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F.S. National Comapny S meter
I found the schematic for an early HRO
(http://www.portabletubes.co.uk/sitefiles/hro1259.djvu), it seems the s meter is in series with the plate circuit of the last IF stage, so it measures the plate current. At maximum signal the plate current of that stage must be close to zero to send the meter to the 60 over nine position. MRe wrote: "sparky" schreef in bericht ... See this picture HR)-60 http://www.universal-radio.com/CATAL...xvr/HRO60.html it has a meter with the zero on the left. On Dec 21, 7:39 pm, Kenneth Scharf wrote: sparky wrote: Why is the meter 'zeroed' against the right peg, is it broken? Or did National design it that way because they had a backwards meter circuit that pulled full current with zero signal? This is a backward meter by National. The meter deflects left when current flows. The radio must have had a backwards meter amplifier then. Weird. Guess one could design a proper solid state amplifier to make it work, but you'd have to 'zero' the meter at full scale with no signal. The AR88 had also a meter with the zero left (when there was a meter anyway, because many had no meter at all) It measured the cathode current of one of the IF tubes. (Less amplification/cathode current means more signal). That leads to the somewhat odd 'zero right' configuration MRe PE1NQr |
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