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Arf!
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609 Posts
Discussion Starter · #1 ·
I noticed that my masthead VHF antenna is not getting any responses from radio check requests. I have a splitter which feeds the VHF and my FM radio.

The FM seems to work, but sensitivity is not what I would expect. Same for the VHF receiver. I can pull in a number of channels, but transmitting doesn't seem to get me anywhere. [I realize I could have a burnt-out transmitter, but I am trying to eliminate things one at a time.]

I disconnect the antenna cable at the base of the mast in the main cabin, and the FM reception seems to improve, while it is connected only to the cable running behind the cabin settees to the mast. I am surprised that co-ax cable can act as an antenna :confused:

I measured the DC resistance of the cable leading to the mast and it is quite low -- a few ohms.

Does anyone know what the resistance of the cable/VHF antenna should be? I think there is a balun coil at the base of the VHF whip, but I have no idea what the circuit looks like.

If this is normal behavior, I will be able to avoid a useless trip up the mast.

thanks ..
 

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Arf!
Joined
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609 Posts
Discussion Starter · #5 ·
I'd recommend getting a fiberglass deck level antenna as a backup antenna for your vhf, and fix your mast antenna. I'd bet you'd get a good response to radio checks when you connect the fiberglass deck antenna to the vhf. The problem with the mast antenna sounds like a corroded cable, connections, or antenna.
Scott
Gemini Catamaran Split Decision
I already have a 6 ft whip and a 2nd VHF at the helm, as well as a handheld. So it is a question of getting the darned thing to function, not an immediate safety question.

The VHF cable down the mast was installed at the beginning of the year. The only thing remaining is the balun coil at the base of the Shakespeare whip on the masthead. The cable was purchased with the masthead connector installed, so if there is a problem it is likely to be with the soldered connector I installed at the bottom of the mast, or with the VHF antenna itself. Could also be the splitter for the FM that is faulty...

I can check most of these things out, but I really would like to know what the DC resistance should be of the cable+antenna. If someone could measure it on a working system that would be a big help.
 
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