I tried the trailing wire bit last spring on the way back across the
GS. Didn't seem to make any difference over just having the
ground connected to a thru-hull. I guess it depends upon the
specifc installation.

Doug, k3qt
s/v Callista

"Larry W4CSC" wrote in message
...
(sigh) Where DO they get these crazy ideas?......

Lionheart's tuner is 2' from the insulated backstay on top of the aft
cabin. Wanna see my QSL card from Osaka, Japan on 15 meters? I was 5
by 6 with just the little 150 watt transmitter. Not bad, given the
awful conditions of the ionosphere these days and all the masts
suckin' up my signal from Ashley Marina......

"Ground" is a relative thing in RF. You don't even need a "ground"
ground. What you need is a slightly longer than 1/4 wavelength radial
system from the tuner laid out flat. But, alas, that's not practical
because my captain keeps bitching at me every time he trips over my
ground screen, so we compromise with a copper strap to the engine
block and my trailing wire behind the boat while at sea, creating a
giant L antenna with the tuner in the corner of the L. Man, that
works great!

Putting the tuner in the bilge, you have a problem. The "radiating
element" starts at that high voltage terminal on the other end of the
tuner. ANYTHING CONDUCTIVE anywhere near (10'?) it will become part
of the tuning problem and part of the load on the radiating element.
Any boat wiring anywhere near that radiating element WILL suck off
your signal into its light bulb loads, and shunt off your signal to
anything it's connected to.....subtracting from what goes on the air.

Nope....doesn't wash. The tuner needs to be as close to the antenna
as possible and the antenna needs to be as far away from any other
metal objects as you can get it. Unfortunately, in a boat, that's
never far enough unless you're on a ship. Go visit any Navy ship and
notice how the antenna tuners are all mounted right UNDER the bottom
of those 35' nice aluminum whips sitting on huge insulators. Lucky
steel hull owners have great ground planes. For the rest of us, hook
as many different ground paths as you can from the ground lug on the
tuner to as much metal and ground plates as you have available. The
more the better.

(Engineers note on trailing grounds - Don't put something shiny on the
trailing end to haul out the wire behind you. "Something" ate my beer
can and half the trailing wire!)



On Fri, 23 Jan 2004 17:22:54 GMT, Gary Schafer
wrote:

An antenna tuner does not belong on the bridge! That is the worst
place for it.

The first thing I would do is to get that tech back and make him put
the tuner where it belongs, In the bilge! Right next to the ground.
You must have a very short ground lead. The length you have now comes
no where near being ground. You might get away with it on 2 Mhz but
not anything higher.

Mount the antenna down near the deck if you have to. Keep the antenna
as far away from other electronics AND wiring as you can.

It will not hurt to have a long antenna lead from the tuner to the
antenna as long as it is in the clear and away from other wires.
Remember that the antenna lead IS part of the antenna, just as much as
the whip is.

The most important thing is to have a SHORT ground lead. Right now
your ground lead is acting as part of your antenna and coupling into
all the other wiring. Especially your LINK system with the leads right
next to the ground lead. (which in your case is part of the antenna)!!

Once you have the proper ground then it is a much easier job to start
to eliminate RF being picked up directly from the antenna. The problem
now is that it is probably being picked up from both the ground lead
and the antenna. It is very difficult to deal with both.

Once a lead leaves the ground connection (connection at the dynaplate)
then the rest becomes antenna. It doesn't matter what side of the
tuner it is on.

Remember "if it isn't ground then it is antenna".

Regards
Gary


On Fri, 23 Jan 2004 08:05:10 -0600, "Keith"
wrote:

OK, more details on the system. Icom 802 going to the AT-140 automatic
antenna tuner. Yes, the tuner is working, you can hear the relays
clicking
when you press the "tune" button or transmit. The antenna (made by the
Digital company... I should have specified!) is on the flying bridge, as
is
the tuner. The tuner is about 3' from the antenna. The antenna is right
behind and above the pilothouse. The base is maybe 10' from the wheel
and
electronics, etc.

2" copper foil runs from the radio to the antenna tuner, and splits off
about midway and goes to the bilge, where it's connected to a dynaplate.
I
plan to add some more foil and connect the fuel tanks and run some
radials
down there as well. Lets see: the run from the radio to the antenna
tuner is
about 25', and the run from that one to the dynaplate is about 10'.

No, we didn't check the SWR. I wanted to add more foil and some ferrite
cores to see how this helps out. I wanted to do the things I can do
rather
than pay the tech all those $$$ for basically grunt work. I can call him
back out whenever.

No, my hand doesn't burn when transmitting! ;-)

Yes, I believe the VHF cable needs replacing. It's old and probably
cracked
somewhere along the line. The Link 20 DOES have the sheilded cabling as
Larry described, but the ground foil runs right alongside in the same
chase.
I don't think I connected the sheild to ground though... I'll fix that.


Larry W4CSC

Is it just me or did the US and UK just capture 1/3
of the world's sweetest oil supply? What idiot wants to
GIVE IT BACK?!!