[Hallicrafters] SX-71 alignment issues

[Roy Morgan]

At 07:15 AM 2/18/2004 -0800, you wrote:
>Good morning again... this time i have an SX-71 alignment question.
>2) on the MW BC band you simply adjust the tuning cap padder to get the
>600kHz point right on the dial, then peak the trimmers at the 1.5mHz point.
>There seems to be no way to peak things at the low end of this band

Bob,

I am not familiar with the SX-71 (and have not looked up the manual..) but:

Do not confuse the frequency to dial marking alignment of the local 
oscillator with peaking the rf amplifier tuned circuit tracking. These are 
two different things.

Normally, you do the local oscillator tracking adjustmen first. If there is 
an adjustment in the L (you say there is not, though) adjust that at the 
low end of the band, and the trimmer cap at the high end.  Then 
repeat.  The result is that the frequency calibration of the dial will be 
about right.  (Where no L adjustment is present, there is sometimes a 
"padder" capatitor in series with the coil.. this effectively adjusts the 
inductance.)

THEN, you adjust any rf amplifier circuits. Again, adjust L (or series 
padder) at the low frequency end and the trimmer cap at the high frequency end.

>3) worst of all, the alignment procedure for band 2 only specifies peaking
>the trimmers at 4mHz - again, there is no way to peak at the low frequency
>end of the band.

The radio may have been designed with compromises in the adjustments. Less 
adjustments, lower cost to produce.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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