VHF radio problems

Well here I am again asking a question I am sure someone here will have the answer to. When I turn on my VHF radio on the lake the radio does not come in really well. I have both my AM/FM and VHF radios on the same antenna. I have disconnected and ran the antenna right to the radio. That did not help. The AM/FM has never really come in well but the VHF works great.
The whole deal that I can not figure out is that as soon as I put the boat on the trailer the VHF radio comes in crystal clear not a scratch or pop or anything undesirable. The AM/FM remains the same.
You guys have never let me down with any of the quest I have posted I hope I can put this problem behind me with your help. Feel free to reply or PM me. As soon as I get it fixed I will surly post the solution.

I’ve sold a number of the “combo” antennas…and I’ve never been happy with there performance. We quit selling them because of it.

I can’t answer your question directly…but just wondering, is it a glass or aluminum boat and where do you have the ant mounted?

You can see it here next to the windshield.

I see the problem right away…that boat has an IA registration

Sorry about that….I’d get a separate antenna for that VHF. Shakespeare Little giant all the way!

I also had a combo, NEVER again. Will never have a short one either.
If you what to get out or receive from a distance go 8 FOOT.
Make sure mount and antenna are compatible. antenna and mount should be the same material, One end should not be metal and the other nylon or plastic.

If you what a good one try the Galaxy 5225-XT VHF Antenna is Shakespeare’s highest quality fiberglass, 8-ft. 6dB VHF antenna.

Hi Shew,

I’ve read your post a few times and I have to admit I’m a little confused. You said the VHF radio doesn’t come in great and then you say that the VHF radio works great
OK, you have one antenna that is supposed to work both with a VHF Marine Radio as well as a standard AM/FM broadcast band radio at the same time, right?

1) Which radio works and which one doesn’t work when you’re on the water?
2) Which radio works and which one doesn’t work when your on the trailer? What changes?
3) What is the brand and model of the antenna?

I can see where the AM reception would be affected by the trailer. Without going into technical details, your boat sitting on a trailer is in a place that is very different electrically than it is sitting in the water.

Rootski

Rootski, you thinking ground plane? Be interesting to see what his SWR is on the water then on the trailer.

WarrenMN

Hi Warren,

Exactly….The first thing I’d like to verify is that the shield of that feedline is connected to the outside of the connector. If the braid side connection is flakey, then his ground return is through some convoluted route through the battery and other wiring in the boat. And of course adding several hundred pounds of trailer metal would further confuse things. Most guys don’t have an SWR meter but a simple ohmmeter will confirm continuity at the connector.

Rootski

In laymans terms…

Check the PL259 connector for a good solder connection as 99% of all vhf radio problems (trasmit/recieve) are located there.

Rootski
Sorry I was unable to reply till now. The VHF comes in broken up at best on the water and the AM/FM does not come in well on the water. Once I put the boat on the trailer then the VHF comes in crystal clear. There is no change in the AM/FM at all. As far as the antenna it is a Shakespeare and I am not sure of the model I can post that when I get home and get to look at it tonight.

I’d be very interested to see what Shakespeare has to say about mounting that antenna on a fiberglass boat. Small vertical antennas need a “ground plane” which means a big piece of metal like the roof of a truck. In this case, sitting the boat on the trailer (which is a lot of metal) makes the radio work better. Maybe we can find the manual on their website.

Another test would be to add something called a counterpoise. This is a piece of wire attached to “ground” at the base of the antenna. It should be a special resonant length. I think VHF radio channels are around 150 Mhz. The length (in feet) works out to be 246/Fmhz or 246/150=1.64 feet or 19 3/4 inches long. That would tell us if it’s a ground plane problem.

Rootski

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In laymans terms…

Check the PL259 connector for a good solder connection as 99% of all vhf radio problems (trasmit/recieve) are located there.

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I’m willing to bet a couple that it is either an incorrectly installed pl259. Incorrectly grounded. Or the poweer wire is too small. I will admit however I have never worked with a combo antenna. Seems like an easy fix to go out and get a am/fm antenna and vhf antenna and install seperately.

When I say grounding problem, here is what you need to check. On the back of your radio, there should be a green screw. Take a 10 guage black wire and run it from that green screw back to either the negative on your battery or one of the mounting bolts on your main engine. Also make sure our main power wire is 10 guage or better.

Good Luck.

-J.

Thanks guys I will check all of this when I get home. Just so you all know the radio in the past has worked like a charm. I will look a bit deeper into the connections. thanks again.

Rootski, those aren’t co-linear?
WarrenMN

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Rootski, those aren’t co-linear?

WarrenMN

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I don’t know one way or the other, I was just brain storming. But even if it was a stacked array of some kind you still need to decouple the feedline. For example the Ringo Rangers and similar 2 meter antennas all have either a sleeve or radials.

Rootski

One more thing to check….just came to mind.

VHF antennas are calibrated for a certain lenght of vhf antenna wire back to the radio. That wire is usually 8-10 feet long. It should not be shortened and it should not be coiled up. Many times installers will shorten up that wire, no problems. Many times it’s a recipe for problems…..

-J.

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VHF antennas are calibrated for a certain lenght of vhf antenna wire back to the radio. That wire is usually 8-10 feet long. It should not be shortened and it should not be coiled up. Many times installers will shorten up that wire, no problems. Many times it’s a recipe for problems…..

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Why in the world would that be? If the antenna is tuned and matched correctly to 50 ohms, then the length of feedline doesn’t matter. And it’s coaxial cable. You should be able to tie it into knots, bury it in the ground, or tape it to a piece of pipe and not affect it’s electrical characteristics at all.

Rootski

Every antenna I have ever purchased said in the directions not to coil or shorten the length.

-J.

Wow, you’re right about the recommendations. I just went to Shakespeare’s website and looked at the directions for one of their antennas and they said don’t shorten the feedline. They also claim that their antennas are tuned to 50 ohms. They’re blowing smoke somewhere. I’ve never seen an antenna manufacturor make that statement before and I’ve been a Ham Radio operator since 1968. If Shakespeare tried to tell that to ham radio operators they’d be laughed out of business.

If the antenna is truly resonant and 50 ohm, then a 50 ohm feedline (like RG-58) will measure 50 ohms anywhere along it’s length. If the antenna isn’t 50 ohms, then the measured impedance will vary all over the map. If they tell you that you can’t shorten the feedline then the antenna isn’t a resonant 50 ohms. That’s not my opinion, that’s a law of physics. Properly installed coaxial cable has all of the RF current flowing on the outside of the inner conductor and back down the inside of the outer conductor. There shouldn’t be ANY current flowing on the outside of the cable at all. That means you can coil it up, position it next to other conductors, etc. with no ill effects. I’ve been doing that to coax for 39 years. If the position of the feedline or coiling it up affects your radio, then the feedline is actually acting like part of the antenna. You just paid good money for that 8 foot long whip, and some of your signal is being radiated by a piece of wire 2 feet above the lake? That doesn’t sound very good to me.

It would be fun to talk to a Shakespeare rep sometime…

Rootski

I actually believe you Root! And I have taken a couple feet off a line with no problems. It was just something that came to mind.

I think the bottom line will end up being that having 2 radios hooked up to one antenna is not good!

-J.

Well guys I found out that I do have a Galaxy 5225-XT I disconnected the splitter and the VHF comes in perfect. I will have to look for an AM/FM antenna for the radio. Thats no problem I have MP3 players that work with this AM/FM radio. Thanks guys you have done it once again.

Rootski and John you guys could have been talking French when you were talking 50 ohm and all that stuff that was way above my head, when you were talking like that I was just seeing dollar signs and wondering what it was going to cost me. Thanks guys.

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and the VHF comes in perfect.

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Excellent! The best news I heard all day. Glad to hear that it all worked out well. Now we can start concentrating on fish again

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and the VHF comes in perfect.

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Excellent! The best news I heard all day. Glad to hear that it all worked out well. Now we can start concentrating on fish again

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LOL I would never ask a guy to put fishing aside for something like that. Thanks again Root.

Hey Shew,

I know the guy you bought the boat from quite well. Hope the chubby little Iowan gave you a good deal. I know he was ready to deal. Some day after you get to drive the boat a little, remind me to show you some pictures from our Lake Erie trips! I just hope at that point you’ll like the boat enough not to give it back!!

To quote, “it was a clean pinch!” Channel clear!

I ran across this while trying to figure out what I needed for a radio. It was on the Shakespeare site.

http://www.shakespeare-marine.com/faq2.asp?ReqNum=1