Rod pentode superhet radio.

[AdrianH]

This has kept me occupied for several days, probably over a week, making IF coils and Osc coil, winding the ferrite aerial, making up a spreadsheet so I could work out the values for the Osc to track the aerial tuning, or best I can anyway. All part of the learning experience.

Looking at the board, it is a bit of a Frankenstein, with trimmer caps strapped to allow for adjustment, wires bridging sections etc.





But it works and has been a very satisfying little project.

6 x 9 Volt battery for HT 4.4 mA HT current.
3 x 1J18B valves, 1 for local Osc, mixer and RF amp. 1 for IF gain stage and 1 for driving a speaker, 1 x Ge diode for detector.

if anyone knows of a Ki-cad library that includes the rod valves I could draw out a circuit.

Inspiration came from http://www.hi-ho.ne.jp/ux-45/russian.html now if only I could get things that small?

Adrian

[kalee20]

Really good! Minimalist!

I made a Russian rod pentode superhet too, it's a bit more sophisticated but works really well.

I'm interested in your frequency changer - I used a pair of 1j29b's in single-balanced configuration with a third 1j29b as oscillator.

[paulsherwin]

Several days? That would take me years

[AdrianH]

I am not doing a lot else at the moment Paul so lots of hours to fill.

Kalee20
Have a look on that web site I have listed, be aware it is an old site and not https:

He sure has a way to get things in a small package and were I got inspiration from and I am happy to share his site although not sure if the site is still maintained as I never got a reply to an email I sent.

I have a basic video showing it working with me talking for 10 minutes: -
https://youtu.be/HSyVBN11v50


Adrian

[murphyv310]

Adrian....
There is only one word to describe this........ Brilliant

[samoca58]

I also found Web inspiration and built a rod pentode based superhet but using the 1j37b as a mixer /oscillator. 1j24b types as If amp stage. Germanium diode detector. Another 1j24b as an AF preamp into a IC based audio output. Works OK.

[AdrianH]

When I bought the rod Pentodes, I did not buy any 1J37b's, now there seems to be only one person selling via the auction site, based in Kiev, postage seems a lot at the moment, probably not considering what is happening.

There is also a thread on the radiomuseum site that suggests the same valve can be used for AGC by feeding the signal to both grids, biasing one grid as normal and winding the voltage down on the other grid to provide the AGC action.

Not sure if the valve could be used to provide both mix and agc functions at the same time, but possibly used as a front end with AGC and then another for mixer stage?

Adrian

[samoca58]

The circuit that I partly used in my radio comes via this link https://www.qsl.net/yt2fsg/tube/tube.html

[samoca58]

My 4 rod pentode homebrew mounted in a basket case Roberts R200 radio.

[AdrianH]

Very nice

Are the two double top cans the if tuning, if so what are they out of?

Adrian

[samoca58]

From the Roberts chassis as well as the oscillator coil tuning cap and ferrite aerial... To minimise alignment problems. ��

[ValvoStef]

AbFab project.