Question for Radio Heads

[Roger Long]

you were heeled and transmitting the attenuated part of the pattern (the doughnut hole) was facing the receiving station?

That's what I'm thinking. I haven't used the radio much while sailing hard. We were heeled and pointing the other side of the doughnut up at the sky when I was trying the automated radio checks.

If the phenomenon was that pronounced though when talking line of sight to a vessel only about six miles away, I think it would be pretty common knowledge.

 

[Forrest15112]

I wonder since the radiation pattern from a VHF whip antenna is like a "doughnut" that at the time you were heeled and transmitting the attenuated part of the pattern (the doughnut hole) was facing the receiving station?

Two problems with this. First, the antenna would have to have very high gain which isn't likely in a typical mast mounted antenna. Second, most marine-type antennas are typically 3-5dB gain and have radiation patterns that resemble light from a light bulb.

 

[FourPoints]

The only significant difference I can think of between when the radio wasn't working and now is that we were sailing hard at 20-25 degrees of heel (Strider is an old fashioned gal and goes best that way.

I wish I had thought to roll up the jib and round up to minimal heel and try again on the radio.

When we did the radio checks from Huntington and Mamaroneck we were motor sailing, not much heel then...

 

[RobG]

Forrest - some good graphics here that depict the radiation patterns from a simple whip antenna. http://www.boat-project.com/tutorials/vhfant.htm
A light bulb pattern - omni - would be generated by a more complex antenna.

Roger - six miles isn't all that far so I don't think the doughnut theory is giong to hold up here.

 

[Roger Long]

When we did the radio checks from Huntington and Mamaroneck we were motor sailing, not much heel then...

That's right. I forgot about that. One of the closer automated stations wasn't coming back at all readable and the farther one was distorted but understandable.

It isn't rain and it isn't heel. It lasted for about 24 hours and it works as well as it ever did now.

Weird.

 

[dparilla]

Just a thought...we have had some pretty amazing ionization patterns lately, and some very significant solar activity, it could be bad atmospherics. I know vhf does not rely on the ionosphere for line of sight, but maybe a bit of st. Elmo caused your problem.