On Jun 1, 2006, at 8:18 PM, k7fm wrote:
> "I have had dozens of Sb-220 amps in my almost 40 years as a ham.
> Most of
> the parasitic suppressors I have changed had their carbon resistors
> value enough to make them not as effective as suppressors should
> be. Most of the
> time a change of resistors will tame a quirky Sb-220."
> Let us follow this statement with basic logic.
> 1. The SB-220 becomes unstable when the carbon resistor changes
The carbon-comp R changes value by an amount not adequately explained
by simple aging. For example, a 300% to 500% increase in R in one
day is not what I would call normal aging. Also, such resistors show
no outward indication of extreme age.
> 2. When that happens, ham A changes out the parasitic suppressor
> by installing Rich's nichrome suppressor kit, which just happens to
> include an excellent and stable replacement resistor for the aged
> carbon resistor.
> 3. Ham A installs the kit, complete with the new and stable
> replacement resistor.
> 4. The SB-220 is stable again.
> 5. Grateful ham A exclaims to the world that it is Rich's
> marvelous suppressor fixed the problem.
The first guy to use this type of parasitic oscillation suppressor
was Mr. F. E. Handy, and it's described on p.72 of the 1926 Amateur
> It seems the poor resistor has been neglected and is not receiving
> the credit it deserves.
> I am not trying to discredit Rich's research or opinions. I just
> want to give a little more credit to the resistor. It seems under
> appreciated in this whole affair.
Matsushita does deserve credit for making incredibly overload-
resistant MOF resistors, but there's more to the story, Colin.
> Colin K7FM
R L MEASURES, AG6K. 805-386-3734
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