>> Do you have any issues with interaction or funky pattern distortion that
>> close to your flag?
>>
>> Scott
>> -----Original Message-----
>
> Just an academic question.. how would one know if the pattern is distorted?
> I've given quite a lot of thought and experimentation to figuring a good way
> to measure HF antenna patterns as installed (for hams.. I know how to do it
> if I had hundreds of thousands of dollars.. RELEDOP, for one)
How would I know if it's distorted? Easy in azimuth with a rotatable
antenna. 1843.2 kHz TTL can oscillator driving a six foot whip
against a short ground spike stuck out along a riverbank about a
wavelength from my antenna. G4HFQ's "polar plot" software and my
radio's AGC turned off, gain adjusted so it doesn't distort.
Patterns here:
http://n3ox.net/projects/flag/160pattern_lg.jpg
The scalloping is from the fact that I was turning the TTL can on and
off (so I could tell it from some random carrier if ever I had one),
and I was doing it too slowly at the time.
However, the big chunk missing from the right side of the pattern was
a problem, and initially something of a mystery (I'll get to it later)
because I detune my transmitting vertical (what you probably really
wanted to know Scott).
My vertical is a base loaded 1/8th wave, so I just take the loading
coil out when I'm receiving and let it float. Problem solved. I
can't really measure the pattern distortion well, because it affects
the flag much less when it's pointed away from the TX vertical than
when it's pointed at it.
I'd have to put my TTL "pinger" in a neighbor's yard a few houses down
to take a pattern toward that direction. But I can hear some changes
in coupling as I switch in and out the detuning.
As far as the big bite out of the pattern, well, I pondered that for a
while and it actually seems to have been coupling to my *radials,* if
you can believe it. I tried to make the radial field more symmetric
under the flag by putting an "X" of wire across the big loop around
the driveway and it seemed to help a lot. I took some patterns but
haven't posted them yet, been busy. Pretty much fixed that
distortion.
73
Dan
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