RS 1003 Power Pentode Series or Screen Modulated

[N4LTA]

I have a couple RS 1003 tubes that Nico, PA0NVD sent me if I promised to build them into a transmitter. I built a two tube amplifier and was testing it about the time my shop fire destroyed it.

I may be able to salvage a few power supply parts like chokes and transformers. The fire hose water destroyed most of it. Nico passed away about the same time as the fire.

One tube survived and I also purchased a spare RS 1003, so I have two.. I'd still like to build a transmitter as I promised.

I am thinking of using a RS1003 in a 3 band AM transmitter either screen or series modulated. It is rated for Class C Telephony at a plate voltage of 800 volts and a scree voltage of 300.
Typical operation is 130 mA plate current and 25 mA screen current and control grid bias of -137 Volts. anode power is 104 Watts. anode dissipation is 34  watts. Output power, I think is 55 watts  at 100 % modulation, but the data is all in German

Max anode dissipation is listed at 60 Watts.

Would Steve's DX 60 screen mod be sufficient as designed to series modulate this tube. I read that it would work with two 6146s in parallel.

Also is there a good series modulation design for modulating one of these tubes?

Thanks for any info in advance.

Pat Bunn
N4LTA

[K1JJ]

Also is there a good series modulation design for modulating one of these tubes?

Thanks for any info in advance.

Pat Bunn
N4LTA

Hi Pat,

This may help you.... my single 813 series modulated by a pair of 813s.   There is a lot of info and a schematic using a 4D32 and 6LF6 sweep tubes before I switched over to all 813s.


http://amfone.net/Amforum/index.php?topic=46165.75

T

[K1JJ]

Schematic of 4D32 rig using 6LF6 series modulator.  The modulator runs class A.  The final runs class C.  Your filament transformer needs to float at HV and pass audio cleanly.  I wound it on an insulated Variac core.     Existing 120V to  >    6.3VAC insulated for 10KV.

All meters are floating - mounted on Plexiglas for HV isolation.

The 813  X a pair is good for about 100 watts of AM carrier. It uses a WA1GFZ MOSFET audio driver into the 813 modulator.  Transformer-less and will pass a 5 Hz squarewave or triangle...  and clean well past 20 KHz.

I key and step start the plate HV (and screen) so that no fixed bias is needed. Otherwise you wud need to float the fixed bias supply.


You could scale down to your  RS 1003 tubes if desired.

This is by far my cleanest AM rig.  Hard to beat  transformer-less series modulation.


T