Same conversation on 3 channels

[tcg]

I am on Lake St. Clair in MI. I have a scanner(old RS Pro-2030) hooked up to a discone antenna in my attic I can receive from up to 40 - 50 miles away.

The last few nights on 156.800(16) 156.200(4) and 156.500(10) I have been hearing what sounds like a conversation you would hear on the ham frequencies. I can only hear one side of the conversation.

The other odd thing to me is it also cause interference on my tv when the scanner is receiving that transmission. Regular marine traffic on those frequencies do not cause interference on the tv.

It is at different times during the day. I can hear the same person on all 3 channels simultaneously. It is strongest on 156.800(16).

He does on occasion end with a call sign but I can never hear it clearly. I can hear it on 2 different scanners.

I have not heard the usual Coast Guard warning that 16 is a hailing channel only.

Very odd to me.

Any thoughts?
Matt

[DDan]

Originally Posted by tcg

I am on Lake St. Clair in MI. I have a scanner(old RS Pro-2030) hooked up to a discone antenna in my attic I can receive from up to 40 - 50 miles away.

The last few nights on 156.800(16) 156.200(4) and 156.500(10) I have been hearing what sounds like a conversation you would hear on the ham frequencies. I can only hear one side of the conversation.

The other odd thing to me is it also cause interference on my tv when the scanner is receiving that transmission. Regular marine traffic on those frequencies do not cause interference on the tv.

It is at different times during the day. I can hear the same person on all 3 channels simultaneously. It is strongest on 156.800(16).

He does on occasion end with a call sign but I can never hear it clearly. I can hear it on 2 different scanners.

I have not heard the usual Coast Guard warning that 16 is a hailing channel only.

Very odd to me.

Any thoughts?
Matt

Sounds like intermod to me. I wonder what the IF is for those scanners.

[tcg]

Originally Posted by DDan

Sounds like intermod to me. I wonder what the IF is for those scanners.

I did a quick search for intermod and it is confusing to say the least. To me any how.

The specs on the scanner say IF frequencies 10.8 MHz and 450kHz

Could this be a defect with my scanner or someone broadcasting in an inappropriate way?

I stream the scanner online and it is annoying to the local boaters that tune in. If it continues is there a way to prevent it from my end?

Matt

[N_Jay]

Intermodulation typically has little top do with your receiver (unless it is being generated in your receiver front end, which is typically not the case).

It could be an image and that does have to do with the IF of your receiver.

[tcg]

Originally Posted by N_Jay

Intermodulation typically has little top do with your receiver (unless it is being generated in your receiver front end, which is typically not the case).

It could be an image and that does have to do with the IF of your receiver.

This is all over my head.

Is this a problem I could narrow done and solve? If so could you guys point me in the right direction.

Matt

[DDan]

Sorry Matt I was dragging you down the primrose path with the intermod. I think the real culprit is an "image response" issue. If you subtract your IF (11 MHz) from the desired freq. of 156 MHz, you are smack in the middle of the 2m ham band. You are not hearing both sides of the conversation because only the nearby freq. is strong enough to overpower the frontend of your scanner.

You could try attenuating the signal coming in from the antenna but that will reduce your reception range. If you can locate the ham that is causing this and if the signals you want to hear are in the opposite direction from the ham, then a directional antenna could help.

[DDan]

Thanks Jay. I was confusing my terminology there but I figured it out when I went to calculate what was happening and found the formula for intermod had nothing to do with IF. Do my possible solutions sound OK?

[tcg]

Originally Posted by DDan

Sorry Matt I was dragging you down the primrose path with the intermod. I think the real culprit is an "image response" issue. If you subtract your IF (11 MHz) from the desired freq. of 156 MHz, you are smack in the middle of the 2m ham band. You are not hearing both sides of the conversation because only the nearby freq. is strong enough to overpower the frontend of your scanner.

You could try attenuating the signal coming in from the antenna but that will reduce your reception range. If you can locate the ham that is causing this and if the signals you want to hear are in the opposite direction from the ham, then a directional antenna could help.

I am a computer geek first. Last year a local boating forum that I follow was talking about a search and rescue that happened one weekend and they decided it would be cool to be able to listen as it happened.

I thought the same thing. So a few days later I had the setup and it's been running 24/7 over a year now. It has been problem free for the most part.

I have been reading these forums for a while but I am by no means a radio guy.

If I am hearing it on my scanner is the Coast Guard also hearing it on channel 16? I would think their reception is far better than mine.

Matt

[DDan]

Originally Posted by tcg

If I am hearing it on my scanner is the Coast Guard also hearing it on channel 16? I would think their reception is far better than mine.

Matt

Probably not. It is not just a strong signal, it is a very strong signal. I am guessing that you have a new neighbor that is a ham or an old neighbor that is a recently licensed ham. Have you noticed any new antennas in the neighborhood? When you are driving around keep an eye out for antennas and ask neighbors if they know anything about a ham in the vicinity. Or you could get your tech license and then locate the signals in the 2 meter band and talk back to the ham.

[tcg]

Originally Posted by DDan

Probably not. It is not just a strong signal, it is a very strong signal. I am guessing that you have a new neighbor that is a ham or an old neighbor that is a recently licensed ham. Have you noticed any new antennas in the neighborhood? When you are driving around keep an eye out for antennas and ask neighbors if they know anything about a ham in the vicinity. Or you could get your tech license and then locate the signals in the 2 meter band and talk back to the ham.

That was my next question how do I determine the actual frequency they are using?

If I understand correctly the 2 meter band is 144 - 148 MHz which my scanner scans. Would it just be a matter of scanning those frequencies when they are transmitting.

I attached a photo of an antenna within eye site of my home it has been there for as long as I can remember.

Possible source?

Thanks
Matt

[DDan]

I think you found the source. Definitely. To nail down the offending frequency just search 144-148 MHz. It should be around 145-146 MHz.

[tcg]

Originally Posted by DDan

I think you found the source. Definitely. To nail down the offending frequency just search 144-148 MHz. It should be around 145-146 MHz.

Thanks for your help. I think I will try and find the frequency this evening when he is transmitting and then go visit. If he is not the source he could probably help.

It's a good opportunity to meet a neighbor I have never met.

I'll post the results.

Thanks
Matt

[DDan]

I sent you a PM. It should help with your neighbor's name.

[rvictor]

I had the same problem due to the interaction between the 2m ham frequency and the scanner IF. In my case it was the output of the 2m repeater that I was hearing so I heard both sides of the conversations. Most ham repeaters have a PL tone on their transmissions these days which was the key to resolving the problem.

The easiest and most effective way to get rid of it for me was to have my scanner search for the PL of the offending transmission and then set that PL as the Tone Lockout for that channel. That way the radio ignores transmissions on that frequency that have the PL (the ham transmission) and still listens for the normal marine traffic which generally doesn't use PL tones.

If it happens to be a nearby ham and you are actually hearing transmissions on the repeater input frequency, PL may still be the solution as many hams use PL for better access to repeaters. In that case, the same approach should resolve the problem.

If you're hearing the ham on the input and he/she has no PL tone on the transmission, then if you locate the ham, he/she may be willing to turn on a PL so that you can use the above approach.

The Tone Lockout function has been very useful for similar problems on other frequencies that occur from time to time, particularly when there is a band opening or ducting is bringing in distant signals. Hams sometimes refer to it as reverse PL.

73,
Dick

[tcg]

Originally Posted by rvictor

I had the same problem due to the interaction between the 2m ham frequency and the scanner IF. In my case it was the output of the 2m repeater that I was hearing so I heard both sides of the conversations. Most ham repeaters have a PL tone on their transmissions these days which was the key to resolving the problem.

The easiest and most effective way to get rid of it for me was to have my scanner search for the PL of the offending transmission and then set that PL as the Tone Lockout for that channel. That way the radio ignores transmissions on that frequency that have the PL (the ham transmission) and still listens for the normal marine traffic which generally doesn't use PL tones.

If it happens to be a nearby ham and you are actually hearing transmissions on the repeater input frequency, PL may still be the solution as many hams use PL for better access to repeaters. In that case, the same approach should resolve the problem.

If you're hearing the ham on the input and he/she has no PL tone on the transmission, then if you locate the ham, he/she may be willing to turn on a PL so that you can use the above approach.

The Tone Lockout function has been very useful for similar problems on other frequencies that occur from time to time, particularly when there is a band opening or ducting is bringing in distant signals. Hams sometimes refer to it as reverse PL.

73,
Dick

On my scanner RS Pro-2030 I can lock out a programed channel but I'm not sure about a tone lock out.

A feature that I don't have or am I misunderstanding you?

Matt

[kb2vxa]

It looks like you may have nailed it down pretty tight. Not only is the scanner experiencing signal overload but TVI is another sign the alleged ham is right in the neighborhood. Here you have a wonderful opportunity to meet him or her and work out a solution AND the possibility the transmitter and/or antenna system may be faulty leaving the operator open to a citation by the FCC. That would be a most unwelcome surprise, better you than Uncle Charlie knocking at the door.

What concerns me is what TV channel or channels are affected? That's a big clue to what band is in use and the possibility of a faulty transmitting system if you're receiving OTA via an antenna. If it's cable interference undoubtedly there is a leak nearby and the strong possibility you're getting signal egress interference on your scanner as well. If it's only cable channel 18 I can tell you right now he's on the 2M band, that's pretty common and in my experience cable leakage makes repeaters like Northeast Connect on 145.250 pretty useless.

Anyway you'll work something out to your mutual satisfaction if you approach the problem in a polite, respectful and intelligent manner. We like making friends and become highly annoyed when some idiot with an attitude comes around.

[tcg]

Originally Posted by kb2vxa

It looks like you may have nailed it down pretty tight. Not only is the scanner experiencing signal overload but TVI is another sign the alleged ham is right in the neighborhood. Here you have a wonderful opportunity to meet him or her and work out a solution AND the possibility the transmitter and/or antenna system may be faulty leaving the operator open to a citation by the FCC. That would be a most unwelcome surprise, better you than Uncle Charlie knocking at the door.

What concerns me is what TV channel or channels are affected? That's a big clue to what band is in use and the possibility of a faulty transmitting system if you're receiving OTA via an antenna. If it's cable interference undoubtedly there is a leak nearby and the strong possibility you're getting signal egress interference on your scanner as well. If it's only cable channel 18 I can tell you right now he's on the 2M band, that's pretty common and in my experience cable leakage makes repeaters like Northeast Connect on 145.250 pretty useless.

Anyway you'll work something out to your mutual satisfaction if you approach the problem in a polite, respectful and intelligent manner. We like making friends and become highly annoyed when some idiot with an attitude comes around.

The interference is only on cable channel 18.

You are right about the opportunity to meet a neighbor. I learned a long time ago to approach these things in a polite manner. I have found people are a lot more likely to be helpful and teach me something if approached that way. It's also why I come to a place like this first to learn as much as I can before talking to someone about something I know nothing about.

Thanks
Matt

[mm]

I'd bet that when you hear the interfering signal that it sounds much wider than a regular Narrow band FM signal, possible even dropping out of your receivers I.F. sounding very strong but distorted, particularly since you mention that it's hard to get a call sign.

Instead of checking 2 meters for an image signal, you may want to try listening around 448.80MHz and 443.800 MHz in the ham 70 cm band.

You'll may find the station there and maybe even a distant repeaters output frequency with the same station.

If you do the math for 156.8 on your receiver for a 10.8 Meg I.F. it doesn't come out to an image that falls in the 2 meter band but possibly from the 70 CM ham band.

I'd bet that your scanners LO has a good 3rd harmonic, 146 MHz is the low side injection frequency for 156.8Mhz and 3 X 146MHz = 438 MHz a nice L.O. for low side injection in the 70 CM ham band also.

The 10.8 Meg image for a 146 MHz LO would fall down at 135.2 MHz and I doubt anyone is using FM down there.

Especially with the wide band front end of most of the newer scanners, you can pick up a real close 3 X LO image from UHF on your 156.8 MHz channel.


This was actually the basis of the 1970's vintage Bearcat ACT-10 scanners, to cover VHF and UHF frequencies using similar Local Oscillator designs with the same cut of crystals operating in 3rd overtone for VHF and 3rd overtone with a X 3 multiplier for UHF.

[tcg]

OK, I just found him on 145.5500 and 156.800 and 156.5700

They talk about video and pictures and then say lets try again and then I hear data or sounds like a 56k modem.

Tomorrow I will go visiting.

Matt

[tcg]

I did manage to get his call sign and he is the owner of the antenna in the picture I posted.

Thanks guys for helping me narrow this down. I will post the results after I talk with him.

Matt