Copper screen??????

[JCG]

While working on my boat I found some copper screen (1/4" mesh) behind my breaker panel. It practically fell apart due to corrosion. What purpose does it serve? I figure it is part of the bonding system but I am not sure.

I would appreciate any information concerning this.

 

[CharlieJ]

It is part of the radio frequency (RF) counterpoise, sometimes called an RF ground; the other half of a vertical antenna used for marine single sideband or ham radio operation. It is not as effective as counterpoise installed inside the hull below the waterline. The old rule of thumb was that a minimum of 100 square feet of counterpoise was required...that number has been greatly reduced as a result of modern antenna tuners.

Charlie
KS4VB

 

[JCG]

Charlie, thanks for the information. The boat did have a single sideband a SSB 220 I think. Obviously it is an older unit. Is it worth anything?

 

[CharlieJ]

The short answer is.....no Sorry, but the world of SSB has changed dramatically in the last 5-10 years...if it works, keep it...if it doesn't don't put any money into it.

 

[Rickysa]

Charlie,

I have a Icom 710 that I removed from a previous boat, that I'd like to install on our Hatt...what is the best way to tie the copper screen to the ground, since my understanding is flat is better than round?

Rick

 

[CharlieJ]

You are correct, sir!! Flat is better than round. The conventional thinking, but most difficult material to use, is 3" wide copper flashing approximately 10 to 20 mils thick. When you get to a corner, you fold a 90; when you get to a deck or bulkhead, you swear . Wear golves.

I have had great success using tinned copper braid above the bilge area. It is easier to install and a lot more robust. 1 1/2" braid is equivalent to 3" wide flashing because the braid is actually the outer shield of large coax cable and is a flattened tube.

If your copper screen is still intact, connect the flashing/braid to it but the best counterpoise is the copper strap bonding system. Remember, you have to tie both the rig and the antenna tuner to the counterpoise. And use GTO-15 between the tuner and the antenna.

BTW, Icom and Sailmail both have excellent primers on antenna systems.

 

[Trojan]

Don't use braid any place. It is junk for any kind of RF. All it does is cause self generating RF noise on recieve and a constant impeadance change at transmit. As it ages it gets worse. Stay with the copper flashing,large solid wire and solder all joints. Bill

 

[CharlieJ]

Trojan-
I have to differ with you...although my preference is the traditional copper foil, it is just impractical to get it through bulkheads and decks in a flat configuration unless you have enough real estate to cut slots. I have had excellent long term results judiciously using 1 1/2" tinned braid. By excellent I mean RST reports of 20 over 9 on any band tuneable by the antenna tuner and by long term I mean longer than 10 years. YMMV.

 

[Trojan]

I hear what you are saying, But every time the braid flexes it generates noise in the receiver. As long as the signals are strong you don't notice it very much. Every time a wire in the braid touches another wire in the braid it generates RF noise in the receiver or can change the impeadance as it corrodes. Its a slow degrading. You would not notice it unless you use it everyday. I use 6 transcievers on my boat. I operate 160m to 1gig. The same in my car. I will not use braid of any type. I use flashing and large dia.wire for joints then solder everything. On a 1.5in wide strip I would use about 8 10ga. wire pieces insulated soldered to make a joint . A pain in the butt,but no noise, signal loss or corrosion.It best to just stick with the strip. Its your choise. I get a little fussy with RF. A cheap antenna system is like cheap tires on a sports car. It works but degrades the performance. Good Luck. BILL

 

[Bcollier]

Found the ceiling of our 48 LRC salon has a copper wire mesh imbedded in the fiberglass. Is this working as a Firaday cage to protect against SSB RF or is this part of the antenna system?

 

[chuckbullett@gmail.com]

Found the ceiling of our 48 LRC salon has a copper wire mesh imbedded in the fiberglass. Is this working as a Firaday cage to protect against SSB RF or is this part of the antenna system?

My short answer is both!

Chuck; W1AEK
1978 53 MY San Francisco