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Minimalist Superhet Radio.

 
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Minimalist Superhet Radio.

Post by Till Eulenspiegel » Fri Sep 20, 2013 6:22 pm

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.
Attachments
NINNOLO.jpg

 
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Re: Minimalist Superhet Radio.

Post by turretslug » Fri Sep 20, 2013 6:55 pm

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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Re: Minimalist Superhet Radio.

Post by rob t » Fri Sep 20, 2013 6:59 pm

strange as they got the detector right
Rob T

 
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Re: Minimalist Superhet Radio.

Post by Michael Watterson » Fri Sep 20, 2013 7:00 pm

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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Re: Minimalist Superhet Radio.

Post by Michael Watterson » Fri Sep 20, 2013 7:02 pm

rob t wrote: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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Re: Minimalist Superhet Radio.

Post by sideband » Fri Sep 20, 2013 7:25 pm

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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Re: Minimalist Superhet Radio.

Post by crustytv » Fri Sep 20, 2013 7:31 pm

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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Re: Minimalist Superhet Radio.

Post by Till Eulenspiegel » Fri Sep 20, 2013 8:15 pm

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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Re: Minimalist Superhet Radio.

Post by turretslug » Fri Sep 20, 2013 8:18 pm

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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Re: Minimalist Superhet Radio.

Post by Till Eulenspiegel » Fri Sep 20, 2013 8:30 pm

turretslug wrote: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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Re: Minimalist Superhet Radio.

Post by Till Eulenspiegel » Fri Sep 20, 2013 8:35 pm

Murphyv310 wrote: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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Re: Minimalist Superhet Radio.

Post by Cathovisor » Fri Sep 20, 2013 9:01 pm

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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Re: Minimalist Superhet Radio.

Post by Michael Watterson » Fri Sep 20, 2013 10:26 pm

That's the German one I was thinking of.
Of course while 2 tubes, it's really 4 valves. :)

 
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Re: Minimalist Superhet Radio.

Post by Stitch » Fri Sep 20, 2013 10:28 pm

Till Eulenspiegel wrote:
Murphyv310 wrote: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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Re: Minimalist Superhet Radio.

Post by Till Eulenspiegel » Fri Sep 20, 2013 10:32 pm

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

Till Eulenspiegel.
Attachments
PW1`.jpg

 
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Re: Minimalist Superhet Radio.

Post by crackle » Sat Sep 21, 2013 10:19 am

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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Re: Minimalist Superhet Radio.

Post by Cathovisor » Sat Sep 21, 2013 11:12 am

Murphyv310 wrote: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.

Till Eulenspiegel wrote: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?

turretslug wrote: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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Re: Minimalist Superhet Radio.

Post by Till Eulenspiegel » Sat Sep 21, 2013 11:19 am

Crackle wrote: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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Re: Minimalist Superhet Radio.

Post by crustytv » Sat Sep 21, 2013 11:22 am

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

vratproj.jpg

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. http://www.radios-tv.co.uk/?q=node/190

 
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Re: Minimalist Superhet Radio.

Post by Till Eulenspiegel » Sat Sep 21, 2013 11:40 pm

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.
Attachments
MetalTubes.jpg

 
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Re: Minimalist Superhet Radio.

Post by Andrewausfa » Sun Sep 22, 2013 10:41 am

Please count me in, sounds an excellent idea Chris. I've not done any valve construction projects before.

Andrew

 
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Re: Minimalist Superhet Radio.

Post by crustytv » Sun Sep 22, 2013 10:56 am

That's five on the project team, list updated.

 
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Re: Minimalist Superhet Radio.

Post by Westcliff » Sun Sep 22, 2013 8:16 pm

I'd like to join in too. The only thing I have made so far is a fuzz pedal, which does not work. No valve-based building experience at all.

I do have a sufficiency of old parts though, enough to build most of a set. My personal preference would not be to use new parts if old ones are available, but that's just my point of view.

Gus.

 
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Re: Minimalist Superhet Radio.

Post by crustytv » Mon Sep 23, 2013 12:32 am

Westcliff wrote:I'd like to join in too.
Gus.



Hi Gus,

I've added you to the project team, six now.

Chris

 
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Re: Minimalist Superhet Radio.

Post by Alistair D » Mon Sep 23, 2013 1:19 am

Michael Watterson wrote:But if this became popular supplies of old parts for restoration would be badly raided.

I can only support use of old parts in "one off" ventures. For multiple builds new parts or at least very very common parts have to be used.


I would class these as temporary builds. They are just as easily dismantled if the parts are needed for more important projects.

Al

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