On Oct 17, 11:42*am, Alejandro Lieber alejan...@Use-Author-Supplied-
Address.invalid wrote:
Since I built my first 80meter/40meter 6aq5 + 6DQ6 transmitter with pi
output in 1972, when I want to vary the inductance of a coil in a
tunner, or loading coil in an antenna, I just short circuit some turns.
I see that this is the usual practice everywhere.

My question is why do we not just leave the turns open circuited instead
of short circuiting them.

It appears to me that in the short circuited turns, a very big current
must be circulating, adding heat losses and lowering the Q of the circuit..

--
Alejandro Lieber *LU1FCR
Rosario Argentina

Real-Time F2-Layer Critical Frequency Map foF2:http://1fcr.com.ar

you are correct. and if the coil is on a core it can overheat the
core also. leaving them open also causes problems since it looks like
a transformer with an open circuit it can develop very high voltages
and flash over the band switch. The best method is to have separate
coils that are not coupled, but that of course gets more expensive and
larger. better amps have a combination, usually shorting turns on an
air core inductor for the high bands and then adding separate toroids
and capacitors for the lower bands.

an example of what can happen with shorted turns:

http://wiki.k1ttt.net/2008%20Mainten....ashx#hf2 500