Posted by
Trevor Day on
Mar 02, 2007; 11:55am
URL: http://elecraft.85.s1.nabble.com/Vetical-Antennas-tp444325p444334.html
Hi Mike,
I just want to respond to one aspect of your post which,
co-incidentally, I have been discussing elsewhere this week. Thats the
business of using an ATU. Essentially the document you read is correct;
any adjustments to obtain a good match to the transmitter in an aerial
of this type (trapped vertical, yagi, dipole etc.) should be done by
adjusting the aerial itself.
Placing an ATU at the tx end of the feeder (or built in as in the K2) is
fine for small adjustments at, for example, band edges to prevent the
SWR protection circuit from reducing the power out whilst still
protecting the PA.
Attempting to compensate for large mismatches with an ATU at the tx end
of the feeder may result in an apparently good match, but will in most
cases cause the feeder to radiate.
Exceptions to this are when the feeder is of the balanced variety, eg.
open wire, where the feeder carries a 'balanced' standing wave as a
matter of course.
In your case, adjust the vertical for best match on each band, starting
with the highest frequency band, and without using the ATU in the K2.
Once you are happy you have the best match you can on each band, then
the K2's ATU can be used to perfect the match before operating.
HTH
Trev G3ZYY
In message <007701c75cb9$5ba76270$0501a8c0@LAPTOP>, Mike Walkington
<
[hidden email]> writes
>Hi All,
>
>I've moved to a new house and I'm trying to get a Hustler 5BTV working
>really well with my K2 in my new location. I plan to install the antenna in
>a ground plane configuration on a 2 storey home and feed it with coax. I was
>planning to use a few quarter wave radial for each of the bands of interest.
>
>I've had problems with TVI using this antenna before, so this time I will
>use some sort of a choke to block currents on the outer surface of the coax
>braid. Any suggestions on what I should use?
>
>How should I protect myself from lightning? I initially thought about
>running a lead from the base of the antenna to ground, but the length of
>this would probably turn the antenna into a vertical dipole.
>
>I was reading some doco for this antenna and read the following: Never use
>an antenna tuner to tune the antenna.Use of a tuner only fools the
>transmitter and does not correct a problem at the antenna.
>This doesn't seem right can I use my K2's tuners?
>
>Finally, I've been reading Moxon's HF Antennas for All Locations, and he
>doesn't seem to recommend quarter wave radials for ground planes. I'm not
>sure I comprehend why. Is anyone familiar with his concerns?
>
>
>Mike
>VK1KCK, K2 #2599
>
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Trevor Day
Sunny Saltash
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