Posted by
wayne burdick on
Jan 07, 2006; 7:13pm
URL: http://elecraft.85.s1.nabble.com/10-meters-on-K1-component-values-tp385086p385089.html
Harry,
Thanks for your 10/12 meter modification details. (And thank you, too,
Stephanie!)
Given your success on these bands, there's the possibility of a future
KFL1-4H option ("H" for "high bands"): a version of the 4-band K1
module that covers some combination of 10, 12, 15, 17, and 20 meters.
But I digress :)
I'd like to offer a suggestion for those considering either 10 or 12
meters. I think I posted this information earlier regarding 10 meters,
but it applies to 12 meters as well. I've also corrected the math in
the examples to reflect a VFO tuning range of 150 kHz -- necessary to
go above 24.900 on 12 meters.
When I designed the Norcal/Wilderness Radio Sierra, which uses the same
I.F. as the K1, I realized that 10 and 12-meter crystals would be
expensive (especially 36 MHz in the case of 10 meters). So I came up
with an alternate mixing scheme where the LO is below the band rather
than above it. The RX and TX image rejection isn't quite as good with
this technique, but that doesn't matter, in most cases, since the
band-pass filters are narrow.
Here's the normal conversion scheme on 10 meters (high-side injection):
RF 28.000 to 28.150
+ IF 4.915
------------------------
= LO 32.915 to 33.065
+ VFO 3.085 to 2.935
------------------------
= XO 36.000
Here's the alternate scheme on 10 meters using low-side injection:
RF 28.000 to 28.150
- IF 4.915
------------------------
= LO 23.085 to 23.135
+ VFO 3.085 to 2.935
------------------------
= XO 26.170
And on 12 meters:
RF 24.800 to 24.950
- IF 4.915
------------------------
= LO 19.885 to 20.035
+ VFO 3.085 to 2.935
------------------------
= XO 22.970
Advantages of these lower-frequency crystals include: (1) more power
output from the premix NE602 (both the crystal oscillator and mixer
output); (2) cheaper; (3) possibly available from Wilderness Radio. If
Wilderness doesn't have any, you might try ICM. I think the ICM part
number for the basic crystal type (not including frequency) would be
#436162.
Low-side injection results in one additional minor issue: the sideband
gets inverted. This just means that the CW pitch will change in the
opposite way from the other bands as you tune. But VFO readings should
still be accurate, since the VFO can be individually calibrated on each
band.
If there's enough interest, Elecraft will supply the crystals and other
parts needed to cover these two bands.
73,
Wayne
N6KR
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