Hallicrafters must have used those mods and built the SX99.
Looks like I am reinventing the wheel. I have made a few changes
(reversable). I replaced the RF amp 6SG7 with a 6AC7 with appropriate
changes to bias, AGC and screen voltage, replaced the 6SA7 with a 6SB7Y and
replaced the first IF with a 6SG7. I also added a tuning eye which plugs
into the S meter socket and added a zener regulator to B+- for the BFO. It is
a VERY sensitive and stable receiver. SSB reception is just OK though.
+ACI-Michael Black+ACI- +ADw-et472+AEA-FreeNet.Carleton.CA+AD4- wrote in message
news:ccfv7m+ACQ-c3a+ACQ-1+AEA-freenet9.carleton.ca...
+AD4- +ACI-TerryJ+ACI- (suptjudno+AEA-comcast.net) writes:
+AD4- +AD4- I am considering adding a product detector to my S40A. Has anyone used a
+AD4- +AD4-
+AD4- You'd be wanting QST for April 1954. +ACI-Modifying the S40 for S.S.B.
Reception+ACI-
+AD4- by Edward Sommerfield. It's also reprinted in the ARRL's +ACI-Single Sideband
+AD4- for the Radio Amateur+ACI-, first edition which came out in '54.
+AD4-
+AD4- He adds a crystal filter for selectivity. Then a third IF stage to
compensate
+AD4- for the loss in the filter. He injects the BFO into the grid of this
stage,
+AD4- complete with a front-panel control for injection level. He changes the
+AD4- detector to a 1N34 diode, but it's still an envelope detector.
+AD4-
+AD4- He even shows a means of modifying the existing BFO for crystal control.
+AD4-
+AD4- At a glance, he also ads a stage of audio, to componsate for the (likely)
+AD4- use of the RF gain control to cut back on gain.
+AD4-
+AD4- He adds a VR tube to regulate the voltage going to the local oscillator
+AD4- and BFO. He even adds a tuning eye tube.
+AD4-
+AD4- Michael VE2BVW
+AD4-


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