Hello everybody,
enlightening discussion I've found just being back from ZL7,
thank's to everybody for the interesting input.
Still my own, more practical question didn't get answered :-)
1. On our earlier DX-peds (VK9XY, VK9CR, VK9LM) we've
always used a ground mounted radial set of abt. 30 radials,
40 .. 70ft in length. Depending on air transport, this nearly
2000ft of radial-wire was always a major part to be taken care
off in our luggage. Beside this it always took nearly a full day
to prepare the antenna (V80 - toploaded 66ft Vertical).
Since S21XX we became lazy - we're just using 4 elevated
quaterwave radials, starting from the antenna feedpoint at
groundlevel to put them up at 45 degree angle until 8 to 10ft
height and then running horizontal (exactly the type Earl was
curious about). The whole radial system is not directly grounded
to earth.
The result - no obvious difference for us. We're still able to make
always at least some 600 Topband- and additionally some
1800 80m-QSO's in not even two weeks per destination
(As you maybe know not all only local chit-chat and with only
400W of HF out).
Obviously the elevated radials are much more practical for our
purpose, so for the time being we'll stick to them.
So - what's out of your experience actually better now -
a 30x 1/8 grounded radial net or 4 elevated quaterwave radials?
2. Only to show how far it can go - at home here in YB I have
no space for any kind of radial-set (max. 12ft in diameter).
What I've done is to put up a 85ft vertical and to use only one
elevated radial in 12ft height, not straight into one direction but
bent somehow around my property. After getting the system
resonated on 1828 with a small additional baseload coil, it
has a 2:1 bandwidth of 25kHz and a total radiation resistance of
abt. 17 Ohms (where it should be abt. 10 Ohms for a lossless
system with the given dimensions of the vertical as calculated
in a NEC-2 model).
Am I wrong to assume, that the efficiency of the antenna is still
better than 50%, or the other way around, that the overall losses
are below 3dB?
At least I've managed with my 500W some 350 QSO's sofar this
season with 44 countries out of my 'black hole' here and probably
would be able to do much more, if I would hear better (You can't
work what you can't hear - but that's another topic). Best DX sofar
K1ZM, VE1ZZ and W1JR.
That's a big improvement compared to last season, when I've used
a Inv-Vee with the center up in some 60ft height (110 QSO's with
12 countries, mainly JA, no USA).
vy73,
Joe YB1AQS
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|