Kudos on the video. Wonderful explanation of the kit. Then the schematics of the radio. Then an example of the sound. And finally a part explaining a very necessary part -- the Antenna... Just the way I like videos. The best part is NO background music !!!
13:40 Funny thing, you mentioned the receiver actually transmits too. This principle was used in the 50's to doctor out to which frequencies the Russians were listening inside their embassy. If you read Peter Wright's "Spy Catcher" there's a whole chapter about it. They codenamed it 'Rafter'
As far as I know the 12AU7 was not designed for 12V operation. Datasheets give operation at 100 and 250V. Operating the tube at these voltages you may get a lot more out of it. Ecc86 on the contrary was specifically design for 12V operation. It was use primarily in car radios. Tuning of a regenerative radio requires the use of both hands, one for the tuning control and one for the regeneration control. At first you increase regeneration until a light hiss is heard through the speaker and then you turn the tuning control. As the tuned frequency changes you may need to adjust regeneration accordingly. I have build 2 regenerative radios so far , one for the MW band and one for the SW band. I’m on the way to build another one that will be mobile. The tubes are the 2V/ 60mA filament types and the HT is 180V. A DC to DC converter will supply the HT.
Cripes, may have said 12AX7, I meant to say 12AU7. It's similar but the 'AU7 has less gain and lower output resistance. The 12AX7 is more popular in guitar amps and stuff because of it's high gain. However, the 12AX7 doesn't perform as well at low voltages because it distorts, but the 12AU7 works great; hence why it is in this radio.
Have you tried configuring 3x 12AU7 vacuum tubes in a Double Balanced Configuration like that of the SO42P so that you can convert the incoming RF to 455KC to feed a TRF second stage.
No, but that sounds like an interesting idea. My concern is that you probably wouldn't be able to make it regenerative without causing image frequency problems. The input of the regen amp may interact to some degree with the doubly-balanced mixer. It may be possible to make a reflex type design. Without regeneration, it might be hard to get enough gain to make it worthwhile. I imagine the selectivity at high frequencies would be better but the overall sensitivity would not compared to the regen radio, unless you had a really good RF amplifier. If you did manage to get some useful form of regeneration going after the conversion, I imagine it would be a very badass, very selective regen radio. I suppose the main issue with low voltage vacuum tubes is gain and noise. If you throw enough tubes at it, you can get better performance. However, it will also become complicated fast and the heater circuit would draw a lot of power.
@@thetuberoaster8321 The Double Balanced mixer created from the 3x 12AU7 tubes connected to be like the internal circuit of the SO42P would contain the Balanced mixer and the oscillator which would drive the TRF demodulation circuit via a Collins 455KC Mechanical Filter to give the wanted filtering, The TRF portion would demodulate and boost the signal to drive a set of 600R headphones or the line input of a HI-FI amplifier.
Not that I know of. The kit just comes with two really long alligator clips for ground and aerial. For the tuned coils, you can try to make your own with litz wire. In fact, the little booklet that comes with the radio briefly explains how to make antennas for other bands.
The feedback pot is the power switch as well as the gain setting. Every station requires a different feedback setting; I find myself moving it around a lot. A multi-turn pot would be accuracy I wouldn't really need. The thing that needs improvement is the tank circuit, specifically the variable capacitor. In the short wave band, keeping a station tuned is a real pain. You basically can't move since your hands have capacitance that affects it. As for 400 - 600MHz operation, I doubt the circuit would have enough gain at that frequency. The wiring would be very lossy at UHF and the 12AU7 is only good up to maybe 150MHz before the Miller effect knocks down all the gain. With short wires and a tube made for UHF, it might work.
After watching this, that I enjoyed greatly. I only have one question. Why are you not an Amateur Radio Operator holding an Extra class license? I hold a General class license. I bet you would Ace the test, and build your own transmitter/receiver rig. Thank you for the video.
I actually have a General class license since I took the test years ago. The way things came together I didn't have much time to study. A lot of the questions were not so much about theory but other technicalities like which power levels are legal where and such. That and I'm not usually a good test taker. I am considering building a proper HF or VHF transceiver one of these days.
It looks like it got discontinued. I imagine it would be hard to get now. I got mine over a decade ago. You might be better off searching on Ebay or rolling your own.
@@thetuberoaster8321 Hi and thanks. I didn't realize it was discontinued. I should have realized when you didn't have a link. I did find one on ebay for $160 which is more than I can spend right now but it does look like a nice place to start.
Hi, can you please tell me an approximate value of big coil inductance between endings(without center tap) Is it in mili Henry or lower like micro? Thank you.
@@thetuberoaster8321 thank you for quick response, I'll try to experiment with that value, but if you have any chance to measure it can you please do it? I'll much appreciate it. Thanks
@@maamon6407 Ok, I actually measured it with an LCR meter and got around 320uH. I miscalculated because I used the wrong frequency but the math does corroborate that.
You can, but it won't work as well as the 12AU7 at low voltage. The other problem is the anode resistor for the first triode would be too small. The feedback potentiometer is also too small and won't affect the gain enough. Basically, the circuit will work, but the gain will be much lower and not very useful. It will work better than the 12AX7 though.
@@utsavprakash It might work if you increase the anode resistor and potentiometer values in the first stage. Try increasing the pot to maybe 100K and the resistor to 47K. You may also need to increase the grid leak resistors from 100K to somewhere between 1M and 2M. If you are lucky, you might get more gain than with the 12AU7.
The "feedback" knob doesn't actually control the feedback it just controls the gain. The feedback is done by the cathode circuit and the feedback amount is constant. If this circuit had no feedback, all but the strongest radio signals would be inaudible. The cathode puts the same signal that arrives at the grid back at the tuning coil in phase to reinforce the input signal. This is known as positive feedback. Too much of it will drive the circuit into oscillation, hence the variable gain control. This radio puts the tap in the center of the coil, some designs put it further down to further prevent the antenna from loading the tank circuit.
Hi, my name is Fernando and I was a collector of old valves. And now I would like to get rid of my collection since it has been like 30 years. I managed to put together some 6000 valves including some very rare ones that are valued at € 400, they are all new and in their respective box. And I am willing to sell them for a very low price, I wanted to know if you are interested, I wait for an answer, thank you.
Very true, although a lot of battery powered tubes are directly heated and probably have a higher perveance. Having said that, the 12AX7 might actually work okay at only 45V and maybe even 22.5V. I've found that there's usually a certain voltage below which the tube just doesn't work very good anymore. Above that, grid leak biasing seems to work fine.
I meant to say battery powered tubes typically use just 45V on the plate supply. My regen radio, which I built from a kit I acquired from ANTIQUE ELECTRONIC'S SUPPLY three decades ago, is a 1G4G
That distortion you get could be cause of a few wrong value parts, The first resistor of 100k is too low! It´s value is not that critical but should be at least 1M or 2m or 3m or more!.your regenarative control of 47k would be better around 100k. the second 100k resistor around 1M too.and some caps in the antenna connection of different values. There is a great video of modification that improves the radio alot.and shows you the modify parts. ua-cam.com/video/2jT6Xass7QU/v-deo.html
The design of this circuit has raised an eyebrow or two for me from time to time. I thought the component values were chosen to optimize the circuit for 12V operation. Of course it doesn't make any sense to me that the grid leak resistor would be any lower than a couple megohms. Thanks for the vid, this circuit makes way more sense now.
Kudos on the video. Wonderful explanation of the kit. Then the schematics of the radio. Then an example of the sound. And finally a part explaining a very necessary part -- the Antenna... Just the way I like videos. The best part is NO background music !!!
6:00 This is a Hartley-style regeneration circuit, not an Armstrong Regeneration. This crkt uses a tapped inductance and not a tickler coil
1:04 Vacuum tubes for battery powered sets typically run on 45V and not "300V"
13:40 Funny thing, you mentioned the receiver actually transmits too. This principle was used in the 50's to doctor out to which frequencies the Russians were listening inside their embassy. If you read Peter Wright's "Spy Catcher" there's a whole chapter about it. They codenamed it 'Rafter'
Please tell me more!
@@JohnSmith-eo5sp You'll have to read the book ;)
Glasslinger used a variable capacitor coming in from the antennae other than the tank. Makes her own tubes also.
Interesting and knowledgeable. Thank you
As far as I know the 12AU7 was not designed for 12V operation. Datasheets give operation at 100 and 250V. Operating the tube at these voltages you may get a lot more out of it. Ecc86 on the contrary was specifically design for 12V operation. It was use primarily in car radios.
Tuning of a regenerative radio requires the use of both hands, one for the tuning control and one for the regeneration control. At first you increase regeneration until a light hiss is heard through the speaker and then you turn the tuning control. As the tuned frequency changes you may need to adjust regeneration accordingly.
I have build 2 regenerative radios so far , one for the MW band and one for the SW band. I’m on the way to build another one that will be mobile. The tubes are the 2V/ 60mA filament types and the HT is 180V. A DC to DC converter will supply the HT.
We used to called Vacuum Tubes in the UK-'Valves'. The UK and The USA: Two Nations-Divided By a Common Language.
CUTE
A well made video and thanks for the information. As my name is Ace, I'm going to have to make and Ace Radio!
Fascinating video!
AM radio doesn't give high fidelity - it isn't meant to, due to the audio cutoff on that type of modulation at about 9 or 10 kHz.
The 12AX7 is a legend. theres 2 of them in my KORG Electribe
Cripes, may have said 12AX7, I meant to say 12AU7. It's similar but the 'AU7 has less gain and lower output resistance. The 12AX7 is more popular in guitar amps and stuff because of it's high gain. However, the 12AX7 doesn't perform as well at low voltages because it distorts, but the 12AU7 works great; hence why it is in this radio.
أهلا وسهلا بك مشكور .
Have you tried configuring 3x 12AU7 vacuum tubes in a Double Balanced Configuration like that of the SO42P so that you can convert the incoming RF to 455KC to feed a TRF second stage.
No, but that sounds like an interesting idea. My concern is that you probably wouldn't be able to make it regenerative without causing image frequency problems. The input of the regen amp may interact to some degree with the doubly-balanced mixer. It may be possible to make a reflex type design. Without regeneration, it might be hard to get enough gain to make it worthwhile. I imagine the selectivity at high frequencies would be better but the overall sensitivity would not compared to the regen radio, unless you had a really good RF amplifier. If you did manage to get some useful form of regeneration going after the conversion, I imagine it would be a very badass, very selective regen radio. I suppose the main issue with low voltage vacuum tubes is gain and noise. If you throw enough tubes at it, you can get better performance. However, it will also become complicated fast and the heater circuit would draw a lot of power.
@@thetuberoaster8321 The Double Balanced mixer created from the 3x 12AU7 tubes connected to be like the internal circuit of the SO42P would contain the Balanced mixer and the oscillator which would drive the TRF demodulation circuit via a Collins 455KC Mechanical Filter to give the wanted filtering, The TRF portion would demodulate and boost the signal to drive a set of 600R headphones or the line input of a HI-FI amplifier.
Are there 3rd party antennas built for this? This looks really interesting. I found one on Ebay still new that I hope I can snag.
Not that I know of. The kit just comes with two really long alligator clips for ground and aerial. For the tuned coils, you can try to make your own with litz wire. In fact, the little booklet that comes with the radio briefly explains how to make antennas for other bands.
What about replacing that feedback pot with a 20 turn 1M0 pot, what about a hair pin coil with a center tap for 400-800mhz
The feedback pot is the power switch as well as the gain setting. Every station requires a different feedback setting; I find myself moving it around a lot. A multi-turn pot would be accuracy I wouldn't really need. The thing that needs improvement is the tank circuit, specifically the variable capacitor. In the short wave band, keeping a station tuned is a real pain. You basically can't move since your hands have capacitance that affects it. As for 400 - 600MHz operation, I doubt the circuit would have enough gain at that frequency. The wiring would be very lossy at UHF and the 12AU7 is only good up to maybe 150MHz before the Miller effect knocks down all the gain. With short wires and a tube made for UHF, it might work.
Very good
After watching this, that I enjoyed greatly. I only have one question.
Why are you not an Amateur Radio Operator holding an Extra class license? I hold a General class license. I bet you would Ace the test, and build your own transmitter/receiver rig. Thank you for the video.
I actually have a General class license since I took the test years ago. The way things came together I didn't have much time to study. A lot of the questions were not so much about theory but other technicalities like which power levels are legal where and such. That and I'm not usually a good test taker.
I am considering building a proper HF or VHF transceiver one of these days.
Is this kit still available? I wish you had supplied a link.
It looks like it got discontinued. I imagine it would be hard to get now. I got mine over a decade ago. You might be better off searching on Ebay or rolling your own.
@@thetuberoaster8321 Hi and thanks. I didn't realize it was discontinued. I should have realized when you didn't have a link. I did find one on ebay for $160 which is more than I can spend right now but it does look like a nice place to start.
Hi, can you please tell me an approximate value of big coil inductance between endings(without center tap) Is it in mili Henry or lower like micro? Thank you.
I don't have the radio with me so I can't be sure, but its got to be something like 27 microhenries.
@@thetuberoaster8321 thank you for quick response, I'll try to experiment with that value, but if you have any chance to measure it can you please do it? I'll much appreciate it. Thanks
@@maamon6407 Ok, I actually measured it with an LCR meter and got around 320uH. I miscalculated because I used the wrong frequency but the math does corroborate that.
@@thetuberoaster8321 Thank you for that😎🍺
Can we use 12AT7 instead of 12AU7?
You can, but it won't work as well as the 12AU7 at low voltage. The other problem is the anode resistor for the first triode would be too small. The feedback potentiometer is also too small and won't affect the gain enough. Basically, the circuit will work, but the gain will be much lower and not very useful. It will work better than the 12AX7 though.
@@thetuberoaster8321 What if I provide more than 40 V, I am asking this because I own a 12AT7 tube. 12AU7 is not available.
@@utsavprakash It might work if you increase the anode resistor and potentiometer values in the first stage. Try increasing the pot to maybe 100K and the resistor to 47K. You may also need to increase the grid leak resistors from 100K to somewhere between 1M and 2M. If you are lucky, you might get more gain than with the 12AU7.
2:45 There is no feedback, that is a volume control that connects to the anode of the first tube. There is no regeneration!
The "feedback" knob doesn't actually control the feedback it just controls the gain. The feedback is done by the cathode circuit and the feedback amount is constant. If this circuit had no feedback, all but the strongest radio signals would be inaudible. The cathode puts the same signal that arrives at the grid back at the tuning coil in phase to reinforce the input signal. This is known as positive feedback. Too much of it will drive the circuit into oscillation, hence the variable gain control. This radio puts the tap in the center of the coil, some designs put it further down to further prevent the antenna from loading the tank circuit.
Hi, my name is Fernando and I was a collector of old valves. And now I would like to get rid of my collection since it has been like 30 years. I managed to put together some 6000 valves including some very rare ones that are valued at € 400, they are all new and in their respective box. And I am willing to sell them for a very low price, I wanted to know if you are interested, I wait for an answer, thank you.
1:41 The typical battey powered tube runs on just 45V
Very true, although a lot of battery powered tubes are directly heated and probably have a higher perveance. Having said that, the 12AX7 might actually work okay at only 45V and maybe even 22.5V. I've found that there's usually a certain voltage below which the tube just doesn't work very good anymore. Above that, grid leak biasing seems to work fine.
I meant to say battery powered tubes typically use just 45V on the plate supply. My regen radio, which I built from a kit I acquired from ANTIQUE ELECTRONIC'S SUPPLY three decades ago, is a 1G4G
@@thetuberoaster8321 Yes, using lower voltages extends the range of regeneration but lowers the over volume
That distortion you get could be cause of a few wrong value parts, The first resistor of 100k is too low! It´s value is not that critical but should be at least 1M or 2m or 3m or more!.your regenarative control of 47k would be better around 100k. the second 100k resistor around 1M too.and some caps in the antenna connection of different values.
There is a great video of modification that improves the radio alot.and shows you the modify parts.
ua-cam.com/video/2jT6Xass7QU/v-deo.html
The design of this circuit has raised an eyebrow or two for me from time to time. I thought the component values were chosen to optimize the circuit for 12V operation. Of course it doesn't make any sense to me that the grid leak resistor would be any lower than a couple megohms. Thanks for the vid, this circuit makes way more sense now.