A possible answer to the question about the obvious chaotic behavior of some elected politicians. Each day they know less. It is all about subtraction.
So now back to some radio stuff. I continue to look at the possibilities of converting the SSB version of the 23 channel CB radios to 10 Meters. The Crystal synthesized versions look particularly attractive for conversion with a specific look at the Cobra Model 134 and Model 138. The chart below is chock full of information on how the synthesis works.
There is a bit of magic taking place and the chart tells the tale. Ten synthesizer crystals plus the BFO crystal give you 3X23 or 69 channels of either AM, LSB or USB signals.
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With a single BFO frequency it is possible to have LSB and USB simply by picking the correct LO. For LSB and AM with a 7.8205 BFO and an LO operating at 19MHz, the output is in the range 26-27MHz which is an additive mix. Now if you shift the LO to 34MHz two things happen: we use the subtractive mix where 34 - 7.8205 puts you in the 26-27MHz range with the 2nd part Sideband Inversion and the signal is USB.
The footnote shows how the A + B frequencies are in the 19MHz range and then adding the C frequencies make the 26-27MHz range. But they don't show how to get to 34 MHz. If we take the A + B + 2*C that equals 34 MHz and then subtract C in the mixer stage and you have A +B +C but Upper Sideband. So, for USB there is mixing circuitry in the radio to add the two crystal frequencies plus sampling the BFO and doubling that output to add to the two crystal frequencies.
This is where the Arduino and the Si5351 can replace the Crystal synthesizer. You would only need one channel as the Si5351 would tune 20.497500 to 21.197500 MHz giving you 28.3 to 29 MHz LSB and AM
For USB the Arduino / Si5351 would have to tune 36.102500 to 36.802500 MHz to tune 28.3 to 29MHz Upper Sideband. Mind you the LO has to shift up in frequency in either mode to cover 28.3 to 29MHz.
BTW something I did with my now gathering dust Bitx 40. Upon getting that radio, I disabled the on board "drifty VFO" and replaced it with an Arduino and Si5351. I used the same approach as above to put the Bitx40 on USB so I could talk to that group that uses USB on 40M and for FT-8. The BFO does not move to give LSB/USB but the simple change in the LO frequency range made USB possible. A simple toggle switch to select LSB or USB signals the range change to the Arduino.
Them that know can make things go. The Cobra 134 or 138A can be had for around $70 and the addition of a digital LO about $20. So, if you had a hundred dollars floating about after donating $100 to feed the hungry on Thanksgiving this would be a candidate.
Speaking of donations, I stopped by the rectory of my local Catholic church to drop off a check to the St. Vincent DePaul Society for food for the hungry. It was shared with me that this year the requests are outstripping the resources available.
Mind you I happen to live in a high-tech town with a world class pharmaceutical manufacturer and even a branch of a company who makes the Si5351 so lots of employers. But it also is home to many who work in agriculture growing, cilantro, strawberries, artichokes and peppers. Many of these workers no longer go to work because of the ICE raids.
We need to focus beyond a deportation mentality and fix the immigration system. But is it more fun to play dress up in BDU's sporting an M-16 and herding aliens into buses bound for detention centers or the really hard work of providing for legal immigration. It will not happen soon and so the cosplay continues.
73'sPete N6QW
There is a bit of magic taking place and the chart tells the tale. Ten synthesizer crystals plus the BFO crystal give you 3X23 or 69 channels of either AM, LSB or USB signals.
.webp)
With a single BFO frequency it is possible to have LSB and USB simply by picking the correct LO. For LSB and AM with a 7.8205 BFO and an LO operating at 19MHz, the output is in the range 26-27MHz which is an additive mix. Now if you shift the LO to 34MHz two things happen: we use the subtractive mix where 34 - 7.8205 puts you in the 26-27MHz range with the 2nd part Sideband Inversion and the signal is USB.
The footnote shows how the A + B frequencies are in the 19MHz range and then adding the C frequencies make the 26-27MHz range. But they don't show how to get to 34 MHz. If we take the A + B + 2*C that equals 34 MHz and then subtract C in the mixer stage and you have A +B +C but Upper Sideband. So, for USB there is mixing circuitry in the radio to add the two crystal frequencies plus sampling the BFO and doubling that output to add to the two crystal frequencies.
This is where the Arduino and the Si5351 can replace the Crystal synthesizer. You would only need one channel as the Si5351 would tune 20.497500 to 21.197500 MHz giving you 28.3 to 29 MHz LSB and AM
For USB the Arduino / Si5351 would have to tune 36.102500 to 36.802500 MHz to tune 28.3 to 29MHz Upper Sideband. Mind you the LO has to shift up in frequency in either mode to cover 28.3 to 29MHz.
BTW something I did with my now gathering dust Bitx 40. Upon getting that radio, I disabled the on board "drifty VFO" and replaced it with an Arduino and Si5351. I used the same approach as above to put the Bitx40 on USB so I could talk to that group that uses USB on 40M and for FT-8. The BFO does not move to give LSB/USB but the simple change in the LO frequency range made USB possible. A simple toggle switch to select LSB or USB signals the range change to the Arduino.
Them that know can make things go. The Cobra 134 or 138A can be had for around $70 and the addition of a digital LO about $20. So, if you had a hundred dollars floating about after donating $100 to feed the hungry on Thanksgiving this would be a candidate.
Speaking of donations, I stopped by the rectory of my local Catholic church to drop off a check to the St. Vincent DePaul Society for food for the hungry. It was shared with me that this year the requests are outstripping the resources available.
Mind you I happen to live in a high-tech town with a world class pharmaceutical manufacturer and even a branch of a company who makes the Si5351 so lots of employers. But it also is home to many who work in agriculture growing, cilantro, strawberries, artichokes and peppers. Many of these workers no longer go to work because of the ICE raids.
We need to focus beyond a deportation mentality and fix the immigration system. But is it more fun to play dress up in BDU's sporting an M-16 and herding aliens into buses bound for detention centers or the really hard work of providing for legal immigration. It will not happen soon and so the cosplay continues.
73's
Pete N6QW