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Old 2nd Aug 2019, 12:33 am   #1
qrpeter
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Default 3 valve SW TRF receiver.

hi
Just been given a part finished trf rx with 3 valves - 6SK7,6J5 and 6V6, apparently from PW Nov 2004. Is anyone familiar with this rx, what bands does it cover, and can I get a circuit diagram for it, or a copy of the original article?
thanks
Peter G0JJI
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Old 2nd Aug 2019, 1:34 am   #2
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Default Re: 3 valve sw trf receiver

Not in PW Nov 2004, any other clues as to it's origin?
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Old 2nd Aug 2019, 2:10 am   #3
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Default Re: 3 valve sw trf receiver

I do remember a similar three-valve (three I think, and I think they were octal) receiver to the OP's description that featured in PW much, much earlier - I should think about 1963 or 1964. But sounds like that's much earlier than his from what he says.

Mike
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Old 2nd Aug 2019, 8:47 am   #4
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Default Re: 3 valve sw trf receiver

Practical Wireless published a 3 valve (plus rectifier for the psu) trf design in Apr 1959 and then published a further article in Dec 61 to add an rf stage.
The original used the following line up
6J7, 6C5 or 6J5, 6V6

The articles are available on the wonderful american radio history website.

Peter
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Old 2nd Aug 2019, 8:49 am   #5
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Default Re: 3 valve sw trf receiver

You could try April/May 1959.
Has 4th valve as rectifier and a 6J7 instead of the the 6sk7.
Don m5aky

https://www.americanradiohistory.com...PW-1959-04.pdf
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Old 2nd Aug 2019, 5:01 pm   #6
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Default Re: 3 valve sw trf receiver

Here's the circuit - I made it on the kitchen table in 1959 at the age of 13 and it introduced me to short-wave listening. Realising that the affliction was serious, my Dad bought me a new (!) HRO with a full set of coils + BS the following year. I still have the HRO but not the F G Rayer TRF. The HT from my mains transformer was later measured at 400 V. The PW and Radio Constructor etc. circuits of the time were all variations on the same basic theme of 0-V-1.
- Peter G3PIJ
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Old 2nd Aug 2019, 6:31 pm   #7
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Default Re: 3 valve sw trf receiver

I posted this about the PW booklet but there wasn't much interest shown.

It has the design and construction details of the 3 valve MW TRF receiver.

https://www.vintage-radio.net/forum/...d.php?t=158003
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Old 6th Aug 2019, 12:06 am   #8
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Default Re: 3 valve sw trf receiver

Thanks for your help guys. The circuit in PW Apr '59 could be of interest, and I have found another possibility on by WD4NKA which covers the bands I am most interested in, ie 80/40 amateur.
73's Peter

Geoff
I found the booklet very interesting.
73's Peter
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Old 6th Aug 2019, 11:28 am   #9
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Default Re: 3 valve SW TRF receiver.

Similar designs were very common in the hobby mags and beginner's books of the 1950s and early 60s. They often used TV valves like EF91s and EF80s which were widely available from scrap sets.
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Old 6th Aug 2019, 3:41 pm   #10
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Default Re: 3 valve SW TRF receiver.

At the time that Rx was designed, almost all amateurs would have been using AM transmitters (or CW) whereas now almost all are using single sideband (SSB). I recall listening to amateurs on 40 or 80m AM on a TRF which I had ~1967, but I don't recall listening to SSB.

Is it the case that to resolve SSB on a TRF, you have to advance the feedback until oscillation occurs? I wonder if anyone has much experience of listening to SSB on a TRF; how well might it work?

B
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Old 6th Aug 2019, 3:54 pm   #11
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Default Re: 3 valve SW TRF receiver.

SSB on a decent regen works ok, ideally you need the ear to brain discriminator feature, some have it but apparently some don't.

For stability on a regen on SW go for the Regenerodyne set up, works really well, hardly any "pitch" shift on SSB when adjusting regen control and on CW if it's built good.

Lawrence.
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Old 7th Aug 2019, 1:46 pm   #12
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Default Re: 3 valve SW TRF receiver.

The PW April '59 design is in the booklet. And a 2 valve battery SW design.
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Old 10th Aug 2019, 9:34 pm   #13
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Default Re: 3 valve SW TRF receiver.

Quote:
Originally Posted by ms660 View Post
For stability on a regen on SW go for the Regenerodyne set up, works really well, hardly any "pitch" shift on SSB when adjusting regen control and on CW if it's built good.
Hi
Interesting you mention Regenerodyne. I found one by WD4NKA. Google that callsign and you will see it. Looks interesting, he uses xtals for bands. He gives the xtal value for 40M but not 80. Perhaps someone can tell me? I emailed him via QRZ but have had no reply.
Peter
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Old 11th Aug 2019, 1:32 am   #14
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Default Re: 3 valve SW TRF receiver.

As described, that receiver https://www.qsl.net/wd4nka/form.html uses an 'IF' which I think is too close to 80m to be practicable.
If you were to push the IF up to say 5.0-5.5MHz then a crystal of about 1.6MHz gets you in the ballpark, but every single coil in the circuit would need to be changed in accordance.

That website has not been updated since 2004; you may not get a reply to your mail.

The simple two valve TRF which I built many years ago, which worked very well, is shown here http://www.vintageradio.me.uk/radconnav/2_valve.htm
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Old 11th Aug 2019, 10:32 am   #15
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Default Re: 3 valve SW TRF receiver.

I built one ages ago (now long since gone) From memory I arranged for the tunable regen detector to be tuned from 2.5 MHz to 3MHz in one version I built and 2Mhz to 3MHz in another version, both worked extremely well.

For the LO source I used the output from a standard bench sig gen, the one I used at the time was the AVO CT378a, that enabled me to tune to any part of the spectrum (with Xtal osc you are more restricted)

The advantage of the Regenerodyne is that the tuning rate of the detector is constant across all bands, a definite bonus, also the fact that regeneration is only across a small frequency range (eg: 500kHz (2.5 to 3MHz)) which is lower compared to a normal regen on shortwave which means that the detector can be built with much better stability which is what is needed for SSB/CW reception.

Lawrence.

Last edited by ms660; 11th Aug 2019 at 10:38 am.
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