Hello the list,
I have been experiencing heating problems with my step-down toroidal
transformer that feeds my transmit loop. Fearing core saturaton issues I have
been going to ever larger cores and more and more turns in an attempt to reduce
the flux density. My latest core is 4 stacked 4" diameter Mix 78 toroids
weighing a total of 3 pounds (1.34 Kg) with 28 turns of #10 on the 50 ohm
winding and 5 turns of 16 mm2 wire on the loop side.
Now for the puzzle: As suggested by J.B., I hooked two transformers back to
back ; the present transformer (described above) and the previous model (4
stacked FT-290-77 toroids with 17 turns on the 50 ohm side and 3 turns on the
loop side. I connected the two transfomers with the the loop windings from one
going into the loop winding of the next. One transformer 50 ohm winding was
hooked to a 50 ohm Bird Dummy Load, the other transformer's 50 ohm winding went
to an AEA VIA impedance bridge. Much to my surprise I had a high swr and
reactance !!!
The swr was on the order of 2.7:1 and the reactance was 45-55 ohm and
increasing with frequency.
Any thoughts on why I should show a reactive component when one transformer
went directly to a 50 ohm load?
--
73 Warren K2ORS/WD2XGJ
FN42hi
http://www.w4dex.com/wd2xgj.htm
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