I wrote the original post on 3/15 because the Ten-Tec Titan 425 is laid out as
described. There is also a 20-ohm 25W wirewound series resistor making up part
of the 11-inch lead-length from the cold end of the choke to the bypass
capacitors on the back panel adjacent to the HV connector.
Turns out that the choke by itself has a series-resonance near 12M. If the
bypass is moved right up to the cold end of the choke, the suckout can be seen
looking in the output connector with, eg, a '259 antenna analyzer. Set the
bandswitch to 10M and tune and load capacitors to min.
Replacing the choke with p/n RFC-3 from rfparts.com, and putting the bypass
right at the cold end, made several differences in circuit operation. The tank
setting for max-power-out, Ip-min, and Ig-max on 15M and up coincide, and there
is more power out on 12M. My guess is that the choke and resistor were
dissipating significant r-f power.
I'm intending to see if changing to this choke will work in an Alpha 89. It
has a relay kluge, which shorts out turns at the hot end of the choke.
Brgds,
Dave Windisch, N3HE
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