday, February 11, 2006 9:28 PM
> >> Subject: Re: [Repeater-Builder] Cheap "Tunnel" Heatsink
> >>
> >> Hi guys does anyone have that circuit diagram I need 
> to build one
> >> to test 12 to 60 volt supply.
> >> Thanks in advance.
> >> Brett
> >>  
> >> - Original Message -
> >> From: [EMAIL PROTECTED] 
> >> To: Repeater-Builder@yahoogroups.com
> >> 
> >> Sent: Sunday, February 12, 2006 10:01 AM
> >> Subject: Re: [Repeater-Builder] Cheap "Tunnel" Heatsink
> >>
> >> In a message dated 2/11/2006 3:10:54 PM Eastern Standard Time,
> >> [EMAIL PROTECTED]  writes:
> >> http://www.ve3tjd.com/pictures/tech%20stuff/
> >>
> >> What a perfect heatsink for that variable power supply 
> load that was 
> >> bouncing around on R-B about a year or two ago. You could 
> vary the Amp 
> >> Load on your power supply using a variable pot control.
> >> Gary  K2UQ
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 





 
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo WN3A]

> I still contend that in a mobile environment, under motion, that the 
> user will not detect the 6 dB difference. It will be barely 
> distinguishable most of the time.

I'm not arguing this point.  There have been times when I've had a 75 watt
Micor PA die and I've had to run the output of the low-level amp (about 1.5
watts) to the antenna for a few days.  A few users noticed, but most didn't.

The point is that the system should be designed to be balanced, and unless
your coverage needs or limitations dictate otherwise, we try to build
repeaters that perform as well as possible.  We worry about fractions of a
dB of insertion loss when tuning a duplexer, spend more money to run 7/8"
instead of 1/2" to the antenna, buy a SuperStationmaster for $750 rather
than a two-bay for $250, even though we know that few users would ever
notice the difference.

--- Jeff





 
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RE: [Repeater-Builder] Andrew connector on Eupon cable

[Jeff DePolo WN3A]

Title: Message





I'm 
almost sure it does, as I've used those connectors before on either Andrew or 
Cablewave 7/8" foam.  If you have an older Tessco catalog (say, from 3 or 4 
years ago), I'm pretty sure they had a chart in there that showed which 
connectors work on which cable.  Most of the 1/2" and 7/8" heliax 
connectors are interchangable between cable manufacturers; it's when you get 
above 7/8" and/or go to air dielectric line that there are more 
differences.  An exception to this is Andrew LDF5-50A versus LDF5-50B; the 
center conductors are slightly different diameter, and although you can 
generally make the connectors for one work on the other, the fit of the center 
pin isn't perfect.
 
The 
odd varieties 7/8" cables like Andrew VXL series and Commscope uncorrugated 
cable require connectors specific to those types.
 
    
--- Jeff
 

  
  -Original Message-From: 
  Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] 
  On Behalf Of Jeff CorkrenSent: Sunday, February 12, 2006 
  2:16 AMTo: Repeater BuilderSubject: [Repeater-Builder] 
  Andrew connector on Eupon cable
  Does anyone know if a Andrew 7/8 
  inch connector (type L5PNF) will fit Eupen 7/8 inch heliax cable ? 
  Thanks in advance for your reply.
   
  Jeff Corkren/W5PPB
  Raymond, Mississippi 













  




  
  
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo WN3A]

And mine too.  Just because the unwashed masses don't notice it doesn't make
it right, better, worse, or otherwise.

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Chuck Kelsey
> Sent: Saturday, February 11, 2006 8:46 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] UHF Power
> 
> 
> And that's my whole point.
> 
> Chuck
> WB2EDV
> 
> 
> 
> Jeff DePolo WN3A wrote:
> 
> >
> >  
> >
> >>I'd be interested in someone actually trying this with a UHF 
> >>system that 
> >>is running 200+ watts. Drop it to 100 watts without telling anyone. 
> >>Leave it there for a week or two and see if anyone notices.
> >>
> >>
> >
> >Chances are nobody will notice.  But then again, they 
> probably wouldn't
> >notice if you put a 3 dB pad between your duplexer and 
> receiver either...
> >
> > --- Jeff
> >
> >  
> >
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 





 
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo WN3A]

OK, here are the results of my quick bench measurements for whatever it's
worth.  All receivers were on the same frequency (448.800 MHz).  Signal
source was a Fluke/Philips 6060A sig gen locked to a rubidium reference
oscillator, modulated by 1 kHz AF at +/- 3 kHz peak deviation.  The output
of the sig gen had a 10 dB pad on it for isolation -- all sensitivity values
below have already been corrected for this 10 dB offset.  SINAD measurement
done on an HP 8920B using the speaker output of each radio (standard EIA
test method), AF PA terminated with an 8 ohm speaker, with a transformer in
parallel with the speaker to provide isolation to the test equipment.  I
used the averaging function on the 8920B to help smooth out the inherent
variation in the SINAD measurement.

The commercial radios (Micor, M2, Delta) were tuned using the factory tuneup
procedure without a preamp in line, i.e. no optimization of the front end
tune was done to improve sensitivity when the preamp was added.  RF patch
cables for all tests included a 4' piece of RG-400 with type N connectors on
each end connected to the sig gen.  A short secondary patch cable (less than
2') with the appropriate connector on the other end (RCA for Micor and M2
receivers, UHF for Delta-S and Kenwoods, N for Icom, etc.) was connected to
the main 4' cable, either with the preamp serving as the connecting point of
the two cables, or a type N "barrel" was used when the preamp was out of
line.  All commercial radios were the standard 450-470 MHz split models,
with no mods done to them.  All sensitivity measurements are for 12 dB
SINAD.  In other words, I did everything I could to make the test setup as
close to identical for all of the scenarios.  

My goal here wasn't to determine which receiver/preamp was more sensitive
than another - even though I've shown resolution down to a tenth of a dB,
there is at least a few tenths of a dB of inherent uncertainty in the
measurements.  SINAD readings fluctuate on a signal that noisy, even with
averaging, so you have to take the absolute values with a grain of salt
(i.e. any of the readings that are within maybe 0.5 dB of each other should
be considered "too close to call").

REPEATER RECEIVERS
--

GE Mastr II Rx
--
-116.3 dBm (0.34 uV) without preamp
-127.7 dBm (0.092 uV) with TE Systems model 4420N GaAsFET
-127.5 dBm (0.094 uV) with Angle Linear 448GNT PHEMT

Motorola Micor Rx
-
-116.2 dBm (0.35 uV) without preamp
-126.3 dBm (0.11 uV) with TE Systems preamp
-126.6 dBm (0.10 uV)with Angle Linear preamp

GE Delta-S
--
-117.9 dBm (0.28 uV) without preamp
-127.5 dBm (0.094 uV) with TE Systems preamp
-127.6 dBm (0.093 uV) with Angle Linear preamp

The simple average of the linear (microvolt) sensitivities WITHOUT a preamp
for the repeater receivers is 0.32 uV (-116.6 dBm).

The simple average of the sensitivies WITH a preamp is 0.097 uV (-127.3
dBm).


MOBILE RECEIVERS


Kenwood TM-732A (my bench radio): -121.1 dBm (0.20 uV)

Kenwood TM-731A (retired, collecting dust for the last few years): -123.5
dBm (0.15 uV)

Icom IC-45A (really old, but a workhorse in its day): -115.6 dBm (0.37 uV)

Kenwood TM-V7A (my most-hated radio): -125.0 dBm (0.13 uV)

Syntor X9000 (with internal preamp): -122.3 (0.17 uV)

As you can see, the repeater receivers with low-noise preamps out-performed
all of the mobile radios.  Even if you throw out the relatively-deaf Icom
IC-45A, the repeater receivers beat the mobiles by a margin of anywhere from
1.3 dB to 6.6 dB.  Personally I'd argue that the TM-V7A should be
disqualified too; it has to have the most intermod-prone receiver of any UHF
radio I've ever used.

Side note: for the heck of it, I also tried using the sig gen in the 8920B
when I had the Delta-S on the bench, and I got SINAD measurements within a
couple of tenths of a dB difference.  I also wish I could have found an ARR
preamp and thrown that into the mix, I know I have one around here
somewhere.

I don't claim any of these tests to be indisputible either in terms of
absolute accuracy of the values, nor reproducibility by others.  I'm just
giving you what I came up with.  Run your own tests and publish the results
if you don't like my methods (or results :-).

    --- Jeff


Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo WN3A]

> No. A "typical" UHF ham rig will have better sensitivity than most 
> repeaters with a preamp. A commercial mobile (without preamp) 
> will have 
> sensitivity slightly worse than the repeater with the preamp. 99% of 
> hams will be using a ham rig, not a commercial one.

OK, tell you what.  It's snowing like hell here this weekend, I've got some
time to kill.  Tomorrow I'm going to put a couple test subjects on the bench
and will report back what I measure.

> Yep. You may experience more intermod with the hotter 
> receiver, but the 
> intermod is most likely going to swamp the mobile receiver no matter 
> what power level the repeater is running, at least most of the time.

Which is why a mobile receiver with a real front end and less sensitivity is
better...  

> I'd be interested in someone actually trying this with a UHF 
> system that 
> is running 200+ watts. Drop it to 100 watts without telling anyone. 
> Leave it there for a week or two and see if anyone notices.

Chances are nobody will notice.  But then again, they probably wouldn't
notice if you put a 3 dB pad between your duplexer and receiver either...

--- Jeff





 
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo]

> On Sat, 11 Feb 2006, Mike Morris wrote:
> > More details at  and it's really worth 
> > reading.  And wait for the photos to load - they are worth 
> it as well 
> > (just for the photo of WA6ITF 40 years ago). The Jampro 
> story is just 
> > under his picture.
> 
> That was an astounding story. That's the sort of stuff that 
> you don't want 
> disappear into the past forever. Thank you whoever documented that. 

If anyone is serious about a antenna project, I've got a few broadcast FM
antenna bays that could be used as the basis for constructing a 2m CP
repeater antenna.  For some of the antennas like the Jampro "penetrator"
series mentioned, it should be a simple matter of shortening the elements
and feeder arms, though modeling it in NEC or similiar would probably be
required to do the job right.  They're probably worth a few bucks, but in
the interest of experimentation, I'll give one (or maybe more) to anyone who
would take this up as a serious project and put together an article worthy
of being posted on the repeater-builder web site.  Email off-line if you're
interested.

--- Jeff





 
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RE: [Repeater-Builder] UHF Power

[Jeff DePolo]

> If we were talking about 6-meters, I'd agree on the 6-dB 
> disadvantage in 
> the mobile environment. I've never seen anything like that on UHF. I 
> don't buy into this argument yet ;-)
> 
> Chuck
> WB2EDV

OK, if you don't like the mobile noise environment model, let's just look at
raw sensitivity and ignore degradation due to ambient noise issues.  Would
you not agree that a good UHF repeater receiver with a GaAsFET ahead of it
will have better sensitivity than a typical mobile radio?  If so, by what
amount?

There are some mobile radios out there that are quite hot.  But my
experiences have been that the hotter the mobile radio, the more prone to
intermod and overload it is.  The high sensitivity comes at a price - lack
of front end filtering.  Where I live, "intermod alley" seems to be more
like "intermod county" thanks to Kenwood's wonderful receiver design, which
is why I use it only as a dial-around radio when I'm travelling but
otherwise I rely on an oldie-but-goodie commercial radio for working the
local repeaters.

--- Jeff




 
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<>

RE: [Repeater-Builder] Re: Duplexer weirdness

[Jeff DePolo]

> Yes but that sounds sort of risky in that the lowest noise 
> figure of an LNA 
> is not necessarily achieved at optimum match.  

Agreed, and most are tuned for lowest NF and not necessarily maximum gain
nor ideal match.

> My previous comments relating to LNAs may also apply to the 
> JFET mixers in 
> G.E. radios, as I've had a few that did not completely 
> optimize by tuning 
> for maximum RX limiter current per the manual; tuning for 
> best quieting 
> yielded a dB or two better S/N.

Agreed, and the effect is not limited to just GE's specifically.

--- Jeff






 
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RE: [Repeater-Builder] Duplexer questions

[Jeff DePolo WN3A]

>> Here's a thought -- if you put a isolator between the PA and 
>> the duplexer, 
>> and a isolator between the duplexer and the antenna, wouldn't your 
>> duplexer see a near perfect 50 ohms at all times? > 
> 
> The isolator in the output of the duplexer would have to 
> replace the output
> TEE - else you would have 25 plus db of rec loss - REC signal 
> would go into
> the isolator load.ssb

And even then it wouldn't work, because the receive side of the duplexer
(connected where a reject load would normally be) doesn't provide a good
match at the Tx frequency, so the isolator ends up providing no isolation
(i.e. the isolator will no longer be the ideal 50 ohm virtual load that you
were hoping for).

--- Jeff





 
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RE: [Repeater-Builder] Re: Duplexer weirdness

[Jeff DePolo WN3A]

> > So, if you lack test equipment and have no choice but to use high-
> level
> > signals for tuning the pass, you should still be tuning for minimum
> > reflected power.
> 
> So bird inbetween TX and cans, tuning on a source like an HT?

Yes.  To take it one step further, a 6 dB pad (with suitable power rating of
course) between the HT and the Bird would help minimize the Z variation that
the PA in the HT sees, thereby reducing the variation in output power, and
possibly help save the PA from destruction if the cans are severely detuned.

> So that's what that is.. Never could find the exact same thing.
> A "rare bird" :)  With the part number, I see that RF parts carries 
> them.

Yeah, and Bird makes other varieties too, including directional coupler
elements.  I have the directional ones for 1 5/8, 3 1/8", etc. line sections
for broadcast work.  The one for the Bird 43 is rated for 500 watts maximum
thru-line power.  The ones for 1 5/8" and larger are rated for much more (I
think the 1 5/8" is rated for 25 kW or thereabouts).

--- Jeff





 
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RE: [Repeater-Builder] Re: Duplexer weirdness

[Jeff DePolo WN3A]

> I thought consistent and optimum performance were pretty 
> much the same animal? 

Only under "lab conditions" :-)

Using a vague definition, I'm thinking consistent = best operation over the
long term, optimum = best short-term.  I've accidentally made a 75 watt
Micor UHF PA crank out 200 watts short term by overdriving it, but the
long-term performance will eventually degrade to 0 watts...

--- Jeff





 
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RE: [Repeater-Builder] Re: Duplexer weirdness

[Jeff DePolo WN3A]

> Well, I'm going to go out on a limb & disagree with Jeff, 
> perhaps for the 
> first time ever.  

That's OK, we'll still let you hang around our tent and drink our beer at
Dayton :-)  Are you going again this year Bob?.

> My conclusion is that if 
> whatever you're 
> using to measure amplitude is sensitive enough & everything 
> is close to 50 
> ohms, tuning for max. trans. is good enough.  

My take on the situation is that I'd rather have everything as close to 50
ohms as possible.  If there is any variation in the system outside the
duplexer/cavities that you can't control (such as Z changing due to antennas
icing up), the transformation effects of the cavities should be minimal.
Also, by keeping all of the passives at 50 ohms in and out, it eliminates
much of the uncertainty when adding additional cavities (e.g. pass cavity
ahead of a receiver) or when adding an isolator that was bench-tuned with 50
ohm loads.  I'll take consistent performance over optimum performance when
we're talking a one or two tenths of a dB in insertion loss difference.

As far as using cavities as matching networks to eek more power out of a PA,
without actually looking at the efficiency at different load Z's, there's no
telling what the PA is truly happy with.  Just because you can squeeze an
extra dB out of the amplifier by providing it with an some odd load Z
doesn't mean that's the ideal load Z to operate it at.  If you have to burn
up 50 more watts in heat to get an extra 10 watts out of the PA, that's bad.
So, if you lack test equipment and have no choice but to use high-level
signals for tuning the pass, you should still be tuning for minimum
reflected power.

> Yes, you can tune your RX cans to maximize power transfer into your 
> RX.  But then what happens to your notches which you've just 
> moved as well?

You can also tune Rx front ends with a network analyzer or SG/TG and RLB.
You will also see that the "window" response of the front end of your
typical two-way radio (Micor, M2, whatever) can be tuned to favor the side
away from interference sources (e.g. your transmitter or other co-located
transmitters) without any significant detriment to insertion loss at the
desired Rx pass frequency.

> Sounds like a nice piece of test equipment to have around: a 50 dB 
> non-directional coupler.

Bird 4274-025 non-directional coupler element.  I keep one in each of my 43
cases.  Handy to have.

--- Jeff


Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 








 
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RE: [Repeater-Builder] Duplexer questions

[Jeff DePolo]

> Can someone please explain what the difference is between a 
> BandPass/BandReject duplexer and a BandPass/Notch duplexer?  

In our little two-way radio world, the answer is that there is no
difference.

Technically speaking, a "notch" is very narrow, targeting only a specific
frequency.  A theoretical definition of a notch might include the phrase
"infinitesimally narrow", but that doesn't exist in the real world - you
can't achive an infinite Q.

Likewise, as is often seen in other RF endeavors, a "band reject" implies a
wider reject response, not just a single targeted frequency.  For example, a
band reject filter used in the TV/CATV world might reject a whole 6 MHz wide
channel, or several contiguous channels.

But the bottom line is that, in two-way, manufacturers seem to use the two
terms interchangably.  So don't lose any sleep over it.

> Also - I just put a new PA online today on my 444.550 
> machine.  The duplexer I have is rated at 100W, and the PA is 
> putting about 150W into it -- I was running about 50W with 
> the old PA.  (BTW - There is an isolator between the duplexer 
> and the PA.)  Will this cause me any grief either now or down 
> the road and if so, in what way??  

Quite possibly, yes.  Duplexers' maximum power rating is usually a function
of one of two factors: either its ability (or lack thereof) to dissipate
heat as a function of insertion loss, or the breakdown voltages of one or
more of its internal components (such as piston trimmer caps or thin
dielectric materials).

--- Jeff





 
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RE: [Repeater-Builder] Re: Mastr II UHF Base Station

[Jeff DePolo WN3A]

The power dividers/combiners are just Wilkinsons.  They are built into
little square chassis with perforations for cooling, with a monolithic 100
ohm resistor mounted to the chassis and the usual quarter-wave 75 ohm
matching sections.  Nothing fancy.

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Coy Hilton
> Sent: Tuesday, February 07, 2006 8:41 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Mastr II UHF Base Station
> 
> 
> Jeff, how's the driver PA harness built and how are the 2 PAs 
> outputs combined? Do you have any information or specs on the RF and 
> matching harnesses and how they are built?   
> 
> --- In Repeater-Builder@yahoogroups.com, "Jeff DePolo WN3A" 
> <[EMAIL PROTECTED]> wrote:
> >
> > > I am looking at acquiring a GE Master II UHF Base station. This 
> is a 300
> > watt solid state transmitter, which how I understand it, has 2 PAs 
> running
> > in parallel.
> > 
> > It's actually 200 watts, and yes, there are two "final" PA's, each 
> capable
> > of 100 watts output, that are combined.  However, each "final" PA 
> requires
> > around 35 watts of drive - the final PA's are really the same as a 
> 100 watt
> > station PA, but without the 40 watt driver board.
> > 
> > Drive to the PA's is provided by a standard 100 watt PA.  So, what 
> you have
> > is the exciter (200 mW) driving the intermediate PA (100 watt, 
> attached to
> > the main station chassis), which gets power-divided to feed the 
> two final
> > PA's, the output of which then are combined to yield 200 watts.
> > 
> > > What I am wondering is, can these amps be run separately, or do 
> they
> > always have to run together in parallel?
> > 
> > Not really, since each requires about 35 watts drive, so you still 
> need
> > something to drive them with.  If you only want 100 watts, then 
> just run the
> > 100 watt IPA to the antenna and leave the two final PA's on the 
> shelf as
> > spare parts. 
> > 
> > --- Jeff
> >
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 





 
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RE: [Repeater-Builder] Re: Dupelxer wierdness

[Jeff DePolo WN3A]

> If I take all the opinions I've seen in the last month as fact, then 
> the pass adjustments on duplexers can't be tuned. 

I'll take most of what you said as being sarcastic, but your point is taken.

If tuned with a quality network analyzer, or with a return loss bridge and
high return loss terminations and pads, you will have pass performance
properly tuned.  The only question is whether or not your transmitter likes
a real 50 ohm load.  If so, great, you're done.  If not, fix it.

With the cavities tuned to resonance, cable lengths are no longer an issue.
Needing to use "magic" cable lengths should be a red flag that you've got a
Z mismatch somewhere.

> (Except by wizards at Mount Wacom, who use equipment that resides in the
fifth dimension.)

Even the demigods that hail from Waco, Marlboro, and Angola aren't
infallible, especially after the evil Brownshirt Brigade percussively
retunes their products while en route to you.  All Hail Maxwell!  All Hail
Maxwell!

--- Jeff





 
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RE: [Repeater-Builder] Micro Strips @ 220 MHz

[Jeff DePolo]

>
> Does anyone have a good way of measuring the frequency of 
PC board micro
> strips (M/S)?  

I'm not exactly sure what you're asking.  Microstrips are basically just
sections of transmission line.  A transmission line doesn't have a
"frequency" - it has a length and a characteristic impedance.

You didn't say if you're trying to use the original devices or if you've
replaced them with something designed for 220.  In either case, you're going
to need to come up with impedance data for the device and then do the math
to design the matching and go from there.  Often the transformation ratio is
fairly high for matching bipolar VHF/UHF devices to 50 ohms, so the
microstrip geometry becomes rather critical.

--- Jeff







 
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RE: [Repeater-Builder] Mastr II UHF Base Station

[Jeff DePolo WN3A]

> I am looking at acquiring a GE Master II UHF Base station. This is a 300
watt solid state transmitter, which how I understand it, has 2 PAs running
in parallel.

It's actually 200 watts, and yes, there are two "final" PA's, each capable
of 100 watts output, that are combined.  However, each "final" PA requires
around 35 watts of drive - the final PA's are really the same as a 100 watt
station PA, but without the 40 watt driver board.

Drive to the PA's is provided by a standard 100 watt PA.  So, what you have
is the exciter (200 mW) driving the intermediate PA (100 watt, attached to
the main station chassis), which gets power-divided to feed the two final
PA's, the output of which then are combined to yield 200 watts.

> What I am wondering is, can these amps be run separately, or do they
always have to run together in parallel?

Not really, since each requires about 35 watts drive, so you still need
something to drive them with.  If you only want 100 watts, then just run the
100 watt IPA to the antenna and leave the two final PA's on the shelf as
spare parts. 

--- Jeff





 
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RE: [Repeater-Builder] Micor Recrystalled Element Problem

[Jeff DePolo WN3A]

> I am moving a 463/468 MHz Micor repeater to 444/449 MHz.  I 
> ordered new 
> xtals from ICM and the receive xtal is OK.  However I can't 
> get the xmit 
> xtal to pull onto freq.  It will pull within 3 KHz above 444.350 MHz. 

I'm assuming this is a real Micor repeater, not a converted mobile, so you
should have a KXN1052 transmit channel element.  Open it up again, and ;ook
behind the trimmer cap.  You should see a ceramic disc cap that is not quite
parallel with the back of the trimmer cap - that's your target.  Further
behind the ceramic disc is a plastic-case transistor (just to verify we're
on the same page).  Look at the value of the ceramic disc; it should be
somewhere in the tens of pF range.  Increase its value by approximately 20%
and you should be in the ballpark for moving from 463 to 444 (i.e. if it was
22 pF originally, use 27 pF instead).  Lacking any other means of real
compensation, use an NP0 cap.

As others have pointed out, this doesn't give you any form of accurate
temperature compensation.  This only lets you center range of the trimmer
cap so you can put the transmitter on frequency.  If the repeater will be in
a temperature-stable environment (say, +/- 10 or 15 degrees ambient as a
ballpark), you might be OK.  Next time, spend the money and send the element
to ICM and let them do it right.

--- Jeff

----
Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] New system's in, but a few problems

[Jeff DePolo]

 

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Bob Dengler
> Sent: Monday, January 30, 2006 12:43 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] New system's in, but a few problems
> 
> At 1/29/2006 11:37 PM, you wrote:
> >About 8 years ago, I tried using a Comet GP-9 antenna 
> combined to serve 
> >two repeaters, one on 2 meters & the other on UHF.  I found the GP-9 
> >worked FAR better on 2 meters than on 445 MHz.
> >
> >I was running good GE Mastr Pro repeaters, good pass/reject 
> duplexers, 
> >good ARR GaAsFET pre-amps, and had NO desence.
> >
> >The comet GP-9 simply is not very good for UHF.  Of course, 
> the water 
> >you foung in the antenna is not good either.
> 
> My experience has been quite different, as I've found the GP9 
> to be overall a very good UHF antenna.  I have a 2 meter & 
> 440 system running off of one in a very similar layout to 
> yours (antenna only a few feet above the equipment); the 440 
> outperforms 2 meters as expected.  No desense on either band. 
>  There is a DB-408 at the site that we once tried but the GP9 
> outperforms it as well.
> 
> Bob NO6B

Mine has been just the opposite of Bob's, and in fact, I'm using the same
antennas!  I had a GP9 top-mounted on a tower, my UHF repeater and an APRS
digipeater on it.  The GP9 developed crackling noises after about a year of
use.  I and the owner of the APRS digi decided to put up separate antennas -
mine a DB408 replacing the GP9 on top of the tower, and his a DB224
side-mounted below it.  When we got the GP9 down, we didn't find anything
obvious wrong with it, either internally or externally, and the guy with the
APRS digi took the antenna and is now using it for something else.  The
DB408 (ham-cut version) plays much better than the GP9 ever did.  As usual,
YMMV.

--- Jeff





 
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RE: [Repeater-Builder] Micor has me stumped

[Jeff DePolo WN3A]

I'm not sure if I'm undertsanding correctly, but you're saying that the UHF
repeater works fine with either A/S board, but the VHF one doesn't?  If so,
it sounds to me like you have a VHF base station and not a VHF repeater, and
my first guess is you didn't remove the diode that mutes the receiver when
PTT is active.  Lookee here:

http://www.repeater-builder.com/rbtip/micorrxintcon.html

--- Jeff
----
Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 



> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of let_cyber
> Sent: Sunday, January 29, 2006 11:13 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Micor has me stumped
> 
> 
> I have both a vhf and uhf Micor repeater that I'm interfacing.
> 
> I now know a whole lot more about Micor repeaters than I 
> really wanted 
> to. The short version of the problem is as follows:
> 
> The COS signal from the audio/squelch board goes away when the TX is 
> enabled. If you transmit a continuous carrier on the input, The COS 
> comes up for a split second, keys the TX then goes away. After the 
> hangtime expires and the TX drops, the whole things starts again.
> 
> I have the exciter and RX into 50 ohm loads. If i put the A/S board 
> and squelch gate into the uhf unit, it works fine. I have checked and 
> double checked everything. It just doesnt make any sense. Any ideas 
> would be greatly appreciated.
> 
> Al KB2AYU
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 





 
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RE: [Repeater-Builder] Woohoo! The rocks are IN!

[Jeff DePolo]

In other words, they think they have the right to force THEIR bandplan on
all of the adjacent coordinators??!??!

I'd give my opinions, "but they would be so profound and disgusting that
decorum prohibits listing them here" (citing Animal House of course ;-).

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of TGundo 2003
> Sent: Friday, January 27, 2006 2:24 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Woohoo! The rocks are IN!
> 
> This is from the March 2005 MIARC newsletter (I have *** the 
> names to protect the innocent) available for public viewing 
> on their website:
>  
> "*  introduced discussion asking for a resolution on 
> how to respond to surrounding states who are using 
> frequencies that we coordinate as links as repeater 
> frequencies. ** has had some communication with 
> surrounding states. The board has determined that requests 
> for NOPC from surrounding states for repeaters that fall 
> outside of our repeater frequency guidelines will be answered 
> with an objection to coordination."
>  
> Draw your own conclusions.
>  
> Tom
> W9SRV
> 
> Jeff DePolo <[EMAIL PROTECTED]> wrote:
> 
> 
>   The coordinator in MI shouldn't object to a 
> coordination from an adjacent
>   council just because their bandplans aren't identical. 
> For better or worse,
>   there isn't a universal bandplan that satisfies the 
> entire amateur community
>   nation-wide.
>   
>   If there is nothing coordinated in MI that is going to 
> be adversely affected
>   by the neighboring coordinator's proposed operation, 
> then they have no
>   reason to object. If they do have something that would 
> be affected (be it
>   of the same operation type or otherwise), then that's a 
> different story.
>   
>   That's the way we ! work here on the east coast among councils.
>   
>   And yes, we have repeaters in the 440-442/445-447 
> range. Our aux link
>   subbands are all below 440.
>   
>   --- Jeff
>   
>   
>   > -Original Message-
>   > From: Repeater-Builder@yahoogroups.com 
>   > [mailto:[EMAIL PROTECTED] On Behalf 
> Of TGundo 2003
>   > Sent: Friday, January 27, 2006 12:44 PM
>   > To: Repeater-Builder@yahoogroups.com
>   > Subject: Re: [Repeater-Builder] Woohoo! The rocks are IN!
>   > 
>   > IL Is doing 440-442 now as well. The problem IL has, and IN I 
>   > imagine, is that Michigan will not recoginize any new 
>   > coordinations in the 440-442 band, and instaead of providing 
>   > useful data to IL when a request is submitted for new coord., 
>   > like MI had a link on that freq, they just say NO (or don't 
>   > even respond from what I have heard) with no reason explained 
>   > other than they will not recoginize a repeater coordinated 
>   > there! because it does not fit the bandplan. I fell victom to 
>   > that with my first pair. We are close enough in northern IL 
>   > that it is important to know what is coordinated in Mighigan. 
>   > From what I hear MI dosen't play well with others so IL and 
>   > some other states are ignoring them now and just dealing with 
>   > the problems after the fact. In my opinion thats BS, but such 
>   > is life. Not to mention the extra $100 I had to spend to 
>   > re-crystal because michigan could't just say "no, we have a 
>   > link there" instead of the blanket No. I think theres a 
>   > commercia! l on TV with David Spade working at the MI 
>   > repeater council right now ;)
>   > 
>   > Sorry for the rant, off my soapbox now.
>   > 
>   > Tom
>   > W9SRV
>   > 
>   > Ken Arck wrote:
>   > 
>   > At 12:09 PM 1/27/2006 -0500, you wrote:
>   > >
>   > >Interesting that IN is assigning below 442. I was 
>   > think! ing about asking 
>   > >around why Ohio doesn't assign repeaters or links 
>   > between 440 and 442...
>   > 
>   > <---Interestingly, Dave was assigned the same channel 
>   > as one of my
>   > repeaters here in Oregon. Which, of course means, OR 
>   > uses < 442 as well!
>   > 
>   > K

RE: [Repeater-Builder] Woohoo! The rocks are IN!

[Jeff DePolo]

The coordinator in MI shouldn't object to a coordination from an adjacent
council just because their bandplans aren't identical.  For better or worse,
there isn't a universal bandplan that satisfies the entire amateur community
nation-wide.

If there is nothing coordinated in MI that is going to be adversely affected
by the neighboring coordinator's proposed operation, then they have no
reason to object.  If they do have something that would be affected (be it
of the same operation type or otherwise), then that's a different story.

That's the way we work here on the east coast among councils.

And yes, we have repeaters in the 440-442/445-447 range.  Our aux link
subbands are all below 440.

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of TGundo 2003
> Sent: Friday, January 27, 2006 12:44 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Woohoo! The rocks are IN!
> 
> IL Is doing 440-442 now as well. The problem IL has, and IN I 
> imagine, is that Michigan will not recoginize any new 
> coordinations in the 440-442 band, and instaead of providing 
> useful data to IL when a request is submitted for new coord., 
> like MI had a link on that freq, they just say NO (or don't 
> even respond from what I have heard) with no reason explained 
> other than they will not recoginize a repeater coordinated 
> there because it does not fit the bandplan. I fell victom to 
> that with my first pair. We are close enough in northern IL 
> that it is important to know what is coordinated in Mighigan. 
> From what I hear MI dosen't play well with others so IL and 
> some other states are ignoring them now and just dealing with 
> the problems after the fact. In my opinion thats BS, but such 
> is life. Not to mention the extra $100 I had to spend to 
> re-crystal because michigan could't just say "no, we have a 
> link there" instead of the blanket No. I think theres a 
> commercia! l on TV with David Spade working at the MI 
> repeater council right now ;)
>  
> Sorry for the rant, off my soapbox now.
>  
> Tom
> W9SRV
> 
> Ken Arck <[EMAIL PROTECTED]> wrote:
> 
>   At 12:09 PM 1/27/2006 -0500, you wrote:
>   >
>   >Interesting that IN is assigning below 442. I was 
> thinking about asking 
>   >around why Ohio doesn't assign repeaters or links 
> between 440 and 442...
>   
>   <---Interestingly, Dave was assigned the same channel 
> as one of my
>   repeaters here in Oregon. Which, of course means, OR 
> uses < 442 as well!
>   
>   Ken
>   
> --
> 
>   President and CTO - Arcom Communications
>   Makers of state-of-the-art repeater controllers and accessories.
>   http://www.ah6le.net/arcom/index.html
>   Authorized Dealer! s for Kenwood and Telewave and
>   we offer complete repeater packages!
>   AH6LE/R - IRLP Node 3000
>   http://www.irlp.net
>   
>   
>   
>   
>   
>   Yahoo! Groups Links
>   
>   
>   
>   
>   
>   
>   
> 
> 
> 
> 
> Do you Yahoo!?
> With a free 1 GB, there's more in store with Yahoo! Mail. 
>  ail.yahoo.com/>  
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RE: [Repeater-Builder] Re: Duplexer retune / recoax

[Jeff DePolo]

> Once a new low-split harness was 
> purchased directly from Sinclair (about $125, as I recall) and 
> installed, the duplexer tuned up with the expected pass loss of 
> about 1.6 dB.  The notch attenuation was within a dB of the previous 
> value, using the incorrect harness.

Well, my guess is that the high insertion loss you saw was not due to the 
incorrect cable lengths *between* adjacent cavities, but rather between the 
first cavity on each side and the tee.  With that length being wrong, the 
two sides of the duplexer are not fully decoupled, i.e. the reject notch on 
one side isn't being "echoed" exactly 1/4 wave away back at the tee.

I'd bet that if you only increased the lengths of the cables between the 
first cavities and the tee that the measured performance would have been 
comparable to replacing the entire harness.

 --- Jeff




 
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RE: [Repeater-Builder] Re: Duplexer retune / recoax

[Jeff DePolo]

> The length of the jumper cables between the cans has a profound 
> effect upon the insertion loss at the pass frequency, and relatively 
> little effect upon the isolation at the notch frequency.
>  
> 73, Eric Lemmon WB6FLY 

Eric,

I'm curious why you say this, as it contradicts what I would believe to be 
the case in theory.

At the pass frequency, the Z should be very close to 50+j0, so having 
the "wrong" cable length won't affect the insertion loss between each of the 
pairs (or three, for a 6-pack) of cavities on either side of the duplexer.

In contrast, for proper reject notch performance, there has to be correct 
phasing between cavities.  The notches are effectively shorts at the notch 
frequency, and if they are not repeated at 1/2 wavelength intervals between 
cavities, they will tend to not align when cavities are cascaded due to 
transmission line transformer effects (ever try tuning a duplexer and the 
notches act like they're "chasing each other" and you can't get them to fall 
into place?).

Likewise, between the antenna T and the first cavity on each side, having 
the wrong cable length will cause the notch "short" to not be properly 
transformed to an open at the tee (via the odd 1/4 wave section between the 
tee and the first can of the opposing side of the duplexer).  This will make 
the insertion loss appear to go up when looking from Tx input to antenna or 
antenna to Rx output, and also throw off the pass Z since the opposing side 
of the duplexer is no longer "invisible" as it should be.

Regarding the question posed by others for finding cable lengths and tuning 
methods:

For experimentation purposes, a line stretcher is the easiest way to find 
optimum cable lengths when re-cabling a duplexer.  However, you can usually 
just scale the lengths of the original harness to the new operating 
frequencies using simple ratios of the old and new frequencies; an error of 
1/4" or so isn't going to make a noticible difference on VHF, and may even 
be tolerable on UHF.  The other option is that if you have a duplexer that 
was, say, originally on 160 MHz and you want to move it down to 2m is to add 
elbow adapters to extend the length of the cables.  Even if you don't leave 
them in on a permanent basis, it gives you a good approximation of how much 
the cables need to be lengthened by.

As far as tuning duplexers, many manufacturers' tuning instructions give a 
simple how-to using just a spectrum analyzer and tracking generator.  While 
this might get you close, the passband performance is almost guaranteed to 
not be properly optimized.  At the factory, duplexers and filter cavities 
are tuned on a network analyzer so both reflection (return loss) and 
transmission (passband insertion loss and reject notch depth) can be 
measured and optimized concurrently.  When looking at insertion loss only, 
pass/reject duplexers appear to have a relatively broad pass response, but 
in reality, if you look at return loss, the pass is really quite sharp.

If you don't have a network analyzer, a return loss bridge is a great, and 
relatively inexpensive, piece of equipment to have to give you the ability 
to measure return loss using a typical spectrum analyzer/tracking generator 
in a service monitor.  You do need good termination loads to go with it - 
most run-of-the-mill high-power dummy loads don't have enough return loss to 
yield accurate results.  Spend a few bucks and get precision terminations to 
screw directly onto the port(s) without patch cables, and measure them with 
the return loss bridge to make sure they're good (30 dB should be the bare 
minimum).  There are lots of good loads floating around on the surplus 
market - I see new Narda 370's show up at hamfests and Ebay regularly in the 
$10 range and they usually do better than 35 dB up through UHF.  I don't lug 
my network analyzer out to sites, but I do keep the return loss bridge in 
the truck in case I have to do a quick-n-dirty retune on-site when I can't 
afford the downtime of transporting and tuning back at the shop.

   --- Jeff





 
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Re: [Repeater-Builder] Re: Shipping an antenna

[Jeff DePolo]

> > 1984 plymoth voyager with 3 stationmasters, 2 UHF eight bay dipoles, 1
> > UHF 16 bay and a VHF 4 bay.. that was a good ride!

How did you mount them?  Mag mounts?

Which antenna held up best at highway speeds, the Stationmasters or dipole 
arrays?  

Did you get poor gas milage?  

What did you do about low overpasses, parking garages, and aerial power 
lines?  

Did the car ever feel like it was going to tip over on sharp curves?

;-)





 
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[Repeater-Builder] UHF Mastr II stations for trade

[Jeff DePolo]

I have a surplus of 100 watt UHF Mastr II repeaters (88 split) that I'm
looking to trade.  I'm looking for high-power (150+ watt) solid-state UHF
amplfiers that will tune in the 440 ham band including TE Systems,
Crescend/Milcom, Vocom, Glenayre, etc..  I'll trade straight across, one
station for one PA, if you have something I want.  I am NOT interested in
selling the Mastr II stations, trades only, unless you're offering enough
for me to pay to buy a new amp that suits my needs.

I also have a few 200 watt Mastr II stations (solid state) as well.  I also
have UHF Micor PURC stations (75 watt solid state and 250 watt tube), UHF
and 900 MHz PURC5000 stations (including high power), duplexers, cavity
filters, isolators, heliax and connectors, power supplies, a new TPL 100
watt 220 repeater amp, mobile radios, and all kinds of other stuff that I
can trade if M2's aren't of interest.  If you have an amp I could use, let
me know what you might be looking for.

Complete stations are available for pickup in the Philadelphia area, or if
you want to make all arrangements and cover costs for picking up, putting on
a palette, and truck freight delivery, that's OK too.  I can ship smaller
items UPS.

Please email direct.  Thanks.

--- Jeff







 
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RE: [Repeater-Builder] OT - NOW NOT SO funny interference story

[Jeff DePolo WN3A]

Nate,

I'd start by doing some "office DF'ing" before spending time on the hill
this time of year.  My first guess would be local oscillator leakage from
something on the hill.  Try doing an FCC ULS database search for anything
within a mile or so of the site, make a list of the Rx frequencies in a
spreadsheet, and make colums for the "usual suspect" IF offsets (+10.7,
-10.7, 11.2 for M2's, 11.7 for Micors, etc.) and see if you find anything on
147.825 +/- 10 kHz or thereabouts).

A local two-way shop here got a visit from the FCC because of excessive LO
leakage.  They were using Mitreks in a repeater installation, and the LO
leakage was strong enough to bother another receiver several miles away.
The FCC wasn't happy with them for using mobile radios in station
operation...

Probably 15 years or so ago I had a dead carrier holding open one of my UHF
ham repeaters (it ran carrier squelch back then).  The repeater is 443.800+,
input 448.800.  The carrier was there for an hour or more, so I figured I'd
take a drive up to the site (it was about 1AM, but hey, I was bored, and the
site was only 10 minutes away).  I couldn't hear the carrier on the input on
my drive to the site until I pulled in the gate, then it started getting
stronger and stronger as I got closer.  Then I saw a Motorola service van
parked next to the shelter with the lights on, engine running, and a girl in
the passenger seat.  I walked into the site, scaring the bejesus out of the
tech, to ask him what he was doing.  He was working on an 800 MHz Ardis box.
I nosed around a bit, trying to find this dead carrier with an HT.  Then all
of a sudden it went away, and a few seconds later, the girl that had been
sitting in the Motorola van came into the site.  Long story short, the girl
in the van was the tech's girlfriend.  He got the service call, and she
decided to come along for the ride to keep him company.  While he was
working, she turned on the radio in the van and was listening to 101.5FM.
The LO in the FM radio, like many FM radios, is 10.7 MHz high-side, so
that's 112.2.  The fourth harmonic would be, you guessed it, 448.8.  And the
mystery was solved.

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Nate Duehr
> Sent: Thursday, January 12, 2006 7:19 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] OT - NOW NOT SO funny 
> interference story
> 
> 
> We're also hunting a "dead carrier" on the repeater input of 
> our 147.225 
> system in Denver.  Total pain in the ***.
> 
> The only antenna that appears to hear it reliably is the one 
> that's up 
> on the tower, on the mountain... of course.  Nothing at 
> ground level has 
> been able to pick it up yet, and it's too cold/windy to 
> really be up the 
> tower with a receiver and yagi this time of year.
> 
> The carrier/mix is not toned, of course, and the repeater is 
> -- so the 
> system is still "usable" but boy does it sound bad when weak-signal 
> users use the system.
> 
> Sigh...
> 
> Nate WY0X
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 






 
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RE: [Repeater-Builder] Duplexer Identification

[Jeff DePolo]

The 522-509 is an odd creature.  There are two pass and two notch on the
transmitter side, and one pass and one notch on the receiver side.
Discussions about this duplexer came up a while back on this list -
maybe it's in the archives?  I think Bob NO6B posted measured
performance of one he put on the bench.

--- Jeff



> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Andrew
> Sent: Tuesday, January 10, 2006 6:45 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Duplexer Identification
> 
> 
> I have a Phelps Dodge/Celwave PD-522-509 according to the factory 
> label. I cannot find any info on this duplexer anywhere, does 
> somebody 
> have the specs of this duplexer set? It almost looks like a PD-526 
> without the Band Reject ADJ, but has the 4 RX/TX/TX,RX ports on the 
> top. Thanks for any help.
> 
> Andy
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.371 / Virus Database: 267.14.16/225 - Release 
> Date: 1/9/2006
>  
> 

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Version: 7.1.371 / Virus Database: 267.14.16/225 - Release Date:
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RE: [Repeater-Builder] Re: Using Visio for rack planning

[Jeff DePolo]

Another quick n' dirty way to lay out racks is to use Excel.  Re-size
the width of a column to make it approximately the same height-to-width
ratio such that one cell is about the size of 1 RU.  Select the number
of cells to equal the number of rack spaces you have available, put a
fat border around the outside of those cells, and then start filling in
the contents of the rack.  Use "merge cells" to make 2U, 3U, 4U, etc.
panels as necessary.

Middle Atlantic (a rack enclosure manufacturer) has some free software
called "Rack Tools" or something like that for laying out racks.
www.middleatlantic.com.  I remember trying it once but for some reason
didn't spend much time with it.

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Dave VanHorn
> Sent: Sunday, January 08, 2006 6:08 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Using Visio for rack planning
> 
> 
> 
> > These may help - they are more suited to IT stuff, but you 
> can name a 
> > 1, 2, 3, 4, 5 or 6 unit rack panel anything you want... a 
> duplexer, a 
> > battery tray, etc.
> 
> Thanks.  Yes, that's what I've been doing.. I may have to figure out 
> how to do my own shapes, there can't be THAT much to it.
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.371 / Virus Database: 267.14.15/223 - Release 
> Date: 1/6/2006
>  
> 

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RE: [Repeater-Builder] Re: had a little power supply trouble the otherday...

[Jeff DePolo]

> Most Sub station  transformers like the one in the video 
> which form the looks of the  bushing size  is at least 69kv 
> or possible 138kv normally have fuseing on the High voltage 
> size and then go to buss work and feed distribution breakers  
> for the journy out to the line system  so for my 2 cents  
> worth i would have to say there was an equiment failure on 
> the lower voltage side of the transformer  and that could be 
> anywhere from 4kv which in getting scarce up to 13.8kv which 
> caust a failure on the transformer tank  that lead to the 
> massive fire ball that followed what looked to be some kinda 
> liquid spraying toward the arc  and from what was stated 
> earlier in the posting  it can take several days to put that 
> kind of fire out once it gets going good  1st because you  
> cant get at it because the heat 
> 2nd from working with fire instructors and hearing the 
> stories they had to tell about fires when there were old 
> trandfomers being scrapped out and got lit off from a cutting 
> torch 1 they  worked several days to control  

I'd say your guess as to what happens was pretty close.  Here's the text
that accompanied the video:

A power arc to ground on the Low Voltage side of this substation creates
an arcing fault that behaves like an uncontrollable welding torch from
Hell, chewing up everything in its path. Protection hardware either
fails to open the High Voltage side or is unable to sense the presence
of the fault. Excessive current eventually causes the windings on the
substation's power transformer to overheat, severely cooking its innards
and causing the mineral oil inside to begin violently boiling. In a vain
attempt to prevent the transformer's tank from exploding, pressure
release valves vent clouds of superheated oil vapor which subsequently
ignites and explodes in a ball of flame. A phase to phase short circuit
occurs, perhaps caused by a flashover within the flames or a heat
induced fault within the transformer. This causes an expulsion fuse to
blow with a flash and a resounding BANG, finally killing power to the
substation. 

However, by this time, the weakened transformer's tank fails, and it
spills hundreds of gallons of flaming mineral oil onto the already
devastated substation. Local firefighters can only watch from a distance
since there's no way to safely fight this fire, and the substation is a
total loss. As one fireman quipped, "Firemen don't mess with their
wires, and linemen don't mess with their fires".  A very sobering look
at the explosive power silently lurking within the quietly humming
substation in your neighborhood...

What I'd like to know is how/why there was someone videotaping a
substation?  Seems kinda fishy...

--- Jeff
 

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RE: [Repeater-Builder] Re: interface to shut off a radio on temporaly base

[Jeff DePolo WN3A]

Title: Message





Kitchen dishwashers are also great for cleaning gunked-up mobile radio 
accessories like control heads, speakers, mics, mounting brackets, etc.  
Remove the speakers, mic elements, PC boards that contain switches, and other 
electronics that don't take kindly to water first of course.  Even cable 
harnesses can go into the dishwasher - just put a baggie over the cable ends and 
seal with electrical tape (better to put these on the top rack away from the 
electric heater/dryer).  Avoid agressive automatic dishwasher detergents if 
there are metallized parts like brushed aluminum estucheons and the 
like.
 
Back 
in the day, after we had collected several PC or terminal keyboards that 
had suffered "coffee contamination" I'd run them through the dishwasher, 
key-side-down to assist in drainage/drying.  Probably 3/4 of them survived 
and could be returned to service.  A simple and non-time-consuming fix when 
you have nothing to lose and can't justify the time or cost to take apart and 
clean manually.

  I'd like to second Skipps comments and add one of my own. At the 
  factory we used ordinary dish washers (until we got the commercial washers) to 
  clean PC boards.  Most components are water safe. Exceptions, are non 
  hermetic parts like switches and transformers; things with paper or bakalite 
  coil forms.  Spic and Span is a little harsh. For general cleaning, 
  including automatic dish washers, useArm and Hammer baking soda. If 
  you think someone has used an acid flux (sometimes necessary to solder nickel 
  or steel) clean with ammonia before the baking soda. Finally if you have rosin 
  flux isopropyl alcohol works well. Don't use rubbing alcohol (contains water) 
  or use alcohol in the automatic dish washer (it will burn).













  




  
  
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[Repeater-Builder] Looking for 800/900 hybrid

[Jeff DePolo WN3A]

Anyone have a hybrid out of an 800/900 MHz combiner or the like?  Needs to
work at 950 MHz.  I don't need an entire combiner, just a hybrid.  Thanks.

--- Jeff

Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant 






 
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RE: [Repeater-Builder] Bad 4" Heliax (Was Polyphaser Help)

[Jeff DePolo WN3A]

A) not enough hoisting grips were used and b) the cable had pulled away from
the tower in a number of places (a mish-mash of butterflies, tie wires, and
even rope were used to attach it).  The end result was that the line
stretched, plus there were several holes in the outer conductor where it had
been rubbing against a tower member.  It had been blowing air for probably a
year or more, but the station waited until it started arcing over before
they decided it was finally time to replace it...

--- Jeff

> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Eric Lemmon
> Sent: Saturday, December 31, 2005 11:26 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Bad 4" Heliax (Was Polyphaser Help)
> 
> 
>  Jeff,
> 
> How does 4" Heliax "go bad?"  If the feedline was properly 
> installed and
> pressurized, what else besides a bullet hole would prompt the 
> removal of
> that cable?  That size Heliax is probably $40 per foot, plus the
> labor...Geez!
> 
> 73, Eric Lemmon WB6FLY
> 
> 
> 
> I've got a better one.  A number of years ago we changed out 
> a 1500' run of
> 4" Heliax that had gone bad on an FM station.  Upon taking 
> down the old line
> and looking at the damage, one of the problems we found was 
> that the ground
> kits (approximately 8) were all installed without removing 
> the outer jacket
> from the cable...
> 
>   --- Jeff
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 





 
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RE: [Repeater-Builder] polyphaser Help

[Jeff DePolo WN3A]

> I actually saw an install where a MSS did just that - they
> had the ground connected to a plastic water pipe!
> 
> Joe M.

I've got a better one.  A number of years ago we changed out a 1500' run of
4" Heliax that had gone bad on an FM station.  Upon taking down the old line
and looking at the damage, one of the problems we found was that the ground
kits (approximately 8) were all installed without removing the outer jacket
from the cable...

--- Jeff





 
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RE: [Repeater-Builder] polyphaser Help

[Jeff DePolo]

If the building has a steel infrastructure, your lowest-R and lowest-L path
will likely be to tie to the building steel.  However, there are code
implications for doing so (as well as any other tower grounding) so be sure
to check local codes and/or NEC.  If building steel isn't an option you may
have to run the ground wire all the way down the side of the building to a
ground rod (electrode).  Again, see NEC.

The AC ground on the recepticle is not a good idea in any case. 

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
> Sent: Friday, December 30, 2005 2:23 PM
> To: repeater-builder@yahoogroups.com
> Subject: [Repeater-Builder] polyphaser Help
> 
> Replacing a small, rooftop (about 90ft)  repeater setup.  The 
> prior system had no lighting protection, just straight coax 
> from antenna to duplexer.  I was looking into getting a 
> polyphaser if needed but there is no way to ground it that I 
> can tell.  Two options I have would be to somehow tap into 
> the metal roof and connect it to that? or at the radio-end of 
> the coax attach it to a nearby AC outlet's ground?  A 
> grounding line/rods aren't a real good option since it is on 
> another businesses property.  Any suggestions?
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> YAHOO! GROUPS LINKS 
> 
> 
>   
> *  Visit your group "Repeater-Builder 
>  " on the web.
> 
> *  To unsubscribe from this group, send an email to:
>[EMAIL PROTECTED] 
>  nsubscribe> 
> 
> *  Your use of Yahoo! Groups is subject to the Yahoo! 
> Terms of Service  . 
> 
> 
> 
> 
> 




 
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<>

RE: [Repeater-Builder] Duplexer tuning with Return Loss Bridge

[Jeff DePolo WN3A]

The Bird is a directional wattmeter.  It's not a return loss bridge (it's
not a bridge at all).  Yes, you can compute a spot-frequency measurement of
return loss that way, that doesn't help you with swept-frequency analysis
using a spectrum analyzer and tracking generator.


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Dick
> Sent: Wednesday, December 21, 2005 12:01 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Duplexer tuning with Return 
> Loss Bridge
> 
> 
> Yes, really.  You measure the forward power, then turn the 
> element around 
> and measure the
> reflected power.  Then use 10 log (FP/RP) and you have the 
> return loss in 
> dB.
> 
> Dick
> 
> - Original Message - 
> From: "Jeff DePolo WN3A" <[EMAIL PROTECTED]>
> To: 
> Sent: 21 December, 2005 08:46
> Subject: RE: [Repeater-Builder] Duplexer tuning with Return 
> Loss Bridge
> 
> 
> > The Bird Model 43 is a typical RLB.
> 
> Oh really???!??!?
> 
> The Eagle return loss bridges are a good value for the buck.
> www.eagle-1st.com.  They have a whitepaper on tuning duplexers too.
> http://www.eagle-1st.com/notes/duplex/body.htm
> 
> I believe IFR (now Aeroflex) sells (or at least sold) the Eagle RLB's.
> 
> --- Jeff
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 





 
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RE: [Repeater-Builder] Duplexer tuning with Return Loss Bridge

[Jeff DePolo WN3A]

> The Bird Model 43 is a typical RLB.  

Oh really???!??!?

The Eagle return loss bridges are a good value for the buck.
www.eagle-1st.com.  They have a whitepaper on tuning duplexers too.
http://www.eagle-1st.com/notes/duplex/body.htm

I believe IFR (now Aeroflex) sells (or at least sold) the Eagle RLB's.

--- Jeff





 
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RE: [Repeater-Builder] Re: Old duplexer tuning question

[Jeff DePolo WN3A]

> I'm assuming that if the old RG-8 cables are being replaced 
> with RG-214 cables that are the same length, that the 
> velocity factors of both types of cable are the same.

Yep, 66%.  Unless it's RG-8 foam, but I'm 99% sure that PD used regular
solid dielectric RG-8.

--- Jeff







 
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RE: [Repeater-Builder] Re: Hamtronics T301 220 exciter Final and microphonics

[Jeff DePolo WN3A]

If the PA microphonic AM'ming is severe enough, there could be enough power
supply modulation, due to the PA current varying by the AM occuring in the
PA, that FM at the same modulation rate can occur in preceding exciter
stages (such as in the crystal oscillator, modulator, active temperature
compensation circuits, etc.).  Not knowing how a T301 is designed I don't
know how likely this is, but it's quite possible.

--- Jeff


> -Original Message-
> From: Repeater-Builder@yahoogroups.com 
> [mailto:[EMAIL PROTECTED] On Behalf Of Bryan Fields
> Sent: Tuesday, December 20, 2005 2:11 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Re: Hamtronics T301 220 
> exciter Final and microphonics
> 
> 
> On Monday 19 December 2005 11:48 pm, Ken Arck wrote:
> > Don't forget that in both PM and FM schemes, the modulation 
> is done early
> > on and multiplied. So for a typical multiplication scheme 
> of x 9, the
> > modulation introduced only needs to be 550 Hz or so (for a 
> 5 Khz spec). And
> > even a paultry 550 Hz requires a fair amount of audio voltage to
> > accomplish.
> 
> In most PLL units I have worked with in the "ham" market the 
> vco is modulated 
> directly on the loop op amp.  There in no multiplication the 
> VCO runs at the 
> output frequency.
> 
> As to the origional question, anyone fixed the microphonics 
> problems with the 
> exciter?
> 
> -- 
> Bryan Fields, KB9MCI
> 
>  01:07:04 up 3 days, 14 min,  2 users,  load average: 0.31, 0.23, 0.26
>  
> Somewhere in DOWNTOWN BURBANK a prostitute is OVERCOOKING a 
> LAMB CHOP!!
> 
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 





 
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RE: [Repeater-Builder] Old duplexer tuning question

[Jeff DePolo WN3A]

> I have been pulling my hair out (I don't have that much more 
> to go) over an 
> old Celwave 6 cavity 526-4 pass reject duplexer.  I can get 
> the notches to 
> tune properly one by one but when I put it all back together 
> it just does 
> not seem to sum out right.  Is there a procedure someone can 
> point me to?

526's usually tune up pretty straightforward.  If it's an older 526, it may
have RG-8 interconnects, which can get noisy (better to replace with RG214).
As far as tuning the notches, they are generally a PITA to tune to begin
with due to the mechanical design (almost as much fun as Motorola T1504's),
but as far as tuning them up separately and then putting it back together
and having it not work right, I can't say that I've seen that effect, but
then again, that's not how I would tune it.  You can get in the ballpark by
doing it that way, but in the end, you'll need to look at return loss to
know when the pass is really tuned right, and you may need additional
amplification to really see the notches, since when it's properly tuned,
notch depth will be over 100 dB (although if yours has RG8 interconnects,
you may not realize that kind of notch depth).  In fact, if yours has RG8,
it wouldn't suprise me if some of the problems you're fighting are related
to cable leakage coupling.

Just to confirm, the one you've got was the 440-470 split model, right?  If
not, then the cable lengths will be wrong and you can expect to see problems
like you're experiencing (notches won't "line up", insertion loss high,
etc.).

As always, isolate your test equipment from the DUT with pads when tuning.

> Also, I am curious if I need to use the same high frequency and low 
> frequency ports which would be the opposite for ham radio out 
> here, or if I 
> need to keep the transmitter port for the transmitter and the 
> receiver for 
> the receiver.

The 526 is symmetrical - you can use either side for high pass or low pass.

--- Jeff






 
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RE: [Repeater-Builder] Re: Multiple receivers one antenna ???

[Jeff DePolo WN3A]

> You can handle the impedance matching by using 1/4 wave 
> sections of 75 ohm 
> coax between the receiver input and the T. The 1/4 wave 75 
> ohm section 
> steps the 50 ohm receiver input impedance up to 100 at the 
> other end, two 
> of those in parallel at the T gets you back to 50 to match 
> the feedline. 
> Any number of receivers other than 'powers of 2' is more 
> complicated. This 
> does nothing for the loss of course.
> 
> Roger Grady  K9OPO

The math works in the case of the tee being at the antenna connection, but
the ASCII drawing that accompanied the previous email put the tees on the
backs of the receivers, sort of like old-style thin Ethernet 10base2, except
instead of having terminations at the ends of the backbone, one end is
connected to the last receiver, and the other end is connected to the
antenna.  Matching goes out the window with this design.

The problem with even doing the tees with odd quarterwave 75 ohm
transformers is that you have virtually no isolation between receivers.  If
your receivers have tight front ends, unless all of the receivers are very
close in frequency, you may end up with more than 3 dB of theoretical loss
due to phase cancellation back at the tee.  If you're really pinching
pennies, Kevin's recommendation of using 75 ohm CATV/MATV splitters is
better since they provide port-to-port isolation, and the losses due to the
impedance mismatch (50 versus 75) are insignificant (theoretically approx.
0.4 dB + normal dividing loss).

--- Jeff





 
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RE: [Repeater-Builder] Re: Multiple receivers one antenna ???

[Jeff DePolo WN3A]

> 
> It's called a Wilkinson splitter. Here is a link to some of 
> the theory.

I don't think it's fair to call it a Wilkinson without a resistor across the
output ports.  A real Wilkinson provides port-to-port isolation due to the
addition of the resistor.  A tee and 75 ohm cables doesn't provide any
appreciable isolation; it's just two transmission line transformers teed
together to yield a proper match assuming that the ends of the cables are
terminated into 50 ohm loads.  In the real world, receivers don't have 50
ohm Z across a wide range due to front end filters and other factors, so you
may end up with additional loss (above and beyond the theoretical 3 dB
power-dividing loss) due to the lack of isolation between receivers.

--- Jeff






 
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RE: [Repeater-Builder] Re: UHF Preamplifier

[Jeff DePolo WN3A]

On a somewhat related note, has anyone used LNA Technology's (Chet Pierson
K3TV) preamps?  He has some interesting designs.  www.lnatechnology.com

--- Jeff





 
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