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-   -   Getting AM radio stations on VHF Radio (https://www.sailnet.com/forums/electronics/65536-getting-am-radio-stations-vhf-radio.html)

L124C 06-12-2010 12:33 PM

Getting AM radio stations on VHF Radio
 
I'm getting a AM Radio station clear as a bell on Chanel 22. Any ideas why? The other channels on the VHF work Perfectly.

ottos 06-14-2010 08:21 AM

What is your location? In the US, 22(A) belongs to the Coast Guard, so if someone were keyed up and rebroadcasting, somebody would probably have found them by now.
Is anybody else in your area reporting the same?

How long has this been going on?

How far away is the transmitter for that station from your boat?

Next - All your other electronics are turned off, right?

oceanscapt 06-14-2010 09:13 AM

It could be a harmonic of the AM station but to go from the 560-1720KHz AM radio band to the 156MHz marine band is a big jump. Add in the AM to FM conversion and I'm more than curious. And since most VHFs are now synthesized frequencies instead of crystal controlled, it's intriguing.

It's possible that the radio station has a transmitter problem but the first thing to do is see if your radio is OK on CH 22.

How close to the radio is your boat?
If the VHF is portable, can you take it a few miles away and see if the problem persists.
Have you tried another VHF at your problem location?

wind_magic 06-14-2010 09:20 AM

Maybe someone is retransmitting the station - CBer's do that sometimes, if their favorite song comes on the radio they'll hold the microphone up to the radio and retransmit the audio over the CB, very annoying. People who do this kind of thing seem to believe they are performing some kind of public service and don't understand why people get irritated about it.

oceanscapt 06-14-2010 10:15 AM

Quote:

Originally Posted by wind_magic (Post 613014)
Maybe someone is retransmitting the station - CBer's do that sometimes, if their favorite song comes on the radio they'll hold the microphone up to the radio and retransmit the audio over the CB, very annoying. People who do this kind of thing seem to believe they are performing some kind of public service and don't understand why people get irritated about it.

Hadn't thought of that wind_magic but channel 22A in the US is a heavily used Coast Guard channel, so I'd think the FCC would be less than amused at the 'rebroadcast", and the anchorage/marina frequency police would be all over that too.

The author didn't say whether the interference was constant or intermittent. Outside the US, the rules, if there are any, are far less enforced.

hellosailor 06-14-2010 06:42 PM

L1, try another VHF or ask another boat to tune it in. If your radio is the only one receiving it--your radio needs repair. (Unless that's a very powerful station with a transmitter located very close to you, in which case all sorts of overloads have been known to happen, unless you have a very good radio.)

wind_magic 06-14-2010 06:46 PM

Quote:

Originally Posted by oceanscapt (Post 613039)
Hadn't thought of that wind_magic but channel 22A in the US is a heavily used Coast Guard channel, so I'd think the FCC would be less than amused at the 'rebroadcast", and the anchorage/marina frequency police would be all over that too.

The author didn't say whether the interference was constant or intermittent. Outside the US, the rules, if there are any, are far less enforced.

Before we entered into this new age of people's cell phones calling each other when they sit down on them, we used to be in an age where people transmitted for days (sometimes) when they accidentally put something on the microphone and the button got pressed. :D

oceanscapt 06-15-2010 10:30 AM

One of the more intelligent mods to radios, especially VHFs, was the 5 minute timer. :D

L124C 06-25-2010 12:05 AM

I asked a dock mate to try his VHF on 22, and gets the same AM Radio station! The marina is below a mountain which has several broadcasting transmitters on it. They sit at 1000 feet, and are probably 3 miles from the marina. Strange! I'll ask the Harbor master if he is aware of the situation.

bljones 06-25-2010 12:07 AM

Have you tried removing your tinfoil hat? :)

ottos 06-25-2010 09:57 AM

Since you are close to the transmitter, you could be picking up the studio-transmitter link (or interference/intermods from it). Usually STL's are in the 900MHz band, but there are some around that are capable of hitting 157MHz. http://www.tftinc.com/products/datasheets/stl5100m.pdf Here is a good write up on STL's Options for studio transmitter links:

I would ask the CG (via land line) if they are aware of the issue. You could also call the radio station and ask to talk to the chief engineer.

L124C 06-25-2010 02:25 PM

Quote:

Originally Posted by ottos (Post 616777)

I would ask the CG (via land line) if they are aware of the issue. You could also call the radio station and ask to talk to the chief engineer.

Yeah... this occurred to me as soon as I made the post regarding contacting the Harbormaster!:p Emailed the station and received the following response:

"Thank you for contacting K*** and reporting our signal on marine channels 22A and 23A.
We’re looking into it. K*** operates two licensed VHF transmitters that carry our programming
and are used to “cue” reporters in the field in cars or aircraft. Of course, they’re not assigned to
Marine radio frequencies, but perhaps one has developed a problem.
In a quick test here at the studio, we can’t hear the interference, but we’re doing testing in
other areas during the next couple of days.
It would be a help to us if we could coordinate testing with you. We have remote control of
both transmitters. If you were available to work with us, we could shut them down one ata time and determine which of them might be causing the problem.
We thank you for letting us know about this, and we want you to know that we take this problem very seriously and aim to fix it promptly.
Could you please give me a call at the number below?
We’d be grateful for your further help, as we are for the effort you’ve already made to contact us."

Nice to see someone care for a change (though, I assume the idea of the FCC and Coast Guard being contacted might have expedited the response!). I'll post the results of the test.

hellosailor 06-25-2010 03:06 PM

Oh yeah, the FCC can give them a very nice penalty fine for "spurious emissions" and interfering with a government safety operation. But the odds are, everyone will play nice and the CBS engineers really *do* want to clean it up.

Usually the engineers are quite proud about maintaining the equipment, but the beancounters in management won't let them spend a cent until something "Must" be spent to remain on the air. FCC violations count as "Must" so that actually makes the engineers happy.<G>

ottos 06-25-2010 03:07 PM

Interesting - that station does seem to have two registered frequencies that are in the area of interest -

San Francisco County, California (CA) Scanner Frequencies and Radio Frequency Reference

160.25000 KCBS Vremote KCBS VHF remote feed FM Media
170.15000 KCBS VHF2 KCBS VHF2 remote feed FM Media

L124C 06-26-2010 03:10 PM

At the engineers request I went to the boat and listen to the VHF while he made some adjustments. I thought they might have had some effect, but he didn't seem to buy it. He is going to try some other things, and get back to me next week. In the meantime, I noticed the CG of the situation. They seem courteous, yet somewhat indifferent. I'll post the outcome. I'm just happy the problem isn't in my radio!

L124C 06-26-2010 03:13 PM

Can you hear me now?
 
At the engineers request I went to the boat and listened to the VHF while he made some adjustments. I thought they might have had some effect, but he didn't seem to buy it. He is going to try some other things, and get back to me next week. In the meantime, I notified the CG of the situation. They seem courteous, yet somewhat indifferent. I'll post the outcome. I'm just happy it's not my radio!

L124C 06-28-2010 11:05 AM

Quote:

Originally Posted by L124C (Post 617126)
In the meantime, I notified the CG of the situation. They seem courteous, yet somewhat indifferent.

Boy was I wrong! Called the CG Friday, and the FCC called me Monday morning! FCC suspects it's the FM Broadcast that I'm receiving. I didn't even know KCBS had an FM signal. Anyway, the FCC guy couldn't have been nicer. Great to see everybody on top of things and without any attitude for a change. Sometimes it's nice to be wrong! Went to the Harbor masters office Saturday (probably 1/4 South of my boat). Their channel 22 and 23 were silent.

L124C 06-30-2010 02:39 PM

Problem Solved!
 
Turns out my VHF radio was in International ("I") mode and Channel 22 and 33 are on the same frequency as the station in International mode. It should be in USA ("U") mode. The FCC rep figured it out. The VHF radio manual hardly mentions International mode. In fact, I had to experiment with the radio to change the mode. Ironically, this means that the radio on the other boat (which I used to confirm it wasn't just my radio) was also tuned to International! Oh Well...At least I can put my "Tin Foil Hat" back on. I've been missing it!

wind_magic 06-30-2010 07:25 PM

Quote:

Originally Posted by L124C (Post 618432)
Turns out my VHF radio was in International ("I") mode and Channel 22 and 33 are on the same frequency as the station in International mode. It should be in USA ("U") mode. The FCC rep figured it out. The VHF radio manual hardly mentions International mode. In fact, I had to experiment with the radio to change the mode. Ironically, this means that the radio on the other boat (which I used to confirm it wasn't just my radio) was also tuned to International! Oh Well...At least I can put my "Tin Foil Hat" back on. I've been missing it!

What an interesting ending to this thread! I didn't even know my radios had an international mode, I am going to check that out. Learn something new every day. Thank you for getting back to us and letting us all know how it turned out. That is funny that both radios had the same issue! :)

L124C 07-01-2010 10:58 AM

Quote:

Originally Posted by wind_magic (Post 618508)
What an interesting ending to this thread! I didn't even know my radios had an international mode, I am going to check that out. Learn something new every day. Thank you for getting back to us and letting us all know how it turned out. That is funny that both radios had the same issue! :)

Yes. It makes me wonder if some radios are sold in "I" mode and few people know the difference. As I indicated, the radio performed perfectly on every other channel. Also, I didn't have the problem when the boat was berthed much farther from the transmitters. However, I could have accidentally switched modes since then. In any case, the manual on my radio certainly should have paid more attention to the distinction between modes.
BTW: When I post a question on a forum and others attempt to help me find a solution, I feel I'm obligated to report the outcome. Hopefully, others will benefit, as many have helped me. OK....I'll get off the soap box now!

sailingdog 07-01-2010 02:23 PM

VHF radios have three modes, at least in the USA... USA, Canadian and International IIRC.





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