Hi,
I need an advice for low band antenna (80-40) which does not need good
grounding system.
So far I have 30' Rohn 25 attached to the house with 2 element shortened
five-band beam on top of it.
I tried to set up an Inverted-L to be used on 80m without any luck. I just
cannot get meaningful impedance out of it.
The length of vertical part along the tower is 8 meters and horizontal -
going all the way to abandoned utility pole - was about 24 meters - longer
than needed for 80... The goal was to shorten it to something like 19...21
to get R=50 plus some X which gonna be compensated with capacitor... No way
- The R was all the way up to a 100, so I kept shortening it until I see
pure 50 ohm there.
I ended up with only 13m of horizontal part, X got compensated and whole
antenna had SWR below 1.5 at 3500....3650.
The thing is - half of EU station would not even answer my calls (100W) and
those who answer gave me reports of 369...559. It was not what I was looking
for.
I played with MMANA and yes, there is a resonance at 3500 for this length,
but R is only 13 ohm there... Where another 37 ohm are coming from????
It is too much for ground loss, isn't it? I managed to put 6 radials (3 in
each direction along the house) with a length of 12...15 meters - that's the
only space I have there... Where do you think I am getting 37 ohm from?
It would be really sad to dump it, but if there is no way to find/fix the
source of the losses - I will need to think about something else...
What kind of antenna I can use in that tiny space? Something which does not
need good grounding system - dipole? Lazy U? Anything multiband either by
design or with some sort of matching network at the feedpoint?
I have a picture of my "antenna yard" -
http://public.fotki.com/malyava/2010/30-mast/photo-12.html
It is shot along the property line... As you can see I have 6 feet wide
strip of land and the only high points there are 30' tower and wooden
utility pole 80 feet away.
Any ideas?
Thanks,
Alex K2BB
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