DIY valve radio kit - UK Vintage Radio Repair and Restoration Discussion Forum

brunel · 7th Jun 2011, 10:02 am

https://www.elektor.com/extra/valve-radio.1843103.lynkx

Peter.N. · 7th Jun 2011, 11:55 am

9v HT? or even 15v using all batteries, doesn't seem enough to drive a loudspeaker.

Peter

Sideband · 7th Jun 2011, 12:01 pm

The I.C drives the speaker.

SB

Herald1360 · 7th Jun 2011, 12:29 pm

Curious circuit..... I suppose a transistor and resistor must be cheaper than a double pole switch!

neon indicator · 7th Jun 2011, 3:48 pm

Elektor losing the plot?

Either have a 2N3819 fet as 1st stage or make it ENTIRELY with valves.

seems a bit pointless.

I'm designing some hybrid stuff with CPU, transistors and valves. But the point of the valves is to do something a bit tricky on transistors and play with Russian 1.2V miniature types.

Making piece of test gear that hopefully can survive accidently being connected to wrong point in circuit. I keep "blowing up" the input stages on various bits of test gear.

I might make an entirely valve radio and use IC to make HT rail and 1.2V heater from arbitrary 3V to 6V in. (Li Poly, 4 x AA, 5V USB charger etc...). But I can't really see the point of that Elektor design. It's really 15V HT and T1 seems a bit mad, only opens P1 from discharging 9V via op-amp. Without T1 the opamp has -9V across supply pins via 22K and T2 is reverse biased, might have a reverse Vbe Zener voltage of about 6V. So yes a double pole switch makes more sense. They need P1 as it's a Super-regen front end. Nasty things without an isolating RF preamp as the V1 with mis-adjustment of P1 off a station is an effective transmitter, especially with long wire aerial.

That's ONE reason they stopped making Super-regenerative receivers in favour of superhet.

Daft.

Loss of heater turns off V1

kalee20 · 7th Jun 2011, 5:28 pm

Quote:

Originally Posted by neon indicator

They need P1 as it's a Super-regen front end.

No, it's just a normal regenerative front-end, adjusted to below threshold of oscillation. While I'm sure it could be made to oscillate continuously (ouch!) by improper adjustment, I doubt quenched (super-regen) mode is possible.

The bit that raised my eyebrows is the grid leak R1 returned to anode! In the text it's described as the screen grid, but unless the circuit diagram is wrong, this is not correct. A bit worrying...

Like others, I'd have thought a FET would be better in this low-voltage circuit. But maybe they particularly wanted to use a valve. A bit like climbing Everest 'because it's there'. After all, why not?

Peter.N. · 7th Jun 2011, 5:36 pm

Sorry, didn't notice the short cut to the manual.

Peter

neon indicator · 7th Jun 2011, 7:00 pm

Well they could have at least had valve headphone amplifier too. As it it's it's plain silly.

davegsm82 · 7th Jun 2011, 7:18 pm

I think people may be missing the point.

Many readers of Elektor may have never experienced a Valve before in their life, that coupled with the fact we no longer live in the 1960's means you can't simply get inexperienced builders to throw together a valve set with a 350V HT line. Its simply not sane.

This is a nice sensible way of introducing builders to the theory of thermionic emission, which when it was first touted to me at the age of about 8 or 9 years, seemed like utter witchcraft. Electrons being fired through empty space at the speed of light? proposterous!

An ECC83 will give satisfactory output for headphones or a quiet speaker from about 18v (2x 9v obviously). This would have been a nice way to finish of the tail end of this circuit, but in all honestly you're getting the idea using just the 1 valve which is sufficient I think.

My £0.02

Dave.

Herald1360 · 7th Jun 2011, 10:43 pm

That sounds like common sense to me.

Quote:

Originally Posted by davegsm82

Electrons being fired through empty space at the speed of light? proposterous!

However, I do have to agree with the quoted statement, literally. It is impossible to fire electrons through empty space at the speed of light.

M0FYA Andy · 8th Jun 2011, 7:24 am

Accepting that 'many readers of Elektor may have never experienced a Valve before in their life', surely a better start would be a one-valve circuit using 90v battery HT of the type that I am sure many of us started with. Much more realistic than a strange muddle of old and new. I remember building receivers using a DF91 and then a 954 acorn at about the age of 10 in the early sivties. Yes, you can get a mild shock off a 90v battery (nowadays made up of 10 PP3s or whatever), that's lesson number 1, but you would have to work hard to do much harm.
Andy

Mullard · 8th Jun 2011, 9:23 am

I am sure a better radio could be made with a couple of DF96s with an IC power amp to run off 45V HT (5 PP3s). The price seems a little on the high side.

neon indicator · 8th Jun 2011, 12:08 pm

Yes, most Elektor readers won't have used valves.

But 2 or 3 x PP3s for HT (even with many 200+ HT valves), and a pure 2 valve radio with crystal earpiece or 3 valve with a small mains transformer ( a 10W one won't saturate with the DC current) as output transformer for 32 Ohm, 16 or 8Ohm speaker.

It's a shoddy worthless introduction to valves as it's not even a very typical valve circuit. With a suitable IC power amp and double pole switch the circuit could work without the silly transistor switch and preamp even if you just want the "fake" valve style radio with only one valve.

No what ever way you look at it, it's 1 out of 10 as a design, and 1 out of ten as a valve radio.

Plenty nice radios here
http://www.andreadrian.de/sdr/

davegsm82 · 8th Jun 2011, 12:33 pm

I'm not disagreeing that its a poor design, and that there are better introductions to the world of thermionics.

However I think you're missing the point, how many people these days want to sit and listen to a radio through a crumby, tinny crystal earpiece? or through a speaker at barely audible levels? No-one does. If I build a project its because at the end of the day it will work and have filled a gap, occasionally just for fun.

In this case the output of the 'set' will be audible, and although possibly unstable, it will work quite reliably.

I'm not sure how many of you work in industry etc, but nowadays, you aren't 'allowed' to work on any voltage more than 35 (or 50 depending on the standard your company follows) volts without proper training. Yes, health and safety has gone mad, but theres nothing you can do about it, do you really think a publication is going to advise you to build a potentially (although unlikely) deadly voltage source? No.

Its a sad fact that we have reached a point in time like this but for now, we simply have to accept it. 15V is safe, no lawsuits, not even for someone with a heart condition.

Dave.

kalee20 · 8th Jun 2011, 12:53 pm

Although I've not built it, I think it's probably a safe, easy introduction to valves. No high voltages, bomb-proof valve, not much to go wrong. And it'll glow in the dark!

A pair of DF96's would make a better radio. But with their 25mA filaments they are nearly as fragile as OC45's. A brief slip with even 9V of "HT" from a PP3 and it's curtains forever. They don't even light up unless you look carefully in pitch darkness! Whereas you'd have to try really hard to damage the mains valve.

The transistor switching of the 9V supply is interesting. It's silly from a pure design point of view, but if they had lots of single-pole switched potentiometers to use up, then it may be a slight cost saving.

As a radio design, it scores low marks. But as a kit to build for a beginner to valves, I'd be tempted to give it a nod of approval.

noble kiwi · 8th Jun 2011, 1:57 pm

As far as I am concerned it makes no sense. What does make sense can be found below and illustrates the first valve project I tackled along with many of my school mates.

Winding coils for short wave reception was not a problem and one could expand to the two valve version. The huge popularity of the simple design was due to expensive battery power not being involved. Modern versions are still being constructed.

HTML Code:

http://oldradios.co.nz/hikers/

For some reason I have been unable to record a hot address. What am I doing wrong when selecting the tags I wonder?

neon indicator · 8th Jun 2011, 2:27 pm

I think an ECC82 will work on 21V

umm, just paste a web link as is in your post and it works.

http://oldradios.co.nz/hikers/

kalee20 · 8th Jun 2011, 5:31 pm

Nice series of articles - thanks noble kiwi!

Sideband · 8th Jun 2011, 7:06 pm

Quote:

Originally Posted by davegsm82

I'm not sure how many of you work in industry etc, but nowadays, you aren't 'allowed' to work on any voltage more than 35 (or 50 depending on the standard your company follows) volts without proper training. Yes, health and safety has gone mad, but theres nothing you can do about it, do you really think a publication is going to advise you to build a potentially (although unlikely) deadly voltage source? No.

Its a sad fact that we have reached a point in time like this but for now, we simply have to accept it. 15V is safe, no lawsuits, not even for someone with a heart condition.

Dave.

Staggering how things have changed so much. My first really successful radio was a mains 3 valve TRF. That would have been in 1967 when I was 14 from a design published in Radio Constructor.....

Lets not stray off topic though......

SB

Heatercathodeshort · 10th Jun 2011, 8:00 pm

Quote:

Originally Posted by M0FYA Andy

I remember building receivers using a DF91 and then a 954 acorn at about the age of 10 in the early sivties.

Hello Andy,
This one http://www.youtube.com/watch?v=ehbqYw1jXd0 works very well at only 18v H.T. using a DF91 or DL92 valve. Most valves will work as reliable detectors down to very low levels of H.T. Another DF91 used as a headphone amplifier with maybe a little more H.T., would have been a better bet but at least it's an introduction to valve technique and any seed sown must be to our advantage. Regards, John.

7th Jun 2011, 10:02 am	#1
brunel Heptode Join Date: Sep 2005 Location: LEEDS.......North of the River Aire. Posts: 872	DIY valve radio kit https://www.elektor.com/extra/valve-radio.1843103.lynkx

7th Jun 2011, 11:55 am	#2
Peter.N. Dekatron Join Date: Jul 2008 Location: Charmouth, Dorset, UK. Posts: 3,601	Re: DIY valve radio kit 9v HT? or even 15v using all batteries, doesn't seem enough to drive a loudspeaker. Peter

7th Jun 2011, 12:01 pm	#3
Sideband Dekatron Join Date: Oct 2003 Location: Croydon, Surrey, UK. Posts: 7,571	Re: DIY valve radio kit The I.C drives the speaker. SB __________________ There are lots of brilliant keyboard players and then there is Rick Wakeman.....

7th Jun 2011, 12:29 pm	#4
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: DIY valve radio kit Curious circuit..... I suppose a transistor and resistor must be cheaper than a double pole switch! __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

7th Jun 2011, 3:48 pm	#5
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: DIY valve radio kit Elektor losing the plot? Either have a 2N3819 fet as 1st stage or make it ENTIRELY with valves. seems a bit pointless. I'm designing some hybrid stuff with CPU, transistors and valves. But the point of the valves is to do something a bit tricky on transistors and play with Russian 1.2V miniature types. Making piece of test gear that hopefully can survive accidently being connected to wrong point in circuit. I keep "blowing up" the input stages on various bits of test gear. I might make an entirely valve radio and use IC to make HT rail and 1.2V heater from arbitrary 3V to 6V in. (Li Poly, 4 x AA, 5V USB charger etc...). But I can't really see the point of that Elektor design. It's really 15V HT and T1 seems a bit mad, only opens P1 from discharging 9V via op-amp. Without T1 the opamp has -9V across supply pins via 22K and T2 is reverse biased, might have a reverse Vbe Zener voltage of about 6V. So yes a double pole switch makes more sense. They need P1 as it's a Super-regen front end. Nasty things without an isolating RF preamp as the V1 with mis-adjustment of P1 off a station is an effective transmitter, especially with long wire aerial. That's ONE reason they stopped making Super-regenerative receivers in favour of superhet. Daft. Loss of heater turns off V1 Last edited by neon indicator; 7th Jun 2011 at 3:59 pm.

7th Jun 2011, 5:36 pm	#7
Peter.N. Dekatron Join Date: Jul 2008 Location: Charmouth, Dorset, UK. Posts: 3,601	Re: DIY valve radio kit Sorry, didn't notice the short cut to the manual. Peter

7th Jun 2011, 7:00 pm	#8
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: DIY valve radio kit Well they could have at least had valve headphone amplifier too. As it it's it's plain silly.

7th Jun 2011, 7:18 pm	#9
davegsm82 Heptode Join Date: Jan 2004 Location: Blyth, Northumberland, UK. Posts: 858	Re: DIY valve radio kit I think people may be missing the point. Many readers of Elektor may have never experienced a Valve before in their life, that coupled with the fact we no longer live in the 1960's means you can't simply get inexperienced builders to throw together a valve set with a 350V HT line. Its simply not sane. This is a nice sensible way of introducing builders to the theory of thermionic emission, which when it was first touted to me at the age of about 8 or 9 years, seemed like utter witchcraft. Electrons being fired through empty space at the speed of light? proposterous! An ECC83 will give satisfactory output for headphones or a quiet speaker from about 18v (2x 9v obviously). This would have been a nice way to finish of the tail end of this circuit, but in all honestly you're getting the idea using just the 1 valve which is sufficient I think. My £0.02 Dave.

8th Jun 2011, 7:24 am	#11
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: DIY valve radio kit Accepting that 'many readers of Elektor may have never experienced a Valve before in their life', surely a better start would be a one-valve circuit using 90v battery HT of the type that I am sure many of us started with. Much more realistic than a strange muddle of old and new. I remember building receivers using a DF91 and then a 954 acorn at about the age of 10 in the early sivties. Yes, you can get a mild shock off a 90v battery (nowadays made up of 10 PP3s or whatever), that's lesson number 1, but you would have to work hard to do much harm. Andy

8th Jun 2011, 9:23 am	#12
Mullard Pentode Join Date: Jul 2007 Location: Clophill, Bedfordshire, UK. Posts: 127	Re: DIY valve radio kit I am sure a better radio could be made with a couple of DF96s with an IC power amp to run off 45V HT (5 PP3s). The price seems a little on the high side.

8th Jun 2011, 12:08 pm	#13
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: DIY valve radio kit Yes, most Elektor readers won't have used valves. But 2 or 3 x PP3s for HT (even with many 200+ HT valves), and a pure 2 valve radio with crystal earpiece or 3 valve with a small mains transformer ( a 10W one won't saturate with the DC current) as output transformer for 32 Ohm, 16 or 8Ohm speaker. It's a shoddy worthless introduction to valves as it's not even a very typical valve circuit. With a suitable IC power amp and double pole switch the circuit could work without the silly transistor switch and preamp even if you just want the "fake" valve style radio with only one valve. No what ever way you look at it, it's 1 out of 10 as a design, and 1 out of ten as a valve radio. Plenty nice radios here http://www.andreadrian.de/sdr/ Last edited by neon indicator; 8th Jun 2011 at 12:13 pm.

8th Jun 2011, 12:33 pm	#14
davegsm82 Heptode Join Date: Jan 2004 Location: Blyth, Northumberland, UK. Posts: 858	Re: DIY valve radio kit I'm not disagreeing that its a poor design, and that there are better introductions to the world of thermionics. However I think you're missing the point, how many people these days want to sit and listen to a radio through a crumby, tinny crystal earpiece? or through a speaker at barely audible levels? No-one does. If I build a project its because at the end of the day it will work and have filled a gap, occasionally just for fun. In this case the output of the 'set' will be audible, and although possibly unstable, it will work quite reliably. I'm not sure how many of you work in industry etc, but nowadays, you aren't 'allowed' to work on any voltage more than 35 (or 50 depending on the standard your company follows) volts without proper training. Yes, health and safety has gone mad, but theres nothing you can do about it, do you really think a publication is going to advise you to build a potentially (although unlikely) deadly voltage source? No. Its a sad fact that we have reached a point in time like this but for now, we simply have to accept it. 15V is safe, no lawsuits, not even for someone with a heart condition. Dave.

8th Jun 2011, 12:53 pm	#15
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,081	Re: DIY valve radio kit Although I've not built it, I think it's probably a safe, easy introduction to valves. No high voltages, bomb-proof valve, not much to go wrong. And it'll glow in the dark! A pair of DF96's would make a better radio. But with their 25mA filaments they are nearly as fragile as OC45's. A brief slip with even 9V of "HT" from a PP3 and it's curtains forever. They don't even light up unless you look carefully in pitch darkness! Whereas you'd have to try really hard to damage the mains valve. The transistor switching of the 9V supply is interesting. It's silly from a pure design point of view, but if they had lots of single-pole switched potentiometers to use up, then it may be a slight cost saving. As a radio design, it scores low marks. But as a kit to build for a beginner to valves, I'd be tempted to give it a nod of approval.

8th Jun 2011, 1:57 pm	#16
noble kiwi Pentode Join Date: Jan 2011 Location: Auckland New Zealand Posts: 175	Re: DIY valve radio kit As far as I am concerned it makes no sense. What does make sense can be found below and illustrates the first valve project I tackled along with many of my school mates. Winding coils for short wave reception was not a problem and one could expand to the two valve version. The huge popularity of the simple design was due to expensive battery power not being involved. Modern versions are still being constructed. HTML Code: http://oldradios.co.nz/hikers/ For some reason I have been unable to record a hot address. What am I doing wrong when selecting the tags I wonder? Last edited by noble kiwi; 8th Jun 2011 at 2:24 pm.

8th Jun 2011, 2:27 pm	#17
neon indicator Retired Dormant Member Join Date: Jun 2010 Location: Co. Limerick, Ireland. Posts: 1,183	Re: DIY valve radio kit I think an ECC82 will work on 21V umm, just paste a web link as is in your post and it works. http://oldradios.co.nz/hikers/

8th Jun 2011, 5:31 pm	#18
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,081	Re: DIY valve radio kit Nice series of articles - thanks noble kiwi!