That is going to be tough, crystals at those frequencies are hard to come by, and if you want a custom frequency they end up costing more that the SR-40. The crystal oscillator I found it 2.2KHz on the high side of 8.830, but there are nothing affordable off by another 48KHz. A crystal is also available and with the right circuitry could be pulled "maybe" an additional 20KHz up for a total of 7.2 KHz on the high side. But that is getting pretty complicated.
There is a 35.251 crystal available, that is 17.5KHz on the low side. I'll have to think about it.
Since this is going to be a dedicated application, a DDS would be overkill and too pricey.
I started building it, I got a really nice lamp, but I've had to work late yesterday so I didn't work very much on it, this stuff is too tiny to work on it when you are tired. We have inventory at work this Friday and I've been having to work late this week. Worst case I will work on it this weekend, I'm not planning on going anywhere.
I have not received your kit yet, but I'm hoping it will be in today or tomorrow, the sound card came in pretty quick.
At 12:41 PM 9/28/2005, you wrote:
Hi Cecil,
In setting the frequency of the SoftRock to use it a a IF amp/demodulator
you will want a frequency offset. For example if you are wanting to work
with a 8.83 MHz IF then you want the SoftRock40 oscillator set to (8.83
+0.012 )*4 MHz or (8.83 -0.012)*4 MHz. This will keep you away from the
noise associated with the sound card around zero Hz and the SoftRock LO
signal. Plus it will give you some tuning range through the IF passband.
Another possibility is sub-harmonic sampling which uses a LO frequency 1/3
of the desired RF input frequency. Thus the frequency of the crystal would
be (f_desired / 3)*4 . The gain of the QSD is only down 6 dB with the
sub-harmonic sampling.
How is the build on your kit coming along and have you received the built
unit I recently sent?
73,
Tony KB9YIG
----- Original Message -----
From: "KD5NWA" <KD5NWA@...>
To: <softrock40@...>
Cc: <soft_radio@...>
Sent: Wednesday, September 28, 2005 12:28 PM
Subject: [softrock40]
For people interested in using the SR-40 for dedicated purpose, I was
nosing through the Mouser Catalog on line and they have for
reasonable prices both crystals and little 3.3Volt oscillator modules
to move the SoftRock 40 to the following useful frequencies;
3.579 MHz 80 Meter watering hole, changes to filter needed (14.318 MHz)
4.912 MHz Popular IF frequency, changes to filter needed (19.660 MHz)
8.830 MHz Kenwood IF frequency, no changes to the filter (35.328MHz)
9.0 MHz Ten-Tec and popular IF frequency, no changes to the filter (36
MHz)
Some of those frequencies come out a KHz or thereabout off the
correct frequency, but since the SR-40 can tune +- 24 KHz it comes
out in the wash.
The crystals are anywhere from $.42 to about $2, and the complete
modules are from $1.92 to $3
I'm going to get me some crystals and Osc. modules for 8.830, and
crystals for the rest, to play around with.
Nothing like a SR-40 with a TS-940sat for a front end, talk about
opposite ends of the spectrum, it will be my SR-40 that can go
everywhere with one heck of a front end, or my TS-940sat with
Panoramic display.
If one or two guys/gals are interested in getting a OSC module for
8.830MHz the Kenwood panoramic output on the back of the radio, let
me know before tomorrow night and I'll include an extra module for
you for cost + shipping. I'll send a last call before sending out the
purchase order.
Cecil Bayona
KD5NWA
www.qrpradio.com
'Never argue with an idiot. They drag you down to their level then
beat you with experience.'
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Cecil Bayona
KD5NWA
www.qrpradio.com
'Never argue with an idiot. They drag you down to their level then beat you with experience.'
Alex, VE3NEA