Simple micro transmitter

[Nick]

I'm sitting on reasonable stocks of sub-miniature so-called "missile tubes", about 2,300 in total and, oddly, 23 different types including over 400 of the JAN 6418 low-power (2.2mW) pentodes.

These are really the pinnacle of valve manufacture - the 6418 is in the "missile tube" group, but the Tung-Sol datasheet doesn't go into that much detail - I can't find the Raytheon one - probably could, but don't have the time - the Raytheon ones have all the QA information and are much more detailed.

Nice thing about these valves is that they are still, mostly, pretty cheap, though there are some whose value has rocketed (deliberate pun  ).

Generally, the missile tubes can survive 1000 G acceleration and 450 G impacts. Completely insane, and more than enough for a a valve that was sometimes used in hearing aids!

[Pat Pending]

Mullard, amongst others did hearing aid valves:

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

Lawrence.

Thanks. I think that they may have been the ones that Gramps aid had in it. It also used a 15 volt battery for HT similar or same as the type used in the AVO 8 meter.

These are the ones that I have a few of, http://www.radiomuseum.org/tubes/tube_ck6418.html I've found them functionaly equivalent to the JAN6148. I think the commercial version was designed to be a long life version of that. Once switched on, a proximity fuse valve wasn't expected to live long I suspect! However I've never had a JAN 6418 fail either when I've used them. The secret is to keep the filament voltage at no more than 1.2volts, they're great little valves at low power, even at low rf, but very microphonic if pushed. Cheep too, if you buy quantities.

And Nick, if you're interested in unloading a few of your stock, let me know, I'm always tinkering!

Andy.

[Nick]

Currently got the following types:

   

However, I work in the Gulf, so won't be back until the end of December.

Most of these are pretty cheap - I have some box loads of other stuff that's unmarked (OEM) that's supposed to be 6021W, but when I plot them on my uTracer they don't look like others of that ilk!

NB. These tubes are marked but in bulk packaging, mostly for US military usage, so no individual pretty boxes

Drop me a PM...

[Mike Watterson]

Will do, Nick, after the holidays.
I've been fascinated with battery valves since 1966 when my mum let me keep the Lady Margaret I found in the attic. I don't remember what happened to it. I bought a battery pack a couple of times and then got an old NOS "battery eliminator" in a perforated metal box. I had a Philips EE set (germanium transistors) and an R1155 set connected to washing line then.

[Mike Watterson]

The JAN7979 / CK7979 is interesting. It's a miniature neon triode, so could be used as synced relaxation oscillator. The grid is intended to turn it on /off. Probably superseded by the DM160 VFD triode indicator.
http://www.radiomuseum.org/tubes/tube_ck7979.html

The 6xxxx types are miniaturised versions of 6.3V indirect mains type, only suitable for Lead Acid / Vehicle battery systems.
The Russians made all the USA kinds of sub-miniature; 6.3V indirect, 0.7, 1.2 & 1.4V pinch base miniaturised battery types and nuvistors (which are really mains applications), there is no non-Russian equivalent of the Rod Pentodes and apart from a Forestry two-way radio, only used in military and space applications.

I think all the Mullard hearing aid types are Philips designs based on Tung-sol, RCA and Sylvania types. I think the only Philips / Mullard designs might have been all B8D button base like DM70 type (though there is USA version of that, I don't know who designed it. It's very a clever and unique Magic Eye. The only other dry battery Magic Eye is a very strange Russian one that seems derived from DM160 style VFD, there is a Russian non-compatible similar design to DM160 VFD indicator).

[Nick]

The corollary of having triodes that light up like VFDs, is that all VFDs are triodes... (DHTs - directly heated cathode, grid & anode).

Several folk have successfully made amplifiers out of VFD displays... (Google is your friend).

[Terry]

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 think you've misinterpreted my comment, Andy, which was in response to Mike Watterson in this post where he said "I don't think very many valves were specifically developed for hearing aids, it was simply a pubic market for them."

I well remember those hearing aids, Andy, using wire ended Mullard valves, I think - I but I doubt your Grandpa wore one in his pubic area, though 

[Mike Watterson]

Arrgh ... edit time out.
Wash out yer brain, Terry, you know I meant public, as in products for the ordinary public, not industrial control, military or aerospace

[Pat Pending]

I well remember those hearing aids Andy, using wire ended Mullard valves, I think - I but I doubt your Grandpa wore one in his pubic area, though 

  It's all cool! And you're very observant young Terry! my gramps wasn't fond of underwear so I doubt he ever stuffed his hearing aid down there!

[Mike Watterson]

The corollary of having triodes that light up like VFDs, is that all VFDs are triodes... (DHTs - directly heated cathode, grid & anode).

Several folk have successfully made amplifiers out of VFD displays... (Google is your friend).

I'm working on a two valve VFD regenerative TRF with reflex audio using two DM160 (or Russian alternative) VFD triodes. The seven segment displays were the next development from DM70 (a VFD based magic eye, not same principle as EM34 to EM87 etc) and DM160, to get round the patent on "Nixie" tubes. It will fit into the cover / case for a compact cassette.

The VFD triodes seem poor gain, it will be interesting to see which of the DM160 (there is exact USA equivalent) or the different Russian part is better at RF.
"DHTs - directly heated cathode" = Filamentary Cathode (might be more familiar). Indirect cathode wastes too much power for battery other than 6V /12V /24V vehicle or other Lead Acid accumulator driven systems.