>It's not practical for me to go through the entire process
>of parasitic construction. To be honest, I don't think it's
>an exact perfect science and my opinions seem much
>different than many amps members. So I go my own
>way and have had very good results with my work. I
>just happen to have the benefit of very good test
>equipment to use.
>I'll try to dig out my suppressor construction file and
>detail some of the steps I used, but from memory only...
>I'll mention some of the high points here. I don't wish
>to tie up a lot of time rehashing things that have been
>posted on here by many, subjects that are detailed on
>Rich's web site. Other information is available in the
>ARRL and Radio Handbooks.
>The last "test sets" of SB-220 suppressors I constructed
>contained both Nichrome Ribbon and wire inductors in
>20 to 80nH values, across Rich Supplied 100 ohm
>3 watt MF resistors (the blue type).
>The most practical suppressor I now use in the SB-220
>is 40nH Nichrome wire wound in a coil, matched on
>the LC-102. The ribbon did not appear to suppress the
>vhf response as well as wire. I prefer the "lumped"
>wound coil vs the "hoop" coil option many use.
>I've tried 5/6 watt MF resistors with great luck and now
>use them in my suppressors.
/\ The 5-watters I bought from Mouser had much internal L. Scrape away
the paint and you can see for yourself.
>To be honest, I have not
>measured the "bare resistor" inductance, but like the
>3w resistors Rich supplies, the stray L appears
>relatively small in value.
/\ According to N7WS, it's c. 11nH.
>I also prefer the coil type inductance for size reasons,
>but avoid the resistor in the center location. Both sit
>happily in parallel adjacent to each other.
>: From: 2 <email@example.com>
>: What band and mode were you using when
>: R-supp burned out?
>: Did R-supp measure infinity (É) with an
>: ohmmeter or just changed R?
>The high end of the 10 meter voice band.
/\ Were you using voice or tuning up when the failure happened? If the
R-supps don't discolor on 10m, L-supp needs to be increased. In other
words, uglier is mo' better - provided the resistors do not open. .
>The old suppressors are actually still in one piece, sitting
>on my server desk. I guess I'll measure one
/\ good news
>: So the self-declared "expert" wants to know how
>: to determine how much L and R goes in a suppressor.
>: I published this info on AMPS. If he was paying attention,
>: he would already know. Will said that Rauch kill-filed me.
>: cheers, Skipp
>: R. L. Measures, 805.386.3734,AG6K
>It would save me a lot of typing to include the above so
>Tom will see it and refer to the amps archives if he
>wishes to debate the topic with you again.
/\ chortle. For over a year, Tom Rauch said he wanted to debate me on
the issue of parasitic oscillation. The debate went forward, but after a
couple of months he apparently changed his mind. It is my opinion that
the problem is that he has an extraordinary conflict between reality and
what he wishes reality to be. For example, he contends that:
1. The RF-ohms of nichrome resistance-wire Decreases with freq. ( In
order for a conductor to do this extraordinary trick it would have to
exhibit a reverse skin-effect.)
2. Since inductive reactance increases as freq. increases, insignificant
current flows in coils at VHF. Thus, he argues that it doesn't matter
what type of conductor material is used. (N7WS' measurements proved
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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