Geoff -
The SPR-4 uses a different mixing scheme than the R-4 Series receivers,
and so uses different frequency crystals.
The "formula" for the SPR-4 is, Crystal frequency is 11.09 MHz above the
"bottom" of the desired frequency range.
Example: for 10.0 to 10.5 MHz coverage, a crystal of 21.09 MHz is
required. This is 10 kHz different than the crystal required for the
R-4 Series receivers. This difference "can" be compensated for by
slipping the skirt on the MAIN TUNING knob, but is inconvenient when the
other bands are correct!
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B, C-Line& TR-4/C Service Supplement CDs
<www.k4oah.com>
geoffrey mendelson wrote:
I've been thinking about getting more crystals for my (new to me)
SPR-4. I know I can get custom crystals cut, but that may be too
expensive.
I found someone who sells reasonably priced crystals for the 4 line
radios, however, his crystals are listed as being slightly different
than the ones in the SPR-4 manual.
For example, his is listed as the one for 10 mHz reception is 21.100
mHz, the manual lists it as 21.09 mHz. (note the difference in decimal
places)
Is this just a rounding error? Is there really a difference? Will
10kHz make a lot of difference? These would be for adding ham band
reception, which except for 40m is missing.
Thanks in advance?
Geoff.
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