VHF Radio Problem

[DennisM]

Yes, it's me again, looking for help and advice on yet another little problem. Sorry. But I'm hoping someone can help. After restepping my mast, my VHF radio now receives a signal only intermittently. Sometimes the signal is scratchy, sometimes it's clear (though rarely), but most of the time, the radio is just dead. The power to the radio, squelch, and everything else seem fine.

I took the radio out of the panel when it wasn't working and discovered that when you remove the antenna wire and then insert it back in only half way (before the screw-on sleeve makes contact), the reception is okay. Also, if you stick a length of wire down inside the connector on the back of the radio, it functions as an antenna, and you get a signal. Two friends, who are far more knowledgeable than I, say that it seems like the antenna is grounding out somewhere.

Should I start hunting for a bad connection somewhere between the back of the radio and the VHF antenna (47 feet above)? Or is there something simpler I should try?

[btrayfors]

If you have good reception when only the center connector is touched, but not with the outer jacket connected, it most likely means you have a short in the coax or coax connectors. Could also be a fault in the antenna itself, but not likely.

Most likely, one or both of the PL-259 UHF connectors wasn't properly put on. If you're real lucky, it's the one on the bottom. But it could be the one at the top, or both.

A less likely cause would be something actually cutting into the coax and shorting the braid to the center conductor.

Since many popular VHF antennas normally show a DC short, you probably can't check out the coax with just a multimeter UNLESS you disconnect the coax at both ends first.

Sorry.

Bill

[St. Elsewhere]

DennisM,

"Stepping the mast" raises the odds that the cable may be damaged where that process and the cable intersect. Try inspecting all of the coax that is accessable that could have been pinched or cut in the process.

Also, test operation only in the receive mode. Transmitting into a short could kill your VHF.

[DennisM]

Thank you, Gentlemen! Interestingly, I reconnected all the wires myself (and successfully, to my surprise) after the mast was restepped. There was no coax among them. I think this means that somewhere along the line, whoever installed the radio converted the coax to something else somewhere inside the boat. Is that possible?

[btrayfors]

Originally Posted by DennisM

Thank you, Gentlemen! Interestingly, I reconnected all the wires myself (and successfully, to my surprise) after the mast was restepped. There was no coax among them. I think this means that somewhere along the line, whoever installed the radio converted the coax to something else somewhere inside the boat. Is that possible?

Anything's possible, but it ain't right :-)

There are no alternatives...you MUST use coax. For a shortish run (smaller boat) the preferred type is probably RG-8X. For boats in the 35' and up range, the preferred coax type is RG-213, 214, or LMR-400. Do not use RG-58 or RG-8. False economy.

Bill

[DennisM]

Hmmm..... my guess is that since I did not reconnect any coax, that what goes all the way up the mast is the wrong stuff. But I'm not really sure... grrrrr....

[St. Elsewhere]

If you decide to redo it with a new proper coax run from radio to antenna, the next important issue is the connector.

Both ends will need a PL259 connector installed. At least one end is likely to need to be installed after the wire is run because the connector is a lot larger diameter than the wire. The path through the mast may be sized for the wire only. Solder type PL259's are the most reliable, and you no doubt would like to avoid a lot of mast stepping. Solder type PL259's require a little soldering skill and the use of a small butane pencil torch to get a good shield connection. You might have the top end PL259 done by a skilled professional before running the wire. The connection at the radio is less critical because it is likely out of the weather and easier to access if you don't get it properly done and need to replace it in the future.

[DennisM]

Thanks, St. Elsewhere. At this point, I'm beginning to think that I might simply have missed that coax coming out of somewhere, or there is a cut or crimp in it. I won't be able to look until later this afternoon. The radio seemed to work fine last season, before the mast was unstepped. Meantime, I keep my handheld VHF turned on. It's okay for day sailing out on the Hudson River, but it won't be sufficient for the cruise I'm planning in June.

[olepedersen]

Hi you must have a connector at the base of the mast ,as you had the mast down, anyhow, tune your vhf to a weather station and wiggle all the connectors you can reach without climbing the mast, you should hear when you come to the bad connection,you have fun ha ha ole

[DennisM]

Thanks to the help I got here, I managed to fix the radio. The problem was, to coin a John Kennedy Toole phrase, "A Confederacy of Dunces."

Dunce No. 1 was the idiot who disconnected the wires when the mast was unstepped. Rather than search for the coax connector in the headliner, he simply decided to snip the wire. Then the moron compounded the problem by trimming back the outer covering of the coax on both ends, snipping the central wire and insulation, and twisting together the copper shield so that it looked like a single wire connection, not a coax connection.

Dunce No. 2 was me. Failing to recognize a coax cable, I took the two twisted ends of the shield and connected them together with a heat-shrink connector. No wonder the darn radio wasn't getting a signal.

Anyway, I undid the connection, put a new coax connector on the spar end, connected it to the already-installed coax connector that was hiding in the headliner, and the radio works great now.

Thanks again for your help!