Signal Fade

Jose Viegas of Lagos, Portugal, asks:

“I have a Navman DSC VHF radio, and last summer I began noticing that when I transmit in bad weather, only boats close by can hear me. But I can always clearly receive transmissions from others, near and far. How can I test to see whether the problem is with the antenna, the connection or possibly the radio itself?”

Tim Bartlett replies:

This might seem a bit simplistic, but if you don’t want to get involved with a lot of test equipment or outside experts I suggest you proceed in the following manner. Since the most likely culprit is the antenna plug, I would first remove the plug and shorten the antenna cable a few inches. When you cut the cable make sure the central core and braided outer sheath are clean and bright. Reattach the plug to the cable, and be sure no stray strands of the braided sheath make contact with either the cable’s central core or with the plug’s central pin. When everything is reconnected, try the radio and see whether your transmissions are more powerful.

If nothing has improved, borrow a radio you know is in good working order and connect it to your antenna. If your transmissions go out at full power, you know your radio is defective. If the problem still remains, buy a new antenna—get a cheap one for this test—and connect it to your radio. Even if you mount the temporary antenna on the stern pulpit, you should be able to be heard 10 to 15 miles away if calling a boat with a masthead antenna. If you can reach them, you know your old antenna needs to be replaced.

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