Hello:
I'm doing a mathematical analysis on the RF PA of the WLW 500 kW transmitter,
which consists of three 167 kW RF amplifiers into a combiner. The RF
amplifiers are RF transformer coupled; the primary and secondary are pancake
coils,
the primary being of about 4 turns and the secondary of about 2 turns, both
about 80 inches in diameter.
I'm wondering if someone here might direct me to a text book that would allow
me to calculate the likely coupling coefficient and mutual inductance. I have
checked many of the famous references (Henny, Terman, ITT Ref Data, etc.) and
have not found anything for two coupled pancake coils.
I do not have exact dimensions for the primary and secondary RF coils; only
approximations based on photographs. The coils look like they are separated by
about 4 to 5 inches with a faraday screen between them. I hope to get to the
site this Summer to make some physical measurements.
Based on my approximate dimensions from the pictures, I've done some
preliminary calculations and it looks like a mutual inductance of 4 uH and a k
of .
143 would make it all work. That coefficient of coupling of .143 seems high to
me, how about you? It would be difficult if not impossible to get unity
coupling with an air core transformer, but I'm not sure if even the .143
coupling is
a practical value. Coupling coefficients found in some of my old textbooks for
low power stuff like receivers, etc. usually run .001, .005 which makes me
think my number is too high. The k value depends on a lot of things, so I just
don't know. Do you think that a k of .143 would even be realizable?
Thanks,
Jeff Glass
Northern Illinois University
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|