Great effort! Traditionally, padding was in series with the tuning capacitor; trimming was in parallel with the tuning capacitor. This method was traditionally called Homodyne detection receiver. I remember reading about it in Wireless World magazine in the70s.
Great stuff Nick, I really like the modular approach here. It makes it easier for this beginner to understand and build. A busy time of year for you and I wish you and yours season's greetings.
Nick, I love the analog approach, and your use of a VFO...I am very much in mind to build one very much like yours...I can't believe all the advice and controversy that came from this one video! You have a careful and thoughtful approach to design, and i just love it! Keep it coming! Merry Christmas, and Happy New!!
Hi Nick, nice build! The reason for tuning 160, 80 and 40 from high-to-low frequency is because it's easier to approach a LSB signal that way - the signal is heard at high pitch, then gradually lowers to normal before cutting off after zero beat with the suppression of the upper side band. Of course, with a DC receiver it makes little difference, as you are not sideband-specific - the signal goes through zero beat and then comes out garbled on the other side. Padding tuning capacitors (for those who don't know) is best initiated with a simple LC frequency spreadsheet where you can substitute series and parallel capacitance values until you get the range you want. Season's Greetings from M1GWZ (Echelford ARS).
Hi Phil! Great to hear from you. Hope you and all the EARS guys are doing OK. That makes sense what you say about approaching an LSB signal from above. I think I must have naturally just got into the habit. I must confess the padding was more cut and try on my part but I got there in the end! Look after yourself. 73, Nick
Nick--It's always a pleasure to see something from MDRF in the wild, and thanks for the plug. Using the TIA-AGC as a variable-gain pre-amp is a great idea, especially with a front-panel gain control as you've done. I've been doing some experiments using low-noise transistors like the BF106 in place of the 2N3904 in the TIA amps. This might have some value in a pre-mixer RF amp since any noise introduced by the amp itself will be amplified in subsequent stages. Whether or not there'd be any noticeable benefit is hard to say, but there's always the placebo effect to come to the rescue if not. --Todd K7TFC
Hi Todd! Thank you so much once again for your fantastic boards! I was really pleased with how the TIA-AGC worked out. Keep up the great work. 73, Nick
Nice. I am a retired pure mathematician that took up electronics as a hobby similar to taking up cooking as a hobby over a decade ago as an outgrowth of using partial differential equations to model simple antennas in order to see mathematics modeling a real world phenomenon. I don't aim for my hobbies to lead to being a 5 star chef nor EE; rather, my aim is much more restricted. None the less, lately I have an interest in building one of each style of receiver up to & including superheterodyne. I am now past the stage of regenerative type receivers and looking forward to a direct conversion receiver. Not having previously built a direct conversion receiver I find sometimes schematic representation on a great design can be a bit cryptic to a new builder by the draftsperson having essentially used a means of representation in the schematic that anyone having previously built the project would immediately recognize, but not necessarily a first time builder. You gave me the notion that the receiver your assembling or a similar receiver is the one for me to start with because in a AM radio club video recently published on RUclips you suggested the instructions and plans for the direct receiver you were demonstrating having a gluestick based variable inductor was really excellent and very detailed. If you could give me a link to the plans & schematic I am implying please do, I'd really appreciate it. It will be a fabulous winter indoor project now that snow has hit my neighborhood in the Catskills. Thanks in advance Mike Boyer
Hi Mike! Thanks very much for getting in touch. I've built a few DCRs over the past few years but if you are interested specifically in the Glue-Stick PTO version then check out my videos 32, 33 & 34. I link to downloadable schematics etc. in the comments. All the very best with your building. Enjoy! 73, Nick
I just used a two-stage version of the hybrid cascode as my IF amplifier in the new transceiver that I'm designing, and it is indeed an excellent RF amplifier with a very large control range. Worked perfectly for the simple AGC system that I implemented. 73 DE NT7S
Hi Jason! Great to hear from you. Yes, I was impressed with the design of the TIA-AGC amp. That Mr. Hayward knows a thing or two doesn't he? In other (unrelated) news I did think of you the other day as I've been doing some experimenting with the Si5351 and an ESP32-powered integrated TFT screen (the so called 'Cheap Yellow Display'). I've managed to get an adapted form of your brilliant code working on it. It'll probably be the subject of a video in the new year. Thanks again for all give to the hobby. 73, Nick
On the three Softrock kits I've built I've had to use an LNA in the front as they always seem to be a little less sensitive than commercial receivers. The LNA design was from the R2Pro LNA by KK7B that I built dead-bug style and yielded around 12 dB gain. Thanks for sharing your work Nick - always a pleasure - 73
Gee, the only thing missing here would be lasers linking all the components together instead of cables, then you could really spread it out all over your shack. 😀 A long time ago I spent a whole day in the Exploratorium in San Francisco which is a science/tech museum set up by scientists from Lawrence Livermore Laboratories using surplus equipment from the labs. This was when lasers were still new and they were using a visible red laser beam to transmit the audio from a broadcast radio up the wall to a mirror, across the ceiling to another mirror and then down the wall to a detector/amplifier/speaker. They encouraged people to put their hand in the beam as a way to verify that the sound was actually being transmitted by light. I thought that was so cool.
I've always been fascinated by the possibilities a direct conversion receiver project offers. But no tuning capacitor local oscillator. I want my oscillator to be a digital synchronous sort - gone would be the tedium of moving from signal to signal with a less than precision tuning mechanism. Good fun this stuff!
Hi there! Check out my video No. 26 - Designing A Digital Oscillator (ruclips.net/video/P71yoWR6-rU/видео.htmlsi=z6B3sqjzeaOoyp11). This is a basic VFO with Arduino Uno, Si5351 PLL module, 2x14 LCD screen + Rotary Encoder. It should hopefully help you on your way. Thanks for commenting. 73, Nick
Nick: Some comments from the SolderSmoke blog: First, let me say FB Nick. It is nice to see you making use of the AGC amp designed by Wes and Bob, using the board from Todd's Mostly DIY RF, using a mix of homebrew pads and Me-Squares from Rex, and finally the Franklin Oscillator that we spent so much time talking about on SolderSmoke. But here are some comments: -- I still don't think you need that RF amplifier in front of the mixer. And I suspect you would be better off without it. We did not use one in our high school 40 meter project, and never missed it. In fact, on one version of the high school receiver I even put in a simple 10k pot as an attenuator (no RF amp). Even up on 20 meters, I do not have an RF amplifier ahead of the diode ring mixer on either of the Mythbuster rigs I have built. Nick, maybe experiment a bit more and try the receiver just going from the BP filter into the mixer and see what happens. Note that Wes W7ZOI DID NOT have an REF amp ahead of the diode ring mixer in his original 1968 40 meter Direct Conversion receiver (the one that launched the solid-state DC recevier revolution). -- The Franklin oscillator is an interesting, but complicated circuit. The gimmick is, well, gimmicky. Here is the thing: You can achieve similar levels of stability using simple conventional, single transistor oscillators. We dispensed with the variable capacitors, and used PTO--style variable inductors. They worked fine. This Franklin oscillator still does seem to drift a bit, right? I would ground the board to the inside of the metal box. I would also try putting all the stages on a single ground plane. This might help. 73 Bill
Hi Bill, Thank you very much for watching and commenting and particularly for posting this on the Soldersmoke blog (soldersmoke.blogspot.com). I appreciate you sharing your experience of these analogue creations! The whole project came about after I watched the series that Charlie ZL2CTM did on building an AM broadcast receiver - with a Franklin oscillator. It just seemed like an interesting thing to try on SSB. In truth I get better stability with my Glue-Stick PTO but it was still a fun thing to experiment with. Like you, I wouldn't normally use any up front RF amplification but I actually blame a re-reading of EMRFD, chapter 8 where Hayward, Campbell and Larkin extol the virtues of an RF amplifier ahead of the mixer. Using the variable gain design also means I can use it for attenuation when needed. But again - it was really just an experiment. I think with a better audio amp I could probably dispense with this. I certainly concur with your comments on grounding. Thanks again for all you give to the homebrewing hobby. I wouldn't be doing this today without the inspiration and encouragement of Pete and yourself. 73, Nick
@M0NTVHomebrewing another great thing about DG mosfets, is that in a breadboard circuit the AGC V can use a sample-hold effect. With the control gate just tied to a 0.1 uF to ground and nothing else, finger skin resistance bridging to supy rails can be used to turn up and down the gain like buttons on a remote control. Another great thing is they make great demodulators or pair of them a double balanced demod. Been 40+ years ago did this!
Thanks. My impression is that DG MOSFETs are not so easy to get hold of these days. I've never actually built with one. I have used a design by Pete Juliano N6QW for a product detector that uses 2 x J310 FETs to simulate a single dual gate MOSFET. It works very well but tends to be susceptible to AM breakthrough on the 40m band. Thanks again. 73, Nick
@@M0NTVHomebrewing I see Digikey USA still stock Harris 3N206 quite pricey but they also have a much more modern 3SK264 200 MHz for 20 cents. Ebay has lots of dualgate fets ,the fake chinese ones probably outperform the originals
Great effort! Traditionally, padding was in series with the tuning capacitor; trimming was in parallel with the tuning capacitor. This method was traditionally called Homodyne detection receiver. I remember reading about it in Wireless World magazine in the70s.
Thanks for that clarification. That's good to know. Best wishes, Nick
Great stuff Nick, I really like the modular approach here. It makes it easier for this beginner to understand and build. A busy time of year for you and I wish you and yours season's greetings.
Thanks very much Ace! 73, Nick
Thank you for sharing we appreciate it very much
Thank you very much Berny. Best wishes, Nick
Nick, I love the analog approach, and your use of a VFO...I am very much in mind to build one very much like yours...I can't believe all the advice and controversy that came from this one video! You have a careful and thoughtful approach to design, and i just love it! Keep it coming!
Merry Christmas, and Happy New!!
Hi Ed! Thank you very much for your support and encouragement. Happy Christmas! 73, Nick
Great design. Thanks so much for your content this year, I’ve learned so much! Merry Christmas to you and your family.
Thank you very much indeed. 73, Nick
Well done Nick, thoroughly enjoyed this series (as I do most of your builds)
All the best for Christmas and the New year from me as well.
Andy G0POY
Thanks so much Andy. 73, Nick
Fun bit of home brew there Nick. Have a great Christmas and looking forward to your 2025 vids!
Thanks very much indeed. 73, Nick
Hi Nick, nice build! The reason for tuning 160, 80 and 40 from high-to-low frequency is because it's easier to approach a LSB signal that way - the signal is heard at high pitch, then gradually lowers to normal before cutting off after zero beat with the suppression of the upper side band. Of course, with a DC receiver it makes little difference, as you are not sideband-specific - the signal goes through zero beat and then comes out garbled on the other side.
Padding tuning capacitors (for those who don't know) is best initiated with a simple LC frequency spreadsheet where you can substitute series and parallel capacitance values until you get the range you want. Season's Greetings from M1GWZ (Echelford ARS).
Hi Phil! Great to hear from you. Hope you and all the EARS guys are doing OK. That makes sense what you say about approaching an LSB signal from above. I think I must have naturally just got into the habit. I must confess the padding was more cut and try on my part but I got there in the end! Look after yourself. 73, Nick
Nick--It's always a pleasure to see something from MDRF in the wild, and thanks for the plug. Using the TIA-AGC as a variable-gain pre-amp is a great idea, especially with a front-panel gain control as you've done. I've been doing some experiments using low-noise transistors like the BF106 in place of the 2N3904 in the TIA amps. This might have some value in a pre-mixer RF amp since any noise introduced by the amp itself will be amplified in subsequent stages. Whether or not there'd be any noticeable benefit is hard to say, but there's always the placebo effect to come to the rescue if not. --Todd K7TFC
Hi Todd! Thank you so much once again for your fantastic boards! I was really pleased with how the TIA-AGC worked out. Keep up the great work. 73, Nick
Nice.
I am a retired pure mathematician that took up electronics as a hobby similar to taking up cooking as a hobby over a decade ago as an outgrowth of using partial differential equations to model simple antennas in order to see mathematics modeling a real world phenomenon.
I don't aim for my hobbies to lead to being a 5 star chef nor EE; rather, my aim is much more restricted. None the less, lately I have an interest in building one of each style of receiver up to & including superheterodyne. I am now past the stage of regenerative type receivers and looking forward to a direct conversion receiver.
Not having previously built a direct conversion receiver I find sometimes schematic representation on a great design can be a bit cryptic to a new builder by the draftsperson having essentially used a means of representation in the schematic that anyone having previously built the project would immediately recognize, but not necessarily a first time builder.
You gave me the notion that the receiver your assembling or a similar receiver is the one for me to start with because in a AM radio club video recently published on RUclips you suggested the instructions and plans for the direct receiver you were demonstrating having a gluestick based variable inductor was really excellent and very detailed.
If you could give me a link to the plans & schematic I am implying please do, I'd really appreciate it. It will be a fabulous winter indoor project now that snow has hit my neighborhood in the Catskills.
Thanks in advance
Mike Boyer
Hi Mike! Thanks very much for getting in touch. I've built a few DCRs over the past few years but if you are interested specifically in the Glue-Stick PTO version then check out my videos 32, 33 & 34. I link to downloadable schematics etc. in the comments. All the very best with your building. Enjoy! 73, Nick
Bravo Nick. What a great radio receiver. I do like you variable RF amp/attenuator. Merry Christmas Greg
Thanks very much Greg. All the best to you! 73, Nick
I just used a two-stage version of the hybrid cascode as my IF amplifier in the new transceiver that I'm designing, and it is indeed an excellent RF amplifier with a very large control range. Worked perfectly for the simple AGC system that I implemented. 73 DE NT7S
Hi Jason! Great to hear from you. Yes, I was impressed with the design of the TIA-AGC amp. That Mr. Hayward knows a thing or two doesn't he? In other (unrelated) news I did think of you the other day as I've been doing some experimenting with the Si5351 and an ESP32-powered integrated TFT screen (the so called 'Cheap Yellow Display'). I've managed to get an adapted form of your brilliant code working on it. It'll probably be the subject of a video in the new year. Thanks again for all give to the hobby. 73, Nick
@@M0NTVHomebrewing Excellent, let me know if I can be of any assistance on your upcoming project. Merry Christmas and HNY!
Thanks very much Jason. Will do!
On the three Softrock kits I've built I've had to use an LNA in the front as they always seem to be a little less sensitive than commercial receivers. The LNA design was from the R2Pro LNA by KK7B that I built dead-bug style and yielded around 12 dB gain. Thanks for sharing your work Nick - always a pleasure - 73
That's interesting to know. Thanks very much Brian. 73, Nick
Glad I’m not the only one whose radios end up sprawled across all creation. 😂
Great video!
Thanks very much indeed. Most of my radios start with an 'open-plan' rat's nest of interconnected modules. Some even stay that way! 73, Nick
Gee, the only thing missing here would be lasers linking all the components together instead of cables, then you could really spread it out all over your shack. 😀
A long time ago I spent a whole day in the Exploratorium in San Francisco which is a science/tech museum set up by scientists from Lawrence Livermore Laboratories using surplus equipment from the labs. This was when lasers were still new and they were using a visible red laser beam to transmit the audio from a broadcast radio up the wall to a mirror, across the ceiling to another mirror and then down the wall to a detector/amplifier/speaker. They encouraged people to put their hand in the beam as a way to verify that the sound was actually being transmitted by light. I thought that was so cool.
Wow! That sounds SERIOUSLY cool! I love it. Thanks very much for commenting. 73, Nick
جيد جدا
Thanks very much. 73, Nick
I've always been fascinated by the possibilities a direct conversion receiver project offers. But no tuning capacitor local oscillator. I want my oscillator to be a digital synchronous sort - gone would be the tedium of moving from signal to signal with a less than precision tuning mechanism. Good fun this stuff!
Hi there! Check out my video No. 26 - Designing A Digital Oscillator (ruclips.net/video/P71yoWR6-rU/видео.htmlsi=z6B3sqjzeaOoyp11). This is a basic VFO with Arduino Uno, Si5351 PLL module, 2x14 LCD screen + Rotary Encoder. It should hopefully help you on your way. Thanks for commenting. 73, Nick
Nick: Some comments from the SolderSmoke blog: First, let me say FB Nick. It is nice to see you making use of the AGC amp designed by Wes and Bob, using the board from Todd's Mostly DIY RF, using a mix of homebrew pads and Me-Squares from Rex, and finally the Franklin Oscillator that we spent so much time talking about on SolderSmoke. But here are some comments:
-- I still don't think you need that RF amplifier in front of the mixer. And I suspect you would be better off without it. We did not use one in our high school 40 meter project, and never missed it. In fact, on one version of the high school receiver I even put in a simple 10k pot as an attenuator (no RF amp). Even up on 20 meters, I do not have an RF amplifier ahead of the diode ring mixer on either of the Mythbuster rigs I have built. Nick, maybe experiment a bit more and try the receiver just going from the BP filter into the mixer and see what happens.
Note that Wes W7ZOI DID NOT have an REF amp ahead of the diode ring mixer in his original 1968 40 meter Direct Conversion receiver (the one that launched the solid-state DC recevier revolution).
-- The Franklin oscillator is an interesting, but complicated circuit. The gimmick is, well, gimmicky. Here is the thing: You can achieve similar levels of stability using simple conventional, single transistor oscillators. We dispensed with the variable capacitors, and used PTO--style variable inductors. They worked fine. This Franklin oscillator still does seem to drift a bit, right? I would ground the board to the inside of the metal box.
I would also try putting all the stages on a single ground plane. This might help.
73 Bill
Hi Bill,
Thank you very much for watching and commenting and particularly for posting this on the Soldersmoke blog (soldersmoke.blogspot.com). I appreciate you sharing your experience of these analogue creations! The whole project came about after I watched the series that Charlie ZL2CTM did on building an AM broadcast receiver - with a Franklin oscillator. It just seemed like an interesting thing to try on SSB. In truth I get better stability with my Glue-Stick PTO but it was still a fun thing to experiment with.
Like you, I wouldn't normally use any up front RF amplification but I actually blame a re-reading of EMRFD, chapter 8 where Hayward, Campbell and Larkin extol the virtues of an RF amplifier ahead of the mixer. Using the variable gain design also means I can use it for attenuation when needed. But again - it was really just an experiment. I think with a better audio amp I could probably dispense with this. I certainly concur with your comments on grounding.
Thanks again for all you give to the homebrewing hobby. I wouldn't be doing this today without the inspiration and encouragement of Pete and yourself. 73, Nick
Amazing project, I am working in the same build. Can you please show more about the Audio amplifier ( video or link ) ? Thanks
Thanks. For the audio amp you need to check out video 56 (ruclips.net/video/DPf6b5j5kR8/видео.html) and if you're really brave 57 and 58! 73, Nick
Dual gate MOSFET makes for great AGC too.
Thanks for the tip. 73, Nick
@M0NTVHomebrewing another great thing about DG mosfets, is that in a breadboard circuit the AGC V can use a sample-hold effect. With the control gate just tied to a 0.1 uF to ground and nothing else, finger skin resistance bridging to supy rails can be used to turn up and down the gain like buttons on a remote control. Another great thing is they make great demodulators or pair of them a double balanced demod. Been 40+ years ago did this!
Thanks. My impression is that DG MOSFETs are not so easy to get hold of these days. I've never actually built with one. I have used a design by Pete Juliano N6QW for a product detector that uses 2 x J310 FETs to simulate a single dual gate MOSFET. It works very well but tends to be susceptible to AM breakthrough on the 40m band. Thanks again. 73, Nick
@@M0NTVHomebrewing I see Digikey USA still stock Harris 3N206 quite pricey but they also have a much more modern 3SK264 200 MHz for 20 cents. Ebay has lots of dualgate fets ,the fake chinese ones probably outperform the originals
@@M0NTVHomebrewing My reply to you just now was CENSORED by youtube. The comment that deleted I wrote where you can get good dual gate mosfets from
Nice
Thanks very much. 73, Nick
Where did u buy ur variable capacitor? I realy like the way it looks including the button on it
Hi there! I think I bought it from a HamFest or suchlike. 73, Nick