[Repeater-Builder] Lon and Lat Locator

[Don KA9QJG]

Hello Hope Everyone is doing well,. Can anyone tell Me if thee is a Program
on the WWW Like Goggle Earth that will let you just put in a Known Lat and
Lon and display the Location, Goggle and others I have found will show You
that info on the Pointer Location but You already know the area You are
looking in. The reason is I have a Ham Friend in Rural Arkansas who has a
PO Box for a Address , He used a Program to sent Me a Sat photo of His
QTH , But I know for a fact I have seen better on Goggle Earth .

Thanks

Don KA9QJG

[Repeater-Builder] Re: Coax length between added cavity and duplexer - test r...

[nj902]

--- In Repeater-Builder@yahoogroups.com, "Jeff DePolo" <[EMAIL PROTECTED]> 
wrote:
"I'm caught in a time warp in Philadelphia."



Time is still unstable there 64 years later?

[Repeater-Builder] Re: Interference from Public-Safety Station (Was: Coax Length...)

[Laryn Lohman]

--- In Repeater-Builder@yahoogroups.com, "Eric Lemmon" <[EMAIL PROTECTED]> 
wrote:
>
> Nate,
> 
> Was the interference present before the duplexer was retuned?  If
not, then
> I suspect that the tuning is not correct. 

I definitely agree with that possibility. 

Another to ponder--  after tuning the duplexer, the system sensitivity
has increased to the point that it can now hear something that was
always there, hence the problem...

Laryn K8TVZ

Re: [Repeater-Builder] Lloyd is Well was Cable Lengths

[cruising7388]

 
Jeff
 
No question about that - cable lengths between the duplexer cavities is  
critical and just as critical
are the lengths between the duplexer and the Tee that feeds the antenna. 
 
Your test equipment is unquestionably more sophisticated than my tracker  but 
I wonder about the figure you recorded for the BP BR pass attenuation at  
.0953. That seems awfully low. I would expect to see something in the  
whereabouts of .5 db.
 
While your pix indicates that the composite pass curve isn't significantly  
affected by the cable length from duplexer to pass cavity, they sure as hell  
show how significantly the reject curves are sensitive to cable length - one  
significantly and the other dramatically.
 
Because of the division scale you used you aren't displaying any changes  
that take place w-a-y out of band and Murphy's law being what it is, this might 
 
be significant in certain situations. It can get even more curious than the  
reject curves you display. For example, the 9 1/2" cable that Lloyd  initially 
scheduled between the duplexer and the pass cavity produced a slightly  
asymmetrical curve slightly steeper on the high side with a quasi-pass spike to 
 
-40db at 342.4 Mhz with little rise from the noise floor on the high side  
through 540Mhz. But when he lengthened this cable to 19 1/4", the low side  
quasi-pass spike shifted to 362.9 Mhz on the low side and a new -40 db  
quasi-pass 
high side spike appeared at 508.1 Mhz. Go figure.
 
I don't much care for right angle connecters either although I don't have  
any solid evidence to support it..
I much prefer in-line stretchers which permit more subtle changes. 
 
Bruce K7IJ
 
 
 
 
 
In a message dated 7/27/2007 6:00:59 P.M. Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

> According to Lloyd, the cable length between a duplexer and 
>  an inline 
> cavity filter and the receiver makes little or no  difference. 

Steve,

Was the question posed (or probably  misunderstood as being) whether the
cable length between the receiver and  the filter being critical, or the
cables between filter sections being  critical? If the latter, then I would
have to humbly disagree with the  answer, as theory and personal experience,
as well as the results of the  test earlier today, has been to the contrary.

---  Jeff








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Re: [Repeater-Builder] Lloyd is Well was Cable Lengths

[Steve S. Bosshard (NU5D)]

The question was a band pass filter between a receiver and a duplexer. 
First thing Lloyd said was lengths between cavities and the output TEE,
comprising a duplexer are extremely critical.  The original post cited a
working system with interference, hence a band pass filter between the
receiver and the duplexer, followed by questions concerning cable
lengths between the receiver and in line filter, and the inline filter
and the duplexer receive port.  The supposition being receiver overload
in the ham repeater coming from the 155? Mhz public safety system. 
Often a BPBR cavity may not reject signals 5 to 10 mhz from the pass
frequency but do a splendid job of rejecting signals 600 khz from the
pass frequency.

Your pdf is excellent and very well done.  Thanks for the great
presentation Jeff.

Best regards,

Steve NU5D


Jeff DePolo wrote:
>> According to Lloyd,  the cable length between a duplexer and 
>> an inline 
>> cavity filter and the receiver makes little or no difference.  
>> 
>
> Steve,
>
> Was the question posed (or probably misunderstood as being) whether the
> cable length between the receiver and the filter being critical, or the
> cables between filter sections being critical?  If the latter, then I would
> have to humbly disagree with the answer, as theory and personal experience,
> as well as the results of the test earlier today, has been to the contrary.
>
>   --- Jeff
>
>
>
>
>
>   

Re: [Repeater-Builder] Coax length between added cavity and duplexer - test results

[Chuck Kelsey]

"Cannot display the webpage" is what I get.

Chuck



- Original Message - 
From: "Jeff DePolo" <[EMAIL PROTECTED]>
To: 
Sent: Friday, July 27, 2007 12:54 PM
Subject: [Repeater-Builder] Coax length between added cavity and duplexer - 
test results


>
> I performed an experiment per previous discussion.  The results are
> available at:
>
> http://www.broadsci.com/900.pdf
>
> Apologies in advance for the terse verbage and any typos; I was trying to
> get it done quickly between "real work" projects.
>
> Feedback would be greatly appreciated.
>
> --- Jeff
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
> 

Re: [Repeater-Builder] Lloyd is Well was Cable Lengths

[Kris Kirby]

On Fri, 27 Jul 2007 [EMAIL PROTECTED] wrote:
> This simply doesn't square with the advice Lloyd gave me during the 
> eighties. For example, he personally set up three sets of VHF systems 
> for me.  Two of them were specials, i.e., the standard WP-642 duplexer 

Lloyd might know better now. :)

--
Kris Kirby, KE4AHR  <[EMAIL PROTECTED]>
* WAR IS PEACE *  FREEDOM IS SLAVERY *
* IGNORANCE IS STRENGTH * KETCHUP IS *
  * A VEGETABLE *

Re: [Repeater-Builder] Coax length between added cavity and duplexer - test r...

[cruising7388]

 
Understood. But take comfort. You're not alone. Report is that everybody in  
Philadelphia is warped.
 
In a message dated 7/27/2007 6:05:10 P.M. Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

>  Just a dynamite presentation. Thanks for the effort. BTW, 
> where are  you (The analysis is dated July 29)

I'm caught in a time warp in  Philadelphia.







** Get a sneak peek of the all-new AOL at 
http://discover.aol.com/memed/aolcom30tour

RE: [Repeater-Builder] Coax length between added cavity and duplexer - test r...

[Jeff DePolo]

> Just a dynamite presentation. Thanks for the effort. BTW, 
> where are you (The analysis is dated July 29)

I'm caught in a time warp in Philadelphia.

RE: [Repeater-Builder] Lloyd is Well was Cable Lengths

[Jeff DePolo]

> According to Lloyd,  the cable length between a duplexer and 
> an inline 
> cavity filter and the receiver makes little or no difference.  

Steve,

Was the question posed (or probably misunderstood as being) whether the
cable length between the receiver and the filter being critical, or the
cables between filter sections being critical?  If the latter, then I would
have to humbly disagree with the answer, as theory and personal experience,
as well as the results of the test earlier today, has been to the contrary.

--- Jeff

[Repeater-Builder] Multi-coupler,how to connect them

[gervais]

hi

is there a diagramm somewhere to know how to connect a series of
multicoupler from sinclair,the vhf,i forgot the number.

it is call"chaine de multicouplage" but i dont know how say it in
english :-((( soryy

hey thanks for the help,

gervais ve2ckn

Re: [Repeater-Builder] Coax length between added cavity and duplexer - test r...

[George Henry]

Maybe his computer is running on UTC?


  - Original Message - 
  From: [EMAIL PROTECTED] 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Friday, July 27, 2007 5:16 PM
  Subject: Re: [Repeater-Builder] Coax length between added cavity and duplexer 
- test r...


  Jeff

  Just a dynamite presentation. Thanks for the effort. BTW, where are you 
(The analysis is dated July 29)


  Bruce K7IJ

Re: [Repeater-Builder] Coax length between added cavity and duplexer - test results

[George Henry]

Very nicely done, Jeff!  At least as good as some manufacturers' reports, 
and color too!

George


- Original Message - 
From: "Jeff DePolo" <[EMAIL PROTECTED]>
To: 
Sent: Friday, July 27, 2007 11:54 AM
Subject: [Repeater-Builder] Coax length between added cavity and duplexer - 
test results


>
> I performed an experiment per previous discussion.  The results are
> available at:
>
> http://www.broadsci.com/900.pdf
>
> Apologies in advance for the terse verbage and any typos; I was trying to
> get it done quickly between "real work" projects.
>
> Feedback would be greatly appreciated.
>
> --- Jeff
>

Re: [Repeater-Builder] Coax length between added cavity and duplexer - test r...

[cruising7388]

 
Jeff
 
Just a dynamite presentation. Thanks for the effort. BTW, where are you  
(The analysis is dated July 29)
 
 
Bruce K7IJ
 
 
 
In a message dated 7/27/2007 10:19:02 A.M. Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

I  performed an experiment per previous discussion. The results are
available  at:

_http://www.broadscihttp://wwhtt_ (http://www.broadsci.com/900.pdf) 

Apologies  in advance for the terse verbage and any typos; I was trying to
get it done  quickly between "real work" projects.

Feedback would be greatly  appreciated.

--- Jeff







** Get a sneak peek of the all-new AOL at 
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Re: [Repeater-Builder] Lloyd is Well was Cable Lengths

[DCFluX]

After just getting through turning a set of Aerial Facilities Limited
SC-220-2N Band Pass cans into a Band Pass Band Reject (tm) duplexer here is
what I am going to share from my
experiences.

The Science Behind It:

Please refere to US Patent #4080601

My Experiences:

Please refere to:
http://blog.myspace.com/index.cfm?fuseaction=blog.view&friendID=85474861&blogID=252104937
http://blog.myspace.com/index.cfm?fuseaction=blog.view&friendID=85474861&blogID=286228333
http://blog.myspace.com/index.cfm?fuseaction=blog.view&friendID=85474861&blogID=289106710

Inner cavity coax length is not critical when the cavity is in Band Pass
mode. Meaning when the can has two inductive coupling loops that work out to
be j0+50 ohms.

Length for inner cavity and the antenna tee becomes critical in BpBr or
reject mode. This will add 6dB of additional isolation if the cable is
sucsessfuly cut to be a electrical 1/4 wave or any odd multiple of 1/4
lambda, (3/4 etc.)

Velocity factor changes between the connectors and coax must be compensated
for. A 8.875" calculated 66% velocity factor cable becomes 9.125" when
connectors are on it.

Coupling loop design can be optimized when the loop is out of the can.
Adjust tuning cap to mid range and sweep loop with spectrum analyzer,
tracking generator and tee until notch appears at target frequency. My
dimensions were 1" by 1.125" square. Using 0.062" X 0.25" brass stock.

Loops work acceptably when not silver plated.

If you have rotatable loops, Rotate the coupling loop for optimum coupling
before final tuning. When viewed on spectrum analyzer this will be when the
distance between the notch and the pass is becomes maximum. Then procede
with fine tuning.

Cavities seem to exhibit approximently .25 to .3dB less loss each when
connected to the phasing harness. A Single cavity scanned at 1.1dB loss, 2
cavities measuered 1.43dB.

Johanson caps work fine for 220 and above. Check function of capacitor
before installing, I had one that had a broken ring and tuning was all over
the place and I could only get like 15dB of notch in some spots.

Something with better Q should be used for 2m and below, such as 1/4"
hardline or a variable di-electric capacitor such as the Wacom 'trombone'.

Now if I can get the rest of the repeater up and running we will be golden.

Re: [Repeater-Builder] Lloyd is Well was Cable Lengths

[cruising7388]

 
In a message dated 7/27/2007 11:16:58 A.M. Pacific Daylight Time,  
[EMAIL PROTECTED] writes:

According to Lloyd, the cable length between a duplexer and an inline  
cavity filter and the receiver makes little or no difference. 


 
 
This simply doesn't square with the advice Lloyd gave me during the  
eighties. For example, he personally set up three sets of VHF systems for me.  
Two of 
them were specials, i.e., the standard WP-642 duplexer plus an additional  8 
inch pure pass cavity on each side - a total of six bottles. Lloyd supplied  
all of the interconnects between the duplexer cans and also supplied the cables 
 
between the duplexer and the pass cavities. To minimize possible cable  
interaction I told Lloyd that I wanted to change the cable length between the  
duplexer and the pass cavities. He said, no, he wouldn't recommend that and 
that  
the cable was selected to provide optimum phasing of the duplexer and pass  
cavitity curves. And when I tried substituting a different cable length, the  
tracker indeed did show a different composite curve. I subsequently had Lloyd  
set up two UHF specials - the standard WP-678 plus WP-478 pure pass cans. Lloyd 
 specified the cable length between the duplexer and the pass cavity as 9 
1/2"  for the low pass and 9 1/4" for the high pass (not including N 
connectors. 
When  I told him that there was no way I could physically arrange the cans 
using this  cable length, he said, no problem, he would use a multiple and the 
cables that  came with the pass cavities were 20 1/4" for the low pass and 20" 
for the high  pass (including connectors).  
 
Now, if the cable length between the duplexer and the pass cavity was of  
little or no difference,  why would Lloyd would have suggested and provided  a 
half wave multiple length? Why wouldn't he have said "use any length that  
works 
for you"?
 
Bruce K7IJ



** Get a sneak peek of the all-new AOL at 
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Re: [Repeater-Builder] Re: Icom IC-FR4000-3

[DCFluX]

A bug in the software or op-amp latch up due to a polarized capacitor
being charged backwards.

On 7/27/07, Paul Finch <[EMAIL PROTECTED]> wrote:
> Hello,
>
> My customer's called the other day complaining that the system was out, they
> could hear the mobile key up but no audio was passed.  I did not have a HT
> with me at the time, I saw them key up and the repeater had power so I
> cycled the power.  I checked with them later trying to find the problem and
> they said it went back to work about the time I cycled power.
>
> Anyone know what's going on?
>
> Paul
>
>
> -Original Message-
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] On Behalf Of barrypal
> Sent: Thursday, July 26, 2007 10:50 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: [Repeater-Builder] Re: Icom IC-FR4000-3
>
> I just installed my FR4000 two weeks ago and have not noticed any
> audio problems yet.  The repeat audio is better then my Mastr II and
> the sensitivity and selectivity is great.  BUT, I can't seem to get
> the ID'er running the way I think it should.  It will id every time
> the repeater is keyed and or dropped out.  You can turn it off
> altogether or have it at some system interval 24/7..  I would like it
> to operate on key up and then every 10 and then on sign off with delay
> but can't seem to find it in the software...
>
> Barry k7pal
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.476 / Virus Database: 269.10.22/921 - Release Date: 7/26/2007
> 11:16 PM
>
>
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.5.476 / Virus Database: 269.10.22/921 - Release Date: 7/26/2007
> 11:16 PM
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>

RE: [Repeater-Builder] Re: Icom IC-FR4000-3

[Paul Finch]

Hello,

My customer's called the other day complaining that the system was out, they
could hear the mobile key up but no audio was passed.  I did not have a HT
with me at the time, I saw them key up and the repeater had power so I
cycled the power.  I checked with them later trying to find the problem and
they said it went back to work about the time I cycled power.

Anyone know what's going on?

Paul


-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:[EMAIL PROTECTED] On Behalf Of barrypal
Sent: Thursday, July 26, 2007 10:50 PM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Re: Icom IC-FR4000-3

I just installed my FR4000 two weeks ago and have not noticed any
audio problems yet.  The repeat audio is better then my Mastr II and
the sensitivity and selectivity is great.  BUT, I can't seem to get
the ID'er running the way I think it should.  It will id every time
the repeater is keyed and or dropped out.  You can turn it off
altogether or have it at some system interval 24/7..  I would like it
to operate on key up and then every 10 and then on sign off with delay
but can't seem to find it in the software...

Barry k7pal





 
Yahoo! Groups Links





No virus found in this incoming message.
Checked by AVG Free Edition. 
Version: 7.5.476 / Virus Database: 269.10.22/921 - Release Date: 7/26/2007
11:16 PM
 

No virus found in this outgoing message.
Checked by AVG Free Edition. 
Version: 7.5.476 / Virus Database: 269.10.22/921 - Release Date: 7/26/2007
11:16 PM
 







 
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[Repeater-Builder] Lloyd is Well was Cable Lengths

[Steven Samuel Bosshard (NU5D)]

Just a few minutes ago I had a really nice chat with Lloyd Alcorn, one 
of the three founders of Wacom Products.  Lloyd's background includes 
being a professional engineer working for Decibel Products and helped 
design the DB 222 folded dipole antenna.  Lloyd Alcorn, Larry Bush 
(W5NCD) and Kit Parsons (deceased) founded Wacom Products and for many 
years Wacom existed in a couple of service bays at Waco Communications, 
an RCC and Land Mobile shop in Waco.  I worked for Waco Communications 
from 1975 thru 1981 in the RCC end of things but had much contact with 
the Wacom folks even after I went into business for myself in 1985.

According to Lloyd,  the cable length between a duplexer and an inline 
cavity filter and the receiver makes little or no difference.  The 
culprit to beware of is - radiation from the receiver toward the inline 
cavity filter.  The LO is the primary source of this radiation, but 
there may also be other signals generated by the receiver.  This low 
level signal sets up standing waves between the receiver and the cavity 
filter and may cause some black magic to enter into the equation.  
Changing the cable length may help reduce the effects of stray radiation 
between the receiver and the cavity should this occur.

Placing a band pass cavity between the receiver and the duplexer will 
make no difference at all if the interfering signal is on the receive 
frequency.

Now the transmitter.  Again most but not all of the time, the cable 
length between the transmitter and the duplexer will make no difference, 
EXCEPT that the transmitter may have other out of band energy that again 
sets up standing waves between the transmitter and the duplexer and 
these unwanted signals bounce back and forward between the transmitter 
PA and the duplexer and intensify.  This is where a magic cable length 
can help.  Also an isolator can help not withstanding the isolator does 
create it's own set of problems.

Lloyd still lives and Waco.  I promised NOT to give his phone number and 
he said he is not in hiding.  He is still very active, golfing from time 
to time and serving in the Baptist Church there in Waco.  His health is 
good, except for the standard maladies of getting older.  He did mention 
that Kit's demise came quickly, having talked with Kit some months 
earlier and Kit made no mention of an illness.

Lloyd gives his best regards to all the folks he worked with over the 
years - said when they get up in the morning, sometime they go back to 
bed - don't have to go to work.

Best 73,  Steve NU5D

-- 
Ham Radio Spoken Here !!!  NU5D EM11
http://www.qrz.com/callsign/NU5D
Nickel Under 5 Dollars

[Repeater-Builder] Re: E F Johnson CR600

[n0qzv_jhorn]

Steve,

I happen to have a Johnson CR600 repeater on the air at 443.975.  I 
think it is a pretty good desktop repeater as compared to Uniden, 
Standard, etc.  It actually was not manufactured by Johnson.  It was 
contracted out to Repco to manufacture in the late 80s.  The raido is 
crystaled however it uses ovens so you can just buy rocks and drop 
them in.  It tunes up well into the ham band and has a relitively 
sensitive receiver.  The duplexer is a 4 can notch manufactured by 
Phelps Dodge or Celwave depending on when it was made.   The 
controller is very simple - it contains options for dual tone boards 
and has built in adjustable time out timer and hang time.  There is a 
squelch control on the control bord independant of the one on the 
front and also a provision for an optional accessory connector.  I do 
have a copy of the service manual and I can try to get scans of it. 
Also the repeater is capable of up to around 25 to 30 watts output 
but as with any compact repeater it is better to run it around half 
power.

James n0qzv
==
--- In Repeater-Builder@yahoogroups.com, "stephenucedu" 
<[EMAIL PROTECTED]> wrote:
>
> Does anyone have experience, or an opinion about, the EF Johnson 
CR600 UHF repeater? We 
> may want to incorporate a low end UHF repeater into our system, but 
we don't want 
> something that is/was known for problems.
> 
> A second question involves its programming. Is it PC based or what? 
I assume if so then the 
> software is out there somewhere.
> 
> 
> steve
> 
> KB3OKL Repeater
>

[Repeater-Builder] Wanted: Johnson CR 1000 or CR 1010

[n0qzv_jhorn]

I am looking for an E.F. Johnson CR 1000 or CR 1010 uhf repeater to 
purchase. Please email me if you have one for sale.

thank you

James N0QZV

Re: [Repeater-Builder] Tektronix TEK-491 spectrum analyzer

[Scott Overstreet]

Jay---

Take warning---

The TEK 491 SA has a very primitive front end mixer in it. This mixer is not a 
balanced type and passes considerable input signal direct to the IF amplifier 
which is in the 150 to 250 mHz region, if I remember right. This mixer blow 
through makes for considerable confusion in off air measurements and actually 
in most VHF applications--it is fine up in UHF and microwave. We have one 
here that was given to us-we have plans to replace the mixer with a Mini 
Circuits balanced type with hopes for improved to usable performance.

Scott, N6NXI



  - Original Message - 
  From: Jay Sario 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Thursday, July 26, 2007 7:30 PM
  Subject: [Repeater-Builder] Tektronix TEK-491 spectrum analyzer


  Hi to everyone,

  A fellow here in our location is selling me a cheap working Tektronix 
  491 spectrum analyzer that doesnt have the standard accessories. My 
  knowledge on how to use this type of equipment is limited at the 
  moment but very interested in getting to know how. Just would like to 
  ask before I buy it, would I still be able to put it in good use or be 
  able to measure things even if the standard accessories are not 
  included, like the waveguide mixers, etc.? Can i substitute them with 
  homebrewed ones?

  Thank you much.

  jay



   

RE: [Repeater-Builder] Coax length between added cavities

[Jeff DePolo]

> We just 
> weren't ready to use the time and materials to add an inch to 
> a set of cables and then make another set of short ones.

"Connector savers" can be incrementally added to a cable when experimenting
to find the optimum length.  Connector savers are male-to-famale adapters of
the same connector type.  They are frequently installed on test equipment to
save wear and tear on the built-in connector, hence their nickname.  They
are about the shortest length you can add from a mechanical standpoint to
cables that use type N connectors.  A line stretcher is the best way to do
it, but connector savers are quick and dirty, and their incremental
electrical length is small enough to make them effective for this purpose at
the frequencies we normally deal with below 1 GHz.

High-quality elbow adapters can be used in a pinch instead, but there are
some caveats with respect to the impedence bump they can create (see the
blurb I put together earlier today that touches on this subject).  They are
also electrically longer than connector savers, typically making them useful
only below about 500 MHz in many cases.

If you do this kind of work on a regular basis like we do, you end up with a
few dozen test cables of varying lengths (nominally 1/2" incremental
difference in length) to use when building a system.  Once the optimum cable
lengths are found, new cables are made for the final installation.

BTW, when making up cables based on manufacturers' recommend cable lengths,
make sure you know whether the cable length they specify is the "cut length"
or whether it's tip-to-tip.  Some manufacturers, like TX-RX, specify their
cable lengths based on the cut length before the connectors are installed,
so the overall tip-to-tip length ends up being about 1.25" longer when type
N crimp connectors are installed.

--- Jeff

[Repeater-Builder] Coax length between added cavity and duplexer - test results

[Jeff DePolo]

I performed an experiment per previous discussion.  The results are
available at:

http://www.broadsci.com/900.pdf

Apologies in advance for the terse verbage and any typos; I was trying to
get it done quickly between "real work" projects.

Feedback would be greatly appreciated.

--- Jeff

[Repeater-Builder] Re: Coax length between added cavity and duplexer

[Harold Farrenkopf]

Knowing what is on the nearby antenna is VERY important and is most
likely involved in the problem!

I used to work at Sinclair as a systems engineer and dealt with
solving IM problems and sources on a daily basis for customers'
solutions so I know what I am asking WILL help in resolving the
original problem of interference.

Putting a pass can between the duplexer and receiver with a non
optimized cable will help in describing the characteristic of the
interference if the interference changes in RF level and then if it
cures it then one can optimize the cable length.

Critical length cable MEANS (to an experienced filter person) that the
total response characteristics are optimized for a given response. 
That could be for VSWR shape or pass frequency response or even
whether the notches add to more rejection than the individual notch
responses or not.  Also the effect of cavity interaction wrt tuning
occurs with non optimized cables.

Yes, I know they ran the frequencies - I can read. One cannot just
look at the receive and transmit frequencies alone.  If the
combination isn't obvious with the differences in frequencies showing
hits, you have to look at synthesizer frequencies, image frequencies,
and other oscillator frequencies for the cause of the IM or spurious
mixing.  That is why I mentioned the 12.8MHz oscillator spur on the
Mastr 3.

Any non-linear junction in the presence of multiple RF signals will
generate intermodulation.  Even ferromagnetic materials like nickel
will generate intermodulation.

Characterizing the interference level changes with the application of
a pass cans or attenuators can help in determining whether the source
is internal to the receiver or external (cables, filters, antenna and
beyond)

Harold, VA3HF

--- In Repeater-Builder@yahoogroups.com, Ron Wright <[EMAIL PROTECTED]> wrote:
>
> I believe the inital posting stated no freq combination/mixing could
be found.  For the most part this would illimate an intermod problem.
 However, since there are so many txs in a typical city part of the
problem could be from a distant unknown tx.
> 
> 73, ron, n9ee/r
> 
> 
> 
> >From: Harold Farrenkopf <[EMAIL PROTECTED]>
> >Date: 2007/07/26 Thu PM 01:50:26 CDT
> >To: Repeater-Builder@yahoogroups.com
> >Subject: [Repeater-Builder] Re: Coax length between added cavity
and duplexer
> 
> >  
> >What are the frequencies of your repeater and the frequencies on the
> >nearby antenna
> >
> >What are the radios used on the nearby antenna?
> >
> >Important information in determining the problem - I had one source of
> >noise caused by a Mastr III that had a spur of considerable strength
> >at 12.8MHz down from the transmitter carrier - synthesizer oscillator!
> >It was received with the correct transmitter modulation as the carrier
> >frequency and a pass on it or a notch at -12.8 MHz solved our problem.
> > The level of the emission was within spec of the Mastr 3 but was
> >still too strong for our antenna at 500' away. 
> >
> >What is the configuration of their filters?
> >
> >4' horizontal separation is not much at all so filters should be
> >designed to all the frequencies used to work together.
> >
> >Then, it only takes one transmitter to cause noise in an antenna if
> >the antenna is "noisy".
> >
> >What does the interference sound like?
> >
> >Harold, VA3HF
> >
> >--- In Repeater-Builder@yahoogroups.com, Ken Arck  wrote:
> >>
> >> At 11:06 AM 7/26/2007, you wrote:
> >> 
> >> 
> >> 
> >> Intermod means there is mixing in YOUR PA with some outside RF
energy.
> >> 
> >>  >> term that has become a generic terms used to describe just about any 
> >> type of received interference. Ya know, kinda like Klenex has become 
> >> the name for any tissue.
> >> 
> >> Intermod is a very specific type of phenomenon and for accuracy, 
> >> should only be used to describe intermodulation issues and not
mixes, 
> >> adjacent channel interference, etc.
> >> 
> >> (more of my 2 cents)
> >> 
> >> Ken
> >>
> >
> >
> 
> 
> Ron Wright, N9EE
> 727-376-6575
> MICRO COMPUTER CONCEPTS
> Owner 146.64 repeater Tampa Bay, FL
> No tone, all are welcome.
>