|[AMRadio] Stock or modify? BC rig "value"|
w5jo at brightok.net
Sat Jun 3 12:53:31 EDT 2006
> ----- Original Message -----
> From: "Jim Wilhite"
>> Some considerations about moving a broadcast transmitter to 75 or 40 that
>> one should make is the design of the RF deck. Keep in mind that lead
>> from the tube to the blocking capacitor, from there to the tune cap and
>> to the coil will exhibit additional inductance beyond the coil
> The Collins 20V series will work on bands up to and including 20 meters
> without making radical changes in the output tank. It was designed by
> Collins for use up to 15 MHz by special order. Changing coil taps and some
> capacitors in the tank would accomplish that. The plug-in tank circuits in
> the lower level stages would have to be rewired for operation on bands
> 160 meters and the 6SJ7 buffer stage would be converted into a frequency
> multiplier, according to information published by Collins. The 21E/M
> transmitters are also capable of operation up to 15 MHz.
> The Gates transmitters are totally unsatisfactory for 40 meter work and
> marginal, at best, on 75. Best to leave them alone and just enjoy them for
> what they are...a fine 160 meter rig! For the amount of work you would
> to do to modify those transmitters for 40, you'd be better off just
> WA1QIX's Web site and building a nice Class E rig. As a bonus, the Class E
> rig uses less electricity and runs cooler.
> Phil K2PG
I knew there was a reason for the 20V series that made sense.
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