Attaching VHF Antenna

Walt352 · #1 (**permalink**) 08-26-2010

Attaching VHF antenna

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I,m about to step the mast on my boat and would like to know the pros & cons of attaching the antenna to the boat or top of the mast? Thanks Walt

sailingdog · #2 (**permalink**) 08-26-2010

If you attach the antenna to the top of the mast, your effective range for the VHF increases. The higher the antenna, the greater its effective range, since the LOS to the horizon increases. However, it does make the antenna more vulnerable to things like birds and bridges...

chall03 · #3 (**permalink**) 08-26-2010

Masthead is pretty much the way to go if you can......

But it does also depends on where you are sailing. If you're on a lake and you are never going to be out of sight of nearest rescue service, you have plenty of Cell phone reception etc then maybe not such a big deal.

If you are however going offshore like me without the benefit of HF, then well I personally want every wee little bit of range I can get.....

Masthead means significantly increased range, increased range means the people you want to hear you can when you most need it.....

So my two cents, put simply is:

If it is an inshore boat, go masthead as long as it is no big hassle, if its a hassle I wouldn't worry too much about it.

If going offshore then for me masthead is compulsory.

Walt352 · #4 (**permalink**) 08-26-2010

Thanks to all, I will put in on the mast.

Hudsonian · #5 (**permalink**) 08-26-2010

Attaching the antenna to the boat rather than the masthead has the following advantages in addition to reducing the vulnerabity to things like birds and bridges mentioned above: no need to pull the mast or go aloft to install or service the antenna and coax; less expensive; shorter coax run with less signal loss; may avoid coax splice at mast butt -- a frequent source of signal degradation; no conflict with internal halyards or other inmast wiring; and less weight aloft.
A masthead VHFantenna may be required to participate in offshore races.

sailingdog · #6 (**permalink**) 08-26-2010

I would point out that it really makes sense to have your primary antenna at the masthead and pushpit mounted one as a backup or for a secondary antenna.

Omatako · #7 (**permalink**) 08-27-2010

Way back in my youth (and that's a long time ago) we used to mess with CB radios and to boost the range we used to (illegally, I believe) use a 3dB gain antenna and it seemed to work wonders for the output.

Would these work on a VHF? And are they still illegal?

dhays · #8 (**permalink**) 08-27-2010

Quote:

Originally Posted by Omatako

Way back in my youth (and that's a long time ago) we used to mess with CB radios and to boost the range we used to (illegally, I believe) use a 3dB gain antenna and it seemed to work wonders for the output.

Would these work on a VHF? And are they still illegal?

Most VHF radios have two power settings. In general, it is recommended to use the low power setting so that your transmissions don't overpower more distance boats transmissions. The extra gain only increases transmit range, and doesn't do anything for reception.

sailingdog · #9 (**permalink**) 08-27-2010

Most of the "sailboat 3' metal whip" type VHF antennas are 3 dB gain designs.

Quote:

Originally Posted by Omatako

Way back in my youth (and that's a long time ago) we used to mess with CB radios and to boost the range we used to (illegally, I believe) use a 3dB gain antenna and it seemed to work wonders for the output.

Would these work on a VHF? And are they still illegal?

SEMIJim · #10 (**permalink**) 08-27-2010

Quote:

Originally Posted by Omatako

Way back in my youth (and that's a long time ago) we used to mess with CB radios and to boost the range we used to (illegally, I believe) use a 3dB gain antenna and it seemed to work wonders for the output.

No, that was not illegal. It was legal to use whatever you wanted for an antenna.

Quote:

Originally Posted by Omatako

Would these work on a VHF? And are they still illegal?

Yes, but understand: There are no free rides. You cannot create gain from nothing. How so-called "gain antennas" work is much like a flashlight: They focus energy in the desired direction. In the case of vertically-polarized, omni-directional antennas this is accomplished by "squeezing" the radiation pattern down--thus lengthening it on a plane at right angles to the antenna. Visualize a donut on a table-top being squashed down.

Now, this squeezing-down of the radiation pattern is all well and good for fixed land stations, automobiles, and even powerboats, because their vertical antennas tend to stay mostly vertical. But for sailboats it may be an issue, for sailboats may spend much of their time heeled-over at 15, 20 degrees or more. So if you have a very high gain antenna atop the mast: On the windward side your radiation pattern may be pointed off into space and on the leeward side it'll be pointed right down into the water.

And it's a two-way street. It may be difficult to visualize: But as goes your transmit, so goes your receive.

Jim