One frequency bleeding over another?

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ST-Bob

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First would be to isolate the ground connections between the two scanners by inserting audio isolation transformers (ground loop eliminators) in the external speaker to computer cables. This will eliminate any potential difference in ground potential between the two scanners and the sound card. The negative side of the external speaker jack on some devices is not at ground potential. In some scanners both the tip and ring are driven in opposite polarity to increase the audio power. Grounding the negative side by sharing a common connection to another scanner will often cause problems.
 

DigitalMDX

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I run a stereo feed and had some bleed over between radios.
There were several things that were causing it.

1) I was sharing an antenna between the two scanners using a splitter made for just that purpose. I bought a second antenna.
2) My sound card had some "bonus" settings I had to turn off. 3D sound along with other enhancements. I turned them all off.
3) The sound mode on the card made a difference. Game mode vs theater mode, etc. I chose the one that stated it was best for voice or spoken word as opposed to music.

With all that I have good separation. Different devices will give you different results. My PC gives me total separation where my phone isn't so clear on the separation unless I drop one of the balance controls all the way down.

Jay
 

saleen49

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I recently realized 154.370 will bleed over 154.235 even with both frequencies programmed on the same radio. I am in fact sharing one antenna to two radios. I've been running this set up for a few years without incident. This problem just popped up a few weeks ago. I will try to seperate the two with independent antennas as soon as i can get around to it.

Thanks for the help.
 

W8RMH

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First of all I would turn off the priority.

It looks like you received a control channel and the scanner switched to channel 51 - 851.2750 either by the priority or maybe by the data from the control channel.

I would do a reset and only program the frequencies for you feed, and don't use the priority. Priority on a feed makes it extremely hard to follow the traffic anyway.
 
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Eng3ineer

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After a year of good audio the trouble is back. Was able to capture the noise on my phone. Is this what INTERMOD sounds like? Ordering a notch filter today.

Apr 2, 2014 - YouTube

It does sound like control channel, but it could also be a paging service or strong signal is overloading your scanner.

This sounds very close to what happens to my scanner when dispatch set off the dispatch tone channel 154.430 for the local VFD which has a tower just few miles from my home. It overloads other local VFD ch. 154.190 and the EMS ch. 155.205 along with couple others as well. I looked into notch filter, but that would cut out most of what I listen to. Lucky this VFD is just about done changing over to digital, so my problem is slowly going away.
 

saleen49

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Update:

I normally get the INTERMOD during transmission of a department I monitor that is roughly a half mile from my locaton. The agency will tone out and the INTERMOD sometimes covers the tone and carries into part of the dispatch.I'm beginning to wonder if anttena design has something to do with it? I've tried just about everything else I can think of to isolate this.
 

jim202

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Update:

I normally get the INTERMOD during transmission of a department I monitor that is roughly a half mile from my locaton. The agency will tone out and the INTERMOD sometimes covers the tone and carries into part of the dispatch.I'm beginning to wonder if anttena design has something to do with it? I've tried just about everything else I can think of to isolate this.


Everyone needs to understand that the adjacent channel rejection and front end overload from strong signals not even close to the channel your trying to hear on most scanners is just plain very very poor. I know you paid a bundle for your scanner, but you have probably heard all this before.

My suggestion might to be to consider obtaining a used commercial radio just for the channel you want to put on a live feed broadcast. This way your getting a good receiver that has good adjacent channel rejection and a front end on the receiver that is not so effected by strong off channel signals.

Just make sure the radio is capable of narrow band operation if your going to use it on VHF or UHF public safety channels. Not all used commercial radios showing up for sale these days can be programmed for narrow band operation. Buyer beware of what your buying.
 
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