Weak Radio Transmission

[Albanach]

As a result of a recent VHF radio check with the local Marine Rescue station I discovered that my transmission is weak/slightly broken up. Any suggestions how to check whether it is a faulty radio or antenna (without climbing the mast) ? couldn’t find anything specific in the ‘Search Forum’.
Both radio and antenna are original, about 2001.

 

[Don S/V ILLusion]

Buy/borrow a power/SWR meter which will tell you whether it is a radio or an antenna problem.

 

[Mike B1026]

I took my radio in to a local radio shop and they tested the output. Didn't even charge me. (I had just replaced my antenna under warranty) Metz checked my antenna for free & sent me a new one, even though it was purchased by a previous owner and was of an unknown age. Great people to deal with.

 

[Bill Roosa]

You might not even have a problem.
how far away was the USCG station? I've gotten CG stations from well over 100 miles away when atmospheric conditions are right. these guys and gals just respond with the facts they don't provide any analysis. If you where communicating with a station that was beyond line of sight then your comms will have some issues, and that is normal.

 

[Forrest15112]

Chances are, you have a problem in the antenna/ feedline. If you have connectors that are exposed to the weather, that is a likely problem. Maybe a neighbor at your marina will let you connect your radio to his antenna to test.

 

[Albanach]

Bill Roosa – The local Marine Rescue HQ is about 15m, with their repeater only approx.4m away. Whilst I could hear them quite well, they had a problem receiving me. Last radio check from this location (my mooring) was some time ago and 5/5. Only reason I discovered this, was because my mobile phone didn’t work when I tried to call the club tender to pick me up –and then the VHF didn’t seem to work either. So much for redundancy.

Shall take up Mike B1026’s suggestion as the cheaper first option and take the radio to be tested first.

 

[Brian D]

Repeater? Are you working split frequencies with an offset? Or are they running a simplex repeater? Have you tried to see if Boat US has a test repeater in your area? They are on Channel 27 usually. But you will have to check to see if there is one in your area or on a different channel.

Three parts exist in your system. Radio, cable (with connectors), antenna. If you are hearing fine, then the antenna and cable may not be the issue. Good recommendations to move your radio to another boat for testing. Power meters if available will only tell you if you are putting out the correct power. They will not tell you if you are having internal tx audio problems (faulty mic, bad mic cable).

As mentioned, corroded connectors will kill a radio. But this will also affect rx performance. As will bad coax. If you have a handheld, you can key the radio (say on channel 68) and wiggle the coax connector on the back of the radio and listen for any noise. Harder to do at the mast top but if you can, try that also. Removing the connectors or taking off and putting back on may help with the electrical and physical connection. Maybe just a cleaning will do.

 

[Ken Cross]

As pointed out earlier a VSWR check is the answer as to the quality of the antenna and cable, however:

If you can receive from long distances the problem is not likely the antenna or cable. Try that. If the receive function compares with that of your neighbor (look for a weak weather channel or ??????????)

IF the receiver is OK check your power supply. Low voltage due to a corroded power or ground connection is likely because the radio uses more current during transmit than during receive. to check this measure the voltage feeding the radio while transmitting with a digital multimeter connected to power and ground as close to the radio as you can get. If you don't own one they are ridiculous cheap right now at
http://www.harborfreight.com/7-function-multimeter-98025.html and I've seen them as low as $3 there.

If all else fails it could be the radio itself, but usually it isn't. (yes I've done this kind of work for many years) The work I've outlined doesn't require a license, however if you get into the radio or transmission line it is a legal requirement.

 

[nolasafari]

I would clean all the connections, antenna and power. I use DeoxIT can be found at RS or purchased off the interwebs. Follow Brian's/Ken's suggestions they are on the money.

Jim N5TJZ

 

[DAVA390]

Not sure Boat US would have a big presence in Sydney...

 

[Brian D]

Sure it would, via VHF ducting. LOL! Sorry, I didn't see the location. I seldom ever look at that.

 

[Albanach]

Sure it would, via VHF ducting. LOL! Sorry, I didn't see the location. I seldom ever look at that.

Took the reference in context, ie. the test was conducted via our main station Marine Rescue Sydney and one of their repeaters they use for conversation and tests. Have tested the radio today connected to another boat’s antenna and it worked fine. Next step is the antenna at the top. All the connections that could be accessed so far are as new.

 

[Forrest15112]

Shakespeare has some videos on their webpage with some basic tests you can do to test the antenna antennas.com/media/default.asp?p=8

 

[Albanach]

Thanks to all contributors to this post. Problem solved. Just put the radio back in (to next check the antenna) and it worked 5/5. Appears to have just been a loose connection. BrianD was right on the money – dissemble and reassemble (similar to a mobile phone) and it may work.

 

[Brian D]

SBO and the fine contributors here are glad to be of service. If for nothing else, I too rely on the many well knowledge folks here. Glad you are back on the air. Your summer is fast approaching, now get out there and have a good time.