[ARC5] Progress on Auzzie AT5-AR8 Set

[Kenneth G. Gordon]

On 17 Apr 2012 at 15:38, David Stinson wrote:

> The WWII Australian AT5 / AR8 set is on-the-air,
> transceiving and making contacts.
> I have had a great deal of help from our Australian members,
> for which I am very grateful.
> 
> http://home.netcom.com/~arc5/AR8AT5/AR8AT5.jpg

What a neat-looking rig! Congrats.

> Speaking of parasitics, I need some advice:
> The PA plate leads lack VHF parasitic suppressors
> and are made in such a way that it would be destructive
> to attempt to insert them at the plate caps of the 807s.
> Should I decide they're needed, I'm thinking small ones
> in the cathode and/or screen leads would work as well.
> What do you think?

Adding parasitic-stoppers to the GRID lead is one way to do this. I had to do 
this many years ago for an ARC-5 a young ham was using as an SSB linear 
amp. Connecting one in the grid lead of each 1625 made the amp 
unconditionally stable after everything else had been tried and had failed.

Also, adding those to the screen-grid lead is common practice for many of 
the older commercial BC band transmitters.

I have never seen one in the cathode lead, but upon thinking about it, that 
might be an excellent idea, especially if the cathode is "floating" in any way 
above ground. If the cathode is grounded, I don't know that connecting a 
parasitic suppressor there would do much good, and might actually make the 
problem worse.

Ken W7EKB