Re: [Repeater-Builder] Pager interference

[Mike Morris]

At 11:38 AM 08/07/10, you wrote:
>Hi, I've got a new pager issue that has come up on a tower where we 
>have a VHF repeater. It's about 400 watts erp and 15 feet horizontal 
>distance and 4.3 and 4.7 MHz away (it switches).
>
>I'm thinking of using one bp/br can that will have the notch wide 
>enough to cover both channels and one pass can on our RX freq. I can 
>also add more pass cans or something like the DCI window filter.
>
>The real question is where to these can go and in what order. We 
>have a standard Q-202 duplexer that worked fine before the pager was 
>put in. I'm thinking that the pager cans will go on the RX side of 
>the duplexer, but does it matter if the pass goes on the duplexer 
>side or the RX side of the bp/br can? I'm kinda thinking that it 
>doesn't matter, but want to do it right in case it does.
>
>Dwayne Kincaid
>WD8OYG

Is this a situation where the paging transmitter is a
new install, or a situation where the paging company
consolidated two transmitters, each a single frequency,
into one that switches, or a new ham system install?

If it's a new paging transmitter install, then 400 watts erp
and 15 feet horizontal distance, is too damn close.  Your
antenna is broadside to its antenna and you have a nice
coupling situation.
It reminds me of a repeater that was located at an FM broadcast
site, and we saw 35 (or so) watts of 90.7 MHz coming DOWN
the ham feedline.  The ham duplexer was nice and warm...

If it's a consolidation I'll bet that the paging transmitter has no
pass cavity, or any other filtering - if it ever had any it was probably
removed in the consolidation.
Digital paging transmitters use square wave modulation and are
DIRTY when they have no filtering and local stories have it that
the FCC has cited several consolidated transmitter systems.

Paging companies are notorious for running overpower.  One local
situation had a license for 90w and they were found to be running
350w.  They were cited, changed transmitters, and a year and a
half later the interference returned.  A no-notice visit from the FCC
found then running 500w.

Don;t order that DCI box yet - the first thing I'd do is reduce the
antenna-to-antenna coupling.  If the master site agreement has a
no-interference clause perhaps you can get them to relocate an
antenna, or go back to the two transmitters with filtering installed.
Look at 
Depending on your antenna gain I'd be very surprised if you are
getting even 15db of isolation.
Once you have reduced the coupling as best as you can, I'd
then re-evaluate the situation by jacking a spectrum analyzer
into your antenna and getting some hard numbers, a screen shot
(even a digital photo of the CRT) posted here, etc.  Then we can
help a lot more.

Mike WA6ILQ

Re: [Repeater-Builder] Pager interference

[Joe]

  Hello Dwayne,

I wonder if the paging company has made a change.  Did they used to have 
two separate transmitters, now only have one that switches frequencies?  
This has been happening at sites since the pager population is 
dwindling.  Paging companies are taking advantage of the multi-frequency 
capabilities of their transmitters and, for example, putting all their 
frequencies in one transmitter.  They then eliminate the other 
transmitters to save rent.  This is a cost effective thing for them to 
do.  They need to page on all their frequencies because they have pagers 
out there on different channels and they don't want to replace 
individual pagers.

If this is the case at your site, here is the downside for you.  Because 
one transmitter is doing many frequencies, they have to eliminate any 
filter cavities they may have had on each individual transmitter.  A 
site can change from no paging interference to tremendous interference 
overnight.

If the original contract for the paging company required filters (some 
did) or had a non-interfering clause you may have some recourse.  If you 
are a "ham freebee" like some of my repeaters are, you may just have to 
live with it.  The real fix is probably going to be on the paging 
transmitter.

73, Joe, K1ike
>
> - Original Message -
> *From:* Dwayne <mailto:ldgya...@ldgelectronics.com>
> *To:* Repeater-Builder@yahoogroups.com
> <mailto:Repeater-Builder@yahoogroups.com>
> *Sent:* Saturday, August 07, 2010 1:38 PM
> *Subject:* [Repeater-Builder] Pager interference
>
> Hi, I've got a new pager issue that has come up on a tower where
> we have a VHF repeater. It's about 400 watts erp and 15 feet
> horizontal distance and 4.3 and 4.7 MHz away (it switches).
>
>
>
>
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Re: [Repeater-Builder] Pager interference

[gervais]

Those pager transmitter are painas some says.
we had a similar problem here some years ago,a telecom company installed a Big  
Motorola Micor  there
when installed suddently the radio-amateur received interference from it and 
even the municipality office radio too and they said "your are the problem"
After intervention,letters,emails the Gov Agency came in the "discussion " and 
they appear that The pager company was transmitting at HIGHER POWER that it was 
suppose to be from their license.

i always known that when those transmitter when the are installed at a radio 
site (ofter in the 140 mhz)many problems will occured BUT it always 
the competence of the tech that must be in consideration also.
you always have for what you pay.

73/s all
gervais ve2ckn
.
..



From: Jim in Waco WB5OXQ 
Sent: Saturday, August 07, 2010 5:07 PM
To: Repeater-Builder@yahoogroups.com 
Subject: Re: [Repeater-Builder] Pager interference





You may have to put a can on the pager transmitter.  Pagers use square waves 
which are very rich in harmonics and need to be filtered at the source.  This 
may be the only way to remove the problem.  I speak from experience.
Jim wb5oxq in Waco
  - Original Message - 
  From: Dwayne 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Saturday, August 07, 2010 1:38 PM
  Subject: [Repeater-Builder] Pager interference 



  Hi, I've got a new pager issue that has come up on a tower where we have a 
VHF repeater. It's about 400 watts erp and 15 feet horizontal distance and 4.3 
and 4.7 MHz away (it switches).

  I'm thinking of using one bp/br can that will have the notch wide enough to 
cover both channels and one pass can on our RX freq. I can also add more pass 
cans or something like the DCI window filter.

  The real question is where to these can go and in what order. We have a 
standard Q-202 duplexer that worked fine before the pager was put in. I'm 
thinking that the pager cans will go on the RX side of the duplexer, but does 
it matter if the pass goes on the duplexer side or the RX side of the bp/br 
can? I'm kinda thinking that it doesn't matter, but want to do it right in case 
it does.

  Dwayne Kincaid
  WD8OYG





--



  No virus found in this incoming message.
  Checked by AVG - www.avg.com 
  Version: 9.0.851 / Virus Database: 271.1.1/3056 - Release Date: 08/07/10 
01:28:00

Re: [Repeater-Builder] Pager interference

[Jim in Waco WB5OXQ]

You may have to put a can on the pager transmitter.  Pagers use square waves 
which are very rich in harmonics and need to be filtered at the source.  This 
may be the only way to remove the problem.  I speak from experience.
Jim wb5oxq in Waco
  - Original Message - 
  From: Dwayne 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Saturday, August 07, 2010 1:38 PM
  Subject: [Repeater-Builder] Pager interference 



  Hi, I've got a new pager issue that has come up on a tower where we have a 
VHF repeater. It's about 400 watts erp and 15 feet horizontal distance and 4.3 
and 4.7 MHz away (it switches).

  I'm thinking of using one bp/br can that will have the notch wide enough to 
cover both channels and one pass can on our RX freq. I can also add more pass 
cans or something like the DCI window filter.

  The real question is where to these can go and in what order. We have a 
standard Q-202 duplexer that worked fine before the pager was put in. I'm 
thinking that the pager cans will go on the RX side of the duplexer, but does 
it matter if the pass goes on the duplexer side or the RX side of the bp/br 
can? I'm kinda thinking that it doesn't matter, but want to do it right in case 
it does.

  Dwayne Kincaid
  WD8OYG



  


--



  No virus found in this incoming message.
  Checked by AVG - www.avg.com 
  Version: 9.0.851 / Virus Database: 271.1.1/3056 - Release Date: 08/07/10 
01:28:00

[Repeater-Builder] Pager interference

[Dwayne]

Hi, I've got a new pager issue that has come up on a tower where we have a VHF 
repeater. It's about 400 watts erp and 15 feet horizontal distance and 4.3 and 
4.7 MHz away (it switches).

I'm thinking of using one bp/br can that will have the notch wide enough to 
cover both channels and one pass can on our RX freq. I can also add more pass 
cans or something like the DCI window filter.

The real question is where to these can go and in what order. We have a 
standard Q-202 duplexer that worked fine before the pager was put in. I'm 
thinking that the pager cans will go on the RX side of the duplexer, but does 
it matter if the pass goes on the duplexer side or the RX side of the bp/br 
can? I'm kinda thinking that it doesn't matter, but want to do it right in case 
it does.

Dwayne Kincaid
WD8OYG

RE: [Repeater-Builder] Pager Interference Revisited

[Mike Besemer (WM4B)]

Barry,

 

If you read the original post you'll see that we have beam headings pointing
every which way.  Been there, done that, gone broke buying gas.  We're not
ever sure what we're hunting yet.

 

73,

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Barry
Sent: Saturday, April 24, 2010 2:38 PM
To: repeater-builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Pager Interference Revisited

 

  

foxhunt maybe ?

  _  

To: Repeater-Builder@yahoogroups.com
From: mwbese...@cox.net
Date: Sat, 24 Apr 2010 13:09:08 -0400
Subject: RE: [Repeater-Builder] Pager Interference Revisited

  

 

That's one I hadn't thought of, Chuck.  Definitely be a bugger to find!

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
Sent: Saturday, April 24, 2010 12:57 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Pager Interference Revisited

 

  

Since it sounds like the "problem" is there continuously (with the correct 
WX conditions) it pretty much rules out another TX that is less than 
continuously "on."

My very first thought was a TV antenna preamp. I've seen those generate a 
lot of crap before. The paging may be mixing at the preamp.

Just a thought.

Chuck
WB2EDV

- Original Message - 
From: "Mike Besemer (WM4B)" 
To: 
Sent: Saturday, April 24, 2010 12:08 PM
Subject: [Repeater-Builder] Pager Interference Revisited

> This is a continuation of the repeater interference issue we started to 
> have
> last October. Maybe with a few new pieces of data, it'll spur some new
> thoughts.
>
> Background:
>
> Last October, our repeater (146.850 MHz) started experiencing pager
> interference. The interference can be clearly heard on the input from
> various diverse locations around town. Most of the time, the interference
> seems to drift across the receiver passband (you can hear it coming and
> going as it drifts through), although this year it seems pretty much stuck
> in the repeater input (don't hear the drifting anymore).
>
> Last year, the interference was also heard on a couple of other area
> repeaters, 145.43 in Macon (15 or so air miles away) and 145.11 in Cochran
> (20 air miles away), so you can see that whatever this is covering a 
> pretty
> large portion of the spectrum. I've also been told that it's been heard 
> on
> public-service frequencies as well, although I don't know what those
> frequencies are (exactly) and have never witnessed it myself. Yesterday,
> the interference moved from the input of 146.85 to the input of 145.11 in 
> a
> very rapid manner. a period of 5 minutes or so, and then reversed itself a
> couple of hours later.
>
> We know that the paging interference is coming from 462.775 MHz. The 
> paging
> company owner is a ham and has been very helpful. The interference can 
> come
> from any one of three different sites, one locally, one in Macon and one 
> in
> Roberta (about 25 air miles away), all on the same frequency. He has set 
> up
> a phone number that I can call and leave a voice page on the local system,
> which help us with the tracking immensely. I believe he's going to do the
> same for the other two systems.
>
> I've sat very near his system locally and heard NOTHING on the repeater
> input while the interference event is occurring. I've also checked all 
> the
> likely mixing products as well as frequencies in his multiplier chain and
> heard nothing.
>
> We feel certain that it's got to be a mixing issue, (it's not likely he 
> has
> three transmitters with the same garbage on the output) but given the way 
> it
> behaves it's hard to locate the source. The large, rapid frequency
> excursions are a bit baffling. If you just consider 462.775 and 146.25, 
> it
> puts you very near the audio carrier of CATV Channel 39, but seeing it 
> move
> to the input of 145.11 and 145.43 puts the possible mix frequency 
> somewhere
> between Channel 39 and Channel 40.
>
> The issue disappeared over the winter months. If it's a hot, sunny day 
> you
> can be sure the problem will be present. A hot, cloudy day is also a 
> fairly
> good bet. Also, a cooler, sunny day will bring it out. Cool and cloudy 
> or
> cold and sunny do not allow the problem to manifest. The issue has been
> present during and after several days of rain, so that seems to eliminate
> the 'rusty bolt' syndrome. I tend to believe it's an amplifier mounted on 
> a
> pole or tower someplace that's going spurious with heat, but that is just 
> a
> theory. Beam headings tend to point to the paging transmi

RE: [Repeater-Builder] Pager Interference Revisited

[Barry]

foxhunt maybe ?

To: Repeater-Builder@yahoogroups.com
From: mwbese...@cox.net
Date: Sat, 24 Apr 2010 13:09:08 -0400
Subject: RE: [Repeater-Builder] Pager Interference Revisited


















 



  



  
  
  








That’s one I hadn’t thought of, Chuck.  Definitely
be a bugger to find!

 

Mike

WM4B

 







From:
Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On
Behalf Of Chuck Kelsey

Sent: Saturday, April 24, 2010 12:57 PM

To: Repeater-Builder@yahoogroups.com

Subject: Re: [Repeater-Builder] Pager Interference Revisited





 

  







Since it sounds like the "problem" is
there continuously (with the correct 

WX conditions) it pretty much rules out another TX that is less than 

continuously "on."



My very first thought was a TV antenna preamp. I've seen those generate a 

lot of crap before. The paging may be mixing at the preamp.



Just a thought.



Chuck

WB2EDV



- Original Message - 

From: "Mike Besemer (WM4B)" 

To: 

Sent: Saturday, April 24, 2010 12:08 PM

Subject: [Repeater-Builder] Pager Interference Revisited



> This is a continuation of the repeater interference issue we started to 

> have

> last October. Maybe with a few new pieces of data, it'll spur some new

> thoughts.

>

> Background:

>

> Last October, our repeater (146.850 MHz) started experiencing pager

> interference. The interference can be clearly heard on the input from

> various diverse locations around town. Most of the time, the interference

> seems to drift across the receiver passband (you can hear it coming and

> going as it drifts through), although this year it seems pretty much stuck

> in the repeater input (don't hear the drifting anymore).

>

> Last year, the interference was also heard on a couple of other area

> repeaters, 145.43 in Macon (15 or so air miles away) and 145.11 in Cochran

> (20 air miles away), so you can see that whatever this is covering a 

> pretty

> large portion of the spectrum. I've also been told that it's been heard 

> on

> public-service frequencies as well, although I don't know what those

> frequencies are (exactly) and have never witnessed it myself. Yesterday,

> the interference moved from the input of 146.85 to the input of 145.11 in 

> a

> very rapid manner. a period of 5 minutes or so, and then reversed itself a

> couple of hours later.

>

> We know that the paging interference is coming from 462.775 MHz. The 

> paging

> company owner is a ham and has been very helpful. The interference can 

> come

> from any one of three different sites, one locally, one in Macon and one 

> in

> Roberta (about 25 air miles away), all on the same frequency. He has set 

> up

> a phone number that I can call and leave a voice page on the local system,

> which help us with the tracking immensely. I believe he's going to do the

> same for the other two systems.

>

> I've sat very near his system locally and heard NOTHING on the repeater

> input while the interference event is occurring. I've also checked all 

> the

> likely mixing products as well as frequencies in his multiplier chain and

> heard nothing.

>

> We feel certain that it's got to be a mixing issue, (it's not likely he 

> has

> three transmitters with the same garbage on the output) but given the way 

> it

> behaves it's hard to locate the source. The large, rapid frequency

> excursions are a bit baffling. If you just consider 462.775 and 146.25, 

> it

> puts you very near the audio carrier of CATV Channel 39, but seeing it 

> move

> to the input of 145.11 and 145.43 puts the possible mix frequency 

> somewhere

> between Channel 39 and Channel 40.

>

> The issue disappeared over the winter months. If it's a hot, sunny day 

> you

> can be sure the problem will be present. A hot, cloudy day is also a 

> fairly

> good bet. Also, a cooler, sunny day will bring it out. Cool and cloudy 

> or

> cold and sunny do not allow the problem to manifest. The issue has been

> present during and after several days of rain, so that seems to eliminate

> the 'rusty bolt' syndrome. I tend to believe it's an amplifier mounted on 

> a

> pole or tower someplace that's going spurious with heat, but that is just 

> a

> theory. Beam headings tend to point to the paging transmitters rather 

> than

> the possible mixing source, which is baffling me as well.

>

> I feel like I must be missing something obvious here, but all the back and

> forth ideas we've all been working on never seem to answer all of the

> questions.

>

> What do you guys think?

>

> 73,

>

> Mike

> WM4B

>

> 





















 









  
_
Browse profiles for FREE! Meet local singles online.
http://clk.atdmt.com/NMN/go/150855801/direct/01/

Re: [Repeater-Builder] Pager Interference Revisited

[Kris Kirby]

On Sat, 24 Apr 2010, Mike Besemer (WM4B) wrote:
> The issue disappeared over the winter months.  If it's a hot, sunny 
> day you can be sure the problem will be present.  A hot, cloudy day is 
> also a fairly good bet.  Also, a cooler, sunny day will bring it out.  
> Cool and cloudy or cold and sunny do not allow the problem to 
> manifest.  The issue has been present during and after several days of 
> rain, so that seems to eliminate the 'rusty bolt' syndrome.  I tend to 
> believe it's an amplifier mounted on a pole or tower someplace that's 
> going spurious with heat, but that is just a theory.  Beam headings 
> tend to point to the paging transmitters rather than the possible 
> mixing source, which is baffling me as well.

Does the paging transmitter have a circulator, or a bandpass cavity 
between it and the antenna? Does it stay on one frequency or hop around?

--
Kris Kirby, KE4AHR
Disinformation Analyst

Re: [Repeater-Builder] Pager Interference Revisited

[Chuck Kelsey]

This kind of problem can come from pretty large distances.

One I was involved with ended up being a paging PA spur landing on my repeater 
input - that was 15 miles away.

Another was a control station that the PA generated spurs induced by a 
commercial FM station that was a mile from it. That spur ended up on our work 
repeater output and we were 20 miles from that source.

Chuck
WB2EDV



  - Original Message - 
  From: Mike Besemer (WM4B) 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Saturday, April 24, 2010 1:09 PM
  Subject: RE: [Repeater-Builder] Pager Interference Revisited





  That's one I hadn't thought of, Chuck.  Definitely be a bugger to find!

   

  Mike

  WM4B

   

  From: Repeater-Builder@yahoogroups.com 
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
  Sent: Saturday, April 24, 2010 12:57 PM
  To: Repeater-Builder@yahoogroups.com
  Subject: Re: [Repeater-Builder] Pager Interference Revisited

   



  Since it sounds like the "problem" is there continuously (with the correct 
  WX conditions) it pretty much rules out another TX that is less than 
  continuously "on."

  My very first thought was a TV antenna preamp. I've seen those generate a 
  lot of crap before. The paging may be mixing at the preamp.

  Just a thought.

  Chuck
  WB2EDV

  - Original Message - 
  From: "Mike Besemer (WM4B)" 
  To: 
  Sent: Saturday, April 24, 2010 12:08 PM
  Subject: [Repeater-Builder] Pager Interference Revisited

  > This is a continuation of the repeater interference issue we started to 
  > have
  > last October. Maybe with a few new pieces of data, it'll spur some new
  > thoughts.
  >
  > Background:
  >
  > Last October, our repeater (146.850 MHz) started experiencing pager
  > interference. The interference can be clearly heard on the input from
  > various diverse locations around town. Most of the time, the interference
  > seems to drift across the receiver passband (you can hear it coming and
  > going as it drifts through), although this year it seems pretty much stuck
  > in the repeater input (don't hear the drifting anymore).
  >
  > Last year, the interference was also heard on a couple of other area
  > repeaters, 145.43 in Macon (15 or so air miles away) and 145.11 in Cochran
  > (20 air miles away), so you can see that whatever this is covering a 
  > pretty
  > large portion of the spectrum. I've also been told that it's been heard 
  > on
  > public-service frequencies as well, although I don't know what those
  > frequencies are (exactly) and have never witnessed it myself. Yesterday,
  > the interference moved from the input of 146.85 to the input of 145.11 in 
  > a
  > very rapid manner. a period of 5 minutes or so, and then reversed itself a
  > couple of hours later.
  >
  > We know that the paging interference is coming from 462.775 MHz. The 
  > paging
  > company owner is a ham and has been very helpful. The interference can 
  > come
  > from any one of three different sites, one locally, one in Macon and one 
  > in
  > Roberta (about 25 air miles away), all on the same frequency. He has set 
  > up
  > a phone number that I can call and leave a voice page on the local system,
  > which help us with the tracking immensely. I believe he's going to do the
  > same for the other two systems.
  >
  > I've sat very near his system locally and heard NOTHING on the repeater
  > input while the interference event is occurring. I've also checked all 
  > the
  > likely mixing products as well as frequencies in his multiplier chain and
  > heard nothing.
  >
  > We feel certain that it's got to be a mixing issue, (it's not likely he 
  > has
  > three transmitters with the same garbage on the output) but given the way 
  > it
  > behaves it's hard to locate the source. The large, rapid frequency
  > excursions are a bit baffling. If you just consider 462.775 and 146.25, 
  > it
  > puts you very near the audio carrier of CATV Channel 39, but seeing it 
  > move
  > to the input of 145.11 and 145.43 puts the possible mix frequency 
  > somewhere
  > between Channel 39 and Channel 40.
  >
  > The issue disappeared over the winter months. If it's a hot, sunny day 
  > you
  > can be sure the problem will be present. A hot, cloudy day is also a 
  > fairly
  > good bet. Also, a cooler, sunny day will bring it out. Cool and cloudy 
  > or
  > cold and sunny do not allow the problem to manifest. The issue has been
  > present during and after several days of rain, so that seems to eliminate
  > the 'rusty bolt' syndrome. I tend to believe it's an amplifier mounted on 
  > a
  > pole or tower someplace that's

RE: [Repeater-Builder] Pager Interference Revisited

[Mike Besemer (WM4B)]

That's one I hadn't thought of, Chuck.  Definitely be a bugger to find!

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Chuck Kelsey
Sent: Saturday, April 24, 2010 12:57 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Pager Interference Revisited

 

  

Since it sounds like the "problem" is there continuously (with the correct 
WX conditions) it pretty much rules out another TX that is less than 
continuously "on."

My very first thought was a TV antenna preamp. I've seen those generate a 
lot of crap before. The paging may be mixing at the preamp.

Just a thought.

Chuck
WB2EDV

- Original Message - 
From: "Mike Besemer (WM4B)" mailto:mwbesemer%40cox.net>
>
To: mailto:Repeater-Builder%40yahoogroups.com> >
Sent: Saturday, April 24, 2010 12:08 PM
Subject: [Repeater-Builder] Pager Interference Revisited

> This is a continuation of the repeater interference issue we started to 
> have
> last October. Maybe with a few new pieces of data, it'll spur some new
> thoughts.
>
> Background:
>
> Last October, our repeater (146.850 MHz) started experiencing pager
> interference. The interference can be clearly heard on the input from
> various diverse locations around town. Most of the time, the interference
> seems to drift across the receiver passband (you can hear it coming and
> going as it drifts through), although this year it seems pretty much stuck
> in the repeater input (don't hear the drifting anymore).
>
> Last year, the interference was also heard on a couple of other area
> repeaters, 145.43 in Macon (15 or so air miles away) and 145.11 in Cochran
> (20 air miles away), so you can see that whatever this is covering a 
> pretty
> large portion of the spectrum. I've also been told that it's been heard 
> on
> public-service frequencies as well, although I don't know what those
> frequencies are (exactly) and have never witnessed it myself. Yesterday,
> the interference moved from the input of 146.85 to the input of 145.11 in 
> a
> very rapid manner. a period of 5 minutes or so, and then reversed itself a
> couple of hours later.
>
> We know that the paging interference is coming from 462.775 MHz. The 
> paging
> company owner is a ham and has been very helpful. The interference can 
> come
> from any one of three different sites, one locally, one in Macon and one 
> in
> Roberta (about 25 air miles away), all on the same frequency. He has set 
> up
> a phone number that I can call and leave a voice page on the local system,
> which help us with the tracking immensely. I believe he's going to do the
> same for the other two systems.
>
> I've sat very near his system locally and heard NOTHING on the repeater
> input while the interference event is occurring. I've also checked all 
> the
> likely mixing products as well as frequencies in his multiplier chain and
> heard nothing.
>
> We feel certain that it's got to be a mixing issue, (it's not likely he 
> has
> three transmitters with the same garbage on the output) but given the way 
> it
> behaves it's hard to locate the source. The large, rapid frequency
> excursions are a bit baffling. If you just consider 462.775 and 146.25, 
> it
> puts you very near the audio carrier of CATV Channel 39, but seeing it 
> move
> to the input of 145.11 and 145.43 puts the possible mix frequency 
> somewhere
> between Channel 39 and Channel 40.
>
> The issue disappeared over the winter months. If it's a hot, sunny day 
> you
> can be sure the problem will be present. A hot, cloudy day is also a 
> fairly
> good bet. Also, a cooler, sunny day will bring it out. Cool and cloudy 
> or
> cold and sunny do not allow the problem to manifest. The issue has been
> present during and after several days of rain, so that seems to eliminate
> the 'rusty bolt' syndrome. I tend to believe it's an amplifier mounted on 
> a
> pole or tower someplace that's going spurious with heat, but that is just 
> a
> theory. Beam headings tend to point to the paging transmitters rather 
> than
> the possible mixing source, which is baffling me as well.
>
> I feel like I must be missing something obvious here, but all the back and
> forth ideas we've all been working on never seem to answer all of the
> questions.
>
> What do you guys think?
>
> 73,
>
> Mike
> WM4B
>
> 

Re: [Repeater-Builder] Pager Interference Revisited

[Chuck Kelsey]

Since it sounds like the "problem" is there continuously (with the correct 
WX conditions) it pretty much rules out another TX that is less than 
continuously "on."

My very first thought was a TV antenna preamp. I've seen those generate a 
lot of crap before. The paging may be mixing at the preamp.

Just a thought.

Chuck
WB2EDV



- Original Message - 
From: "Mike Besemer (WM4B)" 
To: 
Sent: Saturday, April 24, 2010 12:08 PM
Subject: [Repeater-Builder] Pager Interference Revisited


> This is a continuation of the repeater interference issue we started to 
> have
> last October.  Maybe with a few new pieces of data, it'll spur some new
> thoughts.
>
> Background:
>
> Last October, our repeater (146.850 MHz) started experiencing pager
> interference.  The interference can be clearly heard on the input from
> various diverse locations around town.  Most of the time, the interference
> seems to drift across the receiver passband (you can hear it coming and
> going as it drifts through), although this year it seems pretty much stuck
> in the repeater input (don't hear the drifting anymore).
>
> Last year, the interference was also heard on a couple of other area
> repeaters, 145.43 in Macon (15 or so air miles away) and 145.11 in Cochran
> (20 air miles away), so you can see that whatever this is covering a 
> pretty
> large portion of the spectrum.  I've also been told that it's been heard 
> on
> public-service frequencies as well, although I don't know what those
> frequencies are (exactly) and have never witnessed it myself.  Yesterday,
> the interference moved from the input of 146.85 to the input of 145.11 in 
> a
> very rapid manner. a period of 5 minutes or so, and then reversed itself a
> couple of hours later.
>
> We know that the paging interference is coming from 462.775 MHz.  The 
> paging
> company owner is a ham and has been very helpful.  The interference can 
> come
> from any one of three different sites, one locally, one in Macon and one 
> in
> Roberta (about 25 air miles away), all on the same frequency.  He has set 
> up
> a phone number that I can call and leave a voice page on the local system,
> which help us with the tracking immensely.  I believe he's going to do the
> same for the other two systems.
>
> I've sat very near his system locally and heard NOTHING on the repeater
> input while the interference event is occurring.  I've also checked all 
> the
> likely mixing products as well as frequencies in his multiplier chain and
> heard nothing.
>
> We feel certain that it's got to be a mixing issue, (it's not likely he 
> has
> three transmitters with the same garbage on the output) but given the way 
> it
> behaves it's hard to locate the source.  The large, rapid frequency
> excursions are a bit baffling.  If you just consider 462.775 and 146.25, 
> it
> puts you very near the audio carrier of CATV Channel 39, but seeing it 
> move
> to the input of 145.11 and 145.43 puts the possible mix frequency 
> somewhere
> between Channel 39 and Channel 40.
>
> The issue disappeared over the winter months.  If it's a hot, sunny day 
> you
> can be sure the problem will be present.  A hot, cloudy day is also a 
> fairly
> good bet.  Also, a cooler, sunny day will bring it out.  Cool and cloudy 
> or
> cold and sunny do not allow the problem to manifest.  The issue has been
> present during and after several days of rain, so that seems to eliminate
> the 'rusty bolt' syndrome.  I tend to believe it's an amplifier mounted on 
> a
> pole or tower someplace that's going spurious with heat, but that is just 
> a
> theory.  Beam headings tend to point to the paging transmitters rather 
> than
> the possible mixing source, which is baffling me as well.
>
> I feel like I must be missing something obvious here, but all the back and
> forth ideas we've all been working on never seem to answer all of the
> questions.
>
> What do you guys think?
>
> 73,
>
> Mike
> WM4B
>
> 

[Repeater-Builder] Pager Interference Revisited

[Mike Besemer (WM4B)]

This is a continuation of the repeater interference issue we started to have
last October.  Maybe with a few new pieces of data, it'll spur some new
thoughts.

Background:  

Last October, our repeater (146.850 MHz) started experiencing pager
interference.  The interference can be clearly heard on the input from
various diverse locations around town.  Most of the time, the interference
seems to drift across the receiver passband (you can hear it coming and
going as it drifts through), although this year it seems pretty much stuck
in the repeater input (don't hear the drifting anymore).  

Last year, the interference was also heard on a couple of other area
repeaters, 145.43 in Macon (15 or so air miles away) and 145.11 in Cochran
(20 air miles away), so you can see that whatever this is covering a pretty
large portion of the spectrum.  I've also been told that it's been heard on
public-service frequencies as well, although I don't know what those
frequencies are (exactly) and have never witnessed it myself.  Yesterday,
the interference moved from the input of 146.85 to the input of 145.11 in a
very rapid manner. a period of 5 minutes or so, and then reversed itself a
couple of hours later.

We know that the paging interference is coming from 462.775 MHz.  The paging
company owner is a ham and has been very helpful.  The interference can come
from any one of three different sites, one locally, one in Macon and one in
Roberta (about 25 air miles away), all on the same frequency.  He has set up
a phone number that I can call and leave a voice page on the local system,
which help us with the tracking immensely.  I believe he's going to do the
same for the other two systems. 

I've sat very near his system locally and heard NOTHING on the repeater
input while the interference event is occurring.  I've also checked all the
likely mixing products as well as frequencies in his multiplier chain and
heard nothing.  

We feel certain that it's got to be a mixing issue, (it's not likely he has
three transmitters with the same garbage on the output) but given the way it
behaves it's hard to locate the source.  The large, rapid frequency
excursions are a bit baffling.  If you just consider 462.775 and 146.25, it
puts you very near the audio carrier of CATV Channel 39, but seeing it move
to the input of 145.11 and 145.43 puts the possible mix frequency somewhere
between Channel 39 and Channel 40.

The issue disappeared over the winter months.  If it's a hot, sunny day you
can be sure the problem will be present.  A hot, cloudy day is also a fairly
good bet.  Also, a cooler, sunny day will bring it out.  Cool and cloudy or
cold and sunny do not allow the problem to manifest.  The issue has been
present during and after several days of rain, so that seems to eliminate
the 'rusty bolt' syndrome.  I tend to believe it's an amplifier mounted on a
pole or tower someplace that's going spurious with heat, but that is just a
theory.  Beam headings tend to point to the paging transmitters rather than
the possible mixing source, which is baffling me as well.

I feel like I must be missing something obvious here, but all the back and
forth ideas we've all been working on never seem to answer all of the
questions.

What do you guys think?

73,

Mike
WM4B  

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Jim Brown]

Mike, I think the next step would be to try to get the paging operator to 
install an isolator on the output of his VHF pager for a temporary check.  If 
he has one already, he could try putting two in tandem to increase the 
rejection of any RF coming back down the feedline from his antenna.  What you 
may be hearing is a mix in his VHF transmitter with something else in his 
vicinity with an unstable frequency that is sweeping the mix through the VHF 
band.

Years ago we had a problem in the Dallas area with a welder that produced an 
unstable carrier that would sweep through the 2 meter input frequencies of the 
repeaters in the area.  The welder was located on the upper floors of the 
building in progress, and had a nice site for radiating the interfering 
signal.  A foxhunt tracked that one down but it did not go away till the 
building was completed.

Good luck with your QRM.

73 - Jim  W5ZIT

--- On Wed, 10/28/09, Mike Besemer (WM4B)  wrote:

From: Mike Besemer (WM4B) 
Subject: RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public 
Service Band
To: Repeater-Builder@yahoogroups.com
Date: Wednesday, October 28, 2009, 7:03 PM






 





  







Strangely enough, I happen to be an O-O (as is the another club
member, who sponsors the 145.110 repeater… which is also being interfered
with) and have been in touch with our coordinator.  He’s been very
helpful in urging us along and providing us guidance (or reassurance) that we’re
going about this the right way.  He’s also indicated that he’s
willing to go to ARRL HQ with it if we need to and then let them go lateral to
the FCC.  We had a great experience with Laura Smith about a year ago when
we needed help convincing a banned user to stay off our systems.  It took
one letter to her (complete with recordings) and one phone call to get our
banned user a nice letter from Laura reminding him that he really couldn’t
afford to pay what she was prepared to charge him for using our repeater! 
So… I think that, armed with enough ammunition, we can go that route. 

   

However, I REALLY don’t want to.  The fellow who owns
the paging company has tried to work with us, and although it’s not going
as fast as we’d like, I understand that he’s got a different motivation
than we do.    Aside from that, he helped us out with a
professional climbing crew a couple of years ago, got us a good deal on a
DB-224, and cut us a break on some hardline and connectors.  The bottom
line is, it’s not a relationship we want to end through a Federal
intervention!  That being said, I HAVE reminded him that he’s
admitted that we’re carrying his data on our repeater, and whether or not
it’s his equipment at fault or somebody else’s, HE’S going to
be the first person they come looking for and it’ll be a terrible pain in
his butt… and wallet.  He acknowledges that fact.  So…
while I’d like for him to do some things differently… I get where
he’s coming from and I appreciate that he’s helped as much as he
has. 

   

On the other hand, if it turns out to be equipment that belongs
to another company… I’ll drop a dime in a heartbeat if I don’t
get satisfaction from them! 

   

73, 

   

Mike 

WM4B 

   







From: Repeater-Builder@ yahoogroups. com
[mailto:Repeater- buil...@yahoogro ups.com] On Behalf Of Paul Plack

Sent: Wednesday, October 28, 2009 7:48 PM

To: Repeater-Builder@ yahoogroups. com

Subject: Re: [Repeater-Builder] Pager Interference to 2-meter & VHF
Public Service Band 





   

   









Mike, the interference is
clearly not caused by your own rusty roof, and is both eggregious and easily
documented. I know we hate to go there unless it's a last resort, but I'll bet
the FCC is almost as tired of non-compliant pager systems as we are.
Perhaps that "technique" would prove "motivating." 





  







-
Original Message -  





From: Mike Besemer (WM4B)  





To: Repeater-Builder@ yahoogroups. com  





Sent: Wednesday, October
28, 2009 5:34 PM 





Subject: RE:
[Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band 





   



   





I’m with ya on your third
paragraph.  We’ve worked well together so far, but we have very
different techniques and motivations. ..  







. 



 







 











 

  




 

















  

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[mwbesemer]

On Thu, Oct 29, 2009 at 1:45 PM, Joe wrote:

> Mike Besemer (WM4B) wrote:
>>
>> Joe,
>>
>> The problem isn’t traffic dependant (10 am being a busy time), as I 
>> monitor on and off all day and there is PLENTY of traffic all day 
>> long. It seems to have more to do with temperature. You can clearly 
>> hear the signals come on and fade off frequency
>>
> I had thought that you said that 10AM seemed to be a particularity bad 
> time of interference. 10AM does not seem to be a time that the heat 
> load of a site would be high. If the site was overheating, I would 
> think that interference would be worse in the afternoons.

As I mentioned, the interferrence is moving.  At a certain temperature, 
it sweeps through our repeater input.  As the temperature rises, it 
seems to move on.

>>
>> It’s also easy to hear which transmitter is sending the pages. I have 
>> two dual band radios in my vehicle. Typically one is on the repeater 
>> output, one on the input, one of VHF paging and one on UHF paging. 
>> It’s also been confirmed by having the owner send test bursts by 
>> specific transmitters.
>>
> OK, important question. Is the particular paging company you are 
> working with to resolve the problem ALWAYS involved in the 
> interference?

No, but being the strongest signals in the area, they are the primary 
source of frustration.

>>
>> The other two UHF frequencies are also paging transmitters.
>>
>
> How are the other two UHF frequencies involved in the interference? 
> When the two UHF freqs are involved, is the above mentioned paging 
> company ALSO involved?

Not necessarily

>>
>> Good thoughts about the transmitter self-oscillating when unkeyed... 
>> that’s another road we can go down.
>>
> I would guess that if the interference is caused by an 
> self-oscillating transmitter, it would be probably be in the VHF range 
> of frequencies. That way the signal could get out of the transmitter 
> through any filtering that may be involved. Just a guess, mind you.
>>
>> Speaking of going down roads… what I really need is more help! 
>> Several of our club members are engaged in assisting, but what I 
>> really need is a dedicated team of folks. Having to work for a living 
>> is taking a serious bite out my tracking time!
>>
> Someone needs to do some directional finding on the interfering 
> signal, then triangulate. If I were to guess at a location I would 
> look up the the geographical location in your area of all the 
> frequencies involved. 152.480, 462.775, 462.850 and 462.925Mhz. You 
> may find that they share the same location or are very close to each 
> other. Start looking there. Or go to the site that the paging company 
> is at and look for interference.

Working it.  Not getting nearly enough help though.

>
> You said that you are on a water tank. Water tanks are notorious for 
> co-site interference because all of the antennas are usually on the 
> top of the tank and are in the same horizontal plane. In other words, 
> no vertical separation. Keep this in mind as I found my problem at our 
> water tank site by momentarily shutting down the water company 
> telemetry radio (with their permission) and the interference went 
> away. The problem was that the VHF telemetry antenna and the 6 meter 
> ham antenna were only about 10 feet apart.

We're the only one on the site.

>
> 73, Joe, K1ike
>
>
>
> 
>
>
>
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>
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Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Joe]

Mike Besemer (WM4B) wrote:
>
> Joe,
>
> The problem isn’t traffic dependant (10 am being a busy time), as I 
> monitor on and off all day and there is PLENTY of traffic all day 
> long. It seems to have more to do with temperature. You can clearly 
> hear the signals come on and fade off frequency
>
I had thought that you said that 10AM seemed to be a particularity bad 
time of interference. 10AM does not seem to be a time that the heat load 
of a site would be high. If the site was overheating, I would think that 
interference would be worse in the afternoons.
>
> It’s also easy to hear which transmitter is sending the pages. I have 
> two dual band radios in my vehicle. Typically one is on the repeater 
> output, one on the input, one of VHF paging and one on UHF paging. 
> It’s also been confirmed by having the owner send test bursts by 
> specific transmitters.
>
OK, important question. Is the particular paging company you are working 
with to resolve the problem ALWAYS involved in the interference?
>
> The other two UHF frequencies are also paging transmitters.
>

How are the other two UHF frequencies involved in the interference? When 
the two UHF freqs are involved, is the above mentioned paging company 
ALSO involved?
>
> Good thoughts about the transmitter self-oscillating when unkeyed... 
> that’s another road we can go down.
>
I would guess that if the interference is caused by an self-oscillating 
transmitter, it would be probably be in the VHF range of frequencies. 
That way the signal could get out of the transmitter through any 
filtering that may be involved. Just a guess, mind you.
>
> Speaking of going down roads… what I really need is more help! Several 
> of our club members are engaged in assisting, but what I really need 
> is a dedicated team of folks. Having to work for a living is taking a 
> serious bite out my tracking time!
>
Someone needs to do some directional finding on the interfering signal, 
then triangulate. If I were to guess at a location I would look up the 
the geographical location in your area of all the frequencies involved. 
152.480, 462.775, 462.850 and 462.925Mhz. You may find that they share 
the same location or are very close to each other. Start looking there. 
Or go to the site that the paging company is at and look for interference.

You said that you are on a water tank. Water tanks are notorious for 
co-site interference because all of the antennas are usually on the top 
of the tank and are in the same horizontal plane. In other words, no 
vertical separation. Keep this in mind as I found my problem at our 
water tank site by momentarily shutting down the water company telemetry 
radio (with their permission) and the interference went away. The 
problem was that the VHF telemetry antenna and the 6 meter ham antenna 
were only about 10 feet apart.

73, Joe, K1ike







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Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Dick Kittrell]

Mike-



On Thu, 29 Oct 2009 05:33:10 -0500, Mike Besemer (WM4B)  
 wrote:

> I was told (caveat) that he verified the spectrum after the interference
> started.  Since he's investing quite a bit of time into helping clear  
> this
> up, I have to believe he's done that.
>
>

A few years ago we had a similar problem, except the pager location/ID  
was unknown. It took almost 2 years to find it, and one phone call to the  
pager to fix it. The final proof was standing outside the fence with one  
radio listening to the pager traffic and one on our repeater. After the  
pager traffic QUIT, the PA started the spur on our input. The statement  
above could well be true, as most people think of spectrum verification as  
being "while transmitting". In our case the temperature involved was  
outdoor temp, in the range of 10-25 degrees F, causing it to drift through  
our input passband into another repeater's passband, which further  
complicated the foxhunt aspect, hi!

In your case, you are hearing the traffic as well, which suggests a mix 
 
to me. You might juggle the numbers a bit and see what freq would give you  
an interfering mix. It could be generated in the owner's idle PA (as  
someone above suggested ) or a totally foreign TX. As the owner seems  
pretty cooperative, eliminating both his TX's should be pretty easy, If  
you were really lucky, it would be his idle PA mixing with his active PA  
and the site of the fix would be in sight! (Sorry -couldn't resist that  
one.)

Good Luck!!
Dick W0RFX  
-- 
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Doug Bade]

This sounds like a problem I traced about 20 years ago on a VHF 
paging system. The PA was tube and there was some issue the tech had 
with the PA not firing on rf drive .. so he locked the PTT to the PA 
on all the time and then just turned the exciter on and offThe 
problem was the PA was self resonant +- a sweep of our freq  and 
would go there whenever the transmitter exciter was NOT present... 
and it drifted with temperature so was a 300 w moving target 
I guess he never looked at it with a watt meter while the exciter was 
off How we finally identified it was we could hear the tone blips 
at the end of the interference cycle ( when the station was really 
being asked to tx) bleed through from the PURC tones just before it 
went away.. We then watched the TX carrier of the real tx come on 
perfectly synchronouslyto the absence on our end...By watching 
what came on when it went off we figured out the freq... as there was 
no modulation during interference...They toggled perfectly on a wide 
sweep spectrum analyzer...


During the day it was gone as the system was busy.. but at night when 
it got quiet we got hammered...Then I DF'ed the particular 
tx.as it was a simulcastAnd the tech shut it down until it 
could be fixed correctly and our problem went away


The tone sequencing leaked through from the link system which pointed 
us to paging... in this case it was a 152 . to protect the guilty 
:-) and moved to 151. area blocking some control stations inputs 
at a nearby dispatch center...


Doug
KD8B



At 06:28 PM 10/28/2009, you wrote:



Mike,

If it moves around based on time of day, my first guess is a PA 
that's gone bad, and has a parasitic that's temperature-related.


If you've tracked an individual spur drifting 70 kHz up the band 
during a single transmission, this is not some (intentional) 
oscillator drifting, but some combination of failed components or 
tuning which has produced a parasitic.


Sorry to say, but a paging transmitter owner swearing his stuff is 
clean is pretty meaningless. The assumption in his industry is the 
professionals who maintain his stuff are not the problem, it's 
"those damn hams." Sadly, it may more often be the other way around 
these days, as companies maintaining paging equipment have 
transitioned to underpaid, under-trained card-swappers instead of 
component-level technicians with a clue about RF systems.


73,
Paul, AE4KR

- Original Message -
From: <mailto:mwbese...@cox.net>Mike
To: <mailto:Repeater-Builder@yahoogroups.com>Repeater-Builder@yahoogroups.com
Sent: Wednesday, October 28, 2009 12:28 PM
Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF 
Public Service Band




A couple of weeks ago, our repeater system started to experience 
interference from a paging system...



...one evening I tracked it from about 145.120 to 145.190 as it 
swept through each transmission...



.

Re: {Disarmed} Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Marvin Hoffman]

A while back in time, I worked 20 miles south of Chapel Hill, NC.  
During the late morning and afternoon our vhf fire, low band EM, and a 
UHF carrier squelch sheriff mutual aid channels starting getting garbage 
that was noisy but occurred on the various channels from 47 mhs to 453 mhz.

A paging transmitter on 152 mhz at the UNC Hospital was the cause. 

An additional transmitter had been put in an equipment room on the top 
floor of the hospital,.  When the roof heated up, along with the extra 
heat from the added transmitter, the older paging transmitter started 
sending spurs all over the place. Cooling the equipment room caused the 
problem to go away.

Marv, WA4NC

Glenn Little WB4UIV wrote:
>  
>
> Locally, years ago, we had a military transmitter that had a
> wandering spur. I am near Charleston, SC. The spur was strong enough
> to key up amateur radio repeaters in the two meter band from
> Wilmington, NC to Savannah, Ga.
> The offender turned out to be a 250 Watt base station used to cover
> approximately 10 Acres.
> The radio was a Motorola MICOR.
> The service shop could not fix the problem, so, they replaced the 
> transmitter.
>
> This may be a spur from a transmitter.
> The spur that we experienced wandered up the band, then, down the band.
> The wander was slow enough that you could hear it approaching the
> repeater input frequency as a weak off frequency signal.
> It would wander through the passband of the repeater in about 30-45
> seconds and again sound like a weak off frequency signal as the 
> squelch closed.
> The repeater was either in the 148 or the 150 MHz range and
> interfered with a 146.79, 146.82, 146.88 and a 149.94 MHz repeater.
> It took about a week to get the problem taken care of.
> The military had tried to classify the frequency of the repeater on
> this base due to the type of traffic that they handled.
>
> Kind of hard to hide what you are doing when transmitting in the
> clear with that much power and having a spur keying up repeaters over
> the distance that this one did.
>
> There is some software that allows finger printing of a transmission
> base on the lockup signature and oscillator stability as seen on the
> transmitted signal.
> You could possibly compare the known probable offender with the
> offender through one of the interfered with repeaters or it's input 
> frequency.
>
> Wish you well with resolving the problem.
>
> 73
> Glenn
> WB4UIV
>
> At 11:51 PM 10/28/2009, you wrote:
> >I have to wonder how he can say his stuff is clean when this just
> >started a couple weeks ago. Did he perform a PM check within the last
> >two weeks? Unlikely.
> >
> >Stuff can go south in a minute, and seldom just before you check it.
> >
> >Joe M.
> >
> >Paul Plack wrote:
> > >
> > >
> > > Mike,
> > >
> > > If it moves around based on time of day, my first guess is a PA that's
> > > gone bad, and has a parasitic that's temperature-related.
> > >
> > > If you've tracked an individual spur drifting 70 kHz up the band 
> during
> > > a single transmission, this is not some (intentional) oscillator
> > > drifting, but some combination of failed components or tuning 
> which has
> > > produced a parasitic.
> > >
> > > Sorry to say, but a paging transmitter owner swearing his stuff is 
> clean
> > > is pretty meaningless. The assumption in his industry is the
> > > professionals who maintain his stuff are not the problem, it's "those
> > > damn hams." Sadly, it may more often be the other way around these 
> days,
> > > as companies maintaining paging equipment have transitioned to
> > > underpaid, under-trained card-swappers instead of component-level
> > > technicians with a clue about RF systems.
> > >
> > > 73,
> > > Paul, AE4KR
> > >
> > >
> > > - Original Message -
> > > *From:* Mike <mailto:mwbese...@cox.net <mailto:mwbesemer%40cox.net>>
> > > *To:* Repeater-Builder@yahoogroups.com 
> <mailto:Repeater-Builder%40yahoogroups.com>
> > > <mailto:Repeater-Builder@yahoogroups.com 
> <mailto:Repeater-Builder%40yahoogroups.com>>
> > > *Sent:* Wednesday, October 28, 2009 12:28 PM
> > > *Subject:* [Repeater-Builder] Pager Interference to 2-meter & VHF
> > > Public Service Band
> > >
> > >
> > >
> > > A couple of weeks ago, our repeater system started to experience
> > > interference from a paging system...
> > >
> > >
> > > ...one evening I tracked it from about 145.120 to 145.190 as it
> > > swept through each transmission...
> > >
> > >
> > >
> > > .
> > >
> > >
> > >
> > >
> > >
> > >
> > > --
> > >
> > >
> > > Internal Virus Database is out of date.
> > > Checked by AVG - www.avg.com
> > > Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date:
> > 07/31/09 05:58:00
> > >
> >
> >
> >
> >
> >
> >
> >Yahoo! Groups Links
> >
> >
> >
>
> 

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Mike Besemer (WM4B)]

Joe,

 

I was told (caveat) that he verified the spectrum after the interference
started.  Since he's investing quite a bit of time into helping clear this
up, I have to believe he's done that.

 

73,

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of MCH
Sent: Wednesday, October 28, 2009 11:51 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

I have to wonder how he can say his stuff is clean when this just 
started a couple weeks ago. Did he perform a PM check within the last 
two weeks? Unlikely.

Stuff can go south in a minute, and seldom just before you check it.

Joe M.

Paul Plack wrote:
> 
> 
> Mike,
> 
> If it moves around based on time of day, my first guess is a PA that's 
> gone bad, and has a parasitic that's temperature-related.
> 
> If you've tracked an individual spur drifting 70 kHz up the band during 
> a single transmission, this is not some (intentional) oscillator 
> drifting, but some combination of failed components or tuning which has 
> produced a parasitic.
> 
> Sorry to say, but a paging transmitter owner swearing his stuff is clean 
> is pretty meaningless. The assumption in his industry is the 
> professionals who maintain his stuff are not the problem, it's "those 
> damn hams." Sadly, it may more often be the other way around these days, 
> as companies maintaining paging equipment have transitioned to 
> underpaid, under-trained card-swappers instead of component-level 
> technicians with a clue about RF systems.
> 
> 73,
> Paul, AE4KR
> 
> 
> - Original Message -
> *From:* Mike <mailto:mwbese...@cox.net <mailto:mwbesemer%40cox.net> >
> *To:* Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com> 
> <mailto:Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com> >
> *Sent:* Wednesday, October 28, 2009 12:28 PM
> *Subject:* [Repeater-Builder] Pager Interference to 2-meter & VHF
> Public Service Band
> 
> 
> 
> A couple of weeks ago, our repeater system started to experience
> interference from a paging system...
> 
> 
> ...one evening I tracked it from about 145.120 to 145.190 as it
> swept through each transmission...
> 
> 
> 
> .
> 
> 
> 
> 
> 
> 
> --
> 
> 
> Internal Virus Database is out of date.
> Checked by AVG - www.avg.com 
> Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 07/31/09
05:58:00
> 

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Mike Besemer (WM4B)]

Joe,

 

The problem isn't traffic dependant (10 am being a busy time), as I monitor
on and off all day and there is PLENTY of traffic all day long.  It seems to
have more to do with temperature.  You can clearly hear the signals come on
and fade off frequency.

 

It's also easy to hear which transmitter is sending the pages.  I have two
dual band radios in my vehicle.  Typically one is on the repeater output,
one on the input, one of VHF paging and one on UHF paging.  It's also been
confirmed by having the owner send test bursts by specific transmitters.

 

The other two UHF frequencies are also paging transmitters.

 

Good thoughts about the transmitter self-oscillating when unkeyed... that's
another road we can go down.

 

Speaking of going down roads. what I really need is more help!  Several of
our club members are engaged in assisting, but what I really need is a
dedicated team of folks.  Having to work for a living is taking a serious
bite out my tracking time!

 

73,

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Joe
Sent: Wednesday, October 28, 2009 11:51 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

Hello Mike.

The first clue is that the signal is moving up and down the 2 meter 
band. This would tell me that something not frequency controlled is 
causing the interference. Not frequency controlled would mean that the 
transmitter is not crystal or GPS locked to a specific frequency. Now, 
something that is frequency controlled may be involved with the IMD mix, 
but the signal that is free running is possibly causing an IMD mix to 
drift. I have seen this happen in a PA when it was NOT transmitting. 
We had a case of a paging transmitter PA that would go into self 
oscillation when it was not keyed by the exciter. The PA had power to 
it at all times and it would create interference when it was idle.

Some random thoughts:

Your paging company signal may be mixing with it, but they may not be 
the culprit.

10AM can be busy time for a paging company, so the fact that it happens 
around that time would not be unusual.

How do you know the data is from a specific paging company? Did you 
listen to their signal and the interference at the same time? Is it 
exactly the same?

He says that he has remote control of the transmitters. What happens 
when he shuts them both off? As someone else pointed out, does he have 
a link frequency that he ties the sites together with? The link 
transmitter may be causing the interference, or be part of the RF mix.

An IMD program will be useless to figure the IMD of a drifting 
transmitter that is part of a mix.

You said 462.850 and 462.925 are also involved. What is on those 
frequencies? Who is on these frequencies and how are they involved?

A lightning hit may have caused this all to happen.

In my last job I troubleshooted lots of interference. You really need 
to take an antenna and directional find the source of the interference. 
It is time consuming, but will lead you to the physical source of the 
interference. Don't be fooled that it is positively the paging 
companies fault, as it may just be a mix in some other service PA. The 
last one I found was interference on a 53.85 Mhz repeater. At first, 
the culprit seemed to be the NOAA weather station on 162.55Mhz. NOAA 
weather audio was coming through the repeater crystal clear. It turned 
out to be a telemetry station PA that was mixing 4 X 53.85 - 162.55 = 
52.85Mhz. The mix was exactly on the input! The telemetry station was 
owned by the water company that allowed us on the site, so we ended up 
moving the repeater to 53.71Mhz. We could have pushed the water company 
to fix their equipment, but probably would have been asked to leave the 
site. Sometimes diplomacy rules.

I worked for paging companies for quite awhile and know that they get a 
bad rap, probably rightfully so for the most part. This sounds like the 
paging company is willing to work with you. My gut feeling is that you 
are going to find something else causing the problem. Again, diplomacy 
rules.

73, Joe, K1ike

Mike wrote:
> A couple of weeks ago, our repeater system started to experience
interference from a paging system. The repeater is on 146.850 (-600 KHz),
with the antenna system about 120 feet up a water tower. T

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[DCFluX]

I'd use a really fast spectrum analyzer, meaning an analog one and
point a video camera at it

On Wed, Oct 28, 2009 at 10:19 PM, Kris Kirby  wrote:
> On Wed, 28 Oct 2009, Facility 406 DM09 wrote:
>> I am interested in such things!  Anyone have any good suggestions or
>> input regarding software or systems?
>
> Cavity -> digital storage oscilliscope.
>
> --
> Kris Kirby, KE4AHR
> Disinformation Analyst
>
>
> 
>
>
>
> Yahoo! Groups Links
>
>
>
>

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Kris Kirby]

On Wed, 28 Oct 2009, Facility 406 DM09 wrote:
> I am interested in such things!  Anyone have any good suggestions or 
> input regarding software or systems?

Cavity -> digital storage oscilliscope.

--
Kris Kirby, KE4AHR
Disinformation Analyst

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Facility 406 DM09]

: There is some software that allows finger printing of a transmission
: base on the lockup signature and oscillator stability as seen on the
: transmitted signal.

I am interested in such things!  Anyone have any good suggestions or input
regarding software or systems?

Kurt

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Glenn Little WB4UIV]

Locally, years ago, we had a military transmitter that had a 
wandering spur. I am near Charleston, SC. The spur was strong enough 
to key up amateur radio repeaters in the two meter band from 
Wilmington, NC to Savannah, Ga.
The offender turned out to be a 250 Watt base station used to cover 
approximately 10 Acres.
The radio was a Motorola MICOR.
The service shop could not fix the problem, so, they replaced the transmitter.

This may be a spur from a transmitter.
The spur that we experienced wandered up the band, then, down the band.
The wander was slow enough that you could hear it approaching the 
repeater input frequency as a weak off frequency signal.
It would wander through the passband of the repeater in about 30-45 
seconds and again sound like a weak off frequency signal as the squelch closed.
The repeater was either in the 148 or the 150 MHz range and 
interfered with a 146.79, 146.82, 146.88 and a 149.94 MHz repeater.
It took about a week to get the problem taken care of.
The military had tried to classify the frequency of the repeater on 
this base due to the type of traffic that they handled.

Kind of hard to hide what you are doing when transmitting in the 
clear with that much power and having a spur keying up repeaters over 
the distance that this one did.

There is some software that allows finger printing of a transmission 
base on the lockup signature and oscillator stability as seen on the 
transmitted signal.
You could possibly compare the known probable offender with the 
offender through one of the interfered with repeaters or it's input frequency.

Wish you well with resolving the problem.

73
Glenn
WB4UIV


At 11:51 PM 10/28/2009, you wrote:
>I have to wonder how he can say his stuff is clean when this just
>started a couple weeks ago. Did he perform a PM check within the last
>two weeks? Unlikely.
>
>Stuff can go south in a minute, and seldom just before you check it.
>
>Joe M.
>
>Paul Plack wrote:
> >
> >
> > Mike,
> >
> > If it moves around based on time of day, my first guess is a PA that's
> > gone bad, and has a parasitic that's temperature-related.
> >
> > If you've tracked an individual spur drifting 70 kHz up the band during
> > a single transmission, this is not some (intentional) oscillator
> > drifting, but some combination of failed components or tuning which has
> > produced a parasitic.
> >
> > Sorry to say, but a paging transmitter owner swearing his stuff is clean
> > is pretty meaningless. The assumption in his industry is the
> > professionals who maintain his stuff are not the problem, it's "those
> > damn hams." Sadly, it may more often be the other way around these days,
> > as companies maintaining paging equipment have transitioned to
> > underpaid, under-trained card-swappers instead of component-level
> > technicians with a clue about RF systems.
> >
> > 73,
> > Paul, AE4KR
> >
> >
> > - Original Message -
> > *From:* Mike <mailto:mwbese...@cox.net>
> > *To:* Repeater-Builder@yahoogroups.com
> > <mailto:Repeater-Builder@yahoogroups.com>
> > *Sent:* Wednesday, October 28, 2009 12:28 PM
> > *Subject:* [Repeater-Builder] Pager Interference to 2-meter & VHF
> > Public Service Band
> >
> >
> >
> > A couple of weeks ago, our repeater system started to experience
> > interference from a paging system...
> >
> >
> > ...one evening I tracked it from about 145.120 to 145.190 as it
> > swept through each transmission...
> >
> >
> >
> > .
> >
> >
> >
> >
> >
> >
> > 
> >
> >
> > Internal Virus Database is out of date.
> > Checked by AVG - www.avg.com
> > Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 
> 07/31/09 05:58:00
> >
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[MCH]

I have to wonder how he can say his stuff is clean when this just 
started a couple weeks ago. Did he perform a PM check within the last 
two weeks? Unlikely.

Stuff can go south in a minute, and seldom just before you check it.

Joe M.

Paul Plack wrote:
> 
> 
> Mike,
>  
> If it moves around based on time of day, my first guess is a PA that's 
> gone bad, and has a parasitic that's temperature-related.
>  
> If you've tracked an individual spur drifting 70 kHz up the band during 
> a single transmission, this is not some (intentional) oscillator 
> drifting, but some combination of failed components or tuning which has 
> produced a parasitic.
>  
> Sorry to say, but a paging transmitter owner swearing his stuff is clean 
> is pretty meaningless. The assumption in his industry is the 
> professionals who maintain his stuff are not the problem, it's "those 
> damn hams." Sadly, it may more often be the other way around these days, 
> as companies maintaining paging equipment have transitioned to 
> underpaid, under-trained card-swappers instead of component-level 
> technicians with a clue about RF systems.
>  
> 73,
> Paul, AE4KR
>  
> 
> - Original Message -
> *From:* Mike <mailto:mwbese...@cox.net>
> *To:* Repeater-Builder@yahoogroups.com
> <mailto:Repeater-Builder@yahoogroups.com>
> *Sent:* Wednesday, October 28, 2009 12:28 PM
> *Subject:* [Repeater-Builder] Pager Interference to 2-meter & VHF
> Public Service Band
> 
>  
> 
> A couple of weeks ago, our repeater system started to experience
> interference from a paging system...
> 
> 
> ...one evening I tracked it from about 145.120 to 145.190 as it
> swept through each transmission...
> 
>  
> 
> .
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Internal Virus Database is out of date.
> Checked by AVG - www.avg.com 
> Version: 8.5.387 / Virus Database: 270.13.38/2274 - Release Date: 07/31/09 
> 05:58:00
> 

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Joe]

Hello Mike.

The first clue is that the signal is moving up and down the 2 meter 
band.  This would tell me that something not frequency controlled is 
causing the interference.  Not frequency controlled would mean that the 
transmitter is not crystal or GPS locked to a specific frequency.  Now, 
something that is frequency controlled may be involved with the IMD mix, 
but the signal that is free running is possibly causing an IMD mix to 
drift.  I have seen this happen in a PA when it was NOT transmitting.  
We had a case of a paging transmitter PA that would go into self 
oscillation when it was not keyed by the exciter.  The PA had power to 
it at all times and it would create interference when it was idle.



Some random thoughts:

Your paging company signal may be mixing with it, but they may not be 
the culprit.

10AM can be busy time for a paging company, so the fact that it happens 
around that time would not be unusual.

How do you know the data is from a specific paging company?  Did you 
listen to their signal and the interference at the same time?  Is it 
exactly the same?

He says that he has remote control of the transmitters.  What happens 
when he shuts them both off?  As someone else pointed out, does he have 
a link frequency that he ties the sites together with?  The link 
transmitter may be causing the interference, or be part of the RF mix.

An IMD program will be useless to figure the IMD of a drifting 
transmitter that is part of a mix.

You said 462.850 and 462.925 are also involved.  What is on those 
frequencies?  Who is on these frequencies and how are they involved?

A lightning hit may have caused this all to happen.

In my last job I troubleshooted lots of interference.  You really need 
to take an antenna and directional find the source of the interference.  
It is time consuming, but will lead you to the physical source of the 
interference.  Don't be fooled that it is positively the paging 
companies fault, as it may just be a mix in some other service PA.  The 
last one I found was interference on a 53.85 Mhz repeater.  At first, 
the culprit seemed to be the NOAA weather station on 162.55Mhz.  NOAA 
weather audio was coming through the repeater crystal clear.  It turned 
out to be a telemetry station PA that was mixing  4 X 53.85 - 162.55 = 
52.85Mhz.  The mix was exactly on the input!  The telemetry station was 
owned by the water company that allowed us on the site, so we ended up 
moving the repeater to 53.71Mhz.  We could have pushed the water company 
to fix their equipment, but probably would have been asked to leave the 
site.  Sometimes diplomacy rules.

I worked for paging companies for quite awhile and know that they get a 
bad rap, probably rightfully so for the most part.  This sounds like the 
paging company is willing to work with you.  My gut feeling is that you 
are going to find something else causing the problem.  Again, diplomacy 
rules.

73, Joe, K1ike




Mike wrote:
> A couple of weeks ago, our repeater system started to experience interference 
> from a paging system.  The repeater is on 146.850 (-600 KHz), with the 
> antenna system about 120 feet up a water tower.  T

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Mike Besemer (WM4B)]

Strangely enough, I happen to be an O-O (as is the another club member, who
sponsors the 145.110 repeater. which is also being interfered with) and have
been in touch with our coordinator.  He's been very helpful in urging us
along and providing us guidance (or reassurance) that we're going about this
the right way.  He's also indicated that he's willing to go to ARRL HQ with
it if we need to and then let them go lateral to the FCC.  We had a great
experience with Laura Smith about a year ago when we needed help convincing
a banned user to stay off our systems.  It took one letter to her (complete
with recordings) and one phone call to get our banned user a nice letter
from Laura reminding him that he really couldn't afford to pay what she was
prepared to charge him for using our repeater!  So. I think that, armed with
enough ammunition, we can go that route.

 

However, I REALLY don't want to.  The fellow who owns the paging company has
tried to work with us, and although it's not going as fast as we'd like, I
understand that he's got a different motivation than we do.Aside from
that, he helped us out with a professional climbing crew a couple of years
ago, got us a good deal on a DB-224, and cut us a break on some hardline and
connectors.  The bottom line is, it's not a relationship we want to end
through a Federal intervention!  That being said, I HAVE reminded him that
he's admitted that we're carrying his data on our repeater, and whether or
not it's his equipment at fault or somebody else's, HE'S going to be the
first person they come looking for and it'll be a terrible pain in his butt.
and wallet.  He acknowledges that fact.  So. while I'd like for him to do
some things differently. I get where he's coming from and I appreciate that
he's helped as much as he has.

 

On the other hand, if it turns out to be equipment that belongs to another
company. I'll drop a dime in a heartbeat if I don't get satisfaction from
them!

 

73,

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Plack
Sent: Wednesday, October 28, 2009 7:48 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

Mike, the interference is clearly not caused by your own rusty roof, and is
both eggregious and easily documented. I know we hate to go there unless
it's a last resort, but I'll bet the FCC is almost as tired of non-compliant
pager systems as we are. Perhaps that "technique" would prove "motivating."

 

- Original Message - 

From: Mike Besemer (WM4B) <mailto:mwbese...@cox.net>  

To: Repeater-Builder@yahoogroups.com 

Sent: Wednesday, October 28, 2009 5:34 PM

Subject: RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

I'm with ya on your third paragraph.  We've worked well together so far, but
we have very different techniques and motivations... 

.

 
<http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId=
95324/stime=1256772865/nc1=4025338/nc2=5733770/nc3=4836037> 

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Paul Plack]

Mike, the interference is clearly not caused by your own rusty roof, and is 
both eggregious and easily documented. I know we hate to go there unless it's a 
last resort, but I'll bet the FCC is almost as tired of non-compliant pager 
systems as we are. Perhaps that "technique" would prove "motivating."

  - Original Message - 
  From: Mike Besemer (WM4B) 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Wednesday, October 28, 2009 5:34 PM
  Subject: RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public 
Service Band



  I'm with ya on your third paragraph.  We've worked well together so far, but 
we have very different techniques and motivations... 


  . 

  

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Mike Besemer (WM4B)]

Ya'll know as much as I do about what the paging equipment is.  I'm working
with limited knowledge. only what gets passed on to me from the owner.

 

I'll ask about that, as well as the exciter frequencies.

 

 

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Kevin King
Sent: Wednesday, October 28, 2009 6:02 PM
To: Repeater-Builder@yahoogroups.com
Subject: RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

I would look at the exciter freq on the uhf paging transmitter. 

It would help with some info on the paging transmitters. Model and such.

-Original Message-
From: Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com> 
[mailto:Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com> ] On Behalf Of Mike
Sent: Wednesday, October 28, 2009 1:29 PM
To: Repeater-Builder@yahoogroups.com
<mailto:Repeater-Builder%40yahoogroups.com> 
Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

A couple of weeks ago, our repeater system started to experience
interference from a paging system. The repeater is on 146.850 (-600 KHz),
with the antenna system about 120 feet up a water tower. The repeater
itself is an Advanced Communications System KRP-5000 running 35 watts
through a set of 4 WACOM cans. The feedline is 7/8" hardline feeding a
DB-224. All jumpers are RG-214 MILSPEC with MILSPEC connectors. This
system has been in service for years and has never given us any problems,
and we are the only ones at the site.

To be clear, the interference we are experiencing is clearly audible on the
repeater input. I have the capability to monitor via telephone and have
heard it on the receiver, and I've also traveled to the site and heard the
interference on my mobile radio hooked to the repeater antenna. The
interference is also audible on the input in various locations around town.
Also, the interference can be heard on the input regardless of whether or
not the repeater transmitter is on. It also continued to be present during
several days of continuous heavy rain. 

The interference typically shows up at least once a day, although some days
(rarely) it does not show up at all and other days it will show up several
times. Lately, it's been making an appearance around 10 a.m. and hangs
around for an hour or two. As it begins to disappear, it sounds as though
it is moving off frequency. 

This interference has also been heard on at least two other repeaters in the
area. One is about 22 air-miles from the 146.85 machine and is on 145.110
(-600 KHz). It has also been heard on or near the output frequency of that
machine, and one evening I tracked it from about 145.120 to 145.190 as it
swept through each transmission. The other repeater it has been heard on is
147.300 (+600 KHz). I also have reports from a neighboring county a
ham/deputy sheriff there has been hearing it on VHF public safety
frequencies. As you can see, it's all over the place.

I've been working with the owner of a local paging company and we can
clearly tell that the data we're hearing is coming from 152.480 and 462.775.
He has two sites (about 20 miles apart) that simulcasts on both frequencies
and when those transmitters are active it's easy to tell that the data is
the same. He also tells me that he can key each transmitter separately and
the data from each transmitter will be heard on our repeater. We also
believe that there are other systems on nearby frequencies that are being
heard on our repeater, specifically 462.850 and 462.925.

I've run IMD numbers on everything I can think of, but can't come up with a
common thread. For it to be moving all through the 2-meter band and for it
to be mixing with several different frequencies, it seems to me that it's
got to be very ugly and unstable. What am I missing here?

Mike
WM4B



Yahoo! Groups Links

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Mike Besemer (WM4B)]

Paul,

 

I'm with ya on your third paragraph.  We've worked well together so far, but
we have very different techniques and motivations.  

 

Right now, my motivation is to make is stop before I go crazy.  I'm hearing
paging tones in my sleep!  

 

I kinda think one of the sites took a lightning strike about the time this
started (we had a pretty good lightning event about that time), so I think
the PA is a good possibility.  Or an isolator/combiner.  

 

I'd like to have the first whack with a baseball bat when we find it!

 

73,

 

Mike

WM4B

 

From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Paul Plack
Sent: Wednesday, October 28, 2009 6:29 PM
To: Repeater-Builder@yahoogroups.com
Subject: Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

Mike,

 

If it moves around based on time of day, my first guess is a PA that's gone
bad, and has a parasitic that's temperature-related.

 

If you've tracked an individual spur drifting 70 kHz up the band during a
single transmission, this is not some (intentional) oscillator drifting, but
some combination of failed components or tuning which has produced a
parasitic.

 

Sorry to say, but a paging transmitter owner swearing his stuff is clean is
pretty meaningless. The assumption in his industry is the professionals who
maintain his stuff are not the problem, it's "those damn hams." Sadly, it
may more often be the other way around these days, as companies maintaining
paging equipment have transitioned to underpaid, under-trained card-swappers
instead of component-level technicians with a clue about RF systems.

 

73,

Paul, AE4KR

 

- Original Message - 

From: Mike <mailto:mwbese...@cox.net>  

To: Repeater-Builder@yahoogroups.com 

Sent: Wednesday, October 28, 2009 12:28 PM

Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

 

  

A couple of weeks ago, our repeater system started to experience
interference from a paging system...


...one evening I tracked it from about 145.120 to 145.190 as it swept
through each transmission...

 

.

 
<http://geo.yahoo.com/serv?s=97359714/grpId=104168/grpspId=1705063108/msgId=
95309/stime=1256754552/nc1=4025338/nc2=5191953/nc3=5741393> 

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Paul Plack]

Mike,

If it moves around based on time of day, my first guess is a PA that's gone 
bad, and has a parasitic that's temperature-related.

If you've tracked an individual spur drifting 70 kHz up the band during a 
single transmission, this is not some (intentional) oscillator drifting, but 
some combination of failed components or tuning which has produced a parasitic.

Sorry to say, but a paging transmitter owner swearing his stuff is clean is 
pretty meaningless. The assumption in his industry is the professionals who 
maintain his stuff are not the problem, it's "those damn hams." Sadly, it may 
more often be the other way around these days, as companies maintaining paging 
equipment have transitioned to underpaid, under-trained card-swappers instead 
of component-level technicians with a clue about RF systems.

73,
Paul, AE4KR

  - Original Message - 
  From: Mike 
  To: Repeater-Builder@yahoogroups.com 
  Sent: Wednesday, October 28, 2009 12:28 PM
  Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF Public 
Service Band


A couple of weeks ago, our repeater system started to experience 
interference from a paging system...


  ...one evening I tracked it from about 145.120 to 145.190 as it swept through 
each transmission...


  . 

  

RE: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Kevin King]

I would look at the exciter freq on the uhf paging transmitter. 

It would help with some info on the paging transmitters. Model and such.

-Original Message-
From: Repeater-Builder@yahoogroups.com
[mailto:repeater-buil...@yahoogroups.com] On Behalf Of Mike
Sent: Wednesday, October 28, 2009 1:29 PM
To: Repeater-Builder@yahoogroups.com
Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF Public
Service Band

A couple of weeks ago, our repeater system started to experience
interference from a paging system.  The repeater is on 146.850 (-600 KHz),
with the antenna system about 120 feet up a water tower.  The repeater
itself is an Advanced Communications System KRP-5000 running 35 watts
through a set of 4 WACOM cans.  The feedline is 7/8" hardline feeding a
DB-224.  All jumpers are RG-214 MILSPEC with MILSPEC connectors.  This
system has been in service for years and has never given us any problems,
and we are the only ones at the site.

To be clear, the interference we are experiencing is clearly audible on the
repeater input.  I have the capability to monitor via telephone and have
heard it on the receiver, and I've also traveled to the site and heard the
interference on my mobile radio hooked to the repeater antenna.  The
interference is also audible on the input in various locations around town.
Also, the interference can be heard on the input regardless of whether or
not the repeater transmitter is on.  It also continued to be present during
several days of continuous heavy rain.  

The interference typically shows up at least once a day, although some days
(rarely) it does not show up at all and other days it will show up several
times.  Lately, it's been making an appearance around 10 a.m. and hangs
around for an hour or two.  As it begins to disappear, it sounds as though
it is moving off frequency.  

This interference has also been heard on at least two other repeaters in the
area.  One is about 22 air-miles from the 146.85 machine and is on 145.110
(-600 KHz).  It has also been heard on or near the output frequency of that
machine, and one evening I tracked it from about 145.120 to 145.190 as it
swept through each transmission.  The other repeater it has been heard on is
147.300 (+600 KHz).  I also have reports from a neighboring county a
ham/deputy sheriff there has been hearing it on VHF public safety
frequencies.  As you can see, it's all over the place.

I've been working with the owner of a local paging company and we can
clearly tell that the data we're hearing is coming from 152.480 and 462.775.
He has two sites (about 20 miles apart) that simulcasts on both frequencies
and when those transmitters are active it's easy to tell that the data is
the same.  He also tells me that he can key each transmitter separately and
the data from each transmitter will be heard on our repeater.  We also
believe that there are other systems on nearby frequencies that are being
heard on our repeater, specifically 462.850 and 462.925.

I've run IMD numbers on everything I can think of, but can't come up with a
common thread.  For it to be moving all through the 2-meter band and for it
to be mixing with several different frequencies, it seems to me that it's
got to be very ugly and unstable.  What am I missing here?

Mike
WM4B








Yahoo! Groups Links

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[MCH]

Mixing products generally don't sweep through the spectrum, as usually 
both TXs are stable and the mix would be as well.

Joe M.

Matt Harker wrote:
> 
> 
> Sounds like a bad case of mixing products (i.e. 2A-B) where A is 
> frequency A and B is frequency B.  Several years ago, I helped cure a 
> similar problem on 146.820 MHz.  Turned out four transmitters were 
> involved in that fracas and it only took two to start the repeater howling.
>  
> 152.480 is one of the common paging frequencies.  There is another 
> around 157 MHz that is usually a troublemaker for 2m amateur 
> repeaters.  A lot paging transmitters are NOT properly filtered.  I have 
> run across some that were connected directly to the feedline and antenna 
> with no circulator, no isolator, nothing.  This is unacceptable 
> practice.  No transmitter or receiver should be looking directly into a 
> feedline at any fixed site where multiple transmitters are in operation 
> or, where interference could likely erupt.
>  
> I doubt the UHF paging transmitters has a whole lot to do with the 
> problem although there is a slim chance they might.  Chances are, the 
> VHF transmitter is the one involved. 
>  
> The next thing I'd be curious about, given the paging company's comments 
> about the ability to key the transmitters separately, is this:  How are 
> they getting the data from their offices to the transmitters?  By radio 
> link? By wireline? or both?  If by radio, therein may lie the second 
> transmitter in the mix.  If not, keep searching.
>  
> One thing to keep in mind with the spectrum analyzer is that it is not 
> likely as sensitive as the repeater's receiver.  Some spec an's are 
> pretty sensitive, others not so sensitive.  So you may want to visit the 
> paging site with it and see what you find.  Especially around 304.960 
> MHz which is the double of 152.480 MHz.
>  
>  
> KC5DBH Matt
> 
> 
> ------------
> *From:* Mike 
> *To:* Repeater-Builder@yahoogroups.com
> *Sent:* Wed, October 28, 2009 1:28:56 PM
> *Subject:* [Repeater-Builder] Pager Interference to 2-meter & VHF Public 
> Service Band
> 
> A couple of weeks ago, our repeater system started to experience 
> interference from a paging system.  The repeater is on 146.850 (-600 
> KHz), with the antenna system about 120 feet up a water tower.  The 
> repeater itself is an Advanced Communications System KRP-5000 running 35 
> watts through a set of 4 WACOM cans.  The feedline is 7/8" hardline 
> feeding a DB-224.  All jumpers are RG-214 MILSPEC with MILSPEC 
> connectors.  This system has been in service for years and has never 
> given us any problems, and we are the only ones at the site.
> 
> To be clear, the interference we are experiencing is clearly audible on 
> the repeater input.  I have the capability to monitor via telephone and 
> have heard it on the receiver, and I've also traveled to the site and 
> heard the interference on my mobile radio hooked to the repeater 
> antenna.  The interference is also audible on the input in various 
> locations around town.  Also, the interference can be heard on the input 
> regardless of whether or not the repeater transmitter is on.  It also 
> continued to be present during several days of continuous heavy rain. 
> 
> The interference typically shows up at least once a day, although some 
> days (rarely) it does not show up at all and other days it will show up 
> several times.  Lately, it's been making an appearance around 10 a.m. 
> and hangs around for an hour or two.  As it begins to disappear, it 
> sounds as though it is moving off frequency. 
> 
> This interference has also been heard on at least two other repeaters in 
> the area.  One is about 22 air-miles from the 146.85 machine and is on 
> 145.110 (-600 KHz).  It has also been heard on or near the output 
> frequency of that machine, and one evening I tracked it from about 
> 145.120 to 145.190 as it swept through each transmission.  The other 
> repeater it has been heard on is 147.300 (+600 KHz).  I also have 
> reports from a neighboring county a ham/deputy sheriff there has been 
> hearing it on VHF public safety frequencies.  As you can see, it's all 
> over the place.
> 
> I've been working with the owner of a local paging company and we can 
> clearly tell that the data we're hearing is coming from 152.480 and 
> 462.775.  He has two sites (about 20 miles apart) that simulcasts on 
> both frequencies and when those transmitters are active it's easy to 
> tell that the data is the same.  He also tells me that he can key each 
> transmitter separately and the data from each transmitte

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[MCH]

Dirty paging TX. Seen that many times.

Joe M.

Mike wrote:
> A couple of weeks ago, our repeater system started to experience interference 
> from a paging system.  The repeater is on 146.850 (-600 KHz), with the 
> antenna system about 120 feet up a water tower.  The repeater itself is an 
> Advanced Communications System KRP-5000 running 35 watts through a set of 4 
> WACOM cans.  The feedline is 7/8" hardline feeding a DB-224.  All jumpers are 
> RG-214 MILSPEC with MILSPEC connectors.  This system has been in service for 
> years and has never given us any problems, and we are the only ones at the 
> site.
> 
> To be clear, the interference we are experiencing is clearly audible on the 
> repeater input.  I have the capability to monitor via telephone and have 
> heard it on the receiver, and I've also traveled to the site and heard the 
> interference on my mobile radio hooked to the repeater antenna.  The 
> interference is also audible on the input in various locations around town.  
> Also, the interference can be heard on the input regardless of whether or not 
> the repeater transmitter is on.  It also continued to be present during 
> several days of continuous heavy rain.  
> 
> The interference typically shows up at least once a day, although some days 
> (rarely) it does not show up at all and other days it will show up several 
> times.  Lately, it's been making an appearance around 10 a.m. and hangs 
> around for an hour or two.  As it begins to disappear, it sounds as though it 
> is moving off frequency.  
> 
> This interference has also been heard on at least two other repeaters in the 
> area.  One is about 22 air-miles from the 146.85 machine and is on 145.110 
> (-600 KHz).  It has also been heard on or near the output frequency of that 
> machine, and one evening I tracked it from about 145.120 to 145.190 as it 
> swept through each transmission.  The other repeater it has been heard on is 
> 147.300 (+600 KHz).  I also have reports from a neighboring county a 
> ham/deputy sheriff there has been hearing it on VHF public safety 
> frequencies.  As you can see, it's all over the place.
> 
> I've been working with the owner of a local paging company and we can clearly 
> tell that the data we're hearing is coming from 152.480 and 462.775.  He has 
> two sites (about 20 miles apart) that simulcasts on both frequencies and when 
> those transmitters are active it's easy to tell that the data is the same.  
> He also tells me that he can key each transmitter separately and the data 
> from each transmitter will be heard on our repeater.  We also believe that 
> there are other systems on nearby frequencies that are being heard on our 
> repeater, specifically 462.850 and 462.925.
> 
> I've run IMD numbers on everything I can think of, but can't come up with a 
> common thread.  For it to be moving all through the 2-meter band and for it 
> to be mixing with several different frequencies, it seems to me that it's got 
> to be very ugly and unstable.  What am I missing here?
> 
> Mike
> WM4B
> 
> 
> 
> 
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
> 

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[mwbesemer]

 Good question about how the data was getting to both transmitter 
sites.  I've been meaning to ask that question and keep forgetting.


I'll report back.

Mike
WM4B

On Wed, Oct 28, 2009 at 3:16 PM, Matt Harker wrote:


Sounds like a bad case of mixing products (i.e. 2A-B) where A is 
frequency A and B is frequency B.  Several years ago, I helped cure a 
similar problem on 146.820 MHz.  Turned out four transmitters were 
involved in that fracas and it only took two to start the repeater 
howling.


152.480 is one of the common paging frequencies.  There is another 
around 157 MHz that is usually a troublemaker for 2m amateur repeaters. 
A lot paging transmitters are NOT properly filtered.  I have run across 
some that were connected directly to the feedline and antenna with no 
circulator, no isolator, nothing.  This is unacceptable practice.  No 
transmitter or receiver should be looking directly into a feedline at 
any fixed site where multiple transmitters are in operation or, where 
interference could likely erupt.


I doubt the UHF paging transmitters has a whole lot to do with the 
problem although there is a slim chance they might.  Chances are, the 
VHF transmitter is the one involved.


The next thing I'd be curious about, given the paging company's comments 
about the ability to key the transmitters separately, is this:  How are 
they getting the data from their offices to the transmitters?  By radio 
link? By wireline? or both?  If by radio, therein may lie the second 
transmitter in the mix.  If not, keep searching.


One thing to keep in mind with the spectrum analyzer is that it is not 
likely as sensitive as the repeater's receiver.  Some spec an's are 
pretty sensitive, others not so sensitive.  So you may want to visit the 
paging site with it and see what you find.  Especially around 304.960 
MHz which is the double of 152.480 MHz.



KC5DBH Matt

___

From: Mike 
To: Repeater-Builder@ yahoogroups. com
Sent: Wed, October 28, 2009 1:28:56 PM
Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF Public 
Service Band


A couple of weeks ago, our repeater system started to experience 
interference from a paging system.  The repeater is on 146.850 (-600 
KHz), with the antenna system about 120 feet up a water tower.  The 
repeater itself is an Advanced Communications System KRP-5000 running 35 
watts through a set of 4 WACOM cans.  The feedline is 7/8" hardline 
feeding a DB-224.  All jumpers are RG-214 MILSPEC with MILSPEC 
connectors.  This system has been in service for years and has never 
given us any problems, and we are the only ones at the  site.


To be clear, the interference we are experiencing is clearly audible on 
the repeater input.  I have the capability to monitor via telephone and 
have heard it on the receiver, and I've also traveled to the site and 
heard the interference on my mobile radio hooked to the repeater 
antenna.  The interference is also audible on the input in various 
locations around town.  Also, the interference can be heard on the input 
regardless of whether or not the repeater transmitter is on.  It also 
continued to be present during several days of continuous heavy rain.


The interference typically shows up at least once a day, although some 
days (rarely) it does not show up at all and other days it will show up 
several times.  Lately, it's been making an appearance around 10 a.m. 
and hangs around for an hour or two.  As it begins to disappear, it 
sounds as though it is moving off frequency.


This  interference has also been heard on at least two other repeaters 
in the area.  One is about 22 air-miles from the 146.85 machine and is 
on 145.110 (-600 KHz).  It has also been heard on or near the output 
frequency of that machine, and one evening I tracked it from about 
145.120 to 145.190 as it swept through each transmission.  The other 
repeater it has been heard on is 147.300 (+600 KHz).  I also have 
reports from a neighboring county a ham/deputy sheriff there has been 
hearing it on VHF public safety frequencies.  As you can see, it's all 
over the place.


I've been working with the owner of a local paging company and we can 
clearly tell that the data we're hearing is coming from 152.480 and 
462.775.  He has two sites (about 20 miles apart) that simulcasts on 
both frequencies and when those transmitters are active it's easy to 
tell that the data is the same.  He also tells me that he can key each 
transmitter  separately and the data from each transmitter will be heard 
on our repeater.  We also believe that there are other systems on nearby 
frequencies that are being heard on our repeater, specifically 462.850 
and 462.925.


I've run IMD numbers on everything I can think of, but can't come up 
with a common thread.  For it to be moving all through the 2-meter band 
and for it to be mixing with several different

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Matt Harker]

Sounds like a bad case of mixing products (i.e. 2A-B) where A is frequency A 
and B is frequency B.  Several years ago, I helped cure a similar problem on 
146.820 MHz.  Turned out four transmitters were involved in that fracas and it 
only took two to start the repeater howling.

152.480 is one of the common paging frequencies.  There is another around 157 
MHz that is usually a troublemaker for 2m amateur repeaters.  A lot paging 
transmitters are NOT properly filtered.  I have run across some that were 
connected directly to the feedline and antenna with no circulator, no isolator, 
nothing.  This is unacceptable practice.  No transmitter or receiver should be 
looking directly into a feedline at any fixed site where multiple transmitters 
are in operation or, where interference could likely erupt. 

I doubt the UHF paging transmitters has a whole lot to do with the problem 
although there is a slim chance they might.  Chances are, the VHF transmitter 
is the one involved.  

The next thing I'd be curious about, given the paging company's comments about 
the ability to key the transmitters separately, is this:  How are they getting 
the data from their offices to the transmitters?  By radio link? By wireline? 
or both?  If by radio, therein may lie the second transmitter in the mix.  If 
not, keep searching.

One thing to keep in mind with the spectrum analyzer is that it is not likely 
as sensitive as the repeater's receiver.  Some spec an's are pretty sensitive, 
others not so sensitive.  So you may want to visit the paging site with it and 
see what you find.  Especially around 304.960 MHz which is the double of 
152.480 MHz.
 
 KC5DBH Matt 





From: Mike 
To: Repeater-Builder@yahoogroups.com
Sent: Wed, October 28, 2009 1:28:56 PM
Subject: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service 
Band

A couple of weeks ago, our repeater system started to experience interference 
from a paging system.  The repeater is on 146.850 (-600 KHz), with the antenna 
system about 120 feet up a water tower.  The repeater itself is an Advanced 
Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans.  
The feedline is 7/8" hardline feeding a DB-224.  All jumpers are RG-214 MILSPEC 
with MILSPEC connectors.  This system has been in service for years and has 
never given us any problems, and we are the only ones at the site.

To be clear, the interference we are experiencing is clearly audible on the 
repeater input.  I have the capability to monitor via telephone and have heard 
it on the receiver, and I've also traveled to the site and heard the 
interference on my mobile radio hooked to the repeater antenna.  The 
interference is also audible on the input in various locations around town.  
Also, the interference can be heard on the input regardless of whether or not 
the repeater transmitter is on.  It also continued to be present during several 
days of continuous heavy rain.  

The interference typically shows up at least once a day, although some days 
(rarely) it does not show up at all and other days it will show up several 
times.  Lately, it's been making an appearance around 10 a.m. and hangs around 
for an hour or two.  As it begins to disappear, it sounds as though it is 
moving off frequency.  

This interference has also been heard on at least two other repeaters in the 
area.  One is about 22 air-miles from the 146.85 machine and is on 145.110 
(-600 KHz).  It has also been heard on or near the output frequency of that 
machine, and one evening I tracked it from about 145.120 to 145.190 as it swept 
through each transmission.  The other repeater it has been heard on is 147.300 
(+600 KHz).  I also have reports from a neighboring county a ham/deputy sheriff 
there has been hearing it on VHF public safety frequencies.  As you can see, 
it's all over the place.

I've been working with the owner of a local paging company and we can clearly 
tell that the data we're hearing is coming from 152.480 and 462.775.  He has 
two sites (about 20 miles apart) that simulcasts on both frequencies and when 
those transmitters are active it's easy to tell that the data is the same.  He 
also tells me that he can key each transmitter separately and the data from 
each transmitter will be heard on our repeater.  We also believe that there are 
other systems on nearby frequencies that are being heard on our repeater, 
specifically 462.850 and 462.925.

I've run IMD numbers on everything I can think of, but can't come up with a 
common thread.  For it to be moving all through the 2-meter band and for it to 
be mixing with several different frequencies, it seems to me that it's got to 
be very ugly and unstable.  What am I missing here?

Mike
WM4B








Yahoo! Groups Links




  

Re: [Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[mwbesemer]

There are at least two transmitters at two sites... not likely they're 
all bad.  But... the owner has assured me they're clean and I haven't 
seen anything hokey on the spectrum analyzer from the repeater site.

Mike
WM4B

On Wed, Oct 28, 2009 at 2:46 PM, dmur...@verizon.net wrote:
Did you look a the output of the paging transmitters with a spectrum 
analyzer?




Oct 28, 2009 06:29:13 PM, Repeater-Builder@yahoogroups.com   wrote:









A couple of weeks ago, our repeater system started to experience 
interference from a paging system.  The repeater is on 146.850 (-600 
KHz), with the antenna system about 120 feet up a water tower.  The 
repeater itself is an Advanced Communications System KRP-5000 running 35 
watts through a set of 4 WACOM cans.  The feedline is 7/8" hardline 
feeding a DB-224.  All jumpers are RG-214 MILSPEC with MILSPEC 
connectors.  This system has been in service for years and has never 
given us any problems, and we are the only ones at the site.



  To be clear, the interference we are experiencing is clearly audible 
on the repeater input.  I have the capability to monitor via telephone 
and have heard it on the receiver, and I've also traveled to the site 
and heard the interference on my mobile radio hooked to the repeater 
antenna.  The interference is also audible on the input in various 
locations around town.  Also, the interference can be heard on the input 
regardless of whether or not the repeater transmitter is on.  It also 
continued to be present during several days of continuous heavy rain.



  The interference typically shows up at least once a day, although some 
days (rarely) it does not show up at all and other days it will show up 
several times.  Lately, it's been making an appearance around 10 a.m. 
and hangs around for an hour or two.  As it begins to disappear, it 
sounds as though it is moving off frequency.



  This interference has also been heard on at least two other repeaters 
in the area.  One is about 22 air-miles from the 146.85 machine and is 
on 145.110 (-600 KHz).  It has also been heard on or near the output 
frequency of that machine, and one evening I tracked it from about 
145.120 to 145.190 as it swept through each transmission.  The other 
repeater it has been heard on is 147.300 (+600 KHz).  I also have 
reports from a neighboring county a ham/deputy sheriff there has been 
hearing it on VHF public safety frequencies.  As you can see, it's all 
over the place.



  I've been working with the owner of a local paging company and we can 
clearly tell that the data we're hearing is coming from 152.480 and 
462.775.  He has two sites (about 20 miles apart) that simulcasts on 
both frequencies and when those transmitters are active it's easy to 
tell that the data is the same.  He also tells me that he can key each 
transmitter separately and the data from each transmitter will be heard 
on our repeater.  We also believe that there are other systems on nearby 
frequencies that are being heard on our repeater, specifically 462.850 
and 462.925.



  I've run IMD numbers on everything I can think of, but can't come up 
with a common thread.  For it to be moving all through the 2-meter band 
and for it to be mixing with several different frequencies, it seems to 
me that it's got to be very ugly and unstable.  What am I missing here?



  Mike

  WM4B























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[Repeater-Builder] Pager Interference to 2-meter & VHF Public Service Band

[Mike]

A couple of weeks ago, our repeater system started to experience interference 
from a paging system.  The repeater is on 146.850 (-600 KHz), with the antenna 
system about 120 feet up a water tower.  The repeater itself is an Advanced 
Communications System KRP-5000 running 35 watts through a set of 4 WACOM cans.  
The feedline is 7/8" hardline feeding a DB-224.  All jumpers are RG-214 MILSPEC 
with MILSPEC connectors.  This system has been in service for years and has 
never given us any problems, and we are the only ones at the site.

To be clear, the interference we are experiencing is clearly audible on the 
repeater input.  I have the capability to monitor via telephone and have heard 
it on the receiver, and I've also traveled to the site and heard the 
interference on my mobile radio hooked to the repeater antenna.  The 
interference is also audible on the input in various locations around town.  
Also, the interference can be heard on the input regardless of whether or not 
the repeater transmitter is on.  It also continued to be present during several 
days of continuous heavy rain.  

The interference typically shows up at least once a day, although some days 
(rarely) it does not show up at all and other days it will show up several 
times.  Lately, it's been making an appearance around 10 a.m. and hangs around 
for an hour or two.  As it begins to disappear, it sounds as though it is 
moving off frequency.  

This interference has also been heard on at least two other repeaters in the 
area.  One is about 22 air-miles from the 146.85 machine and is on 145.110 
(-600 KHz).  It has also been heard on or near the output frequency of that 
machine, and one evening I tracked it from about 145.120 to 145.190 as it swept 
through each transmission.  The other repeater it has been heard on is 147.300 
(+600 KHz).  I also have reports from a neighboring county a ham/deputy sheriff 
there has been hearing it on VHF public safety frequencies.  As you can see, 
it's all over the place.

I've been working with the owner of a local paging company and we can clearly 
tell that the data we're hearing is coming from 152.480 and 462.775.  He has 
two sites (about 20 miles apart) that simulcasts on both frequencies and when 
those transmitters are active it's easy to tell that the data is the same.  He 
also tells me that he can key each transmitter separately and the data from 
each transmitter will be heard on our repeater.  We also believe that there are 
other systems on nearby frequencies that are being heard on our repeater, 
specifically 462.850 and 462.925.

I've run IMD numbers on everything I can think of, but can't come up with a 
common thread.  For it to be moving all through the 2-meter band and for it to 
be mixing with several different frequencies, it seems to me that it's got to 
be very ugly and unstable.  What am I missing here?

Mike
WM4B