As some of you are aware, I am building a tetrode amplifier mainly because I
have never tried it. All my efforts have always been with triodes. When I
first started collecting parts for this amp, I came across a really nice B&W
852 tank coil. It was originally designed for use with a lower PLI and to
be used in Pi circuits. Indeed, the 852 seems to be tailor made for the
pair of 4CX1500B that I will be using. In looking at its usage in a Pi-L
tank circuit, I find that by juggling the Q for each band, it is
serviceable in a Pi-L configured tank circuit as well. I find that by using
a spreadsheet based tank circuit calculation program, I could take the
inductances that the 852 has for each of the bands(15M thru 75M) and
manipulate the Q so that it will be resonant. The resultant Q's ranged from
12 up to 15. I used actual measured inductances rather than published data
using an AADE meter. I would appreciate hearing from the group whether Q
variations that I came up with will result in an amplifier that will have
good efficiency and at the same time, acceptable harmonic attenuation.
BTW, I ran the same analysis for a Pi tank circuit using the 852 and found
that with the exception of 20M, which needed a Q of 9.4 to resonate, the
other bands fell between 11.5 and 12.5 Q values.
Your comments will be appreciated.
Bob Maser W6TR
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|