Hi
@KOK5CY,
The “annoying frequencies” that you want to get rid of, are they outside the 156 MHz and 800 MHz bands? Also, how strong are the annoying frequencies signal strength-wise? Can you squelch them out or are they very strong? For these annoying frequencies, are they “real” FCC authorized communications signals or are they like “birdies” from nearby radiators like wall-warts?
There are two tests that would also be good to know. First, if the scanner is connected to a small dummy load, preferably directly attached to the scanner’s BNC connector, are the annoying signals present? Second, if a telescopic whip antenna is directly attached to the scanner’s BNC connector, are the annoying frequencies present?
Another thing to try is signal attenuation using the Uniden BCD536HP scanner’s built-in attenuator. You can also try external attenuation just to see at what level of attenuation squelches the annoying frequencies (if possible).
For the Diamond Antennas D130J discone antenna, is it up 20 feet in free space (away from all nearby objects)? Is the coax correctly assembled with PL-259 or N type connectors? Is the jumper from the RG-8 to the Uniden BCD536HP scanner good quality coax and properly assembled with connectors? And finally, is the entire setup properly grounded to the house ground per NEC Article 810?
As for your two primary bands of interest, how strong are those frequencies? How many systems are you monitoring? Knowing the frequencies used by those systems would help us suggest some possible solutions. We really need more specific details in order to assess the overall situation.
Logical troubleshooting is key to understanding the issue so abatement solutions can be suggested for further testing.