Length of Copper Straps for Ground Plane

[Cheechako]

there is Q and A in this months (feb) Sail Mag regarding a no insualtor backstay antenna. It appears to go up the backstay and back down. It's called a Gam/McKim antenna... maybe do a search on that. Ref: Gorden West/Sail Mag.

[RickD]

Originally Posted by btrayfors

This advice is just plain incorrect. Radials do NOT have to be below the waterline. They work perfectly well above the waterline. The goal is NOT to "capacitively couple to the seawater" in this case. See my post on RF Grounds in the Marine Environment: SSCA Discussion Board • View topic - RF GROUNDS IN THE MARINE ENVIRONMENT

There's a good case to be made -- from long experience and from antenna theory and practice -- that elevated radials work better than buried radials. Without getting into too much detail, it's only necessary to know that most any kind of elevated radial on a boat will work just fine: toerails, rubrails, lifelines, under-deck wires and copper strips, etc.

Bill

Hey Bill... that link you give here is either dead or it's incorrect, I get a message about a file not found.

Could you reconfirm please?

Thanks for helping set RF fact straight and clear of the Mythologies too many people believe.

Rick

[RickD]

Originally Posted by moonchaser

i have ask questions, listened, studied, read, etc everything i can find in an attempt to inexpensively yet effectively fashion an ssb antenna without cutting my back-stay. so far it appears the most economical yet effective method is to simply attach a 40'+ stranded copper wire from the mast top to the antenna tuner & a ground wire to a thru hull or copper ground shoe. from what i can gather this appears to not be as complicated as some let on. eton / grundig even suggests this very method in their operators manual for the satellit 750 receiver. can anyone comment on this idea?

A couple of things here.

What you're doing is creating a random-length wire antenna system from the top of the mast down to the tuner, and using the the ground wire and lower half of the boat as the reflector. Essentially a simple, random-length dipole antenna.

The only issue I have is... is the mast metal, and is it grounded to the same place you're connecting your ground too.

I ASSUME you're using an insulator between the wire and the top of the mast (right?) and if so good.

However, the mast is likely grounded directly to your boat ground either via the stays, through some wiring (lighting rod?) or perhaps if you have a VHF antenna up there, the braid in your coax is eventually connected to the mast? There's a lot of possibilities.

The last thing, your mast will tend to couple any RF from the antenna and when the tuner works to find it's tune point it will include that mast as part of your radiation element.

Just some things to consider.

[btrayfors]

Rick,

Yeah, SSCA had to move things around on their Board a bit recently.

Here's the new reference:
SSCA Discussion Board • View topic - RF GROUNDS IN THE MARINE ENVIRONMENT

These RF ground myths just don't die easily. It's a bit like trying to nail jelly to the wall :-)

Cheers,

Bill

[RickD]

Thank you Bill. Long time, no see or chat. Hope you're well. (We are, spent the year sailing the seven seas of Colorado - ok, the lakes set our retirement date, worked out the final bills, working out the house and shoving a crap load of dough into the bank now... we'll be ready to go... soon!)

Thanks for the update.

Rick

[windseeker2]

On your SSB trials to Transmit. Your radio will show all the elements of RF transmission when you press the mike button. However unless your ground plane is working as a counter poise you will not be getting "out" at all unless you really know your antenna system is correct. If you can get someone to provide you with a wattmeter and place this between the RF output of your radio and the feed coax to your tuner. Then when you "whistle up" on the mike, you should see RF output of the radio IF there is a good match to your antenna. Receiving does not need a ground plane to receive. Only transmitting needs this. You need to present to the antenna a 1/4 wave length in a ground plane. Morad in Seattle says 40 sq feet of ground plane minimum.

[lancelot9898]

Originally Posted by RickD

The last thing, your mast will tend to couple any RF from the antenna and when the tuner works to find it's tune point it will include that mast as part of your radiation element.

Is that good or bad? My metal mast is bonded to all things metal in the boat as is the antenna tuner with the copper foil.

[solosailormike]

If you have a backstay as antenna say 45 feet, can you attach the other side of the balanced input to the grounded stay or is this the inverted V that they talk about. Does the SSB need a turner like ham does.