Chris,
I await the cores and wire patiently,
I have a lot of practice in awaiting parts. Chilean customs is delaying
everything by 2 to 3 months...
in the meantime i am wondering
if this transformer could be wound to negate the need for my separate
impedance matching transformer outside, and its associated losses?
Probably. How long is your feedline? Probably just a tiny little
fraction of one wave, at 136kHz! So the correct line impedance is
irrelevant. You can run a 50 ohm coax at 20 or 100 ohm with little
consequences. And you could probably use plain electrical installation
wire without any more loss.
The
set up is Driver - Amps - Combiner - LPF bank- co-ax to outside -
Impedance matching transformer comprising two FT-240 77 material
stacked toroids in a box, with a separate primary and secondary
winding, each with multiple taps that can be manually selected with
banana plugs and flying leads - Loading coil with internal variometer
( BIG plastic bucket wound externally with 2.5mm insulated wire, with
a variometer inside to load to operating frequency - Top hat loaded
vertical antenna about 20 feet high with a horizontal quad loop of
about 480 feet circumference as capacitive top hat.
Really the outside trafo seems superfluous. The bucket coil can be used
to tune out any reactance, and the variometer to perform resistance
matching to a wide range of values.
The matching transformer outside only has a little impedance matching
to do as I see a fairly close match even without it.
More reason to get rid of it.
Could this extra
loss be negated by winding your combiner transformer design
differently?
I do think so.
Now I am running more power the impedance matching
transformer is running quite hot... I did build the impedance matching
transformer as an autotransformer, but I had serious issues with RF
setting the workshop and house alarms off, stopping or slowing my
internet connection, and tripping the house mains panel RCD. When I
changed to a "normal" transformer this immediately stopped.
Hmm... In that case you might still need the transformer, even if it
does no impedance matching at all, just as an isolation transformer. The
alternative is a common mode choke on the line, having enough choking
inductance. The other alternative, which is a better earth connection at
the feedpoint, is probably impractical.
Manfred
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