[AMPS] Mods to TL922A

[Rich Measures]

>I have a 922A amp, the tubes are in good shape
>but its a dog. I've heard there are several Mods
>around that can lift it off its knees, like...
>	1. Change biasing during key down

ungood for ssb linearity - ok for cw.

>	2. Adding cut-off bias circuit during key-up

The 922 needs high speed switching if it to be used with a modern radio.  
When this is added, the amplifier switches into cutoff bias within 10uS 
of key up.  [see my Web site or Jan 1994 QST.  

>	3. Adding QSK using RF sampling

an RF actuated bias switch allows the tubes to switch in and out of 
nonlinear bias during speech.  Sounds rough.  Makes more imd than 
switching that is synchronized with the RF relay(s).  

>	4. Any others

reduce vhf gain with better vhf suppressors.   add glitch protection.  

-  later, Ben


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm