VHF inop

[gfrazzle]

The factory installed Icom M422 VHF quit working. It worked fine the last time I sailed but today- no such luck. The weather channels work fine and I get static on the others when I turn the squelch down but no audio. The display indicates TX when I key the mike but no response to radio checks. I did lower and raise the furling headsail which has an internal mast halyard but I think the wiring (antenna lead) is in a protective conduit.

Does this sound like an antenna problem or radio malfunction and how do I test the antenna at the mast base without climbing to the top?

 

[Tim R.]

First, check all the connections for the antenna. There is likely one behind the radio and one at the base of the mast. Disconnect them and reconnect. Check radio with someone near you or with a handheld. Then do a proper radio check on ch. 9 or if Seatow has an automated radio check in your are it is usually on 26 or 27. Many will not respond to you if you do a check on 16 as that is for hailing and distress only.

 

[Chief RA]

As Tim says, it does sound like a coax or connector problem and using a handheld is the best test method. Chief

 

[Gunni]

You should have a co-ax antenna connection under a panel at the mast base. Connect an inexpensive SWR meter to the cable and see what kind of TX power you get there. Also check the condition of the co-ax as it exits the mast conduit. After that you are either looking at the masthead antenna or the connection up there.

 

[Chief RA]

Gunni: Good morning! I think you may have blown them out of the water with SWR meter . I hope they know what it is! Good advise though. Chief

 

[Don S/V ILLusion]

It's coax, not co-ax.

SWR meters are a common tool to test antenna systems but can sometimes be very misleading unless the op understands that is is measuring the 'system' rather than just the antenna.

The first and easiest step is to simply connect a different radio to the coax and see if that eliminates the problem.

 

[Chief RA]

Don: SWR might be common to people in your ham radio circle but you are not addressing many of them in this forum. The average person has no clue. Chief

 

[Hello Below]

The first and easiest step is to simply connect a different radio to the coax and see if that eliminates the problem.

Be careful, you may end up with 2 unserviceable radios. I would suggest connecting the suspect VHF into a known good antenna system rather than possibly transmitting into an open load.

 

[Don S/V ILLusion]

Don: SWR might be common to people in your ham radio circle but you are not addressing many of them in this forum. The average person has no clue. Chief

Which is another reason to not be easily misled by using one without the knowledge how to interpret the reading. If you call it "co-ax", that would be an indication...

Although there may be some unfamiliar with the term SWR, I suspect they have all heard of a Google search.

As to using a good radio in a bad load, all contemporary transceivers have a fold-back circuit which effectively protects the output section from an open or short circuit load or anything with an SWR greater than 3:1.

 

[Hello Below]

As to using a good radio in a bad load, all contemporary transceivers have a fold-back circuit which effectively protects the output section from an open or short circuit load or anything with an SWR greater than 3:1.

No doubt the manufacturer is just covering their backside when the ICOM M504 manual states: "CAUTION: Transmitting without an antenna may damage the transceiver."

But if there is an easily accessible VHF antenna w/cable handy then I would connect bad transceiver to known good antenna. Usually, if the antenna and/or cable is the culprit then the receive side will also be an issue (no or weak receive signal). If the receiver is functioning normally then it is a good chance that the txer side of the radio is kaput.

 

[Chief RA]

Don: relax! Chief

 

[Don S/V ILLusion]

Now THAT is good advice.

 

[Chief RA]

Merry Christmas! My best, Chief

 

[Ken Cross]

You could also just connect an 18 inch piece of plain wire into the center conductor of the radio and listen. If you then can suddenly pick up some transmissions, the problem is your antenna. Having said that, the fact that you get weather (depending on how strong the signal is) may already be telling you your antenna system is okay.

The proper way to check it is measuring VSWR (Voltage Standing Wave Ratio). You generally want 3:1 or lower. This is a measurement of transmitter power that is reflected back onto the radio from the antenna system. The reason a high ratio is bad is because the reflected energy heats up the internal parts of the radio, and by being reflected back it doesn't go out to those folks you wish to have hear it.

A poor man's test is to just try to pick up a weak station. If you have poor VSWR you will also have a weak receiver.

No VSWR readings are not just a "Ham Radio" thing. It's the industry standard test worldwide. I'm not a ham, but been doing such tests over 40 years.

 

[justsomeguy]

It's coax, not co-ax.

-snip

Well, you're both wrong. It's coaxial.

Coax is to wheedle, persuade or otherwise influence someone or something.

 

[Bill Roosa]

If you are getting static and the weather channels work then the antenna is OK. To be sure just disconnect the antenna at the radio and turn it on. NO static at all no matter what the squelch level and the weather channels don't work of course. Have a friend with a portable confirm a radio check. If you still get static with the antenna disconnected your receive side is bad.

 

[gfrazzle]

Many thanks to all who replied. I'll dig into it next weekend.

 

[rgranger]

Don: SWR might be common to people in your ham radio circle but you are not addressing many of them in this forum. The average person has no clue. Chief

Dang! All this time I thought I was above average.

 

[Bill Roosa]

sobering fact: 50% of the people you know are below average!

I'm of the opinion that folks make thing way to complicated before checking the really simple things to confirm that there is even a problem. Had a call to the rental unit once that the washing machine was not working. After looking at the washer I noticed that there was an extension cord plugged into the outlet that the washing machine usually was plugged into and going out the basement window. I asked if they had had a party in the back yard recently and they (sex withheld) said yes. I plugged the washer back in and charged them $50 for the call. they where insensed that I'd charge for just plugging in the machine!
Live is hard, it is harder if you are stupid

 

[Brian D]

Well, you're both wrong. It's coaxial.

Coax is to wheedle, persuade or otherwise influence someone or something.

LOL! Beat me to it. LOL!

I use two methods when it comes to trouble shooting.

First - start at point A and work towards point B.
In this case, follow the coax cable (coaxial to some LOL) from the radio to the antenna (or as close as possible). Don't start at the mast, that is the middle of the road.

Second - the 4 P's of satellite trouble shooting (modified).
First - Power. That would be DC You obviously have that.
Second - Pointing. Not in this case as it is not a satellite dish.
Third - Parameters. In this case, make sure you are on US channels and not International Channels. Use the SeaTow/Boat US repeater if you have one. Or listen for any other boat then hail them. Also check you power settings (1W or 25W).
Fourth - Parts. It could be coax, antenna, or other parts involved. SWR meters help as do dummy loads and watt meters. But now we are getting really complicated in a way. If you have a ham friend, solicit them to help.

Good luck