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VHF and channel 22Alpha

Old 09-22-2008, 06:36 PM
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Default VHF and channel 22Alpha

dumb question but I will toss it out...

I have 2 newer VHF's on my boat with 19ft antennas to them

When USCG says switch to 22a to hear weather or anything else I dont pick them up. I did before but now I get nothing or either raido.. All the other channels work fine any ideas?
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Old 09-22-2008, 06:48 PM
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Default RE: VHF and channel 22Alpha

22 alpha is regular channel 22 in the United States. It's a reserved frequency for the USCG, usually as a working channel after making contact on 16. While I'm not certain about this, if your radio has a button marked UIC (U.S International Canada) you might want to make sure you're listening under the 'U' for U.S. That might be one reason you don't hear them on 22, but I don't know if UIC effects this particular channel or not.
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Old 09-23-2008, 07:06 AM
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Default Re: VHF and channel 22Alpha

22A is the same frequency for US and Canada. There is no 22a for International. 22 International is a split frequency channel tx on 157.100 receive 161.700.

As Chummer suggest check you UIC setting
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Old 09-23-2008, 07:07 PM
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Default Re: VHF and channel 22Alpha

A little expansion on tculin's excellent post. The 22a of the US and Canadian modes have Coast Guard station transmit on 157.1000, and the receiver is on 157.100.
As he states on the international mode, your set is receiving at 161.700. (duplex) if set on channel 22 international. There are several other channels which are different in the International mode.
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Old 09-24-2008, 06:56 PM
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Default Re: VHF and channel 22Alpha

What are the makes and models of the VHF's. Certain manufactures had problems with particular channel frequencies, with the release of certain DSC models. Please advise on radio types. Icom, Koden, and Sailor had problems with improper programming. The fix was to have an authorized dealer re-zap the radio with a computer and update the frequencies. This problem was more prevalent in 2003-2004. Maybe your radio's are 'newer' from this era.
I still agree with the other posts UIC is set wrong.
MT
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Old 09-24-2008, 09:39 PM
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Default RE: VHF and channel 22Alpha

MarineTechnician--would this type of problem suddenly appear? He noted that the radio was working properly in the past.
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Old 09-25-2008, 08:24 AM
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Default RE: VHF and channel 22Alpha

Not to answer for MT, but I've accidentally hit the UIC key while bumping around in choppy seas. The display is very subtle about showing which mode you're in. Personally, it shouldn't even be a key. You should set it in a setup screen and leave it, unless this is a problem for folks in border areas.
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Old 10-02-2008, 02:20 AM
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Default Re: VHF and channel 22Alpha

sorry for the delay in post.... Was off shore.. but 1. The newer VHF which is less than a month old picked up 22A now no longer does so. The second VHF is older one year and it does not pick up 22a and I am not sure if it ever did. Both Raidos are Icom.. I will get the model number off them.. Both are connected to 19ft shakspears. I have owned many commerical boats and never had this problem so I am stumped for sure. I Do have a ton of eletronics running on the bridge Dar,2-3 chartplotters/gps 2 bottom machines, sat weather and radio. I have no clue if this could interfear with that freq. I know that sounds stupid but it was a thought I had..

Thanks again and I will post model numbers and such
Cant post pic in here for some reason if you shoot me an email I will send pics of unit.

Jon
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Old 10-02-2008, 11:43 AM
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Default Re: VHF and channel 22Alpha

You COULD be picking up what is known as a "birdie". At least that is what all the radio geeks I know call them.

A birdie is simply a stray radio signal. All electrical devices can create a radio signal. Many devices (anything with a computer chip) are designed to create a radio signal. Take your home computer for example - the speed of the processor is expressed in frequency - Ghz in this case. Computer memory runs at 500something mhz. And so on.

It is possible that one (or more) device is leaking some RF energy, and your radios are hearing it. To trouble shoot this turn everything on as normal, then start turning off devices one at a time and see if the signal on 22a return to normal. If you turn off a device and the interference vanishes - then there is your problem.

If this does not work, then borrow a hand held that you know works on 22a from someone. If you take the hand held on your boat and it works fine on 22a then the problem is your radio. If the problem is still there then the birdie could be from two separate devices that only create the interference if they are both on at the same time. You troubleshoot this the same way as the first procedure - only you have more combinations to go through.
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Old 10-03-2008, 08:02 AM
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Default Re: VHF and channel 22Alpha

I thought a birdie was a transient caused by poor receiver design or a problem in the receiver circuit and not a stray radio signal. They can sound like a unmodulated carrier or dead carrier with no audio. Often they will have pops, clicks, hum and whine associated with them. Can happen from the receiver being tuned to a frequency that is a multiple of the output of an internal oscillator used to make up the receiving circuit. I would really hope that Icom would have designed its IF circuits properly so they would work. I know in my Icom's I've not had this problem.

Stray radio signals take all sorts of forms. The same receiver problem can also manifest in the transmitter when harmonics are not properly suppressed. For instance a signal at 28mhz will throw a harmonic about -30db down at 56mhz (transmitter 2nd the 3rd order harmonic suppression). Another weird vhf anomaly is intermod. Intermod is often cause by business band repeaters and paging systems in a VHF band very close the Marine VHF and the 2 meter Ham band. They sound like just about everything depending on how well you receiver is designed. If the band pass filters are not robust enough you will get to hear everyone.

Best put this way, coming down the coax from your antenna is just about every signal on the air that there is. The antenna if it has a low Q or is narrow in band width will help lower the level of signals that are out of band. So 25mhz or so worth of signals might reach the antenna connector on your radio. The band pass filters further filter out the unnecessary signals.
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