DIY Radio

watty

This is the first of a series of cheap radios using 60cent Russian valves.

These valves only ever used by Military and unique Russian 1950s design, some later and made into the 1990s

http://www.techtir.ie/blogs/watty/miniature_valves_3
No external aerial/earth needed and performs better than most superhets, but trickier to tune.

There will be some transmitters and a couple of superhets.

Two more "regenerative" Radios. One a Children's BBC from 1957 and one a 1940s UK/Norwegian Radio for Shortwave.

Fuzzy Clam

Would be a good way for a newbie to valves to start, being low(ish) voltage and not requiring a mains PSU.
I'm curious why you don't advise the use of rechargables in series for the HT supply.
I built a couple of replacement 67.5 V packs using 9v Ni-MH batteries with no problems.

watty

Good question. No simple answer.

Rechargeables are good for high drain devices. Current drain is less than 700uA, i.e. over 250 hours on Alkaline PP3 x 4

They are problematic for high voltages as one cell can be reverse charging and the user unaware. http://www.techtir.ie/node/1003726#comment-1004465 Originally the HT was going to be 60V or 80V. But actually the 4 x PP3 (36 nominal, 39V fresh) is fine. The HT is actually about 37V, 38V, 39V and 40V nominal per valve as the LT is in series.

Use a fuse if using rechargeables. It's more worth while traditionally for the filaments.

Actually, really the LT should be 4 x NiMH. But 4 x Alkaline is a little high. I will do a revised circuit for longer discharge of LT supply. Though the filaments do still "go" at 0.8V!

I have an oscillator circuit that works reliably at 8V HT on the 1j18b at 500kHz to 5MHz, though at 100MHz you need > 40V HT for the gain.

I updated http://www.techtir.ie/construction/herge-wiring to explain a bit about the LT or filament supply, which actually ideally is NiCd! NiCd is obsolete, so the NiMH is next best thing.

watty

Seeing as the "Hergé" is working well I have started a new one! http://www.techtir.ie/construction/sweetheart-clone

Fuzzy Clam

watty wrote: »

Seeing as the "Hergé" is working well I have started a new one! http://www.techtir.ie/construction/sweetheart-clone

I see the original circuit used IT4's which I have in a receiver here.
Shouldn't the combined +4.5 and -30v rail actually be labeled 0v as it's at ground?

watty

That schematic is just a copy of the original 1943 schematic above. I didn't change anything. If it was my design, yes, I'd label that as 0V


IT4 = DF91.
The DF96 is 1/2 the filament current.
The 1j24b is almost as low as 1/4 filament current

But DF91, DF96 sell for about €8 each plus postage and likely production ceased in 1960ish. The 1j24b is about €0.6 each inc postage if buying 10 and production may only have ceased in 1991 approx! All the Military Russian Rod Pentodes are date coded. The oldest I have is 1976!

See
http://www.techtir.ie/blogs/watty/miniature_valves_1
http://www.techtir.ie/blogs/watty/miniature_valves_2


I'll be publishing a "modernised" version when I have the RF part working on 1j24b valve, which has separate screening and G3 connections. You can experiment with raising G3 slightly or even using G3 & Anode tied as a Tetrode. We'll see during the week.

More pictures added.

watty

Fuzzy Clam wrote: »

I see the original circuit used IT4's which I have in a receiver here.

Which receiver?

watty

If you see a €2 "Jensen" AM/FM radio you should pick it up for parts. (I'm using tuning caps in the "Tatiana" from two of them, and possibly the ferrite rod).

I'll do an article later on how to add the self contained clock/Alarm/frequency counter LCD module from "Jensen" to any radio with 455KHz and/or 10.7MHz IF. Just add buttons, 3V and local oscillator. I got mine in the big "euro" store in Limerick's William St.

Dismantled photos here http://www.techtir.ie/construction/sweetheart-clone

Fuzzy Clam

watty wrote: »

Which receiver?

I was trying to PM you the details of the receiver but can't. I don't want to put it up publicly.

watty

That should be sorted

watty

Photos of main board assembly http://www.techtir.ie/construction/tatiana-main-veroboard-1

watty

Hergé radio updated and articles on old Radio tuning indicators and displays

Tuning scale http://www.techtir.ie/construction/herge-radio-base
Circuit revision http://www.techtir.ie/construction/herge-wiring
Vintage Indicators http://www.techtir.ie/technical/vintage-indicators
(With guides on Russian/Chinese magic Eyes to get and Russian VFDs and Nixies)