Join Date: Aug 2006
Location: Arlington, VA
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The electronics guy at the boatyard has it right. Mostly.
I, too, have done dozens of installations -- do it for a living these days. And, each installation is tested on-the-air with the owner present, and most are tested on nets in the days and weeks following the installation as the boat moves north or south.
I did a piece several years ago, published on the SSCA Board, on "RF Grounds in the Marine Environment". Believe that is still valid.
As Gordon West found in his tests, a length of copper stripping from the tuner to the nearest bronze thru-hull will serve as a pretty good ground for most boats. It can be improved, somewhat, by adding radials, bronze plates, etc. But the improvement is often minimal.
Most important is to get a good, clean installation with very tight connections and adequate power to the radio. Keep everything separate from other onboard systems, particularly the boat's AC and DC grounds, lightning grounds, engine, etc.
Many tuners have a capacitor built-into the DC ground circuit, so there's no problem with electrolysis.
The role of seawater as a "ground" is very widely misunderstood, as is the purpose of coupling to it. One of the most beneficial reasons for coupling to seawater is noise reduction...bleeding off static and reducing RFI both ways...from the radio to other instruments, and from other instruments to the radio.
Seawater is an excellent reflector of RF energy. It is a horrible conductor of RF at the HF frequencies used for marine SSB. Signals are attenuated greatly in just a few inches of seawater. Thus, the idea is to bounce signals off the water, not to feed them deep into the water where they will serve only to warm the seawater!
In this regard, it's perfectly possible to construct a good RF ground which doesn't couple directly to seawater at all. This can be done using radials under the deck, s/s rubrails, aluminum toerails, pushpit/pulpit/lifeline complex, big radar arches, and any number of other solutions.
And, of course, the most effective long-distance antenna of all -- the single-band vertical dipole (a balanced, resonant wire antenna) -- works completely independent of any external RF ground.
So, what's the bottom line?
1. By all means, run a 3-4" wide heavy (16oz) soft copper strip from the tuner ground lug to the nearest bronze thru-hull. This will provide a good basic ground and will help reduce noise.
2. If you're so inclined, try adding to the ground....radials, or any of the other ways mentioned above. Often, this isn't necessary.
3. Be sure your antenna is at least 23' long overall (counting from the antenna lug on the tuner)....around 40' is optimal for both low and high band coverage.
4. Be sure your connections are top-notch. Use high quality crimpers, connectors, and adhesive heat-shrink. Pay close attention to the GTO-15 connection to the backstay.
5. Be sure to provide adequate power to the radio. Use AWG6 cabling, minimum, directly to the batteries. Mount a 30A fuse in both the positive and negative wires, close to the batteries.
Do these things and you'll have a good SSB installation.
Last edited by btrayfors; 10-31-2009 at 11:27 AM.