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Old 03-10-2007, 22:40   #1
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Gam split lead SSB antenna

Does anyone have experience with a Gam split lead SSB antenna, instead of using an insulated backstay?

http://gamelectronicsinc.com/ssb.htm

Thanks,

Russ
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Old 04-10-2007, 08:57   #2
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While you're waiting for someone who has actually used the GAM antenna, here are my thoughts:

It ought to work pretty well. The only issue I see is the close spacing between the radiating elements and the grounded backstay. This is a distributed capacitance, and while not as bad as a similar "lumped" capacitance would be, it will affect the ability of the tuner to match this antenna system at the higher frequencies. Reports say that it works, so perhaps it is within the range of the typical tuner's abilities.

If someone wanted to model this, it would look like a section of parallel transmission-line, but being fed via a "phasing loop" consisting of the wiring between the tuner and the antenna, and the tuner and the grounded backstay. This will effectively feed the transmission line section (GAM and backstay) in an unbalanced and out-of phase manner, creating a strong common-mode component -- all being very frequency-dependant.

And then there's still the upper section of the backstay, connected to the mast, connected to the shrouds and ground. It gets complicated, but so does the analysis for all the other antenna designs.
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Old 01-03-2013, 14:56   #3
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Re: Gam split lead SSB antenna

It looks like we may be waiting for a long time for someone to reply who has actually used one of these things. I wonder if they have sold any of them at all?

Al, S/V Finlandia
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Old 01-03-2013, 17:03   #4
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Re: Gam split lead SSB antenna

Nobody is going to quantify how good or bad the GAM is going to be in real life. This cant be done because nobody has access to an antenna test range where its real
world performance can be quantified. Besides a GAM on your boat is not going work exactly the same as a GAM installed on another boat. These comments apply to any antenna in the world. There are many anecdotal reports on many sailing boards on how well or bad the GAM performs.

Everything works, GAM, KISS, Backstays or for that matter even a piece of wire taped directly to the backstay. So luck will be on your side when choosing any antenna. Thats just the nature of HF radio

All these anal debates on many forums about this versus that creates more fear, uncertainty and doubt rather than provide hard answers.

Just look at at the commercial HF users like PRO fisherman and many ocean going container ships. Look at what they use. They use short 23 to 35ft whips that are less efficient than most yacht backstay antennas. They use their HF radios without issue or problems of "getting out" despite their limitations.

I seem to get the impression that many sailors have HF hypochondria. Those trying to install a competitive 70ft ham radio tower with a beam onto a yacht are really having delusions of grandeur and this competitive demolition derby has no place in HF emergency communications.

These debates are really doing more harm to the widespread acceptance and widespread use of HF radio than contributing to making HF more accessible to the masses. We really need to take the ham out of sailing communications needs versus hardcore ham use which many of these performance debates blur into one. HF radio is a tool like hammer and needs to be used as such. It should not be promoted by those wanting to turn it into a secret society full of technical mumbo jumbo. If HF radio was buying a yacht most of us would not even buy because we would be so confused.

Why I make these comments is because in the rest of the world in many sailing forums we dont have these endless silly debates on HF grounds and various pieces of commercial equipment. HF is installed by the book and very few people have problems like some of these forums seem to indicate.

If you use a GAM you will get a MAYDAY out and so it meets its objective for
an easy to install functioning antenna that works. If you want something more than this maybe you can spell out in detail what levels of performance or what exactly the problems are that you are facing when installing a GAM

I once delivered a racing yacht. I used a broom stick wrapped with tin plated wire. This broomstick was attached loosely to the back stay and fed with a Icom marine antenna tuner. It survived across the Atlantic and I got out and was heard on all my HF marine communications. I did this installation because I did not want to be without HF.

If I suggested that you use a broomstick with wire wrapped around it, I would be laughed out of town on most forums. I have been around HF long enough to know that everything works. I am like most people, I am in the " I cant be bothered if I dont have to bothered about it" category. HF radio is that kinda guy! If you have this pragmatic view about HF equipment you will have no problems with the GAM or anything you do on HF. There are many people who love making you feel insecure with their technical genius which helps nobody install a proper effective working yacht HF installation. God help us if they ever wrote a book on doing a HF installation, it would never get done because you would have to read a thesis and consider 1000 conflicting points that has very little to do with reality and what is a pragmatic working HF installation.

Install the GAM and do your own tests. If it meets your requirements then leave it alone. Thats how practical HF systems are installed and used.

Good luck with you HF radio installation. The GAM or any antenna that you install will work. You will be heard and nobody will say you cant be heard because your GAM antenna is not working.





Quote:
Originally Posted by svfinlandia View Post
It looks like we may be waiting for a long time for someone to reply who has actually used one of these things. I wonder if they have sold any of them at all?

Al, S/V Finlandia
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Old 01-03-2013, 19:57   #5
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Re: Gam split lead SSB antenna

Quote:
Originally Posted by plebian99 View Post
Nobody is going to quantify how good or bad the GAM is going to be in real life.

...

Everything works, GAM, KISS, Backstays or for that matter even a piece of wire taped directly to the backstay. So luck will be on your side when choosing any antenna. Thats just the nature of HF radio

All these anal debates on many forums about this versus that creates more fear, uncertainty and doubt rather than provide hard answers.
Of all the sailing forums I haunt, this one seems to be the most, um, verbose when it comes to mini-debates and hair-splitting. Still, when it's given, good advice stands out and most people can recognize it as such.

While I get the gist of what you're saying... and I'm not really your intended audience because I have some specialized RF knowledge too...(eg - I already know about the broomstick antenna and making simple dipoles, etc... no laughing here)... still, there is a time and a place for advice, and asking "does antenna X work?" is an entirely reasonable question. And when you're about to drop $2k or $3k on an SSB rig + ATU, and you don't have ready access to a specialist, advice is valuable.

Have you used a GAM HF split lead antenna? Did it work OK? Was it worth buying? That's all the OP is after.
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Old 01-03-2013, 21:05   #6
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Re: Gam split lead SSB antenna

A boat neighbor installed one. He followed the directions and it worked perfectly straight out of the box.
I used a piece of 14ga insulated wire inside of a piece of doublebraid cover. I strung it up parallel to my backstay. I followed no directions and it works perfectly. It cost almost $10.00.
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Old 01-03-2013, 21:14   #7
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Re: Gam split lead SSB antenna

Used one on passage to Bermuda and had strongest signal in the fleet. Had 100+ sq. ft. of copper foil on hull under cockpit and that may have contributed... For ease and cost, it is a good choice. I hightly recommend it if you aren't in the market to replace your backstay and install insulators...
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Old 02-03-2013, 10:33   #8
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Re: Gam split lead SSB antenna

Cecil,
A great observation!!!
Quote:
Originally Posted by plebian99 View Post
I seem to get the impression that many sailors have HF hypochondria.
And, a very funny one!!





A good comment....and possibly true....
Quote:
Originally Posted by plebian99 View Post
These debates are really doing more harm to the widespread acceptance and widespread use of HF radio than contributing to making HF more accessible to the masses.
HF radio is a tool like hammer and needs to be used as such. It should not be promoted by those wanting to turn it into a secret society full of technical mumbo jumbo.
And, perhaps I've unintentionally contributed some to the intensity of conversation.....if I have, my apologies to all and my assurances to try to push my ego aside, and walk-away from the back 'n forth debate....

(To be clear, I've never started one of these debates....but when presented with an open question, I tend to delve into details....and when pushed, my ego might encourage me to go to into too much detail...)






I'm with 'ya about 99%on this one...
Quote:
Originally Posted by plebian99 View Post
I have been around HF long enough to know that everything works.
I'd just add that some things work better than others!!!




Fair winds to all...

John
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