Can you identify this interference?

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SCPD

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Need a little help here. Please listen to the attached mp3 (I edited out an address). Its a short transmission I recorded from my Pro 164. That very specific interference is happening on any system I listen to with frequencies around 866.4250 through around 868.4375.

File is here: http://mrose.org/867mhz_interference.mp3

Frequencies around 860 through 865 or so are unaffected.

This occurs on two separate TRSs within range. However, the condition exists when monitoring the channels conventionally. Both the systems have frequencies in 860-865 and 866-868. Fortunately, both system's control channels are always in the lower channels. When the system lands on a higher channel, that interference occurs.

Reorient the handheld horizontally seems to weaken the interference and allow the channel to be heard.

I don't expect anyone here to make the interference go away. I am, though, looking for your best guess based on what you hear. Would a better antenna setup improve this situation? Does this sound like the scanners being bombarded? Or??

Any input is much appreciated!
 

b7spectra

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Sounds normal to me. I hear some static in the background, but nothing out of the ordinary. If you are using a high gain antenna, try one with not as much gain. If I have my high gain rubber duckie on my 396XT, some stations I just can't receive when I'm close to the tower, so I switch over to a 3" stubbie and I get everything just fine.
 

SCPD

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Thanks... Check this out... here's another sample. Open carrier with only the EDACS tones.

http://mrose.org/Sample2.mp3

This is on 866.75000 - right in the center of my problem zone, and seems to be the most pronounced interference. Antenna is the popular RS 800Mhz duck. I've switched to the stock fat one that came with the 164. Let's see...
 

DickH

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... That very specific interference is happening on any system I listen to with frequencies around 866.4250 through around 868.4375.

Any input is much appreciated!
Although it's of no immediate help, when the system(s) reband, those 866-868 freqs. will change to 851-853s so that will solve your problem.
 

W6KRU

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I hear kind of a frying sound. It kind of reminds me of the noise caused by the Navy radar that interferes with the local 70cm frequencies sometimes.
 

brandon

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Sounds like your too close to a cell tower causing the scanner to overload. This is a very common problem, especially with GRE scanners. My suggestion is to enable the ATT (attenuator) and the noise should go away.
 

SCPD

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Thank you all for your thoughts.

For now, a combo of the ATT function, plus using this Diamond RH3 Amateur 2 Meter HT Antenna has had an impact. Unfortunately, that configuration seriously limits what else I can listen to on that radio. Fortunately, it sounds like a good excuse to get another radio... one dedicated to the problem system, which is my local PD/FD.

and...

Although it's of no immediate help, when the system(s) reband, those 866-868 freqs. will change to 851-853s so that will solve your problem.
This is very insightful... thanks!

I hear kind of a frying sound. It kind of reminds me of the noise caused by the Navy radar that interferes with the local 70cm frequencies sometimes.
This sattellite facility is a 1/2 mile or so away from me... think this could be the source? Not sure what exactly is operating there. After typing this, it sounds like a rather dumb question, now... that facility is probably radiating all kinds of crap.
 

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W6KRU

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This sattellite facility is a 1/2 mile or so away from me... think this could be the source? Not sure what exactly is operating there. After typing this, it sounds like a rather dumb question, now... that facility is probably radiating all kinds of crap.
Might be. Try getting a little closer and see what happens.
 

gmclam

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Recording from PRO-164

I don't expect anyone here to make the interference go away. I am, though, looking for your best guess based on what you hear. Would a better antenna setup improve this situation? Does this sound like the scanners being bombarded? Or??
I read below that you used a PRO-164 to receive this sound. Tell me more about your setup. Were you at home or mobile? The stock rubber antenna or something else? Is the scanner parked on a specific frequency or are you in SCAN mode and it stopped on a voice channel?

I am hearing three different things:
1. The channel being received that has voice sounds off frequency. If this is an EDACS system, I wonder if you have the correct exact frequency programmed.

2. There is some static mixed in throughout the recording. This could come from a LOT of different places; weak signal, electrical noise, etc. What kind of reading do you see on the S Meter when this signal was recorded?

3. The tone that came through in the middle of the recording. Funny, it sounded like you were tuned to the correct frequency for the tone because it was clear and also overcame the static.

If the cause of 1 above is correct, putting in the correct frequency (or a frequency which clears up the audio) might fix the other issues. Someone posted a similar issue here this week about a problem with a PRO-95 (keep in mind that the PRO-164 is the same radio two generations later). His problem was that the '95 was off frequency in the 800 band. He figured out to program each frequency something like 0.025 MHz off in an EDACS system and all "works".
 

benbenrf

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You're going to need a spectrum analyser if you want to work out exactly whats causing that "noise" - could be one of a dozen different causes/origins.
 

slicerwizard

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This sattellite facility is a 1/2 mile or so away from me... think this could be the source? Not sure what exactly is operating there. After typing this, it sounds like a rather dumb question, now... that facility is probably radiating all kinds of crap.
I doubt they're broadcasting in the 800's.


3. The tone that came through in the middle of the recording. Funny, it sounded like you were tuned to the correct frequency for the tone because it was clear and also overcame the static.
You mean where he "edited out an address"?
 

SCPD

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Thank you all for your input... its been very helpful. So I got to lookin'...

This is the system I'm dealing with.

FCC Callsign WPGR333 Details

It occurs to me that this is a Simulcast system. I am due south of Tower 2 and 4 (the Southern most ones), toward Berkeley.

Could I be suffering from a phasing issue?

I did drive around today and heard the similar "noise", inconsistently depending on where I was. Some areas fine, some others, not so good, particularly on I-80 between tower 1 and 3 (northern ones).

Could the simulcast on this system be less than stellar? Could this be my problem?
 

radioman2001

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Definetly sounds like 2 transmitters up at the same time, someone mentioned simulcast, could be one of the transmitters is out of sync or your scanner can't handle the simulcast as the real radio does. I have the same problem with my Spectra on a 7 site simulcast system here, the XTL's don't hear the phase distortion, but the Spectra does.
 

commscanaus

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Definitely sounds like overlap distortion caused by simulcast sites to me.
Used to suffer the same problem with a UHF simulcast system that used 3 sites on the same frequency.
It was almost impossible to hear any traffic until a yagi was pointed directly toward one site.

Switching to your ducky antenna is having a similar effect. The scanner is hearing one site stronger than the others and you don't hear the overlap distortion.

A directional antenna pointed at your closest site should solve the problem.

Commscanaus.
 

SCPD

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Follow up

Just wanted to post what I ended up doing as a solution.

I'm still not sure about the simulcast interference since I was having problems with two unique systems (ALCO and Richmond/San Pablo, CA). Besides, living in an apartment, directional antennas are not really an option.

"Downgrading" the antennas on the 164 handhelds helped, but obviously isn't the best option.

So I went with the happiest option and just got another radio. I installed a Pro 163 on my workstation with a RS Model: 20-032 mag-mount antenna sitting elevated on my desk. The 163 is connected to the Behringer mixer (existing) which routes out to a stereo.

This configuration has eliminated my original problem and the 163 sounds great without the mixer. The mixer, though, allows the audio to be cleaned up, mixing down the higher noises (static, etc). Sounds nice. A neat configuration that you could connect multiple radios to, mix them up/down or left/right... kinda nice.

Thanks again for everyone's input. I really appreciate it. By the way, the 163 came from Amazon... some group is "re-manufacturing" them - whatever that means. Only $125 w/ free shipping. Comes with everything in the OEM box.
 

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