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[Sticky] Project: VRAT Minimalist Superhet Radio.

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Till Eulenspiegel
(@till)
Famed V-Ratter Registered

Here's a simple radio that might be fun to consruct. It's the Italian "Ninnolo" radio set. Only two valves are employed, an UCH81 frequency changer and an ECL80. An OA72? crystal diode is the detector. the set has no IF amplifier stage so I've no idea what the performance would be like.
A better arrangement I think would employ the triode section as a leaky grid detector with pre-set reaction, rather like the Sobellette. An alternative would be the anode bend detector which would not damp the tuned circuits. A triode-pentode with separate cathodes would be necessary for such a circuit.
Anyone fancy building a similar set?

Till Eulenspiegel.

 

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Topic starter Posted : 20/09/2013 8:22 pm
turretslug
(@turretslug)
Honorable V-Ratter Registered

I recall a posting on UKVRR regarding a Telefunken(?) set with a UCH11, UCL11 and UY11 (IIRC) that apparently worked well considering.

I think whoever drafted the Ninnolo circuit was confused as to which way round these new-fangled solid-state diode thingies should be drawn...

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Posted : 20/09/2013 8:55 pm
Anonymous
(@anonymous)
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strange as they got the detector right
Rob T

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Posted : 20/09/2013 8:59 pm
Anonymous
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There is a German two valve superhet.

There is an Ever Ready with no IF amp as such, but IF regeneration on detector. Perhaps three valves, but multiple valves in one tube only appears minimalistic. It's not on a schematic! :)

If you use a solid diode you can make a superhet with just two pentodes. One as self-oscillating mixer and one as audio amp. It can even work on VHF-FM via slope detection.

Double tuned IF Transformer on Mixer/Osc Anode driving 1N34 or 1N60 with 2M pot as load / volume control to output pentode. Use reed speaker made from 3600 Ohm telephone bell. GE had a transistor radio made in Shannon with Reed speaker.

See near bottom
http://oldradio.tesla.hu/szetszedtem/34 ... egiseg.htm

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Posted : 20/09/2013 9:00 pm
Anonymous
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strange as they got the detector right
Rob T

Indeed.

Also the "diode" symbol pre-dates valves! The point represents the cat's whisker point and the bar the substrate!

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Posted : 20/09/2013 9:02 pm
sideband
(@sideband)
Famed V-Ratter Moderator

I think there was a 'Champion' model set that used a similar circuit. It would be fun to build something like that. It can only be considered as a local station set as all the gain is normally in the IF stage. Probably slightly better than a TRF. Interesting....I might give it a go during the dark nights that will be upon us soon, just for fun. I think I'll put the rectifiers the right way round though...! Bit odd using a UCH81 and an ECL80. If I go ahead, I'll use an ECH81.

There was another radio I was going to build using a circuit from TV mag some years ago. It's built using TV valves with push-pull ECL80 for output.

Rich.

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Posted : 20/09/2013 9:25 pm
crustytv
(@crustytv)
Vrat Founder Admin

Why don't you guys run a VRAT online winter project club. It would be good for the Radio newb's and for those that wish to play along too.

It goes like this.......

    • We have two or three mentors, maybe more.
    • A design is agreed by the mentor team
    • A parts list is provided
    • A basic schematic is drawn
    • Those interested express so in the thread.
    • Gather the parts time
    • Once everyone has all that is required a start date needs to be agreed.

Once/twice a week throughout the winter months the mentors start building and providing photo's as they go. The play along gang, in their shops at home follow and post their progress likewise. Help and advice provided by the mentor team if anyone in the gang gets into difficulty.

Then when you get to the stage of running up, the mentors assist with fault finding etc.

Just a thought.

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Posted : 20/09/2013 9:31 pm
Till Eulenspiegel
(@till)
Famed V-Ratter Registered

Hi Chris,
that's a very good idea. something on the lines of the 1950s Practical Wireless Beginners Constructional course. You start off with a basic TRF one valve receiver and over time add an output stage and later on an RF amplifier.
In the PW article the chosen valves were SP61/VR65As which in those times you could buy for two shillings and sixpence. Nowadays you could use the EF80 or any other general purpose pentode, e g, 6K7, 6J7 etc.

Till Eulenspiegel.

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Topic starter Posted : 20/09/2013 10:15 pm
turretslug
(@turretslug)
Honorable V-Ratter Registered

Circuit as shown will give increasing +ve bias on UCH g1 as signal strength increases- needs to be increasing -ve for appropriate AGC sense.

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Posted : 20/09/2013 10:18 pm
Till Eulenspiegel
(@till)
Famed V-Ratter Registered

Circuit as shown will give increasing +ve bias on UCH g1 as signal strength increases- needs to be increasing -ve for appropriate AGC sense.

The circuit is certainly drawn incorrectly. Just how effective will the AVC be? After all the frequency changer will not contribute much gain.

Till Eulenspiegel.

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Topic starter Posted : 20/09/2013 10:30 pm
Till Eulenspiegel
(@till)
Famed V-Ratter Registered

What a good idea :bba Building things is magic, I still like knocking up little projects and its what you learn from.
I'm happy to help :aad

Count me in. All construction projects should be encouraged. It's almost thirty years since I made something interesting, the standards converter. Although if you think about, I rebuilt it over the winter months. December 2012 to January this year.

Till Eulenspiegel.

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Topic starter Posted : 20/09/2013 10:35 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

Two valves with FM, anybody?

http://www.radiomuseum.org/r/schaub_pirol_56gwu.html

Mind you, it's only a superhet on FM....

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Posted : 20/09/2013 11:01 pm
Anonymous
(@anonymous)
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That's the German one I was thinking of.
Of course while 2 tubes, it's really 4 valves. :)

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Posted : 21/09/2013 12:26 am
Stitch
(@stitch)
Reputable V-Ratter Registered

What a good idea :bba Building things is magic, I still like knocking up little projects and its what you learn from.
I'm happy to help :aad

Count me in. All construction projects should be encouraged. It's almost thirty years since I made something interesting, the standards converter. Although if you think about, I rebuilt it over the winter months. December 2012 to January this year.

Till Eulenspiegel.

Just reading this and thought id like to have a go at building something, then Chris's post came up, great idea :aap

John

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Posted : 21/09/2013 12:28 am
Till Eulenspiegel
(@till)
Famed V-Ratter Registered

And here is the front cover of the April 1958 Practical Wireless magazine showing the stages of the Beginners Consructional Course.

Till Eulenspiegel.

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Topic starter Posted : 21/09/2013 12:32 am
Anonymous
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I would love to join in, I have not built a radio for over 40 years, and have never built anything valve based.
Mike

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Posted : 21/09/2013 12:19 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

Hi.
There was a two valve FM super regenerative set in PW from 1954 that I built a few years ago. It used two Acorn valves and was quite impressive. It was super sensitive and would lock onto the station as well, audio quality was good and easy to build, with a low component count.

Super-regens were quite popular in early German FM adaptors - I have a Loewe set that uses one and by contrast, I also have a SABA add-on (UKW-S3) that uses a nonode as a quadrature detector - the EQ80.

I seem to recall that Chas Miller ran a series of constructional articles in The Radiophile that started with a crystal set and slowly expanded upwards; pretty sure too that I have a book - Understanding Radio, I think - that does this as well.

Here's a simple radio that might be fun to consruct. It's the Italian "Ninnolo" radio set. Only two valves are employed, an UCH81 frequency changer and an ECL80. An OA72? crystal diode is the detector. the set has no IF amplifier stage so I've no idea what the performance would be like.

Didn't Cossor do this in a couple of sets? No IF stage, just straight to the detector? Pretty sure it was the ones that were superhets on SW only - perhaps Cobaltblue would enlighten us?

I think whoever drafted the Ninnolo circuit was confused as to which way round these new-fangled solid-state diode thingies should be drawn...

You used to see that with LEDs too...

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Posted : 21/09/2013 1:12 pm
Till Eulenspiegel
(@till)
Famed V-Ratter Registered

I would love to join in, I have not built a radio for over 40 years, and have never built anything valve based.
Mike

Hi Mike,
No time like the present, kick off with nice big octal valves, 6V6, 6K7 and the like. There still plenty about.

Till Eulenspiegel.

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Topic starter Posted : 21/09/2013 1:19 pm
crustytv
(@crustytv)
Vrat Founder Admin

I will maintain a list of interested members on this post :-

 

The VRAT Team of Builders

    • Till Eulenspiegel ( Mentor)
    • MurphyV310 ( Mentor)
    • Sideband ( Mentor)
    • Crackle
    • Radioman
    • Andrewausfa
    • Westcliff
    • boyblue
    • Stitch

Anyone else who is interested in joining the project, post in this thread. I will update this post as and when required.

Might I be as bold to suggest that the Mentors be David and Trevor, assuming they are happy to take on the tasks. If the project gang becomes large then perhaps another seasoned engineer should become an additional mentor.

To recap ( sorry)

      • Choose Mentors.
      • Mentors liaise and agree on a design.
      • Mentors publish a BOM ( Bill of Materials)
      • Mentors post a suggested schematic
      • As a parallel task VRAT's interested in joining the project express so in this thread.
      • Project team gather the parts
      • Once everyone has acquired all that is required, The mentors suggest a start date.

Once/twice a week throughout the winter months the mentors/team start building and providing photo's as they go. The play along gang, in their shops at home follow and post their progress likewise. Help and advice provided by the mentor team if anyone in the gang gets into difficulty.

Finally, all finished projects get show cased via a special feature on the main website. https://www.radios-tv.co.uk/?q=node/190

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Posted : 21/09/2013 1:22 pm
Till Eulenspiegel
(@till)
Famed V-Ratter Registered

Hi Andy,
I'm delighted at the positive response to this topic, we're getting back to our radio roots, making things.
I mentioned octal valves. Here is a picture of the excellent American metal valves, these still can be picked up cheaply. The 6N7 is an interesting tube. Although hampered by the common cathode connection, this double triode can be used as a general purpose amplifier, it can also be pressed into service as 10 watt audio output valve.
I'm considering using it for my electrostatic CRT TV project. The 6N7 is also available with a UX base, the 6A6. The only drawback with this valve, it's a bit greedy for heater current, 0.8amp.
Other metal tubes: the 6K8 triode-hexode frequency changer, 6K7 vari-mu pentode for IF or RF amplification and the famous 6V6 output pentode, or is it a beam tetrode?

Till Eulenspiegel.

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Topic starter Posted : 22/09/2013 1:40 am
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