Wotname and Paul,
It's not that external ground plates are a bad thing so much as they are, IMHO, completely unnecessary in many installations. I know I'm swimming upstream in this belief, given the preponderance of advice given in most texts and by many techies and satisfied users.
Let me try to explain my reasoning.
1. Since RF is heavily attenuated when travelling thru only a few inches of seawater
, it makes little sense to me to try to "couple to seawater" by connecting to a fitting which is a few feet below the surface of seawater. All you're doing is creating a decent DC ground -- not a bad thing in itself -- and helping to warm seawater as RF energy gets routed to the groundplate.
2. Actual in-water tests were done some years ago by Gordon West
. He and his colleagues found that a ground strap from the tuner to a nearby bronze thru-hull did the job just fine -- and as well as other alternatives they tried.
3. I believe that the reason both solutions work just fine is that the copper strapping leading from the tuner to the thru-hull or ground plate is what is doing the actual work
, not the fact that it's connected to a fitting deep underwater. It's serving as a radial or, if you will, the "other half" of a dipole antenna
4. There are many ways to create a good RF ground
, as noted in the piece on RF grounds referenced above. Wire radials, lifelines/pulpits/pushpits, copper straps, aluminum
swim platforms, stainless rub rails, aluminum hull-to-deck beams, radar
arches, etc., etc. have all been used successfully. Often, in my experience, these solutions work better
than the traditionally-prescribed groundplate or keel
That said, I've come to believe that a "belt-and-suspenders" solution may be optimum for many situations. That is, by all means connect a copper strap or heavy wire from the tuner to the nearest bronze thru-hull or other underwater fitting which is not otherwise grounded to the boat's DC ground system. The purpose is twofold: (1) to serve as a ground to bleed off static electricity and other spurious signals on the antenna system and thereby help reduce noise
; and (2) to provide -- via the copper foil or wire itself -- a radial. This, alone, will work OK. That is, the tuner will tune up on most or all bands.
However, the "suspenders" part is to improve the RF ground by tying in additional radials or metals
which can serve as RF collection devices to route
emitted RF back to the transceiver to strengthen the overall radiated signal. These need not be "coupled" to the seawater. In fact, they are often more effective when they are located above the seawater to serve as "elevated radials". Hams who have experimented with radials know that they work very well, and that elevated radials work better than those buried underground.
Every boat installation
is different. Even those with the same make and model boat. That's why it's important to experiment
a bit, and not be rigorously tied to a single
One final thought. Nothing substitutes for actual experience in communications
. You can take a newbie to radio
and an experienced operator -- give them a shot at exactly the same radio
setup to play with and make contacts. The experienced operator will be able not only to make contacts, but to have a pretty good idea of how well the installation is working.
The newbie, through no fault of his own other than being inexperienced, will not be able to tell whether the installation is a good one or not. He/she may be inclined to say it's a good installation if some contact is made with another boat, and this may not be the case at all. After all, in the ham world there's the guy in hospital with a transceiver coupled to his bedsprings and happily talking away on the air. Yeah, it can be (and has been) done, but no one is gonna say that the setup was a particularly good one :-)
On a bet once when I was stationed in Morocco
in the late seventies, I hooked an Atlas 215X thru a tuner to an 8' long aluminum curtain rod on the wall, called a station stateside, and got an immediate, "Yeah, CN8CW, you're five nine" (a strong signal report). Terrific as a stunt, but no one there was prepared to argue that the 8' curtain rod would outperform the 5-element monoband beam on a 70' tower outside :-)