Trying a Franklin regenerative receiver for HF

Testing a regenerative receiver based on a Franklin free-running oscillator. Video also explains how this oscillator works and how it could provide a stable source of RF for homebrew receiver applications.
Inspired by WU2D - see • Shortwave Crystal Set ...
Contents:
0:00 Introduction
0:47 How Franklin oscillators work
8:21 Receiver circuit description
17:47 Testing the receiver
28:51 Adding an RF gain control
30:58 Books
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[@MIKROWAVE1]

Wow Peter! What hath God wrought? The build. What can I say? I see all kinds of fun brewing here, and more experience will bring more ideas.

[@southernexposure123]

Because of your demonstration of the regenerative RX I'll likely try one. Years ago I made a direct conversion RX using 4 diodes. The audio was pretty low, but I was able to receive cw signals. Also, I would have thought the generation control, when it actually started working, sounded that way because I did something wrong. When other people described how to use it with text I thought it might be too hard to get set right. Your demonstration cured my fearful hesitation about that. I like the way you explain circuits. It helps me know what to expect duting he build process. I watch a lot of your videos. Thank you for taking the time to make them and for sharing your knowledge and experiences.

[@ivanlam1304]

It's quite stable, you could put it in a box and add fine tuning and fine Regen control

[@StephenCooteNZ]

I'm wanting to build my own gear for operating with CW in the 20 metre band. I've been looking for stable VFO ideas. I found snippets of information about the Franklin oscillator, but when I discovered this video I hit the mother lode. I appreciate the way you explain things, and I appreciated the introduction to Mike's MIKROWAVE1 KZbin channel. You two guys are very helpful. I believe it was largely your videos that encouraged me to renew my Amateur Operators Certificate and to start building some simple gear. Thank you.

[@southernexposure123]

Ditto from me. A few months ago I first discovered information on the Franklin. It's the next oscillator I'll make. I'm back to the hobby after a 2 or 3 decade detour because of life's happenings. I'm having as much difficulty recently as I did when I first started, but I'm hard headed and I'll eventually get my act back together. Good luck with your project building.

[@StephenCooteNZ]

@@southernexposure123 My most successful Franklin Oscillator so far was built from a circuit I found posted on the internet. I don't think I can post a link here, but if you search for 'ZL2PD HF RF Signal Generator' hopefully you can find it. When I used this oscillator as a VFO, I think I got improved performance when I changed C4 from the suggested 120pF to a 15pF capacitor. Best wishes....

[@rv6amark]

NICE! I love building up regen receivers. This one looks like my next project once I get settled into my new "retirement" house. I love the fact that you show how smoothly it goes into and out of regeneration. Most KZbin demonstrators fail to do that, but it is critical that it be smooth and controllable in a good regen radio. You also demonstrated nicely how too much signal strength can be a bad thing. You might consider changing that first RF amp from a common emitter configuration to a common base design or possibly a grounded gate design using an FET (another MPF102 should work) which will reduce the front end gain to something the follow-on stages can handle while still isolating the regen signal from the antenna. Keep up the good work. I love your channel. -- Mark, KE6BB.

[@johnwest7993]

Good ideas.

[@youtubeaccount931]

Great build Peter!

[@eletronicaetelecomunicacoe7821]

Hi from Brazil, very well, your projects are excellent, amateur radio and radio listening is really good. Congratulations on the content of the channel!

[@andrewandrosow4797]

Hello! Good device! I made in past a regenerative receiver using two transistors common-base & common-collector.I think - the principle was as you describen in this video. They worked in barrier mode: emitters ware connected together to variable resistor. This resistor sets a mode of the regen - and you may get audio signal from the one (using JFET amplifier - because impedance is quite big and we want to reduce audio noise).

[@ianfoster8908]

Built a Franklin style oscillator on to a Dick Smith Fun Way Short Wave radio kit. The performance was incredible, could float low level AM signals in with the regen just oscillating. Very stable and also selective. Sadly DS stopped selling the SW Radio kit before I could publish my circuit and findings. The audio amplifier using a quad AND gate was not always reliable to get going, clever idea to get lots of gain but fussy to bias.

[@vk3ye]

Was that the Fun Way 2 kit? An RF amp, OA91 diode & CMOS IC amp (74HC4007)? I have one here. It was horrendously deaf as supplied but I added a 3.5 MHz local oscillator and it worked well for SSB reception as a simple direct conversion thing.

[@ianfoster8908]

Yes.@@vk3ye

[@intotheblue50]

Hi Peter, iI am very interested in the franklin oscillator and would like to thank you very much for your explanation on how it works , really helpful to me, thank you.

[@jerryuhte1284]

Peter,that is amazing,great info,think I need to try it ,tks,73, Jerry K9ut

[@davidportch8837]

Thanks Peter (and Mike) ... going to give this a go...

[@roogalater]

Great video Peter, a lot of potential uses for that oscillator. 73 G0IFI

[@spamcan2551]

At first I couldn't interpret your "squiggly lines".... kinda looked like crude sine waves. Those were referred to as "gimmiks" back in the day. They were used to "tweak" an oscillator's crystal frequency or vary (set) the coupling between two stages of a circuit. You have very well explained that a transistor's output signal is 180 degrees out from its input signal. So, that's why two transistors are needed to get a circuit output which "follows" the input; a "follower" circuit. Hmmmm.... Franklin Oscillator circuit looks to have great potential in/as a single frequency audio filter stage.

[@matthiaswilhelm9813]

Geiler Drahtverhau❤😂😂😂

[@johnwest7993]

After watching Mike's video on the Franklin oscillator I was hoping one of you would have a video on a completer regen receiver. Thank you for doing it for me so I don't have to stumble my way through it not nearly as well as you did. BTW, any cheap computer speaker in a box would have given us a better idea of the sound of the receiver. Open drivers are acoustically just a bad idea. They always sound bad.

[@OudeNieuweTechniek73]

This clip is just coming online just in time for me. Was thinking making a DC reciever but this is just as good or maybe even better. I'm going to experiment with this oscillator only using a BF256 FET instead of a MPF102 for the detector. Also using fine tunning with PN diodes for SSB signals.

[@vk3ye]

If you are just interested in CW/SSB a DC receiver is better. This one requires a lot of adjustment of the RF gain control to avoid distortion.

[@OudeNieuweTechniek73]

@@vk3ye Well I'm gonna experiment with a DC and this radio. I'm replacing the 22 pf capacitor for a tuned circuit to see if that will improve the reception and for the distortion. After the experiments I will decide what reciever is going to be build in the Tray radio that I'm constructing.

[@SimonJackson13]

A controlled amount of capacitivly coupled audio into the regen base ... harmonic distortion regen ...

[@dongrimb]

Just a tip for you peter. Build it into a box for greater stability.

[@lampyelektronowe]

👍

[@hobbyrob313]

Hello Peter, can this also be made for WFM say 100MHz? (for me personally 85MHz) Healthy and kind regards from The Netherlands! Rob

[@hobbyrob313]

HOOWWwww wait! I may have found something similar to... www.eleccircuit.com/wp-content/uploads/2012/06/small-fm-radio-receiver.jpg Greetings again! Rob

[@INFO_SELABX]

Can we use bfw10 in place of mpf 102

[@vk3ye]

Not familiar with that FET so can't help, sorry. Try it!

[@INFO_SELABX]

can we add varactor fine tune

[@vk3ye]

Yes.

[@grzesiek1x]

Why are you not using pcbs ? Just curious :)

[@vk3ye]

Don't have the time to use PCBs for everything I build!

[@johnwest7993]

This project can be built in the time that it takes to do a PCB layout. Then there is the bd manufacturing, or outsourcing it time, plus the cost of bds. Although I'd build it on some prototyping bd with 'donut' pad to keep it cleaner and more reliable, although if there are feedback or unwanted stage coupling problems they are a pain to fix. Always trade-offs.

[@ornithopterindia]

Dear peter is this dc receiver or regenerative receiver?

[@vk3ye]

Regen, as per the video title.

[@ornithopterindia]

Thank you sir.