The other unaddressed questions are... Since many/most rf amplifiers power sections are followed with a low pass filter network..., which is designed for 50 ohms nominal input and output... what happens with the addition of the Z match circuit?
Expect not only the preformance of the low pass filter to change, but also voltage and current points within both the power section and the filter to move/change. Would the amplifier remain legal in commercial service? Anyone every had or seen an RF Power Amplifier with chip caps that seem to desolder themselves? I have... cheers skipp ps: I wrote a Email text on the subject which can probably be found by searching the amps archives at www.contesting.com I no longer have a copy of it available. > Eric Lemmon <[EMAIL PROTECTED]> wrote: > Tom, > > Point taken. I just pulled that figure out of the air, for illustration > purposes, with no intention of presenting it as an actual measured > value. I agree that it was an unrealistic example. Mea Culpa! > > Perhaps a better example would have been a typical wirewound power > resistor, which might measure exactly 50 ohms for DC resistance, but > would be highly inductive and almost useless as an RF dummy load. There > are such devices as "non-inductive" power resistors, but that doesn't > necessarily mean that they are okay at RF. I have tested a few "no > name" dummy loads that were close to 50 ohms DC resistance, but nearly > 65 ohms impedance at VHF. The Bird and Microlab dummy loads in my > collection are extremely close to 50 ohms impedance. I completely agree > that a name-brand load that measures close to 50 ohms DC resistance will > likely be close to 50 ohms impedance. > > 73, Eric Lemmon WB6FLY > > Tom Manning wrote: > > > > Eric > > I fully agree with your assessment of the impedance problem except the dummy load statement. I have never seen a good quality dummy load (Bird or other similar quality) measure anything like 50+-j86 ohms... Generally if a good Fluke digital meter reads 50 Ohms at DC the frequency response will be very close to that up to about the upper usable freq level... Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ To unsubscribe from this group, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
