grounding question
 

Greetings,
I am trying to set up an HF station and don't have a readily available
ground at my shack location. I have heard that it's possible to run a
wire from the ground connection on your radio, not connected to anything
else, as a "fake ground" as long as you cover the end of the wire (if
coax, as I'm hoping to do) with teflon tape so that it's not exposed.

I was thinking about using 75 ohm coax for this purpose, but was wondering
if that is a bad idea (i.e., 50 ohm coax to attach to the 10m or 20m
antenna and then 75 ohm wire for the "ground"). Has anyone else has
experience with this set-up?

Thanks,
-john (W4PAH)

Hi John -

IMO, an RF ground is a nice-to-have, but not necessarily a must-have.

In my second-floor shack, I have AC grounds only. But I run 1 kW
on 80, 40, 20, 17, 15, 12, and 10, plus 50W on 144 and 440, with
no known problems, or "rf in the shack." The only thing that was
necessary was to do a good job of adjusting the antenna matches.

73, Ed

"John Shadle" wrote in message
...
Greetings,
I am trying to set up an HF station and don't have a readily available
ground at my shack location. I have heard that it's possible to run a
wire from the ground connection on your radio, not connected to anything
else, as a "fake ground" as long as you cover the end of the wire (if
coax, as I'm hoping to do) with teflon tape so that it's not exposed.

I was thinking about using 75 ohm coax for this purpose, but was wondering
if that is a bad idea (i.e., 50 ohm coax to attach to the 10m or 20m
antenna and then 75 ohm wire for the "ground"). Has anyone else has
experience with this set-up?

Thanks,
-john (W4PAH)

On Thu, 4 Mar 2004 15:22:53 -0500, John Shadle
wrote:

Greetings,
I am trying to set up an HF station and don't have a readily available
ground at my shack location. I have heard that it's possible to run a
wire from the ground connection on your radio, not connected to anything
else, as a "fake ground" as long as you cover the end of the wire (if
coax, as I'm hoping to do) with teflon tape so that it's not exposed.

I was thinking about using 75 ohm coax for this purpose, but was wondering
if that is a bad idea (i.e., 50 ohm coax to attach to the 10m or 20m
antenna and then 75 ohm wire for the "ground"). Has anyone else has
experience with this set-up?

Thanks,
-john (W4PAH)

Hi John,

You have half described what is called a virtual ground. Not just any
length of wire so connected as you describe to the transmitter will
perform the job.

It is, in effect, the other half of your antenna, or for the sake of
reducing complexity, it is a quarter wavelength counterpoise that puts
the shell of your transmitter at neutral (the transmitter is sitting
halfway between two points of high RF potential).

Just as you have an antenna tuner, you need its correlative in this
lead - a ground tuner. There are such devices available commercially
called virtual grounds which can be identical to antenna tuners,
except they connect between this lead and your transmitter's ground,
and you peak the coil current indicator. When peaked, that indicates
the shell of the transmitter is in a low Z (high current) state, and
the end of that wire now supporting a high Z (high voltage) state.

73's
Richard Clark, KB7QHC

Ok John. Run 1/4-wavelength of ordinary wire (smaller guages are okay),
attaching them to the grounding lug of your radio or tuner. Run one wire
for each band, to start with; you can tweak it later. I wouldn't use coax
of any kind for the job.

Bear in mind that this is a "station ground" for R.F. - not an electrical
ground.

If you get a chance, I would suggest reading up on "R.F. counterpoise", or
"station counterpoise"...

73,
Mike KI6PR
El Rancho R..F, CA

"John Shadle" wrote
I am trying to set up an HF station and don't have a readily available
ground at my shack location. I have heard that it's possible to run a
wire from the ground connection on your radio, not connected to anything
else, as a "fake ground" as long as you cover the end of the wire (if
coax, as I'm hoping to do) with teflon tape so that it's not exposed.

I was thinking about using 75 ohm coax for this purpose, but was wondering
if that is a bad idea (i.e., 50 ohm coax to attach to the 10m or 20m
antenna and then 75 ohm wire for the "ground"). Has anyone else has
experience with this set-up?

Thanks,
-john (W4PAH)