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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