Super regen for mw - UK Vintage Radio Repair and Restoration Discussion Forum

boiss · 16th May 2012, 8:37 pm

In a superegen for mw what is best a triode or a pentode for the input stage. Pentode for RF and Detector and Triode for Audio PA?
boiss

boiss · 16th May 2012, 10:10 pm

Sorry Guys and Gals, Changed my mind, need a circuit for Superhet RX using
pentodes, Audio O/P stage not important but up to Audio O/P stage must only use 3 pentode bottles.
Boiss

Herald1360 · 17th May 2012, 12:33 am

Well since it sounds like one will have to be the local oscillator, maybe you could reflex the IF to do duty as 1st AF, or perhaps have a fixed frequency regenerative detector stage instead. Otherwise you will need a high gain output stage.

Of course if you're just using it as a tuner to feed a separate amplifier, then a conventional circuit (apart from the pentode LO and mixer) would be fine, though a solid state diode will be needed for detection / agc.

Feb 1960 Practical wireless gave a circuit for a complete radio using five 6k7 pentodes. The mixer and IF stages of this sound like what you might want.

boiss · 25th May 2012, 10:15 pm

Herald,
those were some interesting ways to go, Had another thought, I seem to remember some solid state direct conversion Rxs being touted some time back, was wondering if anyone had seen a valved set using direct conversion.
B

Radio Wrangler · 25th May 2012, 11:43 pm

Yes, but I can't remember where. It used an ECC81 in an emitter-coupled push-pull oscillator driving the deflection electrodes of a 7360 beam-deflection valve as a mixer, then an ECC82 as a balanced-to unbalanced audio amplifier.

As a Direct Conversion receiver it's not suitable for AM demod unless you phase lock it to the incoming signal. SSB and CW are its forte.

For AM a superhet is easier. If you want to stay thermionic, there are a lot of detectors/AGC built with 6H6 or 6AL5 double diodes. (A double diode works wonders! to nobble an old advert.)

The standard recipe for a solid state DC RX was to use an oscillator and buffer to provide +7dBm drive into an MD108 or equivalent diode ring mixer, then discrete bipolar audio amp (An NE5534 opamp would also be good here)

David

Herald1360 · 25th May 2012, 11:46 pm

There's an example here:

http://i199.photobucket.com/albums/a...matic_6ME8.png

Look up homodyne or synchrodyne or just direct conversion receiver in Google or W.H.Y. You'll have to sift a bit for valve (tube) stuff.

boiss · 3rd Jun 2012, 4:47 pm

Hi Herald,
That looks like a nightmare to set up !!!
I thought that for direct conversion, the LO works at the received frequency
the "IF" being an audio amp with a BW of about 5KHz. The advantage would be that there would not be a tracking error between the front end tuning and the LO freq. I have no problem with an IC filter/audio amp, I seem to remember one that used the ferrite core of a TV LOPT but I don't remember where. I don't want to use more than 4 valves (3 x Beam Tetrodes and a Triode) which I have, and only these are to be seen!
B

boiss · 3rd Jun 2012, 5:49 pm

Ok, have found a LPF circuit (IC) for 5KHz and 8KHz with a 20dB roll off, I have an MD108 that I reckon I can use as the mixer, The LO bottle will have to run at a very low level to avoid injection into the RF stage. This may be rather hard to acheive elegantly due to the visibility of the valves and RF tuning coil(s). Valved line-up will be RF amp,LO,AF pre and AF O/P.
B

16th May 2012, 8:37 pm	#1
boiss Pentode Join Date: Jun 2006 Location: Malaga, Spain. Posts: 235	Super regen for mw In a superegen for mw what is best a triode or a pentode for the input stage. Pentode for RF and Detector and Triode for Audio PA? boiss

16th May 2012, 10:10 pm	#2
boiss Pentode Join Date: Jun 2006 Location: Malaga, Spain. Posts: 235	Re: Superegen for mw Sorry Guys and Gals, Changed my mind, need a circuit for Superhet RX using pentodes, Audio O/P stage not important but up to Audio O/P stage must only use 3 pentode bottles. Boiss

17th May 2012, 12:33 am	#3
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Superegen for mw Well since it sounds like one will have to be the local oscillator, maybe you could reflex the IF to do duty as 1st AF, or perhaps have a fixed frequency regenerative detector stage instead. Otherwise you will need a high gain output stage. Of course if you're just using it as a tuner to feed a separate amplifier, then a conventional circuit (apart from the pentode LO and mixer) would be fine, though a solid state diode will be needed for detection / agc. Feb 1960 Practical wireless gave a circuit for a complete radio using five 6k7 pentodes. The mixer and IF stages of this sound like what you might want. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

25th May 2012, 10:15 pm	#4
boiss Pentode Join Date: Jun 2006 Location: Malaga, Spain. Posts: 235	Re: Superegen for mw Herald, those were some interesting ways to go, Had another thought, I seem to remember some solid state direct conversion Rxs being touted some time back, was wondering if anyone had seen a valved set using direct conversion. B

25th May 2012, 11:43 pm	#5
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,874	Re: Superegen for mw Yes, but I can't remember where. It used an ECC81 in an emitter-coupled push-pull oscillator driving the deflection electrodes of a 7360 beam-deflection valve as a mixer, then an ECC82 as a balanced-to unbalanced audio amplifier. As a Direct Conversion receiver it's not suitable for AM demod unless you phase lock it to the incoming signal. SSB and CW are its forte. For AM a superhet is easier. If you want to stay thermionic, there are a lot of detectors/AGC built with 6H6 or 6AL5 double diodes. (A double diode works wonders! to nobble an old advert.) The standard recipe for a solid state DC RX was to use an oscillator and buffer to provide +7dBm drive into an MD108 or equivalent diode ring mixer, then discrete bipolar audio amp (An NE5534 opamp would also be good here) David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

25th May 2012, 11:46 pm	#6
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Superegen for mw There's an example here: http://i199.photobucket.com/albums/a...matic_6ME8.png Look up homodyne or synchrodyne or just direct conversion receiver in Google or W.H.Y. You'll have to sift a bit for valve (tube) stuff. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

3rd Jun 2012, 4:47 pm	#7
boiss Pentode Join Date: Jun 2006 Location: Malaga, Spain. Posts: 235	Re: Superegen for mw Hi Herald, That looks like a nightmare to set up !!! I thought that for direct conversion, the LO works at the received frequency the "IF" being an audio amp with a BW of about 5KHz. The advantage would be that there would not be a tracking error between the front end tuning and the LO freq. I have no problem with an IC filter/audio amp, I seem to remember one that used the ferrite core of a TV LOPT but I don't remember where. I don't want to use more than 4 valves (3 x Beam Tetrodes and a Triode) which I have, and only these are to be seen! B

3rd Jun 2012, 5:49 pm	#8
boiss Pentode Join Date: Jun 2006 Location: Malaga, Spain. Posts: 235	Re: Superegen for mw Ok, have found a LPF circuit (IC) for 5KHz and 8KHz with a 20dB roll off, I have an MD108 that I reckon I can use as the mixer, The LO bottle will have to run at a very low level to avoid injection into the RF stage. This may be rather hard to acheive elegantly due to the visibility of the valves and RF tuning coil(s). Valved line-up will be RF amp,LO,AF pre and AF O/P. B