Usually I use a simple choke with antennas made
with aluminium (it's usually free in the space) and a transmission line balun (with ratio
1:1 or 4:1) for wire antennas (it usually lower: V-inverted ecc.);
just two word about that:
- you can read that a balun is only a
balanced-unbalanced adapter and NOT an impedance adapter but nobody says why; my opinion
is the following: the first use of a balun is to adapt a balanced device to an unbalanced
one (and avoid I3 flow on the shield of coaxial cable); if balun's ratio is other than 1:1
we have "also"(remember ALSO) an adaptation of impedance (of course if the ratio
is the right one); never use a balun only as impedance adapter;
ie: if we have a 50 ohm coaxial cable (unbalanced) and a 200 hom antenna (unbalanced) we
can NOT use a 4:1 balun: it's a nonsense.
- Now I'll say you something about the use of a
I built a V-inverted dipole (with coil to make it shorter) for 80 meters band and the top
was at about 11 meters (so not very high and closed to objects); but there was no way to
obtain a low S.W.R.: there was no a minimun S.W.R point; it was flat and high.
Than I built a 3-wire transmission line balun and...
here it is the S.W.R. curve with a 1:1 at centre band;
I just used a balun with the dipole at the same height; from that moment I have often
moved my dipole, chanced the angle of the V-inverted: just shortening or lenghtening the
dipole I have again my 1:1 S.W.R.
Well, now you can see my
baluns; about tecnical data see the page "PRACTICE"; more, there're some
1:1 transmission line used with 80 mt V-inverted dipole;
1:1 transmission line used with 40 mt loop;
1:1 choke used with 17 and 20 mt rotative dipole;
1:1 ferrite used with 2 el. quad;
4:1 transmission line used with 20 mt loop;
73 de iz7ath, Talino