[Amps] SB-220 6 meter conversion parasites

[Alek Petkovic]

Hi Steve.

What brings you to the conclusion that its a parasitic oscillation?

Have you measured the frequency?

It sounds more like the amp is simply taking off, in which case, no  
amount of fiddling with suppressors is going to help you.

Component size, layout and lead lengths, etc, are critical factors at 
50MHz. That's where I'd be looking to solve your problem.

Cheers and good luck,
Alek. VK6APK

On 17/07/2015 4:38 AM, Steve London wrote:
> Finished the SB-220 6 meter conversion, but it seems to have major 
> parasitic oscillations.
>
> A little background - I basically followed the 2008 QST article, 
> except I have the original relay in it. I don't have a source of 
> nichrome ribbon, so I made parasitic suppressors recommended by 
> another avid VHF guy - a copper strap U, and a 300 ohm resistor 
> straddling the U. No difference with or without those parasitic 
> suppressors. The tuning capacitor is bigger than the one in the 
> article - Surplus Sales is sold out of the smaller one. However, the 
> tank does resonate on 6 meters.
>
> Just to be sure, I'll describe the symptoms: engage the T/R relay with 
> no input signal. Grid current, plate current and RF output ! I can 
> change the level of these from 0 to potential disaster by adjusting 
> the tuning capacitor. The RF chokes in the grid circuit have not (yet) 
> fried.
>
> Sources for small quantities of nichrome ribbon ?
>
> Other suggestions ?
>
> 73,
> Steve, N2IC
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>

-- 
 From Sunny Binningup


---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus