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?
>Amps mailing list
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,