I’m needing some advice on what to do about my 536hp . I recently erected a new D130J and it’s up at 20’ with RG8X 20’ straight to my scanner . It is receiving unwanted frequencies that are not in my laptop software and I went through the software and deleted most of the low band and everything was fine last night but it seems to be getting worse by the hour. I have permanently locked out the annoying frequencies and more just seem to pop up and all it does is make the noise of encryption and it’s annoying ever since I started using the new antenna. I listen to the 800 trunked and some low band which is in the 156 MHz . I’m not sure what to do about the issue it only does it on the 150 MHz band
Band pass filter
- Thread starter KOK5CY
- Start date
wgbecks
Active Member
I am not familiar with newer Uniden receivers/scanners as I don't use them for this vary reason! However, you might check to see if there
might be a band selectable RF gain setting that could be lowered for VHF.
Another thought, if you primary interests is in the 700/800 bands, then you could try using an Antenna Triplexer to insert between the
D130J and the 536HP whereby you'd only use the 700/800 port connected to the scanner. This would provide sufficient filtering
(attenuation) in the VHF band that may address the overload problem yet allow enough local signals to pass through.
K4EET
Chaplain
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.
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.
It’s call birdies and only time I hear these is early morning like test tones for fire depts I’ve never heard of . I have only 1 low band frequency I listen to and I had lock that 1 out because it became a birdie . My antenna is 2 ‘ above my roof line . It’s 3’ away from the house on a 20’ pole and is grounded to my outdoor water valve . My coax is a RG8X with no jumpers except for the bnc adapter for the scanner end .
Should I just invest in a yagi and point it to the trunked tower which is only 8 miles away
RFI-EMI-GUY
Member
- Joined
- Dec 22, 2013
- Messages
- 7,653
Interference like you describe generally comes from high power NOAA weather transmitters at 162 MHZ or VHF paging often from nearby hospitals. There are filters to reduce those signals. also possible you have a broadcast tower nearby. the 536HP is not a very good receiver in the sense that the designers did not put any thought into front end selectivity.
RFI-EMI-GUY
Member
- Joined
- Dec 22, 2013
- Messages
- 7,653
It could also be cellular towers in the 700 to 800 bands in which case a Yagi might help, but only if pointed away from cellular towers.
K4EET
Chaplain
That may or may not help. What you really need to do, and understandably most people do not have the equipment, is to put a Spectrum Analyzer on your existing discone antenna to see what signals are out there. Based on the strength of those unwanted signals and their azimuth from your antenna, like @RFI-EMI-GUY said, a Yagi antenna may help somewhat but could also make things worse.
You could easily build an 800 MHz Yagi antenna from simple materials purchased at a typical hardware store for probably less than $15. That would give you a feeling for how well a commercially manufactured Yagi antenna could possibly work for you. For the 156 MHz frequencies that you want to listen to, an 800 MHz Yagi antenna may help to “attenuate” the unwanted frequencies in the 150 MHz area as long as your primary 156 MHz frequencies are strong enough to be reliably received.
Since you don’t know specifically what is causing the interference, experimentation may be a good way to discover abatement possibilities for your situation. Keep things simple and inexpensive.
For example, on your discone antenna, instead of the long top whip, replace it with a quarter wavelength 800 MHz coat hanger. Remove all horizontal rods and downward pointing radials.
How is the reception now compared to the 800 MHz homemade Yagi antenna? What can be gleaned from the results? What should be tried next? Inexpensive trials are the best way to discover what design works best. And understand, it is highly probable that you will still have some interference but hopefully you can make it manageable.
Ok . I took down a tram 1091 just to put up a discone and apparently it made my receive worse . Now I still have my tram 1091 should I just switch it back out without a ground plane kit or just use a trunk gutter mount go with it ?
