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-   -   VHF antenna issues? (http://www.sailnet.com/forums/electronics/88360-vhf-antenna-issues.html)

GMFL 06-08-2012 02:35 AM

VHF antenna issues?
 
So, I had a new mast-top antenna installed a few months ago during a re-rig. Had the cable ran (run?) to the base of mast. Installed coax from mast base to the VHF. Then hooked to a "new" Standard Horizon radio.

I can receive from STRONG signals (CG comes in fine, a handheld close by too) Signals from vessels using (I'm guessing) fixed mount radios are not received although they come in fine on the handheld.

SO, the question, WTF is wrong? I'm thinking (OK... hoping) the antenna is fine, the cable from the ant to the radio should be fine ( I did bypass that coax and connected straight to the coax from the mast base, same result)

Could it just be the radio? It was given to me "new" in its box but is several years old. Don't know its origins.

She is about 6 hours away, so not easy for me to diagnose. I, stupidly, didn't try to transmit a radio check to see if it TX's fine.

I guess my first thought is to install a new radio (SH GX1700 looks good) although I really don't want to buy a new $200 radio if it's the antenna that I need.

Thoughts? :confused::confused::confused:

mm2187 06-08-2012 09:02 AM

Re: VHF antenna issues?
 
Did you try adjusting the squelch? maybe it is possible to be on so high that you can not hear anything.

SVAuspicious 06-08-2012 11:16 AM

Re: VHF antenna issues?
 
Find someone with an SWR meter you can borrow, and the expertise to use it. All will be revealed grasshopper. *grin* Your best diagnostic tool in this instance. Check a local ham radio club.

MarkSF 06-08-2012 01:30 PM

Re: VHF antenna issues?
 
I had the same issue on my setup. It turned out to be an issue with the length of cable between radio and mast base. In the end I replaced it with new cable, and new soldered gold-plated plugs. That did the trick.

In my case I believe the issue was age-deteriorated cable and connectors. In your case it is all new, but termination is still a process that is susceptible to human error.

I think I would proceed by measuring the SWR of the antenna and cabling. If your radio is old and you don't mind getting a new one, I would try that. Thirdly, in my case, I found it helpful to buy and try one of those Shakespeare emergency antennas (which told me that the radio was fine). I kept it as a spare just in case.

redline 06-08-2012 05:05 PM

Re: VHF antenna issues?
 
It's a long shot, and depends on which channels you used to compare with the handheld, but if that "new" radio is just new to you, check that the U/I/C (US/International/Canada) setting is correct. There are some channels which are used as duplex pairs in some locales, and simplex in others. US/Can differ in some, and US/Int'l in more.

asdf38 06-08-2012 06:57 PM

Re: VHF antenna issues?
 
That sounds like my boat. When I bought it the old radio didn't work. I bought a new radio and pronounced it as functioning when it could pick up my handheld from within the boat. However the next time I sailed away I quickly lost all nearby signals. Turned out my coax was totally busted at the deck connector. If I were smarter I would have checked that before buying the new radio.

So it's possible you have a bad connection to the mast antenna and are just picking up signals through the coax.

I'll cross my fingers that this season, after running all new wires like you, mine actually works.

As another note, check out the Shakespeare solder-less connectors. They were really easy to install.
Shakespeare Centerpin® Gold-Plated PL-259 Connector

Spyder 06-09-2012 03:17 PM

Re: VHF antenna issues?
 
When my radios act up like that my first place I check is the ground wire. Odd things happen if the ground isn't REAL good at the other end.

hellosailor 06-09-2012 06:06 PM

Re: VHF antenna issues?
 
gm-
One of those "emergency" antennas does make for a real quick and simple way to find out if the problem is in your radio, or your cable and antenna. Worth stowing away because masthead antennas eventually DO fail and then the spare is priceless.
If the problem is with the radio, call Standard Horizon. They're on the very short list of companies that go the extra mile, every time, for every customer. If they can't find some setting to change, they'll ask you to send it in, and the odds are it is worth repairing.
If the problem IS in the antenna or cabling, then an SWR meter and a multimeter will be needed to do some testing and figure out what's wrong. Sometimes even new equipment is DOA. Sometimes even the solderless patent coax fittings simply don't install properly.
Easiest to use the "emergency" antenna first, and make sure the radio isn't the problem. And of course, you can keep using that while you troubleshoot the rest of it.

MarkSF 06-09-2012 10:27 PM

Re: VHF antenna issues?
 
Quote:

Originally Posted by Spyder (Post 882725)
When my radios act up like that my first place I check is the ground wire. Odd things happen if the ground isn't REAL good at the other end.

You've lost me. What ground wire? VHFs are normally connected thus : + and - to the power supply. The VHF antenna cable goes to the antenna. The only requirement for the antenna cable is that the inner core, and the shield, are unbroken, all the way to the antenna. Normally the antenna is isolated from it's mounting bracket. So where does a "ground wire" fit in?

redline 06-11-2012 11:40 PM

Re: VHF antenna issues?
 
I think he meant "ground" as in "battery negative". He raises a good point in that voltage drops in the positive supply are easy to find, but when "ground" isn't really "ground", weird things happen. Not only should there be 12V (more like 12.5 to 13.6) at the radio, but the "negative" supply lead should be very close to the same voltage as the "negative" battery terminal - especially during transmit, when the radio is drawing (or supposed to be) several amps.

If there is a problem with the official netgative/ground wire, it's possible that the radio is getting its ground instead via the coaxial cable shield, via the antenna, via the mast, via other grounding or even the nav light wiring - very roundabout, and not a good ground.

Make sure the radio still operates (at least in receive) with the antenna disconnected (i.e. when it is *not* grounded via its antenna cable). Testing with an (ungrounded) emergency antenna as suggested earlier would also show this.

...and check the U/I/C setting.


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