Help! I'm in need of transformer advice!
My pal just acquired a BC-610 and I'm trying to help him get it on the air. It makes carrier but has no modulation to speak of.
(1) The modulation transformer primary DC resistance is spec'd as 670 ohms.
(2) My reading on it, with 3 different instruments, is about 220 ohms.
Obviously, lots of shorted turns, right? Read on.
(3) The impedances as in the books and marked on the transformer itself are:
Z(pri) = 21,000 and Z(sec) = 8000 ohms. Thus, the spec'd turns ratio calculates as N(p) / N(s) = 1.62. It's in step-down mode.
(4) When applying about 5 V(rms) @ 1 Kc. to the primary, the secondary voltage is such that the voltage ratio calculates to 1.64:1.
(5) Surprised, I re-did the voltage test at about 8 V(rms) to the primary and this time the secondary voltage again produced a step-down ratio of 1.64:1.
QUESTION FOR TRANSFORMER EXPERT OR BC-610 MAVEN:
How can the primary DC resistance imply so many shorted turns, and yet the tested voltage ratios show a turns ratio close enough to be accounted for by measurement error???
I's sure appreciate some technical insight to the question above.
Thanks for any answer!
al hart
al@w8vr.orgwww.w8vr.org