Telamon wrote in
news:telamon_spamshield-D142D9.21371823022005@newssvr21-
ext.news.prodigy.
com:

In article 9,
Conan Ford wrote:

"MC" wrote in
t:

I've just replaced my old cable with some nice shiney new 50ohm
coax attached directly to my 100+ feet of longwire. As I still want
to suck that little extra out of my antenna, I want to add a balun
but I am confused with this transformer ratio stuff. I realise
that a long wire has quite a high impedance. However, should I go
for a 1:4 or a 1:10 ratio balun. If I went for the 1:10 would it
be overkill and will it make any difference over the RF if I only
had a 1:4. I ask because I can get a 1:10 a lot cheaper than a
1:4.

Confused? I am

MC




1:9 is ideal for a longwire (ideal impedence is 450 ohms, matched to
50 ohm coax, so 50:450 = 1:9), so go for the 1:10. The 1:4 is for
something with lower impedence than a longwire.

Not all baluns are created equal, however. What frequencies are they
rated for? This will depend on the turns count of the windings and
also on the ferrite material.

The impedance of the wire depends on the height above ground. The 1:9
is most likely best.


Is there a site that explains this, with a formula that can be used? I
found one once that was for a straight horizontal wire at a fixed
distance above a ground plane, but it wasn't for antennas... I just
assumed 450 ohm was a good value.