There are two schools of thought on the parasitic suppressor, or actually 3.
The first is the traditional one.
The second is Rich Measures' site.
And the third is W8JI (iirc the callsign) who disagrees with Measures.
I think that '8JI is probably more correct.
Otoh, the sucess of your approach depends almost entirely upon the specific tube, and layout, and the actual VHF or UHF positive feedback found (that's a parasitic path) or not found in that situation. The frequency of operation also counts. It's usually not a problem to run on 75m, while it might very much become a problem on 10m.
One of the problems with modern resistors in this application is that they are often inductors at UHF frequencies since they are "wound" around a ceramic core in many cases. That's why the carbon composition resistor is useful for this application, no added self-inductance.
The value of the carbon composition resistor isn't terribly critical - what it does is to reduce the "Q" of the little choke, and to dissipate some of the parasitic energy should it occur. The choke is intended to make the plate circuit "look" like a high(er) impedance to the tube at VHF and UHF frequencies. At frequencies where the coil/choke has not effect (lower ones) then the choke is a wire, no power going through the resistor at all. At frequencies where the choke "works" almost all the power goes through the resistor.
Nichrome wire combines the resistor in the wire. So there is a small resistance
all the time in series with the plate, and if there is a parasitic you get the variation in resistance with temperature characteristic of Nichrome wire (presumably the ohms go up with temp, I don't remember).
IF you've got a smoked parasitic choke's resistor in a low power rig, that does speak to a potential parasitic problem - but again, maybe only on the higher bands.
A run through with a grid-dip meter may or may not reveal a resonance up above the normal operating frequency. If you can find that, you can then design the suppressor to address that, or else you might change the taps or bypasses on the RF choke, or alter the layout a bit to solve the problem.
I read, although I don't have a good reference for it (anyone?) that you can get parasitic supression by putting a large slug of ferrite material on a grounded metal post near the plate(s) of the tubes!?
Seems to me that this is maybe a very good way to go - but while I've seen a pic of it, I don't have a design reference or theory of operation for this technique.
_-_-WBear2GCR
