W0VMC   "Voice Modulated Carrier"       
Robert ..

New Richmond
in western














The "Ultimate" SP-600 J

This is my personal custom built SP-600 J that I designed for a symmetrical look with special chrome strips and SX42/43 backlit meter bezels.

I tested this SP-600 with my best R-390 with a cascaded 6KC  filter installed and  the performance of this SP-600  was every bit as good in the 3885 mix as the tried and tested R-390.


Features include:
bulletCascaded and switch able 6KC and 4KC filters from a 3 position rotary located at the tuning lock position
bulletAudio VU meter on the left side.
bulletS-meter fitted on the right with current sensing bridge from the 3rd IF tube instead of the detector circuit Modified AGC for the big signals without the distortion common on many 600's (2) 6DC6  instead of the 6BA6 for lower front end noise.
bulletComplete electrical and cosmetic rebuild with acrylic enamel PPG  automotive finishes.



This military transmitter started out as a plate modulated 100w ship to shore transmitter with a 4-400 in the final and a built in modulator that included a pair of 807's.  With the optional SRT-15 package that included an external mounted modulator and a high voltage power supply this became a 500 watt transmitter.

What I did was to remove the internal oscillator for the space needed and designed the transmitter to be self contained with a HI-FI modulator that uses a pair of 813's in class AB1.

The speech amp uses  (2) 6SJ7's with dual ladder feed back network and a balanced 600 ohm audio input. This ties in directly into the grids of the 813's which of course uses a mod reactor and the door that covers the modulator tube  was the access door used to change frequency under the old set up. With all the wiring changes this project took longer than building a transmitter from scratch.


copyright w0vmc 2007