[Amps] vhf supression in 6 meter amps

[R.Measures]

>I have an sb 1000 converted to six meters that is definitely oscillating
>it still uses the 3-500z but after reading Rick Measures web site I see 
>now that the 
>anode supressor that was built was not going to supress much. It was an 
>inch wide 
>1 turn copper coil and 10 watt 37.5 ohm resistor network consisting of 2 
>75ohm  resistors, one inside the coil and one outside the coil. When the 
>amp went into oscillation (i think partially due to a combination of an 
>bad zener diode 

•  Typically, zeners go bad (short) during a VHF parasitic oscillation 
due to the surge in grid-I.

>and me playing with the input pi network tuning cap) it 
>blew the outer resistor only. 
>the inner was spared. 
>I now want to try to get this amp to be stable but all the reference 
>material I see on the net or in the ARRL HB deals primarily with 3-500z 
>tubes in HF amps,  not on 6 meters. I know I  had other problems ( maybe a 
>dead tube or the Zener) but I want to
>at least give the tube a fighting chance.  Also is a good test bed for 
>other projects
>including the henry amp that needs a similar upgrade. 

•  I have two ideas for perhaps improving the VHF stability.of the 
3-500Z:  1.  Add a VHF snubber from the cathode to ground (R-C-L series 
circuit).  2. Build an all Ni-Cr  anode lead to decrease VHF Q at the 
anode resonance (usually c. 150MHz..  My guess is that these 
modifications may cost a 5% power decrease at 50MHz, but they may make 
the amplifier stable.  If you are willing to have a go at this, give me 
your telephone number and a suggested calling time so that we can discuss 
it.  Or, you can telephone me if you like.  
-  cheers, George