the coil with a ferrite is also used in car radios in the 60's. I am a luky owner of a couple of those. The construction reminds me many radios and morse oscillators that i've built when i was a kid. Thank you very much for sharing this. big thumb up for you!. (Trivia: My brother, 10 years older, had received the Philips Electronics EE20. I was more curious than him. That toy and an old Argentine magazine, Lupin, made me the engineer I am today. Thank you very much to all people who love electronics)
Thanks Ivan, yes I thought and worked that setup out and what you say is indeed the right thing. The potentiometer of 1K must be set to its middle position to get all the biases right, both for the mixer (kind of bad word, it is a frequency transformation transistor circuit) and the HF stage with that BF 256 A, with the antenna coil connected to its Gate.
It is (very) primitive, though it works quite good to receive SW radio stations, especially the normal broadcast stations between (say) 6 and 8 MC. Thanks.
Really cool best shortwave radio what awesome way you built on top of a wooden board and also mentioned that this type of radio technology was used during world war 2
Thanks & yes, I have one WW2 "portable" (=4 or 5 kg) radio that was used during the invasion at Normandy 6 june 1944. It had 3 tunable coils in the Shortwave band around 4-5 MC (or somewhat higher, I have to test that again, don't pin me on the exact frequency) thus 1 tunable coil for the antenna circuit, 1 tunable coil for the Local Oscillator and 1 tunable coil for another purpose. All had to be set manually, by moving a ferrite core up/down to get these 3 units (HF amp & Local oscillator and the other amp) to the right frequency band. There is one video on my YT channel about this WW2 radio. I will try to find it and give the link, thanks again. 1 March 2023.
Thank you for your video. Do you have make a You Tube video on making the ferrite rod tuning system of the oscillator? The fine tuning of the shortwave oscillator seems interesting method to vary the frequency.
There are a few video's about my experiments with that setup on my YT channel. You can search on "slug tuning" via the looking glass search option on my channel trailer ("Radiofun232 on You Tube"). It is indeed a good way of tuning though everything must be mechanical stable. 2 March 2023.
In this circuit diagram I see that you connect the output of the local oscillator to the collector of the mixer BJT. How can this BJT indeed function as a mixer in this case? A BJT mixer stage has the RF input on its base and the LO input on its emitter, or on its base.
Thanks SV3IRG, and yes it is usable and stable enough to receive the normal broadcast AM radio stations with a bandwidth of 5-8 KC. Of course the circuit can be made more stable, like you know, with a crystal stabilized LO (or a VXO). Thanks, Ko Tilman, member of the VRZA, radio society in the Netherlands. This is more or less a SW radio circuit to show how easy it is to make an (extremely simple with only one 455 ceramic filter) SW radio. It is made to supply radio amateurs at the beginning of their carriere and/or for everyone interested in a simple working SW radio circuit. Thanks again. 1 March 2023.
I think it is possible, but did not test it. The BFO (with the right amplitude) could be injected via a small cap. in the transistor that precedes the IF filter. Thanks. 6 March 2024.
Hi! What is the modern through-hole equivalent or substitute part of the RF transistor BF199? That applies also for the RF transistors of BF494 or BF495. They were used on the RF circuits of hobbyists 40 years ago.
Yes, and also in analog TV sets of those days. Every HF bipolar transistor (here NPN) can be used. There are 2 important things: the max. high frequency that it can reach and where there the transistor is no longer amplifying (=down to 1 x) (= the transition frequency, it is in the datasheet, say 200 MC or 300 MC) and the amplification factor (say: Hfe). The Hfe (I mean the DC amplification) must be (minimal) 70 to make HF radio circuits work. 2 March. 2023.
@@radiofun232 OK. I am obliged for the piece of information of the transition frequency and the amplification factor. BF199 transistor could still be purchased for example from the online shop of Reichelt from Germany or from eBay.
Hi Faisal Abbas, everything that I could tell regarding your project (AM radio 800 KC-1.6 MC) was in our mail conversation during the past months. Study the schematics, photo's, and everything that I have sent you. Best regards, 8 March 2023.
I estimate the antenna coil to be approximately 6,7 microhenrys isn't it ? With a capacitor of 5 picofarads that give a resonant fréquency about 27 Mhertz and 8,7 Mhertz with 50 picofarads
I tested it today. My inductance meter gives only a coarse indication (I test on resonance via an oscillator and a frequency counter). I measured 10 Micro Henry.
Sir, you are a genious 😅
the coil with a ferrite is also used in car radios in the 60's. I am a luky owner of a couple of those. The construction reminds me many radios and morse oscillators that i've built when i was a kid. Thank you very much for sharing this. big thumb up for you!.
(Trivia: My brother, 10 years older, had received the Philips Electronics EE20. I was more curious than him. That toy and an old Argentine magazine, Lupin, made me the engineer I am today. Thank you very much to all people who love electronics)
You are welcome, glad to hear it and thanks for your valuable comment.
That's neat using the potentiometer to optimize the working point of both the bipolar mixer and FET RF amplifier at the same time
Thanks Ivan, yes I thought and worked that setup out and what you say is indeed the right thing. The potentiometer of 1K must be set to its middle position to get all the biases right, both for the mixer (kind of bad word, it is a frequency transformation transistor circuit) and the HF stage with that BF 256 A, with the antenna coil connected to its Gate.
Building one of these myself has been one of my biggest dreams.
It is (very) primitive, though it works quite good to receive SW radio stations, especially the normal broadcast stations between (say) 6 and 8 MC. Thanks.
Really cool best shortwave radio what awesome way you built on top of a wooden board and also mentioned that this type of radio technology was used during world war 2
Thanks & yes, I have one WW2 "portable" (=4 or 5 kg) radio that was used during the invasion at Normandy 6 june 1944. It had 3 tunable coils in the Shortwave band around 4-5 MC (or somewhat higher, I have to test that again, don't pin me on the exact frequency) thus 1 tunable coil for the antenna circuit, 1 tunable coil for the Local Oscillator and 1 tunable coil for another purpose. All had to be set manually, by moving a ferrite core up/down to get these 3 units (HF amp & Local oscillator and the other amp) to the right frequency band. There is one video on my YT channel about this WW2 radio. I will try to find it and give the link, thanks again. 1 March 2023.
Here is the video about the (so called portable) WW2 radio of the American radio corps in the 1940's
ua-cam.com/video/bibrYCtmmjc/v-deo.html
Thank you for your video. Do you have make a You Tube video on making the ferrite rod tuning system of the oscillator? The fine tuning of the shortwave oscillator seems interesting method to vary the frequency.
There are a few video's about my experiments with that setup on my YT channel. You can search on "slug tuning" via the looking glass search option on my channel trailer ("Radiofun232 on You Tube"). It is indeed a good way of tuning though everything must be mechanical stable. 2 March 2023.
@@radiofun232 Good. I shall look for the videos of slug tuning. Thank you!
The slug tuning resembles the idea of tuning of ferrite rod inside a coil for example on a crystal radio.
In this circuit diagram I see that you connect the output of the local oscillator to the collector of the mixer BJT. How can this BJT indeed function as a mixer in this case? A BJT mixer stage has the RF input on its base and the LO input on its emitter, or on its base.
Yes, true, a strange (uncommon) connection. But it worked best that way, I also tested the standard options to mix the LO in. Thanks for your comment.
Nice audio quality also stable rx Ko...73
Thanks SV3IRG, and yes it is usable and stable enough to receive the normal broadcast AM radio stations with a bandwidth of 5-8 KC. Of course the circuit can be made more stable, like you know, with a crystal stabilized LO (or a VXO). Thanks, Ko Tilman, member of the VRZA, radio society in the Netherlands. This is more or less a SW radio circuit to show how easy it is to make an (extremely simple with only one 455 ceramic filter) SW radio. It is made to supply radio amateurs at the beginning of their carriere and/or for everyone interested in a simple working SW radio circuit. Thanks again.
1 March 2023.
@@radiofun232 tnx for infos Ko 73
Interesting. Wanting to use it for ham radio ranges, is it possible to connect a BFO?
I think it is possible, but did not test it. The BFO (with the right amplitude) could be injected via a small cap. in the transistor that precedes the IF filter. Thanks. 6 March 2024.
@@radiofun232 Thank you.
Hi! What is the modern through-hole equivalent or substitute part of the RF transistor BF199? That applies also for the RF transistors of BF494 or BF495. They were used on the RF circuits of hobbyists 40 years ago.
Yes, and also in analog TV sets of those days. Every HF bipolar transistor (here NPN) can be used. There are 2 important things: the max. high frequency that it can reach and where there the transistor is no longer amplifying (=down to 1 x) (= the transition frequency, it is in the datasheet, say 200 MC or 300 MC) and the amplification factor (say: Hfe). The Hfe (I mean the DC amplification) must be (minimal) 70 to make HF radio circuits work. 2 March. 2023.
@@radiofun232 OK. I am obliged for the piece of information of the transition frequency and the amplification factor. BF199 transistor could still be purchased for example from the online shop of Reichelt from Germany or from eBay.
Sir, I have a request to install medium wave 530khz and 1650khz coils to this local oscillator and mixer
Hi Faisal Abbas, everything that I could tell regarding your project (AM radio 800 KC-1.6 MC) was in our mail conversation during the past months. Study the schematics, photo's, and everything that I have sent you. Best regards, 8 March 2023.
I estimate the antenna coil to be approximately 6,7 microhenrys isn't it ?
With a capacitor of 5 picofarads that give a resonant fréquency about 27 Mhertz
and 8,7 Mhertz with 50 picofarads
I will test it. But I think that is the right range.
I tested it today. My inductance meter gives only a coarse indication (I test on resonance via an oscillator and a frequency counter). I measured 10 Micro Henry.
variable frequency oscillator and a local oscillator are the same thing
yes