Topband: "Using Whatever is Already There.."
herbs at surfvi.com
Thu Dec 22 13:17:46 EST 2005
Quoting Tom Rauch <w8ji at contesting.com>:
> noise source arriving from one direction. Unfortunately
> there are even more situations where the is no benefit over
> just using whatever is already there, say the transmitting
> antenna.... or even a forty meter dipole or some other
> antenna that might unexpectedly provide some improvement
> through luck.
Since you raised the subject..."using something that is already there", please
add this this one to the try anything and remember what works, catagory.
One day some years ago I was lucky to stumble into using a 20 meter
corner fed Delta Loop (1005/f) on 160 receive antenna selector and found it
to be much more effective on weak signals at the time than my 1/4 vertical.
The antenna is ironically almost identical in loop dimension (72.5 feet versus
74 feet)to the Delta Pennant designed by K6SE except the for the lack of the
impedance transformer and the 900 ohm resistor in the opposite bottom corner
from the feed. I can not model the 20 meter delta loop on 1.8 but I still
wonder to this day why it worked so well on RX compared to the 1/4 wave
vertical. I have since long ago converted it to a true FO0AAA design (with
resistor, 9:1 impedance matching,and common mode isolation as soon as I got my
20 beam up on the tower. it is a keeper! The new loop takes up the same space
as the original loop. So I never pursued any A/B testing. The K6SE design
FO0AAA is an excellent antenna, easy to construct and it works well for me. It
beats my Beverages at times and under certain conditions.
I am still curious why the insertion of a 2 watt 900 ohm resistor in one
corner and the proper feed point matching in the other would convert this 70
plus feet of wire from a make shift RX antenna to a serious player. Is it all
phase shift, nulling, and directivity? Certainly it is not gain.
Has anyone else tried a 20 meter corner bottom fed delta loop on 160 for RX
with any useful results?
My point here is having a 20 meter delta loop to listening on topband, when
there may not be anything else working, especially for some 160 meter DX-
pedition that finds itself deaf on 160, this might be a simple RX solution.
This could allow for hearing signals that otherwise would not be otherwise
audible in RX challenged locations.
Herb Schoenbohm, KV4FZ
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