Folks
My sincere apologies for asking a question which perhaps has already been
covered from all angles and grounds and in all accents.. To avoid jamming
the forum with an old boring subject any advice based on your practical
experience directly to my email would be appreciated.
What would be the most easy and practical implementation for detuning a
wire Inverted L TX antenna for 160m?
Going to VK9L this September, and having second thoughts regarding my
antennas for 160m.
Having tried K9AY (tried at different locations), beverages (tried at
different locations), and a random wire loop I have failed to launch
effective RX antenna in my earlier 2010 VK9LL operation. Some photos here
http://www.qrz.lt/foto/main.php?g2_view=core:ShowItem&g2_itemId=3793&g2_GALLERYSID=c559c77c61a755e36a005a520b857dc1
Since most of RX antenna experiments have been done at night, in extremely
adverse weather condx, there was little thinking behind what I was doing,
as I had to concentrate on keep my pants dry..
None of RX antennas tried demonstrated much (if any) directivity at all. So
I ended up using wire Inv L TX antenna for RX.
When I now think over it, my TX antenna in all RX antenna location
scenarios was some 50m - 100m away from RX antenna, and there is also
electrical fence around the perimeter of the whole paddock, which was
always some 10m or even less from RX antenna..
Q1) Would a simple relay disconnecting the vertical wire at the TX antenna
feedpoint be good for detuning TX antenna? (I am using a piece of wire
attached to 18m Spidermast for the vertical section) and another piece of
horizontal on the top.
Q2) Are there any practical solutions for detuning TX antenna by using some
circuitry at the shack end instead?
Q3) What in practice could be done about the impact of the electrical
fence? (other then moving RX antenna as far away as possible/ and
considering using a shielded coax loop / or Waller Flag to 'null' the fence
out?)
The fundamental problem is - I could move the RX antenna back to the main
yard to be away from the fence, but it will then be picking up all the
house electrical noises and be close to Telstra ground satellite/ VHF
mobile radio base station.
Some of the challenges represented by VK9L is that the overall baggage
allowance is 14kg so building a full size WF is not an option. Having tried
a coax shielded loop at my backyard in Sydney city i am quite happy, but it
has 2 nulls, and nulling the ground satellite station will null W6..
Enough questions for now..
Many thanks in advance for sharing your practical experience
Tomas
VK2CCC
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Topband Reflector
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