Ham Tips RCA - A Review of Some Modern AM Systems

[aa5wg]

I saw these on the web today.

http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips1804.pdf

http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips2403.pdf

Chuck

[W3RSW]

Enjoyed reading the articles with decent operation explanations using load lines and tube transfer characteristics.  Made sense.
Thanks.

[aa5wg]

Your welcome.

Chuck

[k4kyv]

There appears to be an error in the circuit description and wiring diagram. The primary winding is shown unused and the 5v filament winding in series with with one side of the HV winding.  In order to achieve the turns and impedance ratios given in the equation, the primary winding should be wired in series with the side of the HV winding that feeds audio to the PA plate, with the filament winding remaining unused. In any case, the 5v winding would add negligibly to the difference in number of turns between the two sides of the autotransformer respective to the +HV tap.

Wired up according to the schematic and circuit description in the text, n = (250+5)/250 = 1.02

Using the 5v winding in series would result in a turns ratio of 1.02:1, and a Z ratio of 1.04:1, very little improvement over a conventional Heising modulator.

Actually, it wouldn't hurt to wire both the primary and 5 volt windings in series with one side of the HV winding, with all 3 windings phased properly, to go ahead and take additional advantage of the minuscule improvement in step-up ratio resulting from including the 5v winding in the string.

[aa5wg]

Hi Don:

Thanks.

Chuck