[AMRadio] Stock or modify? BC rig "value"

Jim Wilhite 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
> length
>> from the tube to the blocking capacitor, from there to the tune cap and 
>> on
>> to the coil will exhibit additional inductance beyond the coil
> properties..
> 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 
> above
> 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 
> need
> to do to modify those transmitters for 40, you'd be better off just 
> visiting
> 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.

73  Jim

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