Available again: RF bypass capacitors for anode supplies.
Many commercially manufactured Ham amplifiers use an insufficient amount
of bypass C at the base of the HV-RFC for 1.8MHz operation. It is my
unexpert opinion that 4000pF is about the minimum that is needed to
prevent 1.8MHz RF from eventually compromising the electrolytic filter
capacitors in the PS. As I understand it, one manufacturer currently
uses a single 1000pF capacitor to bypass 160m RF. 1000pF has 88.4?s of
Xc at 1.8MHz. With the typical HV-RFC used in such amplifiers, there
will be c. 100Vrms of RF heading toward the filter C.
At one time, we sold 2500pF, 10kV disc ceramic capacitors for this
application, however, they were discontinued by the manufacutrer.
Meanwhile, back at the ranch, I started looking for another source. I
found a new source, and on Dec. 14, I received 400 of the new ones.
They: exhibit zero leakage 9000VDC; are rated at 2700pF, +/- 10%,
3000-DCWV; have Y5P barium-titanate dielectric and they are blue epoxy
dipped. The part # is 96 and the price is $1.38.
cheerio
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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