[Amps] Parasitic Resister Value

[Bill, W6WRT]

ORIGINAL MESSAGE: 
On Thu, 16 Aug 2012 13:41:03 -0400, K2RK wrote:

>About a ten turn coil, wrapped tight, on the resistor.

REPLY: 
IMO that's too much coil, no doubt that's why the resistors burned. Try just one
or two turns instead. Many amps have literally a half-turn coil, in the form of
a "U" connected across the resistor with a diameter of about one inch or so. 

If you have a grid dip meter, here's a quick check. Temporarily replace the
parasitic choke with a wire. Couple the GDM very tightly to the wire (almost
touching but not quite) and slowly sweep the range of about 50 to 200 MHz. You
should find a very deep but narrow dip, often in the 100-130 or so MHz range.
Then install the parasitic suppressor. Now the dip should be completely gone,
not a trace. 

Use the smallest coil that will completely eliminate the dip. If you so that,
you are about 99% sure of success. 

I like the Heathkit solid state GDMs, usually available on eBay.

I shouldn't have to say this but I will for the benefit of newbies - do this
with ALL POWER REMOVED.  

73, Bill W6WRT