Ham Radio -- How To Build Stable Oscillators

Spasibo Vasily!  

Wow, thanks a lot Todd.   There is some great wisdom in your video.  You clearly demonstrate that it is possible to build your own stable LC VFOs.  Sure, for many the arrival of the synthesizer chip put an end to this kind of project.  But some of us still want to fully homebrew all the stages in our rigs, and not be dependent on mysterious chips and software written by others.  

I really liked the way Todd acknowedged the tremendous contributions of Wes, and Roy, and Rick and others. 

Of course, all of Todd's recommendations are right on the mark.  I have been following most of them (but I do fall short and occassionally use a Manhattan pad or two).  Todd even gets into the mysterious and arcane practice of boiling (three times!) toroidal transformers.  I do have a preference for air-core coils, but that boiling sounds like fun. 

One thing that Todd and Brad might also want to consider:   tuning linearity.  Too often LC VFOs end up having the frequency spacing very close at one end of the dial and very broad at the other end.  "Bob's Electron Bunker" provides some great tools for alleviating this problem:

https://soldersmoke.blogspot.com/2022/09/the-cure-for-frequency-bunching-up-in.html

Thanks again Todd! 

SolderSmoke Podcast #249 -- Travel, Pete's 6BA6 rig, Books!, VFOs, SDR, Computers, Spectrum Analysers, Transistor Man! MAILBAG

New VFO for 15-10 Transceiver

Schematic below

SolderSmoke Podcast #249 is available:  http://soldersmoke.com/soldersmoke249.mp3

There is also a video version of this podcast: https://youtu.be/5xyaYivtOhw

Travelogue:  

HAPPY VETERANS' DAY TO PETE AND GRAYSON AND TO ALL THE OTHER VETERANS WHO ARE LISTENING. 

Trip out to San Francisco. Sticker placed on the corner of Haight and Ashbury:  See picture below.  Note other sticker.  Really Groovy! 

Cuban Cacharreo! Andy CO2AFV's Knack Story  https://soldersmoke.blogspot.com/2023/10/a-cuban-knack-story-and-pandemic-sits.html

Bill's DXCC-100.  DONE.   

Tribal Wisdom:  W1REX on HRWB https://soldersmoke.blogspot.com/2023/11/listen-to-rex-w1rex-lots-of-tribal.html

Pete's Bench:

Pete's 6BA6 rig

Pete's 6BA6 Rig

Pete Re-invents the Shirt-pocket SSB Rig

Pete's remake of the ShirtSleeve Transceiver

Pete Builds Two Computers 

Pete Adds a Second Band to his Homebrew SDR 

 

SHAMELESS COMMERCE DIVISION:  

BEZOS BUCKS ARE BACK!  PLEASE  BUY THERE! >>>>>>>>>>>>>>>>>>>>>>>

Mostly DIY RF:  Work proceeds in the Oregon Silicon Forest on P3ST kit development. Todd is confident the P3ST will be released on December 18th.Many other kits available now:  https://mostlydiyrf.com/ 

Sign up for the newsletter:  https://mostlydiyrf.com/subscribe/ 

Bill's Bench: 

Rebuild of the 15-10 VFO (for improved Dial Spread) (with yet another QF-1 capacitor) https://soldersmoke.blogspot.com/2023/10/dial-scale-linearity-spreading-out.html

Why Building for 10 meters is harder: https://soldersmoke.blogspot.com/2023/09/why-building-for-10-meters-is-harder.html

Copper Tape shielding of 15-10 rig. 

Crushing Spurs with Better Bandpass Filters (see blog post) https://soldersmoke.blogspot.com/2023/09/crushing-17-and-12-meter-spurs-with.html

Another 15-10 rig in the works... for SSSS.   Boards are accumulating... 

More problems discovered with the Herring Aid 5 Receiver . Lots of SS blog posts  Comment from Rick WD5L.  ) https://soldersmoke.blogspot.com/2023/10/a-big-error-discovered-in-1976-qst.html   Did you try to build one?  Did you succeed or did you fail?  Please let us know. 

The Basil Mahon books (blog posts) https://soldersmoke.blogspot.com/2023/11/basil-mahon-is-author-for-us-he.html

The Sunburst and Luminary book of Don Eyles (blog posts) 

The Art of Electronics by Horowitz and Hill (blog posts) 

Spectrum Analysers:  Tiny SA Ultra https://soldersmoke.blogspot.com/2023/09/the-tinysa-ultra-spectrum-analyser-video.html  and Polarad 632C-1; George WB5OYP gave me one of these spectrum analysers  (I NEED a manual! Does anyone have a manual or a schematic? )  : 

Polarad 632C-1

Stabilizing the EB63A (with Pete recommended LP filters from e-Bay. 

MAILBAG:

TRANSISTOR MAN T-SHIRTS!  Thanks to Roy WN3F! 

Todd VE7BPO on AF amplifiers.  Thanks Todd.  

Wes W7ZOI -- Always a privilege to exchange e-mail with Wes. 

E-mail from Jay Rusgrove W1VD. About the Herring Aid 5. 

E-mail from Eamon Skelton EI9GQ!  Amazing! 

HB2HB with Denny VU2DGR https://soldersmoke.blogspot.com/2023/09/hb2hb-contact-with-denny-vu2dgr.html

Nick M0NTV on diode matching for ring mixers: https://soldersmoke.blogspot.com/2023/10/does-matching-matter-diode-matching-for.html

Paul Taylor VK3HN on the new Elecraft CW rig. 

Dean KK4DAS fixed the noise in his Hallicrafters SW receiver.  A long battle, finally won. 

Dean also in contact with G3UUR. 

Ramakrishnan VU2JXN helping me set up a backup of blog on WordPress.  

Mark KA9OOI noticed that SS podcast archive appears gone.  In fact just temporarily relocated to http://soldersmoke.com/podcastarchive.html

(SS PODCAST Archive temporarily relocated to http://soldersmoke.com/podcastarchive.html) 

Andreas DL1AJG - Crystal radio video. https://soldersmoke.blogspot.com/2023/10/building-crystal-set-videos.html

George N2APB on the Herring Aid 5

Grayson KJ7UM experimenting with Varactors and Thermatrons! 

Thomas K4SWL on Mattia's DC receiver. https://soldersmoke.blogspot.com/2023/10/mattia-zamanas-amazing-direct.html

Bob Weaver of Dial Bandspread Linearity  fame.  Electron Bunker

Mike Bryce WB8VGE QRP Hall of famer -- he too couldn't get the Herring Aid 5 working. 

Kirk NT0Z wrote about the Wayback machine.  But this former ARRL staffer he also tried and failed to get the Herring Aid 5 going.  Way back when... https://soldersmoke.blogspot.com/2015/03/kirks-herring-aid-tuna-tin-and-regen.html

New 15-10 VFO with schematic

Dial Bandspread (Before)

At corner of Haight and Ashbury

Back to Divide by 4 -- Big Improvement in Receiver Performance

Thanks for all the comments and advice.  I have come to understand the wisdom of divide by 4 IQ circuits.  

Fortunately it was very easy to convert the divide by two 74AC74 circuit described earlier to a version of the divide by 4 scheme seen above.  (From the SDR Ensemble II Receiver:  http://www.wb5rvz.com/sdr/ensemble_rx_ii_vhf/04_div.htm)

This change provided a great way to observe 1) the improvement in the output signals from the VFO and 2) the resulting improvement in receiver performance, especially opposite sideband rejection.

Here are some numbers. I was very pleased to discover that my Rigol scope will measure duty cycle and phase difference. Thanks Rigol!

AD9850 Divide by 4 :  7.212 MHz  Duty cycle: 48.3  Phase Difference:  87-90 degrees

Si5351 Divide by 2:      7.212 MHz  Duty Cycle 49.6  Phase Difference:   83 degrees

Si5351 Divide by 4       7.212 MHz   Duty cycle 49     Phase Difference:  85-90 degrees

Additional improvement came when I switched the power supply to the IQ inverters and Flip Flops.  I switched from 3.3 to 5 volts:

Si5351 Divide by 4       7.105 MHz   Duty Cycle 49.7    Phase Difference:    90 degrees

When I took the VFO box and put it back in the receiver with the divide by 4 scheme and the 5 volt supply I immediately noticed a big difference in performance.  It was obvious that opposite sideband rejection was back to what I had had with the AD9850, perhaps better. 

I have a quick and dirty method of measuring opposite sideband rejection: I put an RF signal into the antenna connector.  I put the 'scope on the audio output.  I tune (on the desired sideband) for 1kHz audio and I measure the output voltage.  Then, with the audio gain and RF sig gen output in the same positions, I tune to the opposite sideband, again tuning for 1 kHz, again measuring audio output.  With the divide by 4 scheme and the 5 volt supply, the opposite sideband was so weak I had trouble measuring it.  I estimate the rejection to be at least 32 db -- this is back in the range of what I had with the AD9850, and significantly better than I had with the divide by 2 scheme. 

Now I just need to figure out how to get the Si5351 VFO sketch to tune above 42.94 MHz.  For some reason it quits at this point, switching down to 2 kHz output, and keeping me on 30 meters and below.

Thanks again to Todd VE7BPO for a lot of help with the hardware and to Tom AK2B for help with the Arduino code.  
   

Ambition, Greed, and Experiments with a Divide by 2 IQ VFO

Fresh from a great success with the use of the M0XPD divide by 4 I and Q VFO in my Frankenstein Phasing Receiver, I got ambitious.  And greedy.  I wanted more.  More frequency coverage.  More bands.  Divide by 4 can really limit your frequency range.  The AD9850 only goes up to 40 MHz.  Divide by 4 and you can't even get the 30 meter band. 

So I started looking at other options.  Si570 looked nice, but here the lower limit was the problem: 10 MHz.   Even with divide by 4,  that knocks out 160 meters, a band I am very interested in lately, and that seems to sound especially good in a direct conversion receiver.

Once again, the controversial Si5351 was calling my name.  It would go down to 8 kHz and up to 160 Mhz.  Woo Hoo!  If I could build a divide by 2 IQ VFO, I could cover 160-6 meters.   

Here is the basic idea.  From:
http://www.markimicrowave.com/blog/2015/04/top-7-ways-to-create-a-quadrature-90-phase-shift/

 The Flip Flops are set up to change state when the input signal is going up.   By putting an inverter at the input of the bottom FF input, in effect you have that one changing state when the input signal is going down.  Look at this for a minute or so.  Look at the square waves at the bottom.  See it?  See how it takes an ordinary signal and spits out two signals, one 90 degrees off the other?  Pretty cool, don't you think?

With lots of hardware help from Todd VE7BPO, and software help from Tom AK2B (wizards both), I got my Si5351 divide by 2 circuit working today.  You can see the resulting I and Q in the picture at the top.   But I am discovering that there may have been wisdom  behind those divide by 4 circuits.  My opposite sideband suppression isn't as good with this /2 scheme as it was with the AD9850 divide by 4.  I'm still trying to figure out why. I may have to go back to divide by 4.  Stay tuned.    

VE7BPO's QRP POPS IS BACK!

We were all understandably concerned when Todd VE7BPO announced this Fall that he was taking down his beloved QRP POPS web site.    I'm pleased to report that Todd has transitioned from Web Site to blog.   The spirit of QRP POPS lives on here: 

http://qrp-popcorn.blogspot.com/

There are also links on this blog to all the great stuff that was on Todd's site: 

http://qrp-popcorn.blogspot.com/p/blog-page_9.html

Three cheers for Todd!  Hip-hip...

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20