Simple micro transmitter

[Pat Pending]

To date I've added an AF preamp to my Pye black box, made a one valve reaction and regen radio with auto reaction, unbelievable performance, fitted four valves to a Osram Music magnet 4, made a two valve reaction set that drives a speaker, the micro TX and other wee projects.

They would be interesting too Trevor, if you have the time of course!   


And I should start posting some of my own I know.   But other people's stuff is always more interesting than my own, never walked passed a yard sale or a skip   

Cheers,
Andy.

[pwdrive]

Trev, how did you achieve auto regen with the regen you built?

Lawrence.

[Mike Watterson]

The 6418 and similar was developed for military applications, especially proximity fuses in shells and bombs. It may have been for military stock.
I don't think very many valves were specifically developed for hearing aids, it was simply a pubic market for them.
AFAIK no European radios used the USA & European sub-miniature valves, but some USA radios and many Japanese sets did. Often a single B7G for output and 45V HT like an elongated PP3. Usually a C or D torch battery for LT.
I have a few ex-equipment and NOS of the family, including a triode-pentode mixer.
Some US military walkie talkies using valves where still being refurbished and sold abroad by USA even in 1980s!

[Murphyv310]

Trev, how did you achieve auto regen with the regen you built?

Lawrence.

Hi Lawrence.
That was found purely by luck!!! I'd built up a little reaction set on veroboard using 1 1j18b it worked well but I found that reducing the HT it would never go into full oscillation, it was always on the edge which is ideal, later I fiddled around with the circuit and got useful improvements by re-flexing it too, the set used a normal ferrite rod coil with an extra 20 turns wound round the "earthy" end of the coil for the reaction winding. It drove a set of high impedance phones at good volume on locals and even pulled in a few foreigners at night.
I've still got it here, no doubt the circuit is on the PC somewhere.

[pwdrive]

Thanks Trev.

Lawrence.

[AlanBeckett]

My arithmetic or typing was hopeless. That should have been 4,500,00 Valves per year

Alan

[Pat Pending]

Should have realised that about the Raytheon valves Mike thanks, the JAN in the type numbers stand for Joint Army Navy, as I remember?  I think the 6418 was popular as a hearing aid amp as it had such a low heater current maybe?

Andy.

[Terry]

... it was simply a pubic market for them ...

Oh, do explain, Mike - I'm fascinated! 

Explains why they weren't much used in hearing aids, though ... 

[Pat Pending]

Explains why they weren't much used in hearing aids, though ... 

My Grandpa had a valve based hearing aid in the fifties and sixties Terry, I don't recall the type numbers of the miniatures used in it but it was about the same size as a  pocket radio (ie. just fitted a pocket) and used a crystal ear piece. He didn't like going over to the behind the ear type as he maintained that it then looked like he was wearing a hearing aid, and not listening to a new fangled transistor radio as he used to tell people!

Andy.

[pwdrive]

Mullard, amongst others did hearing aid valves:

http://www.r-type.org/exhib/aaa1378.htm

Lawrence.