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[Amps] Parasitics and Amp Supply LK-500

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Subject: [Amps] Parasitics and Amp Supply LK-500
From: (2)
Date: Wed, 28 Aug 2002 10:02:34 -0700
If you have a dipmeter, check the dip between the Tune-C and the blocking 
C.  The VHF dip in a stock LK should be sharp, indicating a high VHF-Q.  
This is hardly good news unless one is trying to build a VHF-oscillator.  
 If you have a spectrum analyzer, with zero drive, put the probe about 
2-inches from the anodes and see what happens when you R/T/R/T/R/T key 
the amp.  My guess is that each time the DC anode current increases or 
decreases you will see damped wave ringing c. 100MHz.  Since 
ringing-amplitude is proportional to Q, lower VHF-Q suppressors will 
reduce the amplitude of the VHF ringing as well as improve VHF stability. 
 The LK  that I modified had numerous arc-marks on the Tune-C plates.  
After modification, Tune-C arcing was no longer heard.
-  If you use a quick-switching modern radio for driving the LK, 
higher-speed switching in the LK would be mo' betta.  Step-start might be 
a good thing.  The lethargic stock T/R relay left over from adding HS 
switching will do the step-start.  [see Figure 1 on my Web site].

gud luck, Mike.

>I have, to the best of my knowledge a stock LK-500.
>Are there any changes that I should make to this unit to prevent VHF
>parasitics?  Any other mods that would be recommended?
>Mike VA3MW
>Amps mailing list

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,  

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