Having problems with new vhf radios

[Gone Fishing]

I purchased all new electronics for the boat this year. I bought 2 Icom 402 radios and 2 Digital antennas. Both units receive very well but neither transmits worth a darn. People have said the can barely hear me and it is definitely on high power. They have also said the transmission might start out strong and then fade away. My antennas are mounted on top of my radar arch along with my gps antennas but the gps/vhf antennas are only about a foot away from each other. I also did some coiling of the excess vhf antenna wire which I plan to change tonight. Do you think the gps/vhf antennas being so close could be causing the problem? Another possibility is that I have all my electronics being powered off 1 terminal strip and I might be exceeding its capabilities. I’ll try powering directly off the battery and see if that solves the problem. Any feedback or other ideas would be greatly appreciated. It’s kind of hard to see in this picture but you can see the gps antennas with the vhf’s mounted directly behind them.

http://www.michigan-sportsman.com/photopost/data/550/P1010018.JPG

[SabikiRig]

Gone Fishing,


Here is what Shakespear has to say about mounting antennas:

" Choosing a location for your antenna is an extremely important part of choosing the antenna itself. Remember to keep the antenna away from large metal objects, and especially away from other radiating devices (like other antennas). The antenna should not be mounted closer than three feet from the radio, but it shouldn't be so far away that the radio's signal is depleted before it gets to the antenna."

Based on your photo there is alot of metal and other antennas on that arch, there is alot going on in such as small spot. Looks like you even have some Rupp Outriggers on there too. You mention Digital Antennas, what are the length of these antennas? Are they the short ones that the Offshore Guys like or are they longer (12 to 16') ones?


Regardless it sounds like you are on the right path. Here are a couple of questions for you:

Truck Drivers running co-phased antennas run into the same problem. Are you running a radio to each antenna or are your running the antennas co-phased to one radio and using the second radio stand-by (backup) which can be manually connected should you have a problem.

The coax loops would cause SWR problems.

How far apart are the two VHF Antenna mounted from each other? You must keep a considerable distance between the two antennas.

Have you tested the radio with all of the other equipment off to isolate which or if the other electronics are the cause of the problem?

With the other electronics shut off can you lower the Outriggers and see if there are still any transmission issues?

As far as power delivery goes it is a good idea for Marine Radios (when possible) to have a fused, dedicated run directly to the battery rather than using a distribution block. Or at the bear minimum on its own dedicated feed. That way your pulling power directly from the battery eliminating any power delivery issues at the distribution block.

[Gone Fishing]

I have the 8 foot Digital antennas. I figured that would be plenty tall since they are mounted on the arch. I know I have a lot going on up there including the outriggers although I had riggers on my old boat without any problems. I really wasn't aware of how bad the transmission problem was till yesterday when I could see the boat I was trying to talk to but he was having trouble hearing me. I tried turning off my kicker auotpilot but that didn't help. I'll try it tonight with nothing else powered up and see what happens. I tending to think that my available power is marginal. It receives great but craps out when I transmit. BTW, the multiple radios are for back up/safety purposes but when I had problems, I tried the back up and the condition did not improve. :(

[SabikiRig]

Gone Fishing,

Start out cleaning up the Coax Loops and power delivery first. That would be the first thing a service technican would do first anyways.

[ih772]

The coax loops would cause SWR problems.

Coiling your coax doesn't cause problems with swr. However if you do make coils, make the diameter of the coils at least 12' for RG-58 and RG8 mini types of coax.


You don't need to phase high gain vhf antennas. If any of you do you will end up with dead spots in the radiation pattern of the antennas and you will have problems with swr mismatch as the antennas fed that way are now longer 50 ohms.


Here is a suggestion for you to try if you are still having problems after running it directly off the battery. Try and removing the antenna to the back up radio by taking it off the arch and having it nowhere near (several feet away from) the transmitting antenna.

[Gone Fishing]

If I have to remove the antenna from the arch, I'm going to cry. All the wiring runs through the arch tube and it's packed in like 10 lbs. of crap in a 5 lb. bag. I don't think I could pull out just one wire. Hopefully, it’s just a voltage issue. As far as the cable coiling, I think I might have done a figure 8 and then used a cable tie to cinch it in the middle. Is that a no no?

[ih772]

As far as the cable coiling, I think I might have done a figure 8 and then used a cable tie to cinch it in the middle. Is that a no no?

If you made the loops of the figure 8 about a foot in diameter there shouldn't be a problem. However if you really tightened the tie-wrap and it caused the coax to crush then there will be a problem. This happens very easily to coax that has a foam dielectric (center).

Now that I understand your situation of feeding the wire through the arch (nice job by the way) try laying the spare antenna horizontal and give the main radio a test and see how that goes. The reason I say this is I suspect the two antennas might be "seeing" each other and doing some kind of coupling that you don't want which causes the radio to reduce it's output power when transmitting.

[WALLEYE MIKE]

Sounds like you need to get a new boat. That one is already worn out. :lol: :lol:

[Jason Adam]

Should be good with the figure 8's. I would start out with nothing powered but 1 radio and test that way. The power up both radios, etc. Your GPS antenna is nothing when its not powered. I would check power first.

If power seems OK, I'd get another antenna from somewhere and plug it into your radio and hold the antenna away from the other crap to test. If the outside antenna fixes it, then you have a world of headache to deal with<sorry>...

[SabikiRig]

Guys,

Here is something to think about. Could the Coax from the Radar and GPS Units being run along with the VHF through the arch be a problem? Bleed through?

If at all possible don't you want to isolate your coax runs from VHF as much as you can?

Instead of tearing the cable out of the Arch like you mentioned Gone Fishing, do you have an extra antenna laying around that your could test with temporarily?

[Gone Fishing]

Yes, I'm pretty sure I have an old antenna in the garage. I also posted this on The Hull Truth website. I ran across a thread over there about problems transmitting with the ICOM 402 radio and that’s the same ones I installed. I don’t know if it could be the radio and not the installation but it makes you wonder. If you care to check out the tread, here’s a link: http://thehulltruth.com/forums/thread-view.asp?tid=64681&start=1

[Gone Fishing]

OK, I just quickly ran some 14 gauge wire directly from the radio to the battery and did a radio check. Received two loud and clears, one from Pike's Creek near the mouth of the Detroit River and one from the Colony Tower near Algonac. I was transmiting from a canal near Metro Beach with quite a few houses and trees between me and the lake. I'm pretty sure I'll be good to go after I hard wire the radios. Thanks for your input gentlemen! :)

[Jason Adam]

I'm assuming you had all your other electronics and such powered up for this test? If so, thats great news that its just dirty power. Re-wiring the arch would not be cool...

[SabikiRig]

Gone Fishing,

Good news. Hope you can sleep better tonight knowing that you do not have have to tear into the wiring in the arch.

Jason brought up a great point. Did you have the other electronics powered up when you did the test?

[Gone Fishing]

No, I didn't have everything powered up so I may not be out of the woods yet. I'll try that tonight powering up one unit at a time and checking for problems. Thanks for the input! :)

[Gone Fishing]

Whew, I had my fingers crossed after I powered up all my electronics and did a radio check. I was talking with Muskie Mania who was fishing the south shore a good 15 miles away or better and he said it was working loud, crisp and clear. I’m sure glad it turned out to be something simple. The thought of pulling the arch and removing antennas for relocation was giving me a sick feeling. Thanks for your advice everybody! :)

[Houghton laker]

Hope it all goes good for you!! Hate when problems like that arise!