I second this motion!~
When I lived in the city for years, I could never put up a decent 80 meter
antenna. I don't work the "high bands" much and don't like BIG beams. Too
easily damaged by high winds, lightning, etc. Also a big maintenance
problem, as I don't REALLY like climbing towers! nowadays I'm too damned old
for that foolishness!
I used a short "L" end fed antenna about 125' long on all bands. When you
run 500-1000 watts out, this makes for a very strong RF field in the shack.
I had a very extensive grounding system using several ground rods in mucky,
very wet/high water table in the New Orleans area. Connections were all
made using 3" wide copper flashing strip, which we commonly used in marine
installations. Regular wire, 10 guage stranded, or "old coax. braid" or
regular 3/4" tinned braid (now prohibitively expensive in 1" or wider
sizes!) usually didn't "cut it". The flashing is easy to get under a window
as well. SOLDERING ALL connections is recommended, especially if exposed to
the weather. Don't rely on "clamped" connections whenever possible.
Anyway the flashing system clears up the "stray RF" problem except in VERY
stubborn cases. Nowadays, all this digitally controlled stuff has a
tendency to go "bananas" with stray RF floating around. If you have any
"control cables" to other devices associated with your transmitter, run a
strip of flashing on the wall, between the devices, tied to the main ground
buss and run your cables on top of the flat flashing. This seems to
equalize the RF potential on both ends and enroute. Some of the last
digital GMDSS stuff I installed years ago refused to work properly until
this was done due to "stray RF" problems. The whole idea is to get all the
chassis/cabling at least at the same rf potential, even if there is still
some RF voltage being induced in the system.
Anyuway, I had pretty good luck with the "voltage fed" antenna even though
it was kind of in a bad location on a small city lot!
73,
Sandy W5TVW
----- Original Message -----
From: "Ron D'Eau Claire" <[EMAIL PROTECTED]>
To: "'Dave Andrus'" <[EMAIL PROTECTED]>; <Elecraft@mailman.qth.net>
Sent: Thursday, February 21, 2008 1:25 AM
Subject: RE: [Elecraft] K1, KX1,K2 antenna tuner high-impedance feed
capabilites
I've used an end fed dipole (i.e. half wave wire) a lot. I'm currently using
an end fed 80 meter dipole in my fixed-station setup. Such an antenna
presents quite a high impedance at the end, of course. That impedance is
outside the range of the KX1, and probably the K2, although I haven't tried
it on the KAT2 tuner for the K2. However, you don't have to be very far off
of exactly 1/2 wavelength for the tuner to find a match.
Normally, I use a link-coupled tuner when feeding such antennas.
As you probably know, the closer you can get the antenna to exactly 1/2
wavelength at the operating frequency, the lower the ground return losses.
Indeed, at 1/2 wavelength long it doesn't really need a ground except that
without an RF ground the rig will tend to "float" up to the high impedance
so you will have "rf on the rig". For that reason, it's a very good idea to
plan on some sort of ground: 1/4 wave counterpoise, etc. The antenna is
efficient without it, but the ground will help hold down the RF voltage on
the rig.
The KX1 tuner has the most limited range of all the Elecraft tuners to date.
That's because of the very small space available for coil/capacitor
combinations on the tiny board inside the KX1 case.
Ron AC7AC
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Dave Andrus
Sent: Wednesday, February 20, 2008 10:36 PM
To: Elecraft@mailman.qth.net
Subject: [Elecraft] K1, KX1, K2 antenna tuner high-impedance feed
capabilites
I'm interested in using portable end-fed halfwave antennas when I'm
out camping. I have a Norcal BLT tuner that is a absorptive Z-match
type, suitable for this type of high-impedance tuning and loading.
I'm finishing my build of a K2 right now, just about to add an
internal tuner to it, and I also plan to build a KX1 in the near
future (and who knows, maybe a K1 as well?). I'm wondering whether I
should add the tuner in, or just carry my BLT around with me?
Since many of you are QRP buffs, and have possibly had occasion to use
this type of antenna (and maybe even the BLT) in portable locations,
could you tell me if the internal tuners in these rigs are capable of
feeding this type of antenna successfully? I don't just mean to ask
whether an L-match or T-match type of tuner will handle a high
impedance load, but also whether the best power transfer is happening,
such as what the BLT will do?
Thanks in advance,
Dave K7DAA
http://www.k7daa.com
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