Re: [Repeater-Builder] Coax length, etc.

[Nate Duehr]

On Aug 14, 2010, at 9:45 PM, Jeff DePolo wrote:

> Well, kinda. Many duplexers are spec'ed for 1.5:1 (14 dB RL) input VSWR
> max. Fortunately, I rarely see any that are that bad. I'll gladly trade
> off a tenth of a dB of insertion loss for several (if not 10 or more) dB of
> return loss improvement when I'm tuning on the VNA, but some hams are greedy
> and don't think along those lines when they're tuning...

Actually I think that even though Service Monitors have finally become 
*relatively* commonplace in the Ham Shack, the VNA is not something "most" hams 
have seen or know how to use.

(I would count myself in that group.)

Like Service Monitors used to be before the flood of HPs on eBay in the last 
few years, I hear rumors of "great deals" on VNAs, and yet never see them in 
any way "plentiful", "easy to acquire", or "affordable", but then again I'm 
also not exactly looking that hard, and perhaps I'm missing one of those 
"everyone knows about Bob's VNA Warehouse!" kinds of sources for such things.

I do find it interesting (sorry another side-thought) that a great many 
*professionals* don't seem to have access to them, nor can convince their 
employers to purchase them.  I have heard the excitement in professional RF 
Engineer's voices when their company finally acquires one... and seen 'em load 
up the car with stuff they've "always wanted to put on the VNA".  A few years 
ago, anyway.

Are they more common than I think?

>From Jeff's comments and other's off-list, they're obviously the "right tool 
>for the job", and tuning duplexers without them seems similar to messing 
>around with taking the engine out of a car without an engine hoist, but unlike 
>engine hoists -- professional RF shops don't even seem to regularly own a VNA 
>or have anyone on staff qualified/trained on how to use one.

Can't count the number of cell site and other RF techs I've talked to over the 
years who were just happy as clams when they finally got TDR equipment to check 
cables too.

What's up with the RF industry not buying these things by the truckload?  Too 
spendy?

--
Nate Duehr, WY0X
n...@natetech.com

Properly designed PAs (was: Re: [Repeater-Builder] Coax length, etc.)

[Nate Duehr]

On Aug 14, 2010, at 9:45 PM, Jeff DePolo wrote:

> I disagree. I would accept the notion that the transmitter may not be
> "happy" (and I put that in quotes not to mock you, but becuase I can't come
> up with a better word either) because it is not *properly matched* when
> looking into a 50+j0 load. This indicates a deficiency in the amplifier; if
> it were designed and working right, it *should* make rated power when
> terminated in a 50 ohm load on-channel.

Okay, I'd love to go off on a side tangent here for a moment.  (By the way, 
loving the discussion. Learning from it.)

Jeff, out of all the PAs you've seen out there, both commonly used and 
not-so-common... which ones (in your opinion) are properly designed (when 
"working right")?

I have this feeling that most, if not all, have various problems... but you've 
seen a heck of a lot more of them in-service than I have.  

Which ones behave the best, as regards to this other discussion that's going on 
about making them "happy".  In other words, which ones have you bought/used 
that you hooked up, and forgot about them completely because you knew they'd 
"just work".

I ask, because this is always the kind of mature, well-developed tech I'm 
looking for.  Price is still a factor, but when you find something that "just 
works"... it's truly grand in the tech world, for all sorts of reasons that 
tend to degrade what something was intended to be, vs. what it really ended up 
being.

I'm also curious to see if your recommendations are new gear, or 20+ year old 
gear.  

I really like MASTR II Stations, but I will admit to some consternation over 
how the PAs *sometimes* act.  We've had 'em run for a decade, and we've had 'em 
pop like light bulbs every few months. Yes, the problem is often in the 
duplexer/feedline/antenna system when this happens, but it's also often subtle 
and not exactly easy to find.  I'm wondering to myself, (and now "out loud")... 
"Is there a PA out there that wouldn't have "cared" or been "un-happy"?  Bonus 
points for it monitoring its own "happiness" and turning on an alarm light, 
closing a contact, etc. 

Is the answer to this question the Crescend amps perhaps?  How did their 
acquisition of Vocom affect their quality?  I haven't looked lately, did they 
mix up the model line and keep the Vocom stuff? 

Just some questioning thoughts, not very well thought out, at almost 1AM... 

--
Nate Duehr, WY0X
n...@natetech.com

Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)

[Nate Duehr]

On Aug 14, 2010, at 7:01 PM, Chuck Kelsey wrote:

> I'm the opposite. I want all my email dumped in one inbox. I'm afraid if it 
> gets sorted to different folders, something's bound to get missed. Just like 
> the mailman puts all my snail mail in one mailbox. Works just fine. Same 
> reason I prefer list servers to forums - I don't want to have to go and look 
> somewhere.
> 
> Chuck
> WB2EDV

All the mail in the individual folders is tagged as "new" and almost all modern 
mail clients show counts of new mail per folder.

If not that, there's always "smart folders" which all now do also -- "All New 
Mail", no matter what folder it's in.  If the mail is light for the day, I just 
go there...

It's virtually impossible to "miss" something, but it will show you your real 
priorities in mail reading if you sort to folders.  Frankly, sometimes RB 
(sorry Kevin & Scott) sits for weeks when the "real" mail gets busy.  The 
little number next to the folder keeps counting up with new messages as a 
reminder that I need to get to them, eventually... but not "now".

I've been unsuccessful thus far in getting all the way to "Inbox Zero" ( 
http://inboxzero.com/inboxzero/ ) but it's a smart long-term goal... 

--
Nate Duehr, WY0X
n...@natetech.com

RE: [Repeater-Builder] Coax length, etc.

[Gary Schafer]

> -Original Message-
> From: Repeater-Builder@yahoogroups.com [mailto:Repeater-
> buil...@yahoogroups.com] On Behalf Of Jeff DePolo
> Sent: Saturday, August 14, 2010 10:45 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Coax length, etc.
> 
> > Jeff, you aren't stepping on my toes at all. Glad to see your
> > comments.
> 
> OK, good.  Since you've never met me, I can assure you, you definately DO
> NOT want me stepping on your toes, it would be painful.
> 
> > I do have to agree with Kevin that most duplexer
> > manufacturers recommend different cable length trials between
> > the transmitter and the duplexer when full power can not be
> > reached into the duplexer.
> 
> Ah, but the crux of the matter is that we're not changing the performance
> of
> the duplexer, we're just getting the transmitter to transfer more power
> into
> the line.

Yes! I fully agree.

> 
> >  Over the years I have been a manufacturers rep for TX-RX,
> > Sinclair and Telewave. All of them recommend the same thing.
> 
> Again, it's a CYA measure as Kevin pointed out.  PA won't make power?
> Don't
> blame us, try mucking with the cable length, see if that helps.

But it is not necessarily the duplexer's problem.

> 
> > I am not a transmitter expert but it is my understanding that
> > the problem is not one of the duplexer not presenting 50 ohms
> > at the wanted frequency but the impedance that it presents
> > off frequency to the transmitter finals. Some solid state
> > devices do not like to see high reactance, even off
> > frequency.
> 
> But why?  If all of the power (or, let's hope, at least 99.99% of it)
> is
> on-channel, *should* a properly-designed and properly-functioning
> transmitter misbehave due to the poor match a duplexer presents at
> frequencies far removed from the channel center?

Well yes, properly designed transmitter. But how much do you want to pay for
it? A built in isolator will solve all of those problems as an example.

> 
> > For one thing the reactance causes them to draw
> > more current than normal.
> 
> Again, why?

Not sure why. I have been told by device engineers that is a characteristics
of some devices.

> 
> > This may be why you find that
> > tuning for minimum pa current and maximum power out don't
> > exactly agree with one another.
> 
> I can promise you they almost never do, but that's not any great mystery.
> 
> > You are probably finding a
> > balance between the off frequency reactance and the on
> > frequency wanted load that the finals see.
> 
> No, that's not it.  The off-frequency Z issue is a totally separate topic
> from the efficiency vs maximum output subject.  Let's keep those two
> topics
> separate for the sake of this discussion.

If what you find in tuning happens directly into a 50 ohm load I agree.

> 
> > If you have the duplexer properly tuned to provide 50 ohms at
> > its input port, the transmitter may still not be happy
> > because of the off frequency reactance presented by the duplexer.
> 
> I disagree.  I would accept the notion that the transmitter may not be
> "happy" (and I put that in quotes not to mock you, but becuase I can't
> come
> up with a better word either) because it is not *properly matched* when
> looking into a 50+j0 load.  This indicates a deficiency in the amplifier;
> if
> it were designed and working right, it *should* make rated power when
> terminated in a 50 ohm load on-channel.

Yes it would be a transmitter problem. Maybe as designed.

> 
> > Changing the cable length in this case really does nothing
> > for the  on frequency load between the duplexer and
> > transmitter, when the duplexer is presenting 50 ohms, but it
> > can change the off frequency impedance transformation that
> > the transmitter sees.
> 
> Yes, but again, I argue that this all points back to a PA problem.  Or the
> input Z of the duplexer really isn't 50 ohms and the line is acting as a
> transformer.

Again I agree. In this instance I was describing a duplexer that "did"
present 50 ohms at the operating frequency and still the transmitter was not
"happy". Because of the off frequency impedance being transformed to
something that the transmitter does not like.

It is almost impossible for a high Q cavity to not present some reactance
away from the tuned frequency. If it didn't then it would not have any
selectivity. The random length cable of course transforms that reactance to
something that the transmitter may or may not be comfortable with as
discussed above.

> 
> > Detuning the duplexer and or changing
> > cable length to get the transmitter power up is the wrong way
> > to go here. First the transmitter should be optimized into a
> > 50 ohm load. Then optimize the duplexer input for 50 ohms input.

Of course I am talking about when the duplexer is presenting a good 50 ohm
input impedance at the operating frequency.

> 
> Yes, yes, yes, amen!
> 
> > Someone asked about a "rule of thumb" for transmitter to
> > duplexer c

RE: [Repeater-Builder] Coax length, etc.

[Jeff DePolo]

OK, I think, for the most part, we're on the same page.  I'm cuttin' and
trimmin' a lot here...
 
> And this is where I believe the duplexer manufacturers are 
> covering their butt.  They don't want the problem with 
> complex reactance presented by the duplexer to be their 
> problem.  Not that I don't agree, because it's usually the 
> transmitter that is really at fault.  

I think that last sentence speaks volumes on the matter.
 
> Joe Ham buys a new duplexer and hooks it up to his 110 Watt 
> MASTR II repeater and gets 50 watts out the antenna port.  He 
> does his homework and realizes that he should only be loosing 
> 29% with the 1.5 dB of insertion loss stated in the paperwork 
> - but he's loosing over 50%.  

Ah, but is he really *losing* 50 percent in the duplexer, or is transmitter
not making the full 110 watts output to start with?  Maybe his transmitter
is really only delivering 70 watts to the duplexer.  Is it an issue of the
duplexer's loss being high, or is the problem the transmitter's not making
power?  Seems to me it's really the latter.  

> The duplexer manufacturer 
> supposedly engineered and tuned it for a 50 Ohm system.  

Well, kinda.  Many duplexers are spec'ed for 1.5:1 (14 dB RL) input VSWR
max.  Fortunately, I rarely see any that are that bad.  I'll gladly trade
off a tenth of a dB of insertion loss for several (if not 10 or more) dB of
return loss improvement when I'm tuning on the VNA, but some hams are greedy
and don't think along those lines when they're tuning...

> He 
> knows that the cable he connected to the transmitter is good, 
> because when he disconnects the end going to the transmitter 
> port of the duplexer and connects it to his Bird 43 
> terminated with a good load - it reads 110 watts.

Yes, but did he have a second Bird between the Tx and the duplexer when he
was measuring power output?  That would have told the real story.

> Now, is the transmitter becoming spurious 

Now all bets are off.

> and the cable 
> length being changed in length satisfies the match between 
> the duplexer and transmitter - I don't know...   All I can 
> tell you is I have followed the suggestions written in the 
> WACOM manual and it has worked.  I had one instance of a ham 
> radio club loosing PA's left and right on their 2M machine.  
> They told me of the situation and I offered to do a little 
> testing.  The 110 watt PA would put out 110 watts into a Bird 
> and dummy, but only 45 watts was coming out the antenna port 
> of the duplexer.  At the time I didn't own a spectrum 
> analyzer.  The repeater wouldn't duplex without desense.  I 
> changed the length of the line between the PA and duplexer 
> until I got the power to read about 75 Watts as I remember.  
> That was 13 years and they still have the same PA - no desense either.

Out of morbid curiosity, what kind of PA was it?

> You are changing the VSWR when tuning the cavity closest to 
> the transmitter.   

Yes, but once you've adjusted that cavity, from that point on, changing the
cable length doesn't vary the VSWR.  That was my point - changing the cable
length doesn't change VSWR.  

> I realize that impedance transformation 
> cannot occur when you have a 50 Ohm cable (of any length) and 
> a perfect 50 Ohm load - but I think you will agree that a 
> duplexer doesn't, in any way shape or form, present a nice 50 
> Ohm load.  

Well, it can get pretty damn close.  I can send you some VNA plots of
duplexers with input Z's well in excess of 30 dB return loss, some
approaching the limits of my test equipment.  Of course, when hooked up to
an antenna instead of being terminated in a precision load, all bets are
off, but hey, that's not the fault of the duplexer...

> Some transmitters just cannot deal with it without 
> some form of matching after the fact - like a Z-Matcher, 
> Isolator, Circulator, or even a critical cable length.

I don't like those transmitters  :-)

> GE MASTR II 110 watt 150.8 to 174 MHz PA and WACOM WP-641.  

Thinking...thinking...no, haven't done that one.

> Motorola MICOR 150.8 to 162 MHz PA and WACOM WP-641.  

Yes, have done that combo, several times that I can think of.  Actually, one
of the repeaters was low-split from the factory (out of Canada) now that I
think about it, so that doesn't count, the others were all H split with no
PA mods.  Didn't do anything special with cable lengths.

> Hamtronics 45 Watt 2M PA and Sinclair Q-202.

Haven't done any Hamtronics.

> Well, I cannot believe that I'm the only person on this list 
> that has had success with optimizing the length of cable 
> between the duplexer and transmitter/PA.  

I don't doubt that others have seen positive (or negative) effects from
varying cable lengths - I just said I've never had to resort to doing it,
using the equipment that I've used, with the equipment tuned the way I've
tuned it.

> I'll get us some tickets for Vegas - Jeff.

I think ZZU has the right idea.  He's down in MX-land right now, probably

RE: [Repeater-Builder] Coax length, etc.

[Jeff DePolo]

> Jeff, you aren't stepping on my toes at all. Glad to see your 
> comments.

OK, good.  Since you've never met me, I can assure you, you definately DO
NOT want me stepping on your toes, it would be painful.

> I do have to agree with Kevin that most duplexer 
> manufacturers recommend different cable length trials between 
> the transmitter and the duplexer when full power can not be 
> reached into the duplexer.

Ah, but the crux of the matter is that we're not changing the performance of
the duplexer, we're just getting the transmitter to transfer more power into
the line.

>  Over the years I have been a manufacturers rep for TX-RX, 
> Sinclair and Telewave. All of them recommend the same thing.

Again, it's a CYA measure as Kevin pointed out.  PA won't make power?  Don't
blame us, try mucking with the cable length, see if that helps.

> I am not a transmitter expert but it is my understanding that 
> the problem is not one of the duplexer not presenting 50 ohms 
> at the wanted frequency but the impedance that it presents 
> off frequency to the transmitter finals. Some solid state 
> devices do not like to see high reactance, even off 
> frequency. 

But why?  If all of the power (or, let's hope, at least 99.99% of it) is
on-channel, *should* a properly-designed and properly-functioning
transmitter misbehave due to the poor match a duplexer presents at
frequencies far removed from the channel center?

> For one thing the reactance causes them to draw 
> more current than normal. 

Again, why?

> This may be why you find that 
> tuning for minimum pa current and maximum power out don't 
> exactly agree with one another. 

I can promise you they almost never do, but that's not any great mystery.

> You are probably finding a 
> balance between the off frequency reactance and the on 
> frequency wanted load that the finals see.

No, that's not it.  The off-frequency Z issue is a totally separate topic
from the efficiency vs maximum output subject.  Let's keep those two topics
separate for the sake of this discussion.

> If you have the duplexer properly tuned to provide 50 ohms at 
> its input port, the transmitter may still not be happy 
> because of the off frequency reactance presented by the duplexer.

I disagree.  I would accept the notion that the transmitter may not be
"happy" (and I put that in quotes not to mock you, but becuase I can't come
up with a better word either) because it is not *properly matched* when
looking into a 50+j0 load.  This indicates a deficiency in the amplifier; if
it were designed and working right, it *should* make rated power when
terminated in a 50 ohm load on-channel.

> Changing the cable length in this case really does nothing 
> for the  on frequency load between the duplexer and 
> transmitter, when the duplexer is presenting 50 ohms, but it 
> can change the off frequency impedance transformation that 
> the transmitter sees. 

Yes, but again, I argue that this all points back to a PA problem.  Or the
input Z of the duplexer really isn't 50 ohms and the line is acting as a
transformer.

> Detuning the duplexer and or changing 
> cable length to get the transmitter power up is the wrong way 
> to go here. First the transmitter should be optimized into a 
> 50 ohm load. Then optimize the duplexer input for 50 ohms input.

Yes, yes, yes, amen!

> Someone asked about a "rule of thumb" for transmitter to 
> duplexer cable length. There is none! 

Yes there is. You take out a tape measure and the distance from the
transmitter to the duplexer.  You make the cable at least that length.

> The cable length between multiple cavities is predictable. As 
> an example between two notch cavities; the first notch 
> presents a very low impedance. With a quarter wave line to 
> the next cavity that low impedance is transformed to a high 
> impedance at the input to the next cavity. That high 
> impedance is then presented with a very low impedance of the 
> second cavity. This critical length cable increases the 
> ultimate notch depth because the high impedance that the 
> cable presents and the low impedance of the cavity form a 
> voltage divider. The greater the ratio the better the rejection.


'zactly.  When done right, you can pick up close to 6 dB additional net
notch depth when cascading notch (or pass/notch) cavities when the
intra-cavity cables are cut this way.

 Jeff WN3A

RE: [Repeater-Builder] Coax length, etc.

[Jeff DePolo]

> So will someone post a simple rule of thumb. If you have the 
> option of optimizing cable length from PA to first cavity, IE 
> you haven't made them yet what's the best "simple" rule of 
> thumb to follow to build them to avoid reactance. 1/2wl if 
> allowed minus coupling loop depth? Or is that past a simple 
> thumb. Also, This will obviously not work well for 220 or 440 
> or a most vhf repeater setups. So what would the next ideal 
> cable wl be? And so forth. The reason I ask, if your building 
> new cables why not? Answers on here seem to range a lot.

There is no simple rule of thumb, and if anybody tells you that there is,
ask them how do you account for the unknown-length of coax that's *inside*
your transmitter/amplifier before it gets to the antenna jack.

--- Jeff WN3A

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Ross Johnson wrote:



So will someone post a simple rule of thumb... If you have the option 
of optimizing cable length from PA to first cavity, IE you haven't 
made them yet what's the best "simple" rule of thumb to follow to 
build them to avoid reactance. 1/2wl if allowed minus coupling loop 
depth? Or is that past a simple thumb.




Simple rule - there is none.  The length can be determined 
experimentally as outlined in several publications of various duplexer 
manufacturers.


I use the length I need to do a good job - then, if the transmitter is 
unhappy, I build a cable long enough to do the job and satisfy the 
transmitter.


Kevin

Re: [Repeater-Builder] Re: Coax length, etc.

[Russ Hines]

 Sid, I think I found your formula.  Look on page 62 of:

http://www.repeater-builder.com/antenna/pdf/ve2azx-duplexerinfo.pdf

BTW, my guess was wrong.  Length is expressed in inches.

73, Russ WB8ZCC

On 8/13/2010 1:44 PM, Russ Hines wrote:
Hmm, the formula is a bit off, but... 30 x 32.785 = 983.55.  I'll also 
bet length is expressed in feet.


Looks eerily like someone wants you to cut a one-wavelength piece of 
coax cut at the mean repeater frequency.


Just a guess.

73, Russ WB8ZCC

On 8/13/2010 11:38 AM, Sid wrote:


I have a note in my file that I do not recall where it came from 
relative to cable length between the duplexer and the TX or between 
the duplexer and additional filter. Length = (30)(32.785)(vf/freq).
30 is for 30 degrees, vf is velocity factor, freq is the average of 
the pass and reject frequencies. If too short add 180 degrees. Don't 
know if this is good info or not. The article would be appreciated. Sid.



--- In Repeater-Builder@yahoogroups.com 
, Nate Duehr  wrote:

>
>
> On Aug 5, 2010, at 11:20 AM, Kevin Custer wrote:
>
> > Allan Crites and I are currently in discussion which will be used 
as the basis of a RB web article that will explain exactly what is 
happening, why it happens, and why an 'optimized' cable length can be 
used to transfer power ending up with the stated loss of the duplexer 
and have little reflected power toward the transmitter - so long as 
the duplexer is tuned properly and exhibits good return loss on the 
frequency it's designed to pass.

>
> There's already a great book on that topic, it's called the ARRL 
Antenna Handbook, and the chapter on transmission lines covers it in 
more detail than anyone will ever need to know in the real-world, 
who's not a practicing RF Engineer.

>
> That book if read cover-to-cover, is also damn good for insomnia. 
Or at least it'll keep you distracted while you can't sleep! :-)

>
> --
> Nate Duehr
> n...@...
>
> facebook.com/denverpilot
> twitter.com/denverpilot
>

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Russ Hines wrote:



Some related comments, if you don't mind.

Temperature changes seem to be the biggest "detuner" of largely 
mechanical devices like cavity duplexers.  We often send our repeaters 
off to live in less-than-ideal environments, then expect cavity 
input/output impedances to remain as we measured them in the shop?  
Don't think so.


I largely disagree.  Most modern duplexer designs (within the last 25 
years or so) use compensating elements to make the duplexer or cavity 
temperature stable.  Invar is a nickel-steel alloy that exhibits about 
1/10 the thermal expansion as a common carbon steel counterpart.  Invar 
is used to make the tuning rod - many times it's threaded.  The rest of 
the duplexer or cavity is usually made of similar metals and generally 
thermal expansion occurs across these components equally, resulting in 
extremely low frequency drift over its rated operating temperature.





Our in-line power meters, like our trusted Bird 43, do not directly 
measure power.  They're really voltage meters calibrated in watts at a 
specific impedance.  That's why they can be fooled into displaying an 
erroneous reflected power reading, perhaps lulling us into a sense of 
security that the VSWR on the line is acceptable when it may not be.


What?  Maybe you would like to have another chance at that one

Kevin Custer

Re: [Repeater-Builder] Repeater Stuff For Sale!

[Maire-Radios]

what is the input power on the 200 watt Vocom amp?

K+John


  - Original Message - 
  From: n2len 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Saturday, August 14, 2010 9:24 PM
  Subject: [Repeater-Builder] Repeater Stuff For Sale!



  Motorola RKR-1225 VHF Repeater with Rack Mount
  Currently programmed for Hamsplit
  $475 Shipped and Insured
  Motorola R-1225 UHF Repeater
  Just Radio and Control Head Unit
  Hamsplit down to 444MHZ
  $425 Shipped and Insured
  Cat 400 Linking Controller and RME-200L Rack Mount with Ed-400W Windows 
Programming Software
  $325 Shipped and Insured
  Cat RLS-1000B Remote Link Switch Board with RME-200L Rack Mount Enclosure. 
$125.00 Shipped
  Pacific Research RI-310 Repeater Controller 
  Ror the VXR-5000 Repeater
  Direct Replacement for the stock Internal Controller Plug & Play
  $400.00 Shipped
  TPL RXR Series VHF 150 Watt Repeater Amplifier
  Rack Mount/Fan
  $375.00 Shipped
  TPL RXR Series UHF 100 Watt Repeater Amplifier
  Rack Mount/Fan
  $350.00 Shipped
  Two Vocom UHF Repeater Amplifiers
  Working Condition of both Unknown
  100 Watt Factory 462.925
  UVC100-10RF
  $125 Shipped
  Vocom UHF Repeater Amplifier
  Working Condition Unknown
  200 Watt Factory 462.925
  UVC200-80RFF
  Rack Mount/Fan
  PAYMENT PAYPAL!

  E-mail too:
  n2...@aol.com



  

RE: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)

[Andrew Seybold]

And I am one of those with separate folders for two reasons, first it
makes things easier to see, and I have never had a problem with getting
email mixed up, I subscribe to multiple yahoo groups and each one has
its own folder which makes it easy to see when there is new email from
each group.

Secondly and most important to me I get so much business related email
on my Blackberry that by using folders I don't get groups to my BB, and
so I can concentrate on business emails and when I check in with my
desktop or laptop I can see the groups with messages since the last time
I have looked at them.

In this case, then, a few spam messages are just easy to delete. I know
from experience that spammers don't have to have access to your email
account to spoof your email address, since mine has been spoofed
multiple time.

 

Andy

W6AMS

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
Sent: Saturday, August 14, 2010 6:01 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group
posts - a butter way - no popcorn)

 

  

I'm the opposite. I want all my email dumped in one inbox. I'm afraid if
it 
gets sorted to different folders, something's bound to get missed. Just
like 
the mailman puts all my snail mail in one mailbox. Works just fine. Same

reason I prefer list servers to forums - I don't want to have to go and
look 
somewhere.

Chuck
WB2EDV

- Original Message - 
From: "Nate Duehr" mailto:nate%40natetech.com> >
To: mailto:Repeater-Builder%40yahoogroups.com> >
Sent: Saturday, August 14, 2010 8:41 PM
Subject: Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group
posts - 
a butter way - no popcorn)

>
> On Aug 14, 2010, at 12:57 PM, Scott Zimmerman wrote:
>
>> I am subscribed to all of my groups in 'single e-mail' form. I have
>> configured Thunderbird to sort those groups into individual folders.
By
>> doing this, I can look at things in a digest mode. If I want to get
rid
>> of a bunch at one clip, I can select all and hit delete.
>>
>> Just my 2c worth of ideas.
>>
>> Scott
>
> I agree with Scott, and take this one step further. I use an IMAP
server 
> (the real deal, not Microsoft's wacked-out IMAP in Exchange), and have
the 
> *server* sort all the mail into folders before it ever even gets
looked at 
> by my mail client software.
>
> 

Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)

[Chuck Kelsey]

I'm the opposite. I want all my email dumped in one inbox. I'm afraid if it 
gets sorted to different folders, something's bound to get missed. Just like 
the mailman puts all my snail mail in one mailbox. Works just fine. Same 
reason I prefer list servers to forums - I don't want to have to go and look 
somewhere.

Chuck
WB2EDV


- Original Message - 
From: "Nate Duehr" 
To: 
Sent: Saturday, August 14, 2010 8:41 PM
Subject: Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - 
a butter way - no popcorn)


>
> On Aug 14, 2010, at 12:57 PM, Scott Zimmerman wrote:
>
>> I am subscribed to all of my groups in 'single e-mail' form. I have
>> configured Thunderbird to sort those groups into individual folders. By
>> doing this, I can look at things in a digest mode. If I want to get rid
>> of a bunch at one clip, I can select all and hit delete.
>>
>> Just my 2c worth of ideas.
>>
>> Scott
>
> I agree with Scott, and take this one step further.  I use an IMAP server 
> (the real deal, not Microsoft's wacked-out IMAP in Exchange), and have the 
> *server* sort all the mail into folders before it ever even gets looked at 
> by my mail client software.
>
> 

Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)

[Nate Duehr]

On Aug 14, 2010, at 12:57 PM, Scott Zimmerman wrote:

> I am subscribed to all of my groups in 'single e-mail' form. I have 
> configured Thunderbird to sort those groups into individual folders. By 
> doing this, I can look at things in a digest mode. If I want to get rid 
> of a bunch at one clip, I can select all and hit delete.
> 
> Just my 2c worth of ideas.
> 
> Scott

I agree with Scott, and take this one step further.  I use an IMAP server (the 
real deal, not Microsoft's wacked-out IMAP in Exchange), and have the *server* 
sort all the mail into folders before it ever even gets looked at by my mail 
client software.

Thunderbird, Apple's Mail.App on the Macs, the iPhone, the mail provider's mail 
web interface... all have the same "view" of the mail when I log on, and I can 
choose whether to read list mail (all nicely sorted and tagged as "new mail" in 
various folders) or just read the important stuff in my Inbox.

The tools for managing e-mail are out there.  They're just not commonly used.  
I'd go nuts if all this stuff came directly to my Inbox.  That'd be crazy.  
List mail isn't personal mail, and the two don't need to ever mix. 

A challenge: For a highly "technical" hobby, very few hams have *really* done a 
deep-dive into their mail software and learned the feature-set.  Give it a 
shot, it's well worth it!  :-)

You might be able to reward yourself with a nice "Repeater-Builder" folder, 
where all the RB mail goes, all by itself... and you can then read (or delete 
large swaths by subject line, even... since that's what the Subject line was 
created for, after all...) at your leisure! 

Have fun with it,
--
Nate Duehr
n...@natetech.com

Re: [Repeater-Builder] new member introduction

[Nate Duehr]

On Aug 12, 2010, at 9:09 PM, Zephyr wrote:

> Thanks for having me in your group. I am a long-time military veteran and a 
> paramedic. I hope to learn a lot from the group. One of the reasons I joined 
> the group is to find out what kind of EMP hardening is considered when 
> designing and building repeaters?

Very little, typically.  Almost all have solid-state components that would be 
utterly dead after an EMP.  Tube gear that survives EMP better is virtually all 
gone.  And user radios are required for any repeater to be useful, and they'd 
all be totally dead too.

So... the rest of your posting sure sounds like an advertisement for another 
list, which is generally bad Netiquette, unless the lists had something a 
little bit more in common.  But I'll give you the benefit of the doubt since 
you used a real callsign and name on your signature line, even though your 
"From" is a pseudonym.  

Personally, I find pseudonym-bearers on the Internet usually need this advice: 
"If you want to be somebody else, change you mind."  Seriously.  Or at least 
have the pseudonym match something you are, or something you do.

Anyway, to finish answering the question: 

About the closest repeaters get to EMP Hardening outside of the military world 
(if even then...), is that a lot of repeaters in the West are in old AT&T 
microwave facilities that were built as blast-hardened for specific distances 
and levels of nuclear bombs.  The gear that used to live in them was hardened 
for various levels of EMP, but that gear is long-gone, removed from the 
buildings when AT&T scrapped them and the military stopped paying.  They have 
other communications systems and links today.

The buildings will probably be standing for another 100 years.  The towers are 
built hellaciously strong, too... but are showing signs of age.  Even the 
outhouses were over-engineered, and I have an engineering drawing of an 
official AT&T outhouse around here somewhere.  Those were not blast-hardened 
nor EMP hardened, so apparently if you were unlucky enough to be caught at the 
site during a nuclear exchange, you might not have modern toilet facilities 
afterward.  A small price to pay, I suppose.

;-)

--
Nate Duehr
n...@natetech.com

Re: [Repeater-Builder] HYT Repeater vs. Trbo Repeater

[Gareth Bennett]

The HYT repeater is actually a "Proper" repeater and has been designed around 
the Spectra Engineering MX800 
http://www.spectraeng.com.au/So if you are looking at implementing a DMR 
repeater into a RF dense site, I'd definitely know which way I'd go. No 
questions


Gareth Bennett

RadioSystems Limited
P.O. Box 5202
Dunedin  9024
New Zealand
 
DDI:   (03) 489 1101
FAX:   (03) 489 1151
MOB: (0224) 588 377

gare...@radsys.co.nz


  - Original Message - 
  From: k2aau 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Sunday, August 15, 2010 1:49 AM
  Subject: [Repeater-Builder] HYT Repeater vs. Trbo Repeater



  Has anyone done any comparison testing between the HYT Repeater and The 
Motorola Trbo repeater? I am particulary interested in making a future purchase 
of either one. I have read about the IPsec concerns and that to me is really 
not an issue. I am sure that HYT will address that concern as time goes forward.

  From what I have been told, the Trbo consists of 2 mobile radios used for 
receive and the other for transmit. Whereas, HYT is one radio with a Duplexed 
receiver and transmitter well isolated from each other.

  It is also my understanding that the company HYT's vendors are more user 
friendly in pricing and support compared to Motorola when it comes to 
accessories, firmware updates and programming.

  Thanks in advance for any information.

  Artie
  k2aau



  

RE: [Repeater-Builder] Coax length, etc.

[Gary Schafer]

One correction here; the Bird power meter is not just a "voltage measuring"
meter. It does in fact measure voltage and current to calculate power. It
will give true power even if used in a non 50 ohm circuit. But you must
always subtract reflected power from indicated forward power to find true
power delivered to the load.

 

When measuring SWR you must always calculate it (or use the chart) and
compare reflected to forward indicated on the meter. It is easy to be fooled
as indicated forward power also drops as reflected power drops.

 

73

Gary  K4FMX

 

  _  

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Russ Hines
Sent: Saturday, August 14, 2010 4:30 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Coax length, etc.73

 

 



Some related comments, if you don't mind.

Temperature changes seem to be the biggest "detuner" of largely mechanical
devices like cavity duplexers.  We often send our repeaters off to live in
less-than-ideal environments, then expect cavity input/output impedances to
remain as we measured them in the shop?  Don't think so.

IMHO, we're making the same mistake I made in a post the other day, saying
"VSWR" when what we really mean is "reflected power" as indicated on a
meter.  

Jeff is correct, VSWR along a transmission line doesn't change if source,
load and line impedances are stable, the ratio remains the same.  What does
change, and what is affected by line length, are actual impedances along the
line under not-so-perfect-or-stable conditions; the actual impedances along
the line change but the ratio does not.  For example, 100+j0, 25+j0, 40+j30,
and 40-j30, are different impedances yet all exhibit a VSWR of 2:1 in a
50-ohm impedance system.  

Voltage is proportional to impedance.  We can't really have a voltage
standing wave ratio greater than 1:1 without a voltage differential, and
that really can't happen if impedances along the line remain the same.

Our friends at Agilent have put together a Java applet demonstrating what
happens along a transmission line. Maybe you're aware of it, it's really
kind of cool.  The applet allows you to change the load impedance of the
model and see the changes, so have fun with it.

http://education.tm.agilent.com/index.cgi?CONTENT_ID=6

Our in-line power meters, like our trusted Bird 43, do not directly measure
power.  They're really voltage meters calibrated in watts at a specific
impedance.  That's why they can be fooled into displaying an erroneous
reflected power reading, perhaps lulling us into a sense of security that
the VSWR on the line is acceptable when it may not be.

With most transmitters I'm familiar with, a "high VSWR" condition is
detected from a reflected RF sample from a directional coupler at the
transmitter's output, so it's not a "real" VSWR measurement per se, it's a
voltage measurement.  Worse, these couplers tend not to be very selective,
so out-of-channel and even out-of-band energy can cause "high VSWR trips"
even when our measurements indicate all is well on our frequency of
interest.

Great discussion, keep it going.  If I repeated what was already mentioned,
my apologies.

73, Russ WB8ZCC


_._,___

[Repeater-Builder] Cable lengths

[Chuck Kelsey]

Here's an excerpt from a TX RX publication that ties in with this 
discussion"

"Adverse cable length between Duplexer and transmitter using varactor or 
broadband hybrid combining type
transmitter outputs. Even though the Duplexer VSWR is flat on frequency, the 
reflected impedance of the
Duplexer off resonance, transformed by changing cable lengths, can cause 
parasitics to be generated.

Change the length of cable between the transmitter and duplexer, traversing 
through a half wave in increments of between 1 and 2 inches until the 
desensitization ceases or is minimal. A ferrite isolator will also cure this 
condition when it is installed between the transmitter and duplexer. 
However, this is a much more expensive remedy."


Chuck
WB2EDV 

[Repeater-Builder] Re: Fs: (/\/\)otorola UHF Desktrac

[kc8gpd]

Um Ok, I want this gone. Tried swapping it, and selling it so how low do i have 
to go before someone will bite.

not that i will necessarily let it go extremely cheap, but i am just curious 
about how low i have to go to get it sold. also want to know the reasoning of 
why it is so hard to get it sold since GMRS and Ham are still wideband.

i will also toss in a small cushcraft uhf ringo as well.

again will swap to a rebandable p25 mobile scanner or ???

here are pic's
http://img405.imageshack.us/i/sales8910018.jpg/
http://img188.imageshack.us/i/sales8910017.jpg/
http://img842.imageshack.us/i/sales8910016.jpg/
http://img683.imageshack.us/i/sales8910015.jpg/
http://img706.imageshack.us/i/sales8910021.jpg/

Re: [Repeater-Builder] Coax length, etc.

[Russ Hines]

 Some related comments, if you don't mind.

Temperature changes seem to be the biggest "detuner" of largely 
mechanical devices like cavity duplexers.  We often send our repeaters 
off to live in less-than-ideal environments, then expect cavity 
input/output impedances to remain as we measured them in the shop?  
Don't think so.


IMHO, we're making the same mistake I made in a post the other day, 
saying "VSWR" when what we really mean is "reflected power" as indicated 
on a meter.


Jeff is correct, VSWR along a transmission line doesn't change if 
source, load and line impedances are stable, the ratio remains the 
same.  What does change, and what is affected by line length, are actual 
impedances along the line under not-so-perfect-or-stable conditions; the 
actual impedances along the line change but the ratio does not.  For 
example, 100+j0, 25+j0, 40+j30, and 40-j30, are different impedances yet 
all exhibit a VSWR of 2:1 in a 50-ohm impedance system.


Voltage is proportional to impedance.  We can't really have a voltage 
standing wave ratio greater than 1:1 without a voltage differential, and 
that really can't happen if impedances along the line remain the same.


Our friends at Agilent have put together a Java applet demonstrating 
what happens along a transmission line. Maybe you're aware of it, it's 
really kind of cool.  The applet allows you to change the load impedance 
of the model and see the changes, so have fun with it.


http://education.tm.agilent.com/index.cgi?CONTENT_ID=6

Our in-line power meters, like our trusted Bird 43, do not directly 
measure power.  They're really voltage meters calibrated in watts at a 
specific impedance.  That's why they can be fooled into displaying an 
erroneous reflected power reading, perhaps lulling us into a sense of 
security that the VSWR on the line is acceptable when it may not be.


With most transmitters I'm familiar with, a "high VSWR" condition is 
detected from a reflected RF sample from a directional coupler at the 
transmitter's output, so it's not a "real" VSWR measurement per se, it's 
a voltage measurement.  Worse, these couplers tend not to be very 
selective, so out-of-channel and even out-of-band energy can cause "high 
VSWR trips" even when our measurements indicate all is well on our 
frequency of interest.


Great discussion, keep it going.  If I repeated what was already 
mentioned, my apologies.


73, Russ WB8ZCC


On 8/14/2010 12:53 PM, Kevin Custer wrote:


Jeff DePolo wrote:


Because the impedance is not matched between the transmitter
and duplexer, the 'apparent' loss of the duplexer is greater
than the manufacturers stated loss of the duplexer.  Changing
the cable length is not changing the loss of the duplexer,
it's changing the power that is accepted at the transmitter
port of the duplexer by matching the output impedance of the
transmitter to the input impedance of the transmitter port of
the duplexer.
 


But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying
the cable length isn't going to change the Z seen by the transmitter.  Or
are you suggesting the duplexer is purposely de-tuned from 50 ohms?
   


Purposely, accidentally, by lack of good design - people not having 
the right equipment to tune it correctly - whatever.
   

And also that by varying the cable length between the
transmitter and the duplexer that you can vary the reflected
power on that same line?


Yes.
 


With all due respect, that's not possible, regardless of what the Z is of
the duplexer.  The only time it could have an effect on the reflected power
would be if the transmitter/PA were spurious, and the amplitude/frequency of
the spurs changed with varying load Z, and I think we can both agree that if
that's the case, we have bigger fish to fry.
   


And this is where I believe the duplexer manufacturers are covering 
their butt.  They don't want the problem with complex reactance 
presented by the duplexer to be their problem.  Not that I don't 
agree, because it's usually the transmitter that is really at fault.


Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II 
repeater and gets 50 watts out the antenna port.  He does his homework 
and realizes that he should only be loosing 29% with the 1.5 dB of 
insertion loss stated in the paperwork - but he's loosing over 50%.  
The duplexer manufacturer supposedly engineered and tuned it for a 50 
Ohm system.  He knows that the cable he connected to the transmitter 
is good, because when he disconnects the end going to the transmitter 
port of the duplexer and connects it to his Bird 43 terminated with a 
good load - it reads 110 watts.


Now, is the transmitter becoming spurious and the cable length being 
changed in length satisfies the match between the duplexer and 
transmitter - I don't know...   All I can tell you is I have followed 
the suggestions written in the WACOM manual and it has worked.  I had 
one instance of a ham radio 

Re: [Repeater-Builder] Coax length, etc.

[Russ Hines]

 That's because there are as many "rules" as there are thumbs.  ;-)

I don't know about anyone else, but I can tell you about the highly 
scientific method I use.


I start with a multiple of 1/2 electrical wavelength and trim as 
necessary.  I'd stay away from an odd-multiple of 1/4 wavelength in this 
application... no good reason, just because (black magic and all that).


Try cutting the transmitter-to-duplexer line using the receive frequency 
length, and vice versa.  If that doesn't work out, you can swap them.


I know, on a 2m amateur system, the length difference is about 1/4".  In 
that case, make a cable 1-2" shorter and see what happens.


An alternative is to use multiple short lengths of coax connected 
together to find a "happy" length, then replace with a single coax cut 
to that length.


As I said, highly scientific. :-P

73, Russ WB8ZCC


On 8/14/2010 2:59 PM, Ross Johnson wrote:


So will someone post a simple rule of thumb... If you have the option 
of optimizing cable length from PA to first cavity, IE you haven't 
made them yet what's the best "simple" rule of thumb to follow to 
build them to avoid reactance. 1/2wl if allowed minus coupling loop 
depth? Or is that past a simple thumb. Also, This will obviously not 
work well for 220 or 440 or a most vhf repeater setups. So what would 
the next ideal cable wl be? And so forth... The reason I ask, if your 
building new cables why not? Answers on here seem to range a lot...


Ross kc7rjk

Re: [Repeater-Builder] unsubscribe

[Bill Smith]

What link?





From: Richard 
To: Repeater-Builder@yahoogroups.com
Sent: Fri, August 13, 2010 11:35:07 PM
Subject: RE: [Repeater-Builder] unsubscribe




Well, I think it's funny.

Richard, N7TGB
www.n7tgb.net
The problem with socialism is that eventually you run out of other people's 
money
--Margaret Thatcher





From: Repeater-Builder@yahoogroups.com 
[mailto:repeater-buil...@yahoogroups.com] 
On Behalf Of Kenneth Cook
Sent: Friday, August 13, 2010 9:27 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] unsubscribe

  
This is an experiment to see if I could make the link stand out. This is NOT to 
start problems!
73…de Ken Cook , W8DZN
Switch to: Text-Only, Daily Digest • Unsubscribe• Terms of Use
.

Re: [Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)

[Scott Zimmerman]

I am subscribed to all of my groups in 'single e-mail' form. I have 
configured Thunderbird to sort those groups into individual folders. By 
doing this, I can look at things in a digest mode. If I want to get rid 
of a bunch at one clip, I can select all and hit delete.

Just my 2c worth of ideas.

Scott

Scott Zimmerman
Amateur Radio Call N3XCC
474 Barnett Road
Boswell, PA 15531


skipp025 wrote:
> 
> 
> You guys are silly... 
> 
> Consider changing your group settings to "read on the web" 
> using a web browser. Then... simply locate the group with 
> your web browser bookmark anytime you want to read the group 
> posts. 
> 
> No flood of inbound Emails for each post or large digest 
> Emails required. Probably drive one to drink (more) if they 
> were subscribed to more than 3 or 4 Groups at one time. 
> 
> Having a yahoo email address automatically signs me into 
> all the groups for which I am subscribed.  To read this,
> the Repeater Builder Group I simply click on the below 
> Bookmark saved in my Web Browser. Once you change your 
> settings to web only (I prefer the "traditional" or "classic 
> view") try the below url and enjoy life again. 
> 
> http://groups.yahoo.com/group/Repeater-Builder/messages 
> 
> If you don't use Yahoo Mail, you might be asked to sign in 
> at the start of your web browsing session, but once you're 
> in, you are in for all the groups for which you subscribe. 
> 
> cheers,
> s. 
> 
> ps: If you're subscribed to more than one group, here's the 
> page that helps you get your book marks set up. 
> 
> http://groups.yahoo.com/mygroups 
> 
> Now resume normal programming. 
> 
>> Your best bet is to setup your email to receive each post in "digest" form 
>> meaning once a day on average you will receive a bunch of postings in just 
>> one email into your inbox. When you get around to opening up your inbox you 
>> can just scroll through each individual posting, read the ones that interest 
>> you and when finished, hit the delete key and they all go away!!!  Seeing 
>> 15-30 separate, individual emails in my inbox during the course of one day 
>> is a bit too much. Try it, you'll like it OM!!73
>>
>> --- In Repeater-Builder@yahoogroups.com, "Jim in Waco WB5OXQ"  
>> wrote:
>>> I do not need to read these anymore.  I am not mad just getting too many 
>>> emails.
>>>
> 
> 
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 

RE: [Repeater-Builder] Coax length, etc.

[Ross Johnson]

FORGOT to multiply cable VF then subtract coupling loop depth!!! Forgive
me :-)
 
 
-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Ross Johnson
Sent: Saturday, August 14, 2010 11:59 AM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Coax length, etc.
 
  
So will someone post a simple rule of thumb. If you have the option of
optimizing cable length from PA to first cavity, IE you haven't made
them yet what's the best "simple" rule of thumb to follow to build them
to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is
that past a simple thumb. Also, This will obviously not work well for
220 or 440 or a most vhf repeater setups. So what would the next ideal
cable wl be? And so forth. The reason I ask, if your building new cables
why not? Answers on here seem to range a lot.
 
Ross kc7rjk

RE: [Repeater-Builder] Coax length, etc.

[Ross Johnson]

So will someone post a simple rule of thumb. If you have the option of
optimizing cable length from PA to first cavity, IE you haven't made
them yet what's the best "simple" rule of thumb to follow to build them
to avoid reactance. 1/2wl if allowed minus coupling loop depth? Or is
that past a simple thumb. Also, This will obviously not work well for
220 or 440 or a most vhf repeater setups. So what would the next ideal
cable wl be? And so forth. The reason I ask, if your building new cables
why not? Answers on here seem to range a lot.
 
Ross kc7rjk

RE: [Repeater-Builder] Coax length, etc.

[Eric Lemmon]

Kevin,

Don't feel bad- look at the number of postings that use you instead of your,
your instead of you're, mhz instead of MHz, Khz instead of kHz, it's instead
of its... the list is endless!

But, back to the thread... it's refreshing to see that more than a few list
members know that a dummy load is purely resistive, while a duplexer cavity
is reactive- explaining why a transmitter that works perfectly when feeding
a dummy load can be unstable when connected to a duplexer.  This discussion
is both informative and quite entertaining!

73, Eric Lemmon WB6FLY
 

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin Custer
Sent: Saturday, August 14, 2010 10:15 AM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Coax length, etc.

 Kevin Custer wrote: 

Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II
repeater and gets 50 watts out the antenna port.  He does his homework and
realizes that he should only be loosing 29% 

Wow - loosing -  that should have been losing - that's what I get for being
in a hurry

Re: [Repeater-Builder] Re: Wanted - UHF Amplifier

[NORM KNAPP]

DB-420's are about as good as they get. I like the big blue Telewave's, but so 
does lightening if you are on top of the tower.

- Original Message -
From: Repeater-Builder@yahoogroups.com 
To: Repeater-Builder@yahoogroups.com 
Sent: Sat Aug 14 09:02:42 2010
Subject: [Repeater-Builder] Re: Wanted - UHF Amplifier

  

Larry:

I am using a version 2 TKR 850 with an Angle Linear GAas Fet Pre-amp with a 
bandpass cavity. Exc results without desense. The preamp is before the cavity.

As I agree with the other writers, you will need to retune the receiver for 
optimum performance.

Invest in a Good Commercial Antenna is key. Don't waste your money on a Ham 
Antenna as I learned not too long ago. Huge difference in performance!

Good Luck!

Artie
k2aau

--- In Repeater-Builder@yahoogroups.com 
 ,  wrote:
>
> Larry,
> 
> 
> 
> Last week there was someone trying to sell several Henry UHF amps on the
> list. You may want to check your email box.
> 
> 
> 
> 
> 
> Mike Mullarkey K7PFJ
> 
> 6886 Sage Ave
> 
> Firestone, Co 80504
> 
> 303-736-9693 
> 
> 
> 
> 
> 
> _ 
> 
> From: Repeater-Builder@yahoogroups.com 
>  
> [mailto:Repeater-Builder@yahoogroups.com 
>  ] On Behalf Of Larry Watkinson
> Sent: Monday, July 19, 2010 12:11 PM
> To: Repeater-Builder@yahoogroups.com 
>  
> Subject: [Repeater-Builder] Wanted - UHF Amplifier
> 
> 
> 
> 
> 
> K5In and I are looking for a couple of UHF Amplifier's that will have 10 to
> 25 watts in and 70 to 100 watts out. We would prefer n-connectors but will
> accept other connectors.
> 
> Thanks,
> 
> Larry KC7CKO
>

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Kevin Custer wrote:
I had one instance of a ham radio club loosing PA's left and right on 
their 2M machine.


Indeed - I am loosing my mind - 

K

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Kevin Custer wrote:


Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II 
repeater and gets 50 watts out the antenna port.  He does his homework 
and realizes that he should only be loosing 29%


Wow -* loosing -*  that should have been losing - that's what I get for 
being in a hurry

RE: [Repeater-Builder] Re: Coax length, etc. GE Z-Matcher

[Ross Johnson]

HOLY CRAP I've been wondering that for some time. Guess the "manual"
isn't always right. and maybe that's why the GE Z-match is there for the
recruiting of true GE tuners.. Never-mind keeping your PA happy at 100%
DC. I always wanted to ask but never did (for thought of flames from the
GE manual) because I thought I heard somewhere that tuning procedure
wasn't ideal for most cavity/duplexer applications (on this list in a
unrelated post) so investigated. Now I always settled for the best low
ratio of the two. PA current/TP1 from z-match. You'll see that the
relationship of the two is not even close to linear. What I've found is
you basically want to try to be on the edge of both curves knee's.. I
think I have the right idea, for a 50mV gain from the TP1 z-match null I
could drop PA current by 2500mA. And this was until now (a month ago)
that I finally have a good HP8924 SM to help take the guess work out.
Plus your PA and TX cavity temps go way down. Just glad to hear I was
probably doing the right thing. Also I always did the final 1st 2nd pass
cavity tuning this way. Retuning cavities for highest output power with
least current vs. low TP1 on z-match. One tuning session on a friends
machine with this method dropped TX cavity temps by more then 10deg to
almost ambient temp while dropping PA temp, and current by 2 amps with
no drop in output power or RX sense. This probably means the match in
the cavity coupling or cabling was off but hey that PA will live longer.
If I'm wrong or missing something here, let me know.
 
73's groupies
Ross www.kc7rjk.net    
 
-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of larynl2
Sent: Saturday, August 14, 2010 8:17 AM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Coax length, etc. GE Z-Matcher
 
  


--- In Repeater-Builder@yahoogroups.com
 , "Jeff DePolo" 
wrote:

> 
> c) Although not explictly described in GE's tuning procedures,
significant
> improvement in efficiency can be obtained with proper tuning of the
> Z-matcher. Tuning for 50+j0 at the input to the Z-matcher is NOT
> necessarily the RIGHT match!

Right, GE's instructions on tuning the Z-Matcher in their base stations
are not correct. Instructions should instead describe a procedure that
reduces current draw of the amplifier while simultaneously maintaining
or increasing the output power.

> 
> d) To charge more. I'm half-joking on this; I can't say I've
statistically
> seen more or less failures on M2 PA's with or without the Z-matcher,
so I'll
> give this answer half a smiley: .-,

If the failures you've seen are in amps with Z-Matchers that were tuned
following GE's Z-Matcher instructions, that *could* explain why you've
given half a smiley... :-)

Laryn K8TVZ

Re: [Repeater-Builder] Coax length, etc.

[Kevin Custer]

Jeff DePolo wrote:
Because the impedance is not matched between the transmitter 
and duplexer, the 'apparent' loss of the duplexer is greater 
than the manufacturers stated loss of the duplexer.  Changing 
the cable length is not changing the loss of the duplexer, 
it's changing the power that is accepted at the transmitter 
port of the duplexer by matching the output impedance of the 
transmitter to the input impedance of the transmitter port of 
the duplexer.



But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying
the cable length isn't going to change the Z seen by the transmitter.  Or
are you suggesting the duplexer is purposely de-tuned from 50 ohms?
  


Purposely, accidentally, by lack of good design - people not having the 
right equipment to tune it correctly - whatever.
  
	  And also that by varying the cable length between the 
transmitter and the duplexer that you can vary the reflected

power on that same line?


Yes.



With all due respect, that's not possible, regardless of what the Z is of
the duplexer.  The only time it could have an effect on the reflected power
would be if the transmitter/PA were spurious, and the amplitude/frequency of
the spurs changed with varying load Z, and I think we can both agree that if
that's the case, we have bigger fish to fry.
  


And this is where I believe the duplexer manufacturers are covering 
their butt.  They don't want the problem with complex reactance 
presented by the duplexer to be their problem.  Not that I don't agree, 
because it's usually the transmitter that is really at fault. 

Joe Ham buys a new duplexer and hooks it up to his 110 Watt MASTR II 
repeater and gets 50 watts out the antenna port.  He does his homework 
and realizes that he should only be loosing 29% with the 1.5 dB of 
insertion loss stated in the paperwork - but he's loosing over 50%.  The 
duplexer manufacturer supposedly engineered and tuned it for a 50 Ohm 
system.  He knows that the cable he connected to the transmitter is 
good, because when he disconnects the end going to the transmitter port 
of the duplexer and connects it to his Bird 43 terminated with a good 
load - it reads 110 watts.


Now, is the transmitter becoming spurious and the cable length being 
changed in length satisfies the match between the duplexer and 
transmitter - I don't know...   All I can tell you is I have followed 
the suggestions written in the WACOM manual and it has worked.  I had 
one instance of a ham radio club loosing PA's left and right on their 2M 
machine.  They told me of the situation and I offered to do a little 
testing.  The 110 watt PA would put out 110 watts into a Bird and dummy, 
but only 45 watts was coming out the antenna port of the duplexer.  At 
the time I didn't own a spectrum analyzer.  The repeater wouldn't duplex 
without desense.  I changed the length of the line between the PA and 
duplexer until I got the power to read about 75 Watts as I remember.  
That was 13 years and they still have the same PA - no desense either.




Not to belabor the point, but whatever the VSWR is on a length of
transmission line, that's the VSWR that's on the line *regardless of
length*.  You can't change the VSWR by changing the length of the line.  As
you vary the length, you go round n' round the Smith Chart in a constant
VSWR circle, with the Z repeating cyclicly every half-wavelength, but you've
still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the end
of whatever length of line you choose (cable loss effects notwithstanding).
There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut
the line to any random length and you'll hit one of them.

  
In a situation where the duplexer and transmitter have 
differing impedances, and a cable optimized in length matches 
these impedances, the mismatch at the duplexer is minimized, 
therefore the power reflected by the duplexer is minimized.  



I think what you're really saying is that the mismatch at the *input to the
matching section* (i.e. the cable between the PA and the duplexer), NOT the
mismatch at the duplexer, is minimized.


Sorry - that is what I meant to say.  Many of us use converted 
commercial gear in the ham band.  Many don't take the time to properly 
convert the receiver and especially the transmitter to properly operate 
in the adjacent ham band.  So, when you run a 150.8 to 174 MHz amplifier 
in the 2M ham band or a 450 to 470 MHz amplifier in the UHF ham band is 
it going to represent a good 50 Ohm impedance?  Likely not...


We need to realize that most duplexer manufacturers know what they are 
doing and their products are presenting a 50 ohm match on its intended 
frequencies - unless somebody has adjusted on it.  But, because the 
duplexer is not a perfect load, it creates reactance and the 
transmitter/PA may not like it.  If it doesn't like it, it may become 
spurious.  If it becomes spurious, it isn't putting out all of its power 

[Repeater-Builder] Re: unsubscribe (reading yahoo group posts - a butter way - no popcorn)

[skipp025]

You guys are silly... 

Consider changing your group settings to "read on the web" 
using a web browser. Then... simply locate the group with 
your web browser bookmark anytime you want to read the group 
posts. 

No flood of inbound Emails for each post or large digest 
Emails required. Probably drive one to drink (more) if they 
were subscribed to more than 3 or 4 Groups at one time. 

Having a yahoo email address automatically signs me into 
all the groups for which I am subscribed.  To read this,
the Repeater Builder Group I simply click on the below 
Bookmark saved in my Web Browser. Once you change your 
settings to web only (I prefer the "traditional" or "classic 
view") try the below url and enjoy life again. 

http://groups.yahoo.com/group/Repeater-Builder/messages 

If you don't use Yahoo Mail, you might be asked to sign in 
at the start of your web browsing session, but once you're 
in, you are in for all the groups for which you subscribe. 

cheers,
s. 

ps: If you're subscribed to more than one group, here's the 
page that helps you get your book marks set up. 

http://groups.yahoo.com/mygroups 

Now resume normal programming. 

> Your best bet is to setup your email to receive each post in "digest" form 
> meaning once a day on average you will receive a bunch of postings in just 
> one email into your inbox. When you get around to opening up your inbox you 
> can just scroll through each individual posting, read the ones that interest 
> you and when finished, hit the delete key and they all go away!!!  Seeing 
> 15-30 separate, individual emails in my inbox during the course of one day is 
> a bit too much. Try it, you'll like it OM!!73
> 
> --- In Repeater-Builder@yahoogroups.com, "Jim in Waco WB5OXQ"  wrote:
> >
> > I do not need to read these anymore.  I am not mad just getting too many 
> > emails.
> >
>

[Repeater-Builder] Re: Coax length, etc. GE Z-Matcher

[larynl2]

--- In Repeater-Builder@yahoogroups.com, "Jeff DePolo"  wrote:

> 
> c) Although not explictly described in GE's tuning procedures, significant
> improvement in efficiency can be obtained with proper tuning of the
> Z-matcher.  Tuning for 50+j0 at the input to the Z-matcher is NOT
> necessarily the RIGHT match!

Right, GE's instructions on tuning the Z-Matcher in their base stations are not 
correct.  Instructions should instead describe a procedure that reduces current 
draw of the amplifier while simultaneously maintaining or increasing the output 
power.

> 
> d) To charge more.  I'm half-joking on this; I can't say I've statistically
> seen more or less failures on M2 PA's with or without the Z-matcher, so I'll
> give this answer half a smiley:   .-,

If the failures you've seen are in amps with Z-Matchers that were tuned 
following GE's Z-Matcher instructions, that *could* explain why you've given 
half a smiley...  :-)

Laryn K8TVZ

 

[Repeater-Builder] Re: HYT Repeater vs. Trbo Repeater

[skipp025]

Hi Artie, 

Regardless of what make and model repeater equipment you 
choose, be sure to actually check the receiver discriminator 
output performance. I traced problems in a system running 
LTR and DCS Data back to one model of lower priced desktop 
repeater receiver. (also known as a two mobiles made into 
a repeater). 

The receiver discriminator output was just horrible for 
any type of data output. 

I replaced the low cost receiver (the entire repeater 
actually) with a Kenwood TKR-850 (I sold them) and their 
LTR/DCS system now works mucho great.  

CTCSS operation is relatively easy to implement but reliable 
data requires a faithful receiver discriminator output. Or 
make sure you have the ability to return the equipment if it 
doesn't pass the technical muster (requirements)

cheers, 
skipp 


>"k2aau"  wrote:
>
> Has anyone done any comparison testing between the HYT 
> Repeater and The Motorola Trbo repeater?  I am particulary 
> interested in making a future purchase of either one.  I 
> have read about the IPsec concerns and that to me is really 
> not an issue.  I am sure that HYT will address that concern 
> as time goes forward.
> 
> From what I have been told, the Trbo consists of 2 mobile 
> radios used for receive and the other for transmit.  Whereas, 
> HYT is one radio with a Duplexed receiver and transmitter 
> well isolated from each other.
> 
> It is also my understanding that the company HYT's vendors 
> are more user friendly in pricing and support compared to 
> Motorola when it comes to accessories, firmware updates 
> and programming.
> 
> Thanks in advance for any information.
> Artie
> k2aau
>

[Repeater-Builder] Re: unsubscribe

[Doug]

Your best bet is to setup your email to receive each post in "digest" form 
meaning once a day on average you will receive a bunch of postings in just one 
email into your inbox. When you get around to opening up your inbox you can 
just scroll through each individual posting, read the ones that interest you 
and when finished, hit the delete key and they all go away!!!  Seeing 15-30 
separate, individual emails in my inbox during the course of one day is a bit 
too much. Try it, you'll like it OM!!73

--- In Repeater-Builder@yahoogroups.com, "Jim in Waco WB5OXQ"  
wrote:
>
> I do not need to read these anymore.  I am not mad just getting too many 
> emails.
>

[Repeater-Builder] Re: Wanted - UHF Amplifier

[k2aau]

Larry:

I am using a version 2 TKR 850 with an Angle Linear GAas Fet Pre-amp with a 
bandpass cavity.  Exc results without desense.  The preamp is before the cavity.

As I agree with the other writers, you will need to retune the receiver for 
optimum performance.

Invest in a Good Commercial Antenna is key.  Don't waste your money on a Ham 
Antenna as I learned not too long ago.  Huge difference in performance!

Good Luck!

Artie
k2aau

--- In Repeater-Builder@yahoogroups.com,  wrote:
>
> Larry,
> 
>  
> 
> Last week there was someone trying to sell several Henry UHF amps on the
> list. You may want to check your email box.
> 
>  
> 
>  
> 
> Mike Mullarkey K7PFJ
> 
> 6886 Sage Ave
> 
> Firestone, Co 80504
> 
> 303-736-9693 
> 
>  
> 
>  
> 
>   _  
> 
> From: Repeater-Builder@yahoogroups.com
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Larry Watkinson
> Sent: Monday, July 19, 2010 12:11 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Wanted - UHF Amplifier
> 
>  
> 
>   
> 
> K5In and I are looking for a couple of UHF Amplifier's that will have 10 to
> 25 watts in and 70 to 100 watts out. We would prefer n-connectors but will
> accept other connectors.
> 
> Thanks,
> 
> Larry KC7CKO
>

Re: [Repeater-Builder] Re: Sorry everyone

[Dave E Stephens Sr]

oh i know that it wasnt sent from any of the computers that the YL or myself 
use nor was it sent through the local networks both here and at my house. i am 
of the belief that both of us were fished while on the laptop i bought for mom. 
i thought i installed spybot S&D but i guess not. as soon as i can get her off 
of Farmville for a few minutes i will fix that. 
 
thanks again everyone. 
 
Dave E Stephens Sr
KF6WJA
Grants Pass Or

--- On Fri, 8/13/10, Bob - AF6D  wrote:


From: Bob - AF6D 
Subject: [Repeater-Builder] Re: Sorry everyone
To: Repeater-Builder@yahoogroups.com
Date: Friday, August 13, 2010, 4:51 PM


  



I haven't read all of the relies on this, but I also haven't read that there is 
proof that your computer actually sent the messages. All that is needed is your 
email address int he reply-to field in the message header and you get the 
blame. I own and operate a mid-sized web hosting company and we deal with spam 
issues daily. Recipients running anti-spam software that rejects and sends back 
to the real sender actually end up causing backscatter and getting their own IP 
blacklisted. SPAM will never end...

--- In Repeater-Builder@yahoogroups.com, Dave E Stephens Sr  wrote:
>
> i would like to thank all of you for understanding. right after i sent out my 
> original appology i figured out which computer might be sending the cause of 
> this. not long ago i got mom a new HP laptop. She wanted a computer just so 
> she could play a few games. well mom is what i call a techno-tard (didnt even 
> know how to turn it on). Before i knew it, her friend got her on facebook 
> playing farmville and who knows what. Its the WHO KNOWS WHAT that i am 
> worried about. 
>  
> not long ago the YL was over there on the computer, checking her email. next 
> day i discovered her account sent out a similar email to what mine sent. i 
> used it the day before yesterday and BAM, i discover the same email sent out. 
>  
> There is no evidence of a message being sent in my sent box here on Yahoo BUT 
> i got 2 replys saying they couldnt be delivered. 
>  
> I was going to fix the issue yesterday but i got busy. AVG and Spybot S&D 
> will be installed a little later on today. 
>  
> You know, its funny... i spend 8 to 12 hours a day, 6 to 7 days a week, 
> dealing with this issue and others like that. For 16 years i have never had 
> an account of mine hit till now. i am supprised it didnt hit sooner. 
>  
> Thanks again everyone for understanding... 73's
>  
> Dave Stephens Sr
> KF6WJA
> Grants Pass Or
>  
>  
>  
> 
> --- On Thu, 8/12/10, Mark Tomany  wrote:
> 
> 
> From: Mark Tomany 
> Subject: Re: [Repeater-Builder] Sorry everyone
> To: Repeater-Builder@yahoogroups.com
> Date: Thursday, August 12, 2010, 6:51 AM
> 
> 
>   
> 
> 
> 
> 
> 
> 
> 
> 
> AVG Free anti-virus software also has a built-in spyware removal tool.  I 
> also use the ones George captioned below - and even I get bit every once in a 
> while by some new bug.
>  
> It's amazing that so many people have the time on their hands to be able to 
> propagate all this crap...
>  
> Mark - N9WYS
> 
> --- On Wed, 8/11/10, George Henry wrote:
> 
> Nonsense!  Spybot Search & Destroy, Ad-Aware, Malwarebytes Anti-Malware, and 
> SuperAntiSpyware are all EXCELLENT free anti-spyware programs.  I routinely 
> use all 4 of them to clean up infections for people.  No spyware in ANY of 
> them and, between the four programs, I have yet to run into something I 
> couldn't clean.
> 
> 
> George, KA3HSW / WQGJ413 
> 
> - Original Message - 
> From: "Tim Sawyer"
> 
> >Was your machine on while you were away? If so you may have gotten a virus 
> >or spyware. Sounds like your wife got it too. Spamers like to >infect 
> >machines just to get control of them for sending spam. The really bad news 
> >is that most free spyware removal software is spyware itself. A >really 
> >good PC guy might be able to remove it. Good luck man!
> >--
> >Tim
>









  

Re: [Repeater-Builder] unsubscribe

[Frank C.]

I think that stands out :D

Regards,

-Frank C.

On Aug 13, 2010, at 9:26 PM, Kenneth Cook wrote:

> 
> This is an experiment to see if I could make the link stand out. This is NOT 
> to start problems!
> 
>  
> 
> 73…de Ken Cook, W8DZN
> 
>  
> 
> Switch to: Text-Only, Daily Digest • Unsubscribe • Terms of Use
> 
> .
> 
> 
> 
> 
> 
> 

[Repeater-Builder] Re: Wanted - UHF Amplifier

[k2aau]

Larry:

I am using a version 2 TKR 850 with an Angle Linear GAas Fet Pre-amp with a 
bandpass cavity.  Exc results without desense.  The preamp is before the cavity.

As I agree with the other writers, you will need to retune the receiver for 
optimum performance.

Invest in a Good Commercial Antenna is key.  Don't waste your money on a Ham 
Antenna as I learned not too long ago.  Huge difference in performance!

Good Luck!

Artie
k2aau

--- In Repeater-Builder@yahoogroups.com,  wrote:
>
> Larry,
> 
>  
> 
> Last week there was someone trying to sell several Henry UHF amps on the
> list. You may want to check your email box.
> 
>  
> 
>  
> 
> Mike Mullarkey K7PFJ
> 
> 6886 Sage Ave
> 
> Firestone, Co 80504
> 
> 303-736-9693 
> 
>  
> 
>  
> 
>   _  
> 
> From: Repeater-Builder@yahoogroups.com
> [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Larry Watkinson
> Sent: Monday, July 19, 2010 12:11 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Wanted - UHF Amplifier
> 
>  
> 
>   
> 
> K5In and I are looking for a couple of UHF Amplifier's that will have 10 to
> 25 watts in and 70 to 100 watts out. We would prefer n-connectors but will
> accept other connectors.
> 
> Thanks,
> 
> Larry KC7CKO
>

[Repeater-Builder] HYT Repeater vs. Trbo Repeater

[k2aau]

Has anyone done any comparison testing between the HYT Repeater and The 
Motorola Trbo repeater?  I am particulary interested in making a future 
purchase of either one.  I have read about the IPsec concerns and that to me is 
really not an issue.  I am sure that HYT will address that concern as time goes 
forward.

>From what I have been told, the Trbo consists of 2 mobile radios used for 
>receive and the other for transmit.  Whereas, HYT is one radio with a Duplexed 
>receiver and transmitter well isolated from each other.

It is also my understanding that the company HYT's vendors are more user 
friendly in pricing and support compared to Motorola when it comes to 
accessories, firmware updates and programming.

Thanks in advance for any information.

Artie
k2aau

RE: [Repeater-Builder] unsubscribe

[Kenneth Cook]

It appears to work too. I have to be honest it is very hard to see it at the
bottom of the messages. Maybe that could help it some to find it.

 

Kenneth Cook, W8DZN

 

  _  

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Richard
Sent: Saturday, August 14, 2010 12:35 AM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] unsubscribe

 

  

Well, I think it's funny.

 

Richard, N7TGB
www.n7tgb.net
The problem with socialism is that eventually you run out of other people's
money
--Margaret Thatcher

 

 

  _  

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kenneth Cook
Sent: Friday, August 13, 2010 9:27 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] unsubscribe

  

 

This is an experiment to see if I could make the link stand out. This is NOT
to start problems!

73.de Ken Cook, W8DZN

 

Yahoo! Groups

Switch to:
 Text-Only,
 Daily Digest .

Unsubscribe .   Terms of Use

.

 
 

Re: [Repeater-Builder] Coax length, etc.

[Joe]

  On 8/14/2010 8:44 AM, Jeff DePolo wrote:
> But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying
> the cable length isn't going to change the Z seen by the transmitter.  Or
> are you suggesting the duplexer is purposely de-tuned from 50 ohms?
I use a Network Analyzer to tune duplexers.  Although I can usually get 
an impedance of 50 ohms, many times the L or C reactance is not 
perfect.  Maybe the transmitter is responding more to the reactance 
mismatch rather than the impedance mismatch.

This area of RF black magic very quickly gets me lost in the ether.

73, Joe, k1ike

Re: [Repeater-Builder] Coax length, etc.

[Chuck Kelsey]

FWIW,

TX/RX Systems talks about "adverse length" cable between the transmitter and 
the duplexer in their technical papers.

Chuck
WB2EDV



- Original Message - 
From: "Jeff DePolo" 
To: 
Sent: Saturday, August 14, 2010 8:44 AM
Subject: RE: [Repeater-Builder] Coax length, etc.


>> Because the impedance is not matched between the transmitter
>> and duplexer, the 'apparent' loss of the duplexer is greater
>> than the manufacturers stated loss of the duplexer.  Changing
>> the cable length is not changing the loss of the duplexer,
>> it's changing the power that is accepted at the transmitter
>> port of the duplexer by matching the output impedance of the
>> transmitter to the input impedance of the transmitter port of
>> the duplexer.
>
> But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying
> the cable length isn't going to change the Z seen by the transmitter.  Or
> are you suggesting the duplexer is purposely de-tuned from 50 ohms?
>
>>   And also that by varying the cable length between the
>> transmitter and the duplexer that you can vary the reflected
>> power on that same line?
>>
>>
>> Yes.
>
> With all due respect, that's not possible, regardless of what the Z is of
> the duplexer.  The only time it could have an effect on the reflected 
> power
> would be if the transmitter/PA were spurious, and the amplitude/frequency 
> of
> the spurs changed with varying load Z, and I think we can both agree that 
> if
> that's the case, we have bigger fish to fry.
>
> Not to belabor the point, but whatever the VSWR is on a length of
> transmission line, that's the VSWR that's on the line *regardless of
> length*.  You can't change the VSWR by changing the length of the line. 
> As
> you vary the length, you go round n' round the Smith Chart in a constant
> VSWR circle, with the Z repeating cyclicly every half-wavelength, but 
> you've
> still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the 
> end
> of whatever length of line you choose (cable loss effects 
> notwithstanding).
> There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut
> the line to any random length and you'll hit one of them.
>
>> In a situation where the duplexer and transmitter have
>> differing impedances, and a cable optimized in length matches
>> these impedances, the mismatch at the duplexer is minimized,
>> therefore the power reflected by the duplexer is minimized.
>
> I think what you're really saying is that the mismatch at the *input to 
> the
> matching section* (i.e. the cable between the PA and the duplexer), NOT 
> the
> mismatch at the duplexer, is minimized.  The duplexer's input Z isn't
> changing; you can't change that unless you re-tune the cavities or change
> the load at the antenna port.  Whether or that the transmitter
> likes/dislikes the different Z it sees as you change cable lengths is, I
> guess, what's up for debate...
>
>> I have found that when you get a transmitter that is 'picky'
>> about the length of interconnecting cable, power being read
>> at the output port of the duplexer is low and you cannot
>> alter the tuning of the cavity closest to the transmitter to
>> make things right.  In other words, the place where lowest
>> VSWR and maximum power transfer occurs is at two completely
>> different places, and power transfer is not up where it
>> should be (transmitter makes 100 watts into a dummy load but
>> only shows 50 watts on the output port of the duplexer that
>> has a stated 1.5 dB loss (29 %)).
>
> That would imply that either duplexer is presenting a load Z substantially
> far removed from 50+j0, OR the transmitter doesn't like a 50 ohm load, or
> something inbetween, would it not?
>
>> As you get close to the
>> 'optimum' cable length, the lowest VSWR and maximum power
>> transfer occur near the same place when tuning the cavity
>> closest to the transmitter.
>
> But again, *you're NOT changing the VSWR*!  You can't change the VSWR by
> varying the length of the line!  I just want to make sure we're on the 
> same
> page - the VSWR on a transmission line doesn't vary with length (loss
> notwithstanding).
>
>> I usually pay more attention to what is coming out the
>> antenna port of the duplexer - first.  Then, when things are
>> right, comparing forward power going to the duplexer and
>> power going to a good dummy load will be very close the same,
>> since matching the impedance of the transmitter to the
>> impedance of the duplexer was accomplished by some means.
>
> Can you give me some real-world examples of what combinations of duplexers
> and transmitters you've run across that just didn't want to "play nice"
> without having to resort to changing cable lengths?  Like a highband Micor
> 110 watt H split paired with a Q2220E or whatever.  I'm just curious if 
> I've
> done any of the same combinations.
>
> I think you know me well enough by now Kevin that I'm not looking to pick 
> a
> fight, I'm just a hard-ass when it comes to

RE: [Repeater-Builder] Coax length, etc.

[Jeff DePolo]

> Because the impedance is not matched between the transmitter 
> and duplexer, the 'apparent' loss of the duplexer is greater 
> than the manufacturers stated loss of the duplexer.  Changing 
> the cable length is not changing the loss of the duplexer, 
> it's changing the power that is accepted at the transmitter 
> port of the duplexer by matching the output impedance of the 
> transmitter to the input impedance of the transmitter port of 
> the duplexer.

But if the duplexer is tuned to 50 ohms, and the cable is 50 ohms, varying
the cable length isn't going to change the Z seen by the transmitter.  Or
are you suggesting the duplexer is purposely de-tuned from 50 ohms?

> And also that by varying the cable length between the 
> transmitter and the duplexer that you can vary the reflected
>   power on that same line?
> 
> 
> Yes.

With all due respect, that's not possible, regardless of what the Z is of
the duplexer.  The only time it could have an effect on the reflected power
would be if the transmitter/PA were spurious, and the amplitude/frequency of
the spurs changed with varying load Z, and I think we can both agree that if
that's the case, we have bigger fish to fry.

Not to belabor the point, but whatever the VSWR is on a length of
transmission line, that's the VSWR that's on the line *regardless of
length*.  You can't change the VSWR by changing the length of the line.  As
you vary the length, you go round n' round the Smith Chart in a constant
VSWR circle, with the Z repeating cyclicly every half-wavelength, but you've
still got a complex Z that nets a 1:5:1 VSWR relative to 50 ohms at the end
of whatever length of line you choose (cable loss effects notwithstanding).
There are an infinite number of complex Z's that yield a 1.5:1 VSWR - cut
the line to any random length and you'll hit one of them.

> In a situation where the duplexer and transmitter have 
> differing impedances, and a cable optimized in length matches 
> these impedances, the mismatch at the duplexer is minimized, 
> therefore the power reflected by the duplexer is minimized.  

I think what you're really saying is that the mismatch at the *input to the
matching section* (i.e. the cable between the PA and the duplexer), NOT the
mismatch at the duplexer, is minimized.  The duplexer's input Z isn't
changing; you can't change that unless you re-tune the cavities or change
the load at the antenna port.  Whether or that the transmitter
likes/dislikes the different Z it sees as you change cable lengths is, I
guess, what's up for debate...

> I have found that when you get a transmitter that is 'picky' 
> about the length of interconnecting cable, power being read 
> at the output port of the duplexer is low and you cannot 
> alter the tuning of the cavity closest to the transmitter to 
> make things right.  In other words, the place where lowest 
> VSWR and maximum power transfer occurs is at two completely 
> different places, and power transfer is not up where it 
> should be (transmitter makes 100 watts into a dummy load but 
> only shows 50 watts on the output port of the duplexer that 
> has a stated 1.5 dB loss (29 %)).  

That would imply that either duplexer is presenting a load Z substantially
far removed from 50+j0, OR the transmitter doesn't like a 50 ohm load, or
something inbetween, would it not?

> As you get close to the 
> 'optimum' cable length, the lowest VSWR and maximum power 
> transfer occur near the same place when tuning the cavity 
> closest to the transmitter.

But again, *you're NOT changing the VSWR*!  You can't change the VSWR by
varying the length of the line!  I just want to make sure we're on the same
page - the VSWR on a transmission line doesn't vary with length (loss
notwithstanding).
 
> I usually pay more attention to what is coming out the 
> antenna port of the duplexer - first.  Then, when things are 
> right, comparing forward power going to the duplexer and 
> power going to a good dummy load will be very close the same, 
> since matching the impedance of the transmitter to the 
> impedance of the duplexer was accomplished by some means.

Can you give me some real-world examples of what combinations of duplexers
and transmitters you've run across that just didn't want to "play nice"
without having to resort to changing cable lengths?  Like a highband Micor
110 watt H split paired with a Q2220E or whatever.  I'm just curious if I've
done any of the same combinations.

I think you know me well enough by now Kevin that I'm not looking to pick a
fight, I'm just a hard-ass when it comes to basing technique on solid
engineering foundation.  I can't say I've ever had to play with cable
lengths to either get a transmitter/PA to make rated power, or to get the
"apparent" loss of a duplexer to meet spec.  Have I just been lucky?  Maybe.
But if I'm *that* lucky, I'm in the wrong business, I shouldn't be sitting a
hotel room in Harrisburg on a Saturday waiting for a tower crew to show up,
I sh

Re: [Repeater-Builder] Strange noise on our club repeater

[Chuck Kelsey]

Sounds like intermod involving your repeater's transmitter as part of the 
mix.

Chuck
WB2EDV


- Original Message - 
From: "Robert" 
To: 
Sent: Saturday, August 14, 2010 7:32 AM
Subject: [Repeater-Builder] Strange noise on our club repeater


> We have a MSR2000 for our club repeater. Every so often on a weak signal 
> we get a noise that sounds like...well you know when you go to the dentist 
> and get your teeth cleaned. The little tube that they put in your mouth 
> and sucks all the spit out.  Wel... that is on the tail of some 
> signals, sometimes. (sorry for the gross analogy ;-) This only happens a 
> few times a day and not often on a stronger signal.  When the user unkeys, 
> it will have the "sucking sound" for a second or sometimes a few 
> seconds...then the squelch closes.  The user has unkeyed...but the 
> repeater stays keyed up with the noise.  We know that there are some 
> strong signals near by the input.  Also with the input at 144.61... 
> there is a DStar repeater with a input of 144.60 up the road by 30 miles 
> or so.  Also... we have pretty fair amount of APRS traffic in the area 
> (digi about 8 miles away).
>
> Ideas?
> Robert
> KD4YDC
>

[Repeater-Builder] Strange noise on our club repeater

[Robert]

We have a MSR2000 for our club repeater. Every so often on a weak signal we get 
a noise that sounds like...well you know when you go to the dentist and get 
your teeth cleaned. The little tube that they put in your mouth and sucks all 
the spit out.  Wel... that is on the tail of some signals, sometimes. 
(sorry for the gross analogy ;-) This only happens a few times a day and not 
often on a stronger signal.  When the user unkeys, it will have the "sucking 
sound" for a second or sometimes a few seconds...then the squelch closes.  The 
user has unkeyed...but the repeater stays keyed up with the noise.  We know 
that there are some strong signals near by the input.  Also with the input 
at 144.61... there is a DStar repeater with a input of 144.60 up the road by 30 
miles or so.  Also... we have pretty fair amount of APRS traffic in the area 
(digi about 8 miles away).

Ideas?
Robert 
KD4YDC