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LF: Re: Vertical grounded tower for LF antenna.

To: rs[email protected]
Subject: LF: Re: Vertical grounded tower for LF antenna.
From: "g3ldo" <[email protected]>
Date: Sun, 17 Feb 2002 22:49:04 -0000
References: <[email protected]> <[email protected]> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>

Not long after performing this adjustment I received an email with
screen capture asking me if I knew what that signal was in the TA
window.  The time and frequency confirmed it was my signal.  This
reception report came from a station 543 KM away at mid day with the
generator power of 0 dbm!  I knew this arrangement worked fairly well
for receive but to find it would radiate so well was a surprise.  I
thought most of the signal would be shunted to ground since the
radiating wire was so close to the tower.
I had a look at your antenna mast - quite impressive.
When we started out on LF most of our antenna thinking was conditioned by
commercial designs. After a while it became apparent that the shape of the
antenna didn't matter; an electrically small antenna has the same polar
diagram no matter what shape you make it. Your successful test illustrates
this point. Most antenna losses appear to be caused by ground resistance.

Now my question to the few who have read this far.  Can I expect this to
be a good high power transmitting LF antenna with the addition of a good
coil?  All cables from the tower route down to about half a meter above
ground where they run horizontal under the shack floor.  I suspect these
cables would be hot with RF unless they are choked off by some method.
The coupling with the LF/HF antenna and the mast is small because the wire
is near at right angles to the mast and anyway doesn't carry much current.
As for coupling into other feeders I haven't found this a problem. My LF
transmitter is located at the bottom of the garden and feeder cables for RF
and remote control run parallel to the antenna which has an average height
of 35ft. Try the antenna on transmit and only resort to remedial actions if
they prove necessary.
The LF coil shown on your website is excellent for transmitting with the
sort of power that amateurs are allowed to use; a very good design if I may
say so. You will need a good long ceramic insulator to isolate the antenna
wire from the mast to cope with the high voltage and the Canadian winters.

When can we expect to hear (see) you on?

Peter, G3LDO

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