SDS100 - Mobile antenna interference

[andy404ns]

Hello all!

I recently purchased an SDS100 and have a question about interference with different antenna types. Using the stock rubber duckie and also the Diamond RH77CA, I get constant interference on a UHF channel 451.3000 and, oddly, the associated input channel (I think?) of 456.3000 at 3 bars of reception. When I switch to my attic mounted antenna, the interference stops. To test that it's interference from the antenna, I took the scanner with me today and drove about 20 miles from home. There I still get the interference with the same indicated 3 bars of reception.

Frequencies between 451.3 and 456.3 do not have this same problem.

The attic antenna is a basic discone with something like 100 feet of RG-6 feeding into an Electroline zero-loss splitter.

The frequency in question is licensed to a local business as DMR that I'd like to monitor so I'm trying to figure out what's going on.

I have video of the sound of the interference and can try to figure out how to upload if that would be helpful.

Thanks in advance!

 

[dave3825]

The frequency in question is licensed to a local business as DMR that I'd like to monitor so I'm trying to figure out what's going on.

Which business is that?

The only confirmed as in use entity on the freq for CT (radio reference database) comes up as Onevoice DMR system and the site with that freq is listed in NH.


These entries are FCC licensed users (FCC website) in your county and may or may not be using the freq. They also reflect DMR. Not saying you, but lots of people think because a freq is licensed that it also means in use and that is not the case.

MARCUS COMMUNICATIONS	451.300000	FB6	11K2F3E	100.000	WQZW330	A	HARTFORD	HARTFORD	CT	IG
MARCUS COMMUNICATIONS	451.300000	FB6	11K2F3E	200.000	WQZW330	A	HARTFORD	HARTFORD	CT	IG
MARCUS COMMUNICATIONS	451.300000	FB6	7K60FXE	100.000	WQZW330	A	HARTFORD	HARTFORD	CT	IG
MARCUS COMMUNICATIONS	451.300000	FB6	7K60FXE	200.000	WQZW330	A	HARTFORD	HARTFORD	CT	IG
THREE-WAY COMMUNICATIONS, INC.	451.300000	FB6	11K0F3E	180.000	WPLX798	A	GRANBY	HARTFORD	CT	YG

 

[Whiskey3JMC]

Does said "interference" sound something like this by chance? (turn speakers down, a bit loud)

The frequency in question is licensed to a local business as DMR that I'd like to monitor so I'm trying to figure out what's going on.

And you have the DMR upgrade installed?

 

[andy404ns]

Thanks for the replies. My profile needs to be updated. I'm not in CT any longer - I'm in NH. The business is a local school. I do have the DMR upgrade applied and I can confirm that I do receive the school transmissions when they key up as they overpower whatever the interference is. Further to that - the interference will only pop up if I'm using a general search. If I have the frequencies programmed as either "Digital Code Search" or as the proper DMR One Frequency system, the interference is not an issue.

I'm mostly just curious what could be happening with the mobile antennas that lead to the interference in the first place.

 

[dave3825]

451.00 is listed as a control channel on Onevoice dmr system. Site in Cheshire County

OneVoice Network Site: Hinsdale

OneVoice Network Site: Hinsdale Details

www.radioreference.com

The input of 456.3 is also listed on that license.

FCC Callsign WQWE675 (CENTRAL VERMONT COMMUNICATIONS INC)

FCC Callsign WQWE675 (CENTRAL VERMONT COMMUNICATIONS INC)

www.radioreference.com

 

[Ubbe]

I get constant interference on a UHF channel 451.3000 and, oddly, the associated input channel (I think?) of 456.3000 at 3 bars of reception. When I switch to my attic mounted antenna, the interference stops.

I get the same 3 bars using the antenna on the SDS100 and using either Wide Normal or Wide Invert in filter settings. Using external antenna or any other filter selections will indicate no signal strength when squelch are set to 0.

It could be some internal clock or oscillator signals that radiate from the scanners electronics, like what was from the BCD436 in the UHF band when a filter capacitor where not installed on its circuit board.

/Ubbe

 

[andy404ns]

@Ubbe Very interesting. Thanks for providing that feedback. Do you suspect this is anything Uniden would want to know about? It's not like it's causing a big issue unless I'm doing a direct search.

 

[Ubbe]

Do you suspect this is anything Uniden would want to know about?

Uniden created extra filter settings, and IFX, to be able to handle those kinds of problems. There's a huge amount of internal interferences in a SDS100 receiver so it would be impossible to do anything about them, except to try and move them to a frequency where they do not disturb reception.

/Ubbe

 

[andy404ns]

Makes sense. When I get around to it I'll run a test applying each available filter to this channel and monitor if the interference is resolved. If I discover anything interesting I'll post back here.

Thanks all very much for the information and help here!