VHF Antennas

[Lew Barrett]

Last summer I began to notice an annoying VHF symptom. I had squealing (an audio guy would call it feedback) during VHF reception. I assumed people were using two radios and transmitting on one of them, thus creating feedback loops. Of course, I cursed them roundly for their stupidity and just lived with the infrequent annoyance.
This year, the problem escalated to the point that even the weather channels were feeding back. Now, I could no longer blame the Bayliner drivers and had to admit that there was a fault in my system. Since using a VHF is such a critical part of boating fun and safety, my wife (this was a first!) said; go ahead and spend some money. Get a new radio.
My 15 year old Icom has always been reliable, but I decided to just replace the whole shooting match, an ordered an M504 and a new VHF antenna....Shakespeare Galaxy 5225XP.
As an experiment, I decided to replace one component at a time, starting with the antenna, which I installed yesterday. My system requires a barrel connector to meet the antenna (the run is greater than the 20 feet of RX8G provided) so I always start 6dB down, but that has never been a problem in the past. However, in removing the
the antenna connections at the barrel, I noted some corrosion (not unexpected) and also some wear at the grommet where the antenna lead comes out of the ferrule at the antenna end. Visible signs of wear, in other words. The antenna wasn't happy about spinning off the mast extension, either; over the years they'd developed that unique and frustrating fondness for each other that happens between dissimaler metals in the salt water
environment.:D Some carefully applied heating with my torch fixed that!
I put the new antenna on, cleaning all the threads and very carefully applying a light coating of anti-seize. I used one of those new solderless connectors as well. I went into the pilothouse to test my new rig (using the old radio) and man.....what a contrast! Clean, loud, clear communications reception on all channels. I don't know if just cleaning the connections by themselves of all the crud and detritus of the years made the difference (like chicken soup....it couldn't hurt) but it sure as hell taught me a lesson.
Check your antenna connections regularly.
I wonder what adding the new DSC radio will do for my range? I'll keep you all posted.
Lew

[capt jake]

Connections in radios equipment are critical. I find that transmission and reception problems are usually due to a loose connection or corrosion, seldom in the unit itself.

[paladin]

Range should not increase with the DSC radio..although you may be able to better hear existing stations. Rule of thumb on marine antennas...take everything apart at least once a year and clean all terminals, including all ground(counterpoise) terminals.....

[Lew Barrett]

I don't really expect I will either. In fact, I think the new antenna solves the problem. But the specs on the radio (whatever that's worth) indicate a bit less noise and better selectivity. I won't be throwing the old one away....got a sweet spot for it in the cockpit.
Yea! mighta' saved some dough with a spritz of tuner cleaner and a good scrub! But then....no new radio, and I had a permission slip:D

added: the DSC is of course just a safety feature, not a transmission booster. It's what I'd call "justification."

[Bill R]

I cannot emphasize enough the importance of clean connections. Corrosion can be a VERY bad thing, especially when you get into the 25-30Kw power range some FM band transmitters put out.

Whenever we start having satellite or microwave issues, the first place we check is the connections. A corroded antenna connector may not show up as a VSWR (reflected power) issue. Good ground connections are also essential. Any corrosion there will give you a real headache.

Make sure you always use high quality connectors and cable- silver plated connectors as opposed to the chrome plated crap. I would recommend a marine rating on the jacket as well. Any water getting in between the jacket and shield braid can cause problems. Always weather seal your connectors making sure to go past the threaded connection on both ends. Electrical tape is not enough- a "courtesy wrap" of electrical tape, a layer of butyl (the taffy like black sticky stuff) followed by a couple wraps of electrical tape sealing the whole thing.

If you can get an continuous run of cable from the transmitter to the antenna so much the better. You eliminate the loss in the barrel as well as eliminating 3 potential failure points- 2 connectors and the barrel.

Also, personally, I would shy away from crimp on connectors. I have had problems with bad crimps and/or corrosion on the center conductor pin with the crimp on type. I have also had them fail much sooner than soldered types. YMMV.

If there is any interest, I am willing to do a Smalser-esque photo essay on weatherproofing connectors when I change out an STL jumper this week.

[capt jake]

If there is any interest, I am willing to do a Smalser-esque photo essay on weatherproofing connectors when I change out an STL jumper this week.

Are you kidding? Of course we would all love to see that! Anxiously awaiting. That would be a very good addition to the other 'how to' threads.

[Lew Barrett]

Bill, I'm interested. There's no way for me to escape the connector or the inherint loss unless I move the antenna to the coach roof. But then I would sacrifice the extra 14 feet of height I get from mounting the antenna on the mast. The antennas only come with 20 feet of cable, so you need a junction in many big boat applications.
I left a small service loop in the run leading to the barrel connector so I could re-do it as necessary. The crimp on is a supplied Shakespeare accessory, gold plated. Wrapping the connection sounds like a plan.

[Bill R]

Lew- how long of a cable run do you have, what type of cable (RG-58 I assume?) and what type of connectors are on the cable ends?

[Bill R]

I will take some pictures when I do it then. Give me a few days. I have scheduled it for Wednesday, assuming the Radio Gods smile on me. I will put it up later next week if everything else goes as planned.

[Lew Barrett]

Bill,
The cable, which is somewhat thicker (but only just marginally) than the RG58 on my last antenna, is called RG 8X in the literature.
The run from the base of the antenna to the connector is about 17 feet. The cable length provided with the antenna was 20 feet, so I snipped the last 3 feet and added the connector. From the barrel connector, the second run of cable runs about 15' or so to the radio.
To avoid using a connector, the last owner mounted the radio at the rear of the pilot house, but I compromised and added the second connector so that as the pilot, I could use the radio while steering the boat. If I were doing a lot of offshore work, I might have not considered that as an option, but then I'd have an SSB in addition to the VHF!
The connector is a PL259, gold plated, off the antenna to a matching barrel connector and then off to another pair of PL259 (?). Here's the spec on the new antenna. It's the 5225XP.
http://pdf.nauticexpo.com/pdf/shakespeare/shakespeare-galaxy-antenna-2007-catalog/21795-2233-_3.html

Oh....and it seems to be working great! Big improvement but the simple act of replacing it and cleaning all the connections could have been 90% of the deal.

[paladin]

Crimp on connectors are great if you use the mil-spec stuff. If Bill writes up the procedure I can send you 20 feet of RG-214, the connectors, and the mil spec crimp tools to do the work if you're interested. Specify the connectors which I assume to be the PL-259 stuff......

[Lew Barrett]

:DMighty kind, Chuck!:D I could take you up on that, but I do think the exit from the antenna is potted, so the improvement would have to be at the first connector, the barrel, and the internal run, which I could make up using anything I like. The cable coming from the antenna looks like it's immutable.

My connector isn't any military connector, that a promise! Although, it seems reasonably well made. It absolutely is not gas/water tight in it's current configuration. I could wrap as Bill instructs, and I had been considering shrink wrapping it, but too late for that now unless I change connectors.

[paladin]

WellllllllllI could help with that too....but ya gotta come get the antennas....When a local shop was going out of business I bought their last half dozen Hy-Gain antennas for a song and short whistle.....and never used them....and these came equipped with an SO-239 connector at the base so you can use whatever cable that you want....I have a BIG warehouse.:D

[Lew Barrett]

Sweet! Love to see the cherry blossoms:D One of these days I am going to get to Mystic too. That would probably occasion an east coast holiday. I'd have to bring Lindy, but she doesn't eat much:D I'm thinking I don't want to put off the east coast run too much longer.

[Peter Malcolm Jardine]

Antenna's are the usual cause of problems... I just bought a new one, a 8900 series Shakespeare. Works great with the old radio, but it's due for replacement too...

[Bob Adams]

Sweet! Love to see the cherry blossoms:D One of these days I am going to get to Mystic too. That would probably occasion an east coast holiday. I'd have to bring Lindy, but she doesn't eat much:D I'm thinking I don't want to put off the east coast run too much longer.

Lew if you get over here to see Chuck, I'll take you both out for a spin on the Chesapeake! (If I can get Chuck to set foot on my stinkpotter)

[Hwyl]

Surely you are referring to antennae.

Back to my myself now: Great thread, Lew I've never done it with antennae, but there are oh so many other simple repairs I could have done and in fact ended up going the hard and/or expensive way. The must be a psychological reason.


P.S. I'd love to see the instructions on connections too.

[paladin]

I'd rather cruise down the bay with this,.......


http://www.imagestation.com/picture/sraid225/p2fb44b802902a14f9cb14b02c8b12030/e7a7c095.jpg
http://www.imagestation.com/picture/sraid225/p6f9c39c454c06c07eddb30e45512f2cc/e7a7c094.jpg
http://www.imagestation.com/picture/sraid225/pa8c9c7f35e05618e61c94b755ea88cfb/e7a7c093.jpg

[Bob Adams]

I'd rather cruise down the bay with this,.......


http://www.imagestation.com/picture/sraid225/p2fb44b802902a14f9cb14b02c8b12030/e7a7c095.jpg
http://www.imagestation.com/picture/sraid225/p6f9c39c454c06c07eddb30e45512f2cc/e7a7c094.jpg
http://www.imagestation.com/picture/sraid225/pa8c9c7f35e05618e61c94b755ea88cfb/e7a7c093.jpg
Well yeah, but I don't have one of those. I could borrow a 75' Trumpy though.

[Lew Barrett]

You two battle it out and I'll be happy to ride in either, and see you both. The fantail looks remarkably like this boat, and Bob, I'd love a ride around in your boat.

http://i240.photobucket.com/albums/ff76/LewBarrett/argosy-penrose.jpg

http://i240.photobucket.com/albums/ff76/LewBarrett/argob.jpg

The Argosy, 65 foot twin 671, now in La Conner, WA.

[Peter Malcolm Jardine]

My birthday is coming up... I would like one of dose. :D

[Lew Barrett]

Peter, they're the same boat, I'm positive. It's for sale in La Conner, WA. I hear she needs some work. Right up your alley.

[paladin]

Lew...I thought you might recognize her....I was aboard several years ago and took a lot of measurements, and considered having a new one built in Thailand, all cold moulded......I didn't know that she was for sale. A naval architect owned her at the time IIRC.:D

[Lew Barrett]

Exactamundo! She was owned by Rick Edsel, a good friend. She has a couple of interesting secrets I'll get to tonight; off to LA for a day, and getting on an aeroplane.
Lew