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- Mar 7, 2010
- San Diego
I will try to take a video of the issue, maybe I can identify particular problem freq's on the system that I can throw an IFX at. I think that if I throw a freq at IFX, the scanner will apply that IFX to any time the scanner hits that freq, even if it comes up in a trunking CC grant? I know I have IFX enabled for another systems control channel, but I can't remember how I did it. The SDS's are really really bad with selectivity...on 800 they perform similarly to old pre triple conversion scanners, where I can hear paging signals and data bursts from nearby 800 frequencies beeping and squaking over the voice traffic of analog.If you have a -50dBm signal and then enable the scanners 20dB attenuator you should receive a -70dBm signal, not a -100-110dBm. That's almost no signal at all. It's probably the multicoupler that gets overloaded so try and add an attenuator between it and the antenna. Stridsberg multicouplers doesn't take kindly to strong signals and gets easily overloaded. There are fixed 20dB attenuators to be had for $5 and adjustable ones for $20. You'll probably need to reduce the signal to a level just under where the multicoupler doesn't get into problems. It can be done by expensive filters that only take out the cell phone frequencies or you could try to attenuate all signals coming from the antenna to a level that works and probably still receive the systems you want to monitor.
As the scanner seems to partly receive and decode the control channel but then on the voice channel it looses reception, try and set IFX to the voice channels and try the filter settings again. Cellular frequencies can be either in 750, 800 or 850MHz band and the system you try to monitor are probably at 860 or 770MHz that are very close to those cellular frequencies.
The filter setting in the scanner are in the RF side of the receiver, at the first IF frequency, but could be too late in the receive chain as the receivers front end have already been hit by the full force from the whole frequency band, as also the multicoupler are exposed to.