Topband: How much ground independence?

Anthony Muttillo k8alm at
Fri Dec 13 10:04:26 EST 2013

I use a reduced size flag (50%) antenna about 7 feet above the ground
mounted on our deck right above our pool (comes down in the summer so we can
swim) and I use a KB-5 for the feed line transformer.  I rotate this antenna
with a TV rotor.  It sits about 20 feet from the house and about 50 feet
from the transmit antenna.  I have not tried any other height above ground
simple because where I have the flag mounted is the best location I can find
on my lot.  This year I added remote variable termination with a photo cell
and white LED.  I see no difference in F/B with the variable termination on
any band except when the resistance goes above 1500 then the F/B nears zero.
Most of the time I leave it at 800-1000 and F/B seems to be a consistent
25db in most directions.  I really have no other equipment to accurately
measure F/B besides the S meter on my TS590 and a signal source from WWV.  I
live on an urban lot with lots of noise from various sources and the flag is
almost always much more quite than my transmit antenna.  I tried very hard
to decouple the feed line, rotor line and LED feed line prior to entering
the shack.  I don't find that this antenna nulls the local big signals (1000
miles and in) very much and I always appreciate when a DX station operates
split.  I also use a Pixel loop.  They both do well to null out local noise
but sometimes the flag hears better and sometimes the Pixel loop hears
better.   I should add that on top band and 80 meters with the flag I use
the DXE RPA-1 preamp.
Tony - K8ALM

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