[Hammarlund] SP-600 HFO Alignment

[Roy Morgan]

Mike,

Thanks for your suggestions. My SP-600 is not available now due to travel being cancelled, but is on the to-do list. 

We see long standing advice to do the IF alignments to the *actual* crystal filter frequency and not just assume it is 455 kc or whatever. 

-It seems to me that unless the filter crystal is hugely off frequency, any likely drift in it over the years would still let filtered signals easily pass through the wider following IF bandwidth. 

-Has anyone carefully looked into this situation to either debunk or confirm that advice?

-Setting the BFO to center on the crystal frequency does make sense to me. 

My unmodified BC-779 is at hand and is next up for overhaul. I don't yet know it's filter crystal actual frequency. 

Roy

Roy Morgan
K1LKY Western Mass

> On Mar 24, 2020, at 11:11 AM, k2cby at optonline.net wrote:
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> 1.    On the frequencies below 7.4 MHz (the 3 lower bands) be sure that the IF is actually centered at 455 kc.
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