[Collins] 32S-3 final neutralization question ??

[Glen Zook]

The basic difference between the 6146 and the 6146A /
8298 is the fact that the 6146A / 8298 uses the "dark
heater".  The "dark heater" was developed basically
for mobile VHF FM operation and not for SSB.  This is
because in mobile service the voltage applied to the
heater could vary all over the place.  The varying
heater voltage would cause the output power of the
tube to vary as well.  RCA basically "cured" this
output power variation by the "dark heater".

When used with an AC supply the heater voltage is
usually pretty steady and under those circumstances
the mixing of a 6146 with a 6146A / 8298 will work. 
However, I personally don't mix the versions.  But, in
an "emergency" mixing the two earlier versions won't
cause any problems.  Mixing one of the earlier
versions with a 6146B / 8298A definitely causes
problems the vast majority of the time.

The original RCA specification sheet on the 6146
definitely shows technical specifications for AB-1 and
AB-2 operation as well as Class "C".  Now the 6146 and
6146A / 8298 are rated for 90 watts input maximum for
Class "C" telegraphy, for 85 watts input maximum for
SSB, and 67.5 watts input maximum for AM phone.

The 12 volt equivalents of the tubes are as follows:

6146 - 6883

6146A / 8298 - 6883A / 8032

6146B / 8298A - 6883B / 8032A / 8552

Glen, K9STH


--- "Dr. Gerald N. Johnson" <geraldj at ispwest.com>
wrote:

At the Des Moines hamfest last April, Warren Amfahr
took credit for the RF feedback and general linearity
of the KWM-1 and claimed that the 6146 was rated by
RCA as purely a class C tube, but for him, RCA created
the 6146A with significantly better linearity. That
would say we ought to avoid the 6146, though my 32S-1
manual lists the PA tube as 6146. The Rockwell 3A
manual calls for a 6146B in the parts list but 6146A
on the schematic. Now to add confusion, my 32S-3
manual shows 6146A on the schematic and in the parts
list but shows the same part number as the 3A book has
for 6146B. Both schematics show the air trimmer for
neutralization which is the 6146B modification.
Somebody wasn't watching very closely!









Glen, K9STH

Website:  http://k9sth.com

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