Regenerative reflex receiver - UK Vintage Radio Repair and Restoration Discussion Forum

val33vo · 28th Jun 2011, 6:54 am

Just built a 1959 receiver which I am in the process of trying to get working it uses the first transistor to amplify at radio and then at audio frequencies and also has regenerative feedback via a gimmick capacitor ( a couple of wires twisted together ) it also has a tuned collector load ( a 455 khz if transformer with the capacitor cut away and instead tuned by the second gang of the main tuning capacitor ) its partly working ( I can hear faint audio ) I strongly suspect the phasing of the IF transformer is wrong and I am not getting regeneration but degeneration instead which I will investigate the next time the wife stops nagging me over tedious chores

What I am pretty sceptic about the design is the tuned collector circuit being accurately able to follow the main tuning circuit ( any thoughts here ? ) though the concept is interesting in minimalisation of component count and its also supposed to be superior to a superhet in terms of audio bandwidth

regards

val33vo

Sideband · 28th Jun 2011, 7:45 am

How about posting a picture of the circuit so we can see whats going on. A picture paints a thousand words!

SB

neon indicator · 28th Jun 2011, 8:46 am

I think some of those used two separate variable capacitors,
One for Tuning and other for Reaction?

A Superhet has what ever audio bandwidth you want depending on design of IF filter.

A regenerative, super regen, syncrodyne, homodyne, direct conversion, Zero IF etc receiver has bandwidth set by filter on audio.

Modern Ceramic and Crystal filters replace IF "coils" which can be less accurate in implementation of bandwidth and out of band rejection.

You can use a "regen" as last IF amp and no diode detector. Then you will be able to receive weaker signals with less distortion if the background noise permits

AlanC · 28th Jun 2011, 12:20 pm

As SB has said, it would be great to see the circuit.

As a general rule of thumb, if you want two RF circuits to track (gang) accurately, the coils you use for both will need to be identical. It also helps to have the coils adjustable (which I guess the IFT will be) and also have trimmer caps in parallel so you can set the ganging at the LF and HF end of the range respectively.

HTH
Alan

kalee20 · 28th Jun 2011, 12:48 pm

Quote:

Originally Posted by neon indicator

A regenerative, super regen, syncrodyne, homodyne, direct conversion, Zero IF etc receiver has bandwidth set by filter on audio.

Synchrodyne and homodyne yes, but a conventional TRF receiver has bandwidth set by the Q of the tuned circuits. If you then apply regen, then the Q is increased and bandwidth thus reduces.

neon indicator · 28th Jun 2011, 4:13 pm

TRF definitely. TRF with some "regenerative" feedback and diode detector, yes.

Super regen detector/amp? You could be right. Of course some alleged regenerative one transistor/valve receivers may be really "direct conversion". If it's actually oscillating, the Q is the Q of the coils (usually very broad) and then it becomes a direct conversion receiver, with ability to filter adjacent channel at audio baseband and no AM detector.

A circuit diagram will end speculation

val33vo · 5th Jul 2011, 2:18 pm

Hi fellow enthusiasts I have not been able to post for a few days but find attached the circuit diag I have not used the original trannies as I dont like the unrealiabilty of germanium types instead I have used BC547,s with the bias resistors changed to take account of a 0.6v instead of 0.2v base emitter junction drop

5th Jul 2011, 10:24 pm

Built a few of those in my youth, the voltage doubling detector is ingenious. Shame I used things like Bush TR86's for the parts (20p at the most from the local auction). I don't think germainuim devices (except the AF117 series, but that wasn't germaniums fault) are inherently unreliable, my 50 year old Perdio still works and that is full of them.

I know I am wrong but my heart says germainium is soft and gentle silicon hard an harsh, probably a sign of the time I was first learning all this (1960's 70's), before I upset anyone, valves are just brilliant!

G8HQP Dave · 7th Jul 2011, 3:01 pm

There is no tracking adjustment, so tracking may be poor, but on strong AM local signals you might not notice. My guess is that ganging two tuned circuits in this way may create as many problems as it solves. You could be unlucky and get it oscillating at two different but nearby frequencies.

The bias on Fig 2 probably won't need any change. Fig 1 might need a bigger resistor because of the high current gain of silicon BJT.

AlanC · 7th Jul 2011, 6:04 pm

I'm just trying to figure out what's going on around L2- is that neutralisation, or reaction? Ganging the tuned ccts will be the hardest thing to do; build them exactly like the instructions or else if you have another to hand, fit two separate tuning caps to investigate the tracking law.
Good luck!
Alan

G8HQP Dave · 7th Jul 2011, 9:38 pm

L2 is basically the second tuned circuit. It is coupled to the diode detector, and also provide feedback via the small trimmer cap. The collector goes to a tap for impedance matching reasons.

28th Jun 2011, 6:54 am	#1
val33vo Retired Dormant Member Join Date: Apr 2008 Location: Banffshire, Scotland, UK. Posts: 191	Regenerative reflex receiver Just built a 1959 receiver which I am in the process of trying to get working it uses the first transistor to amplify at radio and then at audio frequencies and also has regenerative feedback via a gimmick capacitor ( a couple of wires twisted together ) it also has a tuned collector load ( a 455 khz if transformer with the capacitor cut away and instead tuned by the second gang of the main tuning capacitor ) its partly working ( I can hear faint audio ) I strongly suspect the phasing of the IF transformer is wrong and I am not getting regeneration but degeneration instead which I will investigate the next time the wife stops nagging me over tedious chores What I am pretty sceptic about the design is the tuned collector circuit being accurately able to follow the main tuning circuit ( any thoughts here ? ) though the concept is interesting in minimalisation of component count and its also supposed to be superior to a superhet in terms of audio bandwidth regards val33vo

28th Jun 2011, 7:45 am	#2
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,572	Re: regenerative reflex receiver How about posting a picture of the circuit so we can see whats going on. A picture paints a thousand words! SB __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

28th Jun 2011, 8:46 am	#3
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: regenerative reflex receiver I think some of those used two separate variable capacitors, One for Tuning and other for Reaction? A Superhet has what ever audio bandwidth you want depending on design of IF filter. A regenerative, super regen, syncrodyne, homodyne, direct conversion, Zero IF etc receiver has bandwidth set by filter on audio. Modern Ceramic and Crystal filters replace IF "coils" which can be less accurate in implementation of bandwidth and out of band rejection. You can use a "regen" as last IF amp and no diode detector. Then you will be able to receive weaker signals with less distortion if the background noise permits

28th Jun 2011, 12:20 pm	#4
AlanC Hexode Join Date: Jul 2006 Location: Sheffield, South Yorkshire, UK. Posts: 312	Re: regenerative reflex receiver As SB has said, it would be great to see the circuit. As a general rule of thumb, if you want two RF circuits to track (gang) accurately, the coils you use for both will need to be identical. It also helps to have the coils adjustable (which I guess the IFT will be) and also have trimmer caps in parallel so you can set the ganging at the LF and HF end of the range respectively. HTH Alan __________________ Always expect the unexpected...

28th Jun 2011, 4:13 pm	#6
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: Regenerative reflex receiver TRF definitely. TRF with some "regenerative" feedback and diode detector, yes. Super regen detector/amp? You could be right. Of course some alleged regenerative one transistor/valve receivers may be really "direct conversion". If it's actually oscillating, the Q is the Q of the coils (usually very broad) and then it becomes a direct conversion receiver, with ability to filter adjacent channel at audio baseband and no AM detector. A circuit diagram will end speculation

5th Jul 2011, 2:18 pm	#7
val33vo Retired Dormant Member Join Date: Apr 2008 Location: Banffshire, Scotland, UK. Posts: 191	Re: Regenerative reflex receiver Hi fellow enthusiasts I have not been able to post for a few days but find attached the circuit diag I have not used the original trannies as I dont like the unrealiabilty of germanium types instead I have used BC547,s with the bias resistors changed to take account of a 0.6v instead of 0.2v base emitter junction drop Attached Thumbnails

5th Jul 2011, 10:24 pm	#8
Guest Guest Posts: n/a	Re: Regenerative reflex receiver Built a few of those in my youth, the voltage doubling detector is ingenious. Shame I used things like Bush TR86's for the parts (20p at the most from the local auction). I don't think germainuim devices (except the AF117 series, but that wasn't germaniums fault) are inherently unreliable, my 50 year old Perdio still works and that is full of them. I know I am wrong but my heart says germainium is soft and gentle silicon hard an harsh, probably a sign of the time I was first learning all this (1960's 70's), before I upset anyone, valves are just brilliant!

7th Jul 2011, 3:01 pm	#9
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Regenerative reflex receiver There is no tracking adjustment, so tracking may be poor, but on strong AM local signals you might not notice. My guess is that ganging two tuned circuits in this way may create as many problems as it solves. You could be unlucky and get it oscillating at two different but nearby frequencies. The bias on Fig 2 probably won't need any change. Fig 1 might need a bigger resistor because of the high current gain of silicon BJT.

7th Jul 2011, 6:04 pm	#10
AlanC Hexode Join Date: Jul 2006 Location: Sheffield, South Yorkshire, UK. Posts: 312	Re: Regenerative reflex receiver I'm just trying to figure out what's going on around L2- is that neutralisation, or reaction? Ganging the tuned ccts will be the hardest thing to do; build them exactly like the instructions or else if you have another to hand, fit two separate tuning caps to investigate the tracking law. Good luck! Alan __________________ Always expect the unexpected...

7th Jul 2011, 9:38 pm	#11
G8HQP Dave Rest in Peace Join Date: Sep 2008 Location: Solihull, West Midlands, UK. Posts: 4,872	Re: Regenerative reflex receiver L2 is basically the second tuned circuit. It is coupled to the diode detector, and also provide feedback via the small trimmer cap. The collector goes to a tap for impedance matching reasons.