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SSB Un Insulated Backstay

5K views 13 replies 7 participants last post by  btrayfors 
#1 ·
I have read alot about backstay isolators, Can anyone tell me if I can use my backstay as is for SSB radio use. I have read the more length you have the better as long as your ground plane is good. I have also read the reason the isolators are there are to prevent getting burned from touching the backstay durring transmission. My Islander 37MS had the tuner wire clamped to the backstay. I had the standing rigging replaced and opted not to put isolators in. Please can anyone tell me if it will work.
 
#2 ·
Backstay antenna isolators

Nope, it won't work properly. The insulators are what separates the active antenna part of the backstay from the rest of the rigging. Without the insulators the RF energy would be conducted to your entire rig. If the mast is grounded, it would short out the signal to ground. You need the insulators.
 
#3 ·
ranes,

I hear the frustration in your post. Let me try to clarify a couple of things.

Virtually anything will work. The question is, how well?

It is best to have insulators at the ends of an end-fed antenna (like a backstay). However, a fiberglass hull is a pretty good insulator for the lower end, so on most boats you can, indeed, attach the feed wire (GTO-15) from the tuner directly to the backstay. You can even do this UNDER the deck to avoid having to put a hole in the deck. HOWEVER, the usual reason for installing a lower backstay insulator is to avoid potential RF burns. When you transmit, some pretty high voltages can be present on the antenna, especially at the ends. If someone were to grab the lower end of the antenna while you were transmitting, he/she could get an RF burn. If this isn't likely or possible on your boat, then go ahead and forget the lower insulator.

An upper insulator is a good idea; otherwise, your backstay is likely electrically connected to the mast and the rest of the standing rigging. This could limit its effectiveness as a radiator.

One thing which works very well is to install a separate backstay-like antenna off to one side. I've done this on my boat, and it's worked well for 18 years now. Every bit as effective as a standard insulated backstay, and you don't have to break up the integrity of the main backstay by installing insulators.

I built mine from s/s lifeline. You can see a pic of the lower end at: http://gallery.wdsg.com/Misc-Stuff-SBF/AltBksty2_0130?full=1

Also, there's lots of discussion about "anternative backstay antennas" on the SSCA board and others.

Don't forget the RF ground....that's VERY important, too.

Bill
 
#5 ·
Alan,

The insulation won't hurt the signal at all. It MAY help to quieten things a bit in precipitation. It's not likely to help much if at all with obviating the chance of RF burns.

However, the chance of RF burns is very low in most situations. You can only get one if you're grabbing the antenna in the right place when someone is actually transmitting (not listening). Further, you've got to be holding onto it for awhile. Anyone touching an antenna while transmitting is likely to feel a sharp tingle and will remove their hand quickly...long before any problem occurs.

Still, if you're going to have an antenna which is mounted anywhere within the crew's reach, then you should: (1) warn all crew not to touch the antenna; and (2) warn the crew whenever you are using the radio.

Finally, in many decades of boating and hamming I've never seen an RF burn occur or heard directly of anyone getting one. It's theoretically possible, of course, but in practice is extremely rare.

Bill
 
#6 ·
Bill- I was looking at the picture of your antenna, is it necessary to use that large of wire, would a smaller diameter work as well? I'm buying a boat with an insulated backstay and I'm not fond of the idea. Sorry to hijack the thread. John
 
#7 ·
John,

No, any size will work OK. But, the larger diameter may help offset just a bit the fact that s/s isn't a great conductor of RF (as compared, e.g., to copper), thus more surface area (where RF travels) is good. That's more of a gut feeling than anything I've tested or proven.

Why use s/s, then? Because it's STRONG....very strong....and will last practically forever in the rough marine environment. In a rough sea it can be set up tight, and it's not gonna break and cause you to lose a halyard, lose comms, etc. And, best of all, I've never been able to discern much difference in either received or transmitted signals from s/s vs. copper antennas :)

Bill
 
#9 ·
Bill- thanks very much for the explanation, I've never had an SSB before so I have a lot to learn.

BillMc- looks very interesting, how long have they been used, any corrosion issues inside the coating?

John
 
#11 ·
FWIW, one of our split back stays has both insulators at each end and a 3/4" i.d. thin wall pvc, split plastic pipe covering the first 10 feet of of the stay, from the chain plate up. It's obviously bigger than the wire itself so that water does no get trapped inside and can drain.

Have fun with all of this stuff--my friend just did the 3 day class with G/West is was most impressed. The stuff that you can do with SSB now is pretty amazing. Just be warned, the gear adds up very quickly, $-wise.......
 
#13 ·
SSB Antenna

Hello, I found this thread because I'm a little unsure about how to proceed with my SSB antenna setup. I'm interested in the option Bill has presented above made from a separate lifeline running up the mast. Unfortunately, I couldn't see the picture linked to, it appears to be gone. I'm trying to figure out how I'll set up an antenna in my rigging. I'm on a tight budget, so cost is important. Also, I have a steel boat, so I have a good counter poise, but complications with insulation. Do you have any suggestions for me, and is it possible to get that picture of your antenna rig?
 
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