If I have followed the thread correctly, this interference happens from
either of the paging transmitters, not just one or the other.
I would suggest you check to see if there is a TV linear translator very nearby
it could be the source.
--- In Repeater-Builder@yahoogroups.com, Mike Besemer \(WM4B\)
mwbese...@... 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.
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
