Portland P25 - OSP - TG:1087 - AM/FM Broadcast Bleedover?

[ScottPDX]

Just an observation from my East base Mt. Tabor listening location: Does anyone else hear a distinct AM/FM Broadcast bleedover on the Portland P25 - OSP - TG:1087 ?

Or is it just me and my SDS200 and Tram mobile antenna in the house window?

Don’t hear it in the other Portland P25 TG’s.

ScottPDX

 

[Baker845]

You are likely close to the fm broadcast transmitter.

 

[ScottPDX]

Yes, but why would I only hear the bleedover on just one TG of many I listen to on the same P25 system?

 

[ScottPDX]

I was wondering if anyone else might just listen and tell me if they can hear what I’m hearing on same TG:

Otherwise, altogether, it was just an observation, and overall none of this is of any real importance.

 

[KC7VH]

I've listened on and off to TG 1087 today and have not heard the interference you are describing. I have an SDS100 and am on the NW side of Mt. Tabor. Perhaps you are getting a really strong FM signal from Mt. Scott?

 

[ScottPDX]

I think that must be it. I am not far and line of sight to Mt. Scott’s broadcast antennas. Just weird that I listen to Mult. Co. Sheriffs on same P25 System and don’t hear it their talkgroups, and there was no bleedover on PPB dispatch when I could still get them awhile back. Maybe I’ll try a stubby antenna or some attenuation.

Thanks to all for the feedback.

ScottPDX

I've listened on and off to TG 1087 today and have not heard the interference you are describing. I have an SDS100 and am on the NW side of Mt. Tabor. Perhaps you are getting a really strong FM signal from Mt. Scott?

 

[Fielder3]

Looking for a control channel for PDX P25 system site: PCC on SW 49th. I’m getting 2-4 “bars” signal strength RX on The EACH channel listed but my Uniden BCD996p2 is not finding the control ch. for that one. Any thoughts? (RR says it should be 852.2875.)

 

[Fielder3]

I’m using a 800 MHz directional Yagi roof antenna , 30’ of LMR cable, from Salem Keizer area. I also programmed in Headworks, West Simulcast, East simulcast, Corn Pass, and Forest Heights. All are coming in with 2-3 bars strength but no audio or control channel found.

 

[Ubbe]

Set the squelch to 0 and manually go through each frequency and listen if there's really a carrier of some sort on the frequencies and if you can hear any datasignals. The scanner needs to receive a fairly strong signal with not too much noise to be able to decode a datasignal.

/Ubbe

 

[devicelab]

Yes, but why would I only hear the bleedover on just one TG of many I listen to on the same P25 system?

I can' t begin to tell you how much my scanning has improved since I installed a FM notch filter in my antenna path. It's really worth the $20 or so.

Amazon.com: Broadcast FM Block Filter (88 - 108 MHz Block) by RTL-SDR Blog: Home Audio & Theater

Amazon.com: Broadcast FM Block Filter (88 - 108 MHz Block) by RTL-SDR Blog: Home Audio & Theater

www.amazon.com

 

[sparklehorse]

I think I've heard the same thing as the OP. I'm not sure that it's broadcast AM/FM bleedover. I have no idea what the source is, but it sounds like voices to me, not music. Not loud, more of a background thing. In fact I only really notice it when/if there is a silent moment at the end of a transmission right before the carrier drops. I hear this all over town as I commute, so I don't think it's related to proximity to a broadcast tower or anything. I've heard this sound on the OSP crosspatch on my Unication G5 as well as SDS100 and 200.
.

 

[Fielder3]

Set the squelch to 0 and manually go through each frequency and listen if there's really a carrier of some sort on the frequencies and if you can hear any datasignals. The scanner needs to receive a fairly strong signal with not too much noise to be able to decode a datasignal.

/Ubbe

Tried that and nothing. No control channel but signal meter shows fairly strong. I’m going to start over and download the RR list and put it in open scan, not ID scan. I will let you know if that works or not.

 

[Ubbe]

Tried that and nothing. No control channel but signal meter shows fairly strong.

If you remove the antenna will the signal strenght go to zero, no bars? Then you must have some really strong interferencies in the frequency band that probably makes reception of weak signals really difficult.

It's unfortunate that you in US have a mix of cellular and 2-way radio systems so close in frequency to each other. Your scanner have one bandpass filter of 760-1300MHz and if there's a strong cellular site nearby it might interfere and desense your scanner so it will only receive really strong signals from radiosystems. Cellular are so close in frequency that's there's no external filter available within a reasonable cost. A high performance receiver that use narrower tracking filters and/or a better strong signal handling are then the only solution.

Some 2-way radios use a circuit that can switch modes from high sensitivity but low strong signal handling and a good strong signal handling but worse sensitivty. It's the operation parameters of the mixer that often are changed. I wish scanner manufactures would use the same type of design instead of the more or less useless 20dB attenuator design they have now, that probably no one actually use.

/Ubbe

 

[Fielder3]

If you remove the antenna will the signal strenght go to zero, no bars? Then you must have some really strong interferencies in the frequency band that probably makes reception of weak signals really difficult.

It's unfortunate that you in US have a mix of cellular and 2-way radio systems so close in frequency to each other. Your scanner have one bandpass filter of 760-1300MHz and if there's a strong cellular site nearby it might interfere and desense your scanner so it will only receive really strong signals from radiosystems. Cellular are so close in frequency that's there's no external filter available within a reasonable cost. A high performance receiver that use narrower tracking filters and/or a better strong signal handling are then the only solution.

Some 2-way radios use a circuit that can switch modes from high sensitivity but low strong signal handling and a good strong signal handling but worse sensitivty. It's the operation parameters of the mixer that often are changed. I wish scanner manufactures would use the same type of design instead of the more or less useless 20dB attenuator design they have now, that probably no one actually use.

/Ubbe

Thanks, I will look into that. I have two huge cedar trees 100' away that seem to block my Yagi "northernly path". If one was on my property, I'd be tempted to try and climb it and place an antenna, HA! I did that when I was living in Beaverton, and Linn County came in awesome.

 

[Fielder3]

If you remove the antenna will the signal strenght go to zero, no bars? Then you must have some really strong interferencies in the frequency band that probably makes reception of weak signals really difficult.

It's unfortunate that you in US have a mix of cellular and 2-way radio systems so close in frequency to each other. Your scanner have one bandpass filter of 760-1300MHz and if there's a strong cellular site nearby it might interfere and desense your scanner so it will only receive really strong signals from radiosystems. Cellular are so close in frequency that's there's no external filter available within a reasonable cost. A high performance receiver that use narrower tracking filters and/or a better strong signal handling are then the only solution.

Some 2-way radios use a circuit that can switch modes from high sensitivity but low strong signal handling and a good strong signal handling but worse sensitivty. It's the operation parameters of the mixer that often are changed. I wish scanner manufactures would use the same type of design instead of the more or less useless 20dB attenuator design they have now, that probably no one actually use.

/Ubbe

Squelch at level 2 and using the radio set antenna it came with ..inside the house from Salem/Keizer area. After multiple attempts over many days I finally got my first confirmation hit on the Goat Mountain site, "MC Fire Dispatch" talk group 1809 with 3 bars signal strength. Audio quality is really good. Total of three fire dispatches so far. I'm curious why the rest of the system is quiet, so I will do some more listen.

 

[Fielder3]

I have Multnomah Co./Portland on Goat Mtn site programmed in the BCD996P2 and only getting MC Fire Dispatch, NO other fire or police talk groups. Strange..