[ARC5] SCR-522 vs TR-1143

[Jack Antonio]

Thanks to John F for the tip, I downloaded the TR-1143 manual
and compared it to the SCR-522 manual.

Overall, the TR-1143 R/T unit, and control box look very similar
in looks and size to the corresponding SCR-522 units. There was
no picture of the externals of the power unit, but the internal
picture looked very similar to the PE-94 and  -98.  There was not
enough detail provided to tell if they would use the same mounting
arrangements.

Internally, the sets are very different.  The TR-1143 uses 3 main
plug in chassis, receiver, transmitter and amplifier (rx audio and
modulator), the SCR-522 only used 2.

Electrically, the TR-1143 covered 100 to 125, vs 100 to 156 for the
-522.  The receiver IF is 9.72Mc vs 12Mc.  I find it interesting and
probably not a coincidence that the AN/ARC-1 also used a 9.72Mc IF.
The receiver crystal multiplier is 18 for the whole range.

As an aside, wasn't there a companion unit that covered 125 to 156?
What was its designation? I'd be interested to learn its IF and
crystal multiplication factor.

I didn't do a rigorous comparision of schematics, but it appears the
connector pinouts are the same between the two radios, or at least
very close. The control box and power unit looks like they could
interchange, and the lines I looked at on the R/T unit seemed like
they corresponded.  However it would take some considerable time to
actually verify that the components of the two sets would be plug 
compatible.

On the receiver IF.  I've always wondered about the complexity of
the SCR-522 receiver crystal scheme, using different multipliers for
different ranges.  The end result is that the crystal frequency is
always between 8 and approximately 8.5Mc.  One semi-educated  guess is
that it was done to avoid receiver birdies or spurious responses, one
such case is the necessity to avoid a 6Mc crystal as the second harmonic
would swamp the IF.

Jack Antonio WA7DIA/4