tube

I have a few of these plus some 954's left over from an old pre-amp we used when I was in the U. S. Army Signal Corps. They were in two 1942 Plymouths, "borrowed" from the FCC, and sent to us in North Africa and used there and later in Italy. The pre-amp connected a loop antenna in the roof of the car to a standard "all wave" SW receiver.

This was state of the art in 1943. The whole thing, including the SW receiver was powered by a vibrator type 6V DC to 110V AC inverter running from a 6V battery in the trunk. It did work, and located several enemy transmitters.

I never saw the cars after we returned to the U. S. in 1945, but I kept the spare tubes as souvenirs.

--
Virg Wall

So? Light it up and get to work! Should be roughly comparable to a 2N5179, I'd guess.

Plate resistance is slightly high and Gm noticably low, but capacitance is quite small and the plate curves look nice (mu and Rp are fairly constant in the operating range). Offhand, give it a ~20k plate resistor and you'll get around 7k || 1.4pF = 16.2MHz -3dB point if driven hard (not counting miller or probe C). Okay, I suppose a 2N5179 will switch faster than that, but in terms of fundamental performance, once it cuts off at fT, it doesn't really do anything anymore; with tubes, add some L to cancel the C and you'll get narrow-band performance for another decade or two.

Funny how tubes do that. BJTs don't, they kind of just stop working, fT limited by recombination more than circuit parameters. Do FETs do that? I know power MOSFETs are typically limited by gate spreading resistance (~a few ohms, so IRF540 stops being practical at ~10MHz). Do JFETs? What's the step response of a JFET?

Good MOSFETs, too, but they're hard to find. You'd think a few more microns of sputtered aluminum over the gate connection wouldn't be worth $20 more, or whatever it is they do with 'em.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

"John Larkin"  wrote in message 
news:m1n9n5dokeg2obl8vfj99rd0mresa8783f@4ax.com...
>
> A 955 acorn tube:
>
> ftp://jjlarkin.lmi.net/Acorn.JPG
>
> John
>
>

I give up; where is the oak?

Tubes get killed, eventually, by transit time problems. There were some lighthouse (planar) tubes with really tiny spacings that would work at 3 GHz or some such. It took other tricks, like bunching, to break that limit.

MOSFETs seem almost infinitely fast if you drive their gates hard enough. Here's a 50 volt pulse being generated by two 5-cent 2N7002s in parallel:

ftp://jjlarkin.lmi.net/HV_mosfet_pulse.jpg

which is a lot faster than the datasheet suggests. People push mosfets to places like 500 volts in 2 ns. DEI invented some tricky packaging to get the packaging parasitics down, and that seems to help a lot.

John

The packaging details make it very hard to keep stable -- the inner element's gain goes up to UHF or higher, and those wires start looking awfully inductive. AFAIK "pencil" tubes and lighthouse triodes were designed in large part to be a better mechanical fit to coaxial cavities.

Which is why tubes are still king for really high power VHF and microwave stuff. Uneasy on the throne, though.

--
www.wescottdesign.com

GaN fets are getting up into tube territory. You can't get an SO8 tube with Ft in the GHz and a Gm of 5.

The terawatt radar-as-a-weapon things are apparently solid state, some sort of impulse generators based on (maybe?) dumping capacitors into antennas through laser-triggered (diamond?) films.

John

Don't forget nuvistors. :)

And then there's these guys;

although now we are actually talking electron drift and bunching. I've always wondered if I could operate this thing as a planar tetrode though. S'pose I should try some time. I don't have the equipment to detect microwave oscillations if it misbehaves though.

Y'think magnetrons will be around forever?

GaN and etc. would have to get pretty damn cheap to offset them.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Hmm, interesting correlation. They are about as old. Figure another fifty years at least? ;-)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Probably disappear about the same time as hard disk drives disappear.

This is a great book,

written by Russel Varian's widow. All about California in the 1930s, early aviation, the invention of the klystron, and even has a villain, Frederick Terman.

I see that new copies are going for $150. Mine is signed by Dorothy herself!

John

From an article on "Creative Thinking" by John R. Pierce:

"Another example is provided by the development of the 416A triode. The original and startling germ of a creative idea was that after all these years a triode might still be the best amplifier for microwaves, if only the spacing were close enough and the grid fine enough. An auxiliary idea was that close enough spacings could be attained and held by grinding the cathode and a surrounding ceramic co-planar, and then supporting the grid from the ceramic. These were, however, mere germs of an idea. Something real and complete was brought into existence only after years of concentrated effort, including the inauguration of a program of cathode studies which is still being pursued for other purposes."

I was at Bell Labs while this work was going on. I still have some tubes in conventional noval configuration that were used in doing the above cathode studies.

Here's an interesting summary of some strange vacuum tubes:

--
Virg Wall, P.E.

Ah! The good old days when you could do your own glass work ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Cool. I won a science fair prize, ca 1962, which was a trip to Bell Labs in Murray Hill. Being a poor kid from New Orleans, I had never flown before. Neither had I ever seen snow or rocks. They put us up at the Algonquin Hotel in Manhattan for the weekend (me and my high-school physics teacher) and then bussed us to Jersey.

It was fabulous. Anechoic chambers, lectures on information theory, plasma jets, cool stuff. I saw what I think was the first LED, and had lunch with Walter Brattain.

John

2N5179,

in

get

So! You ornery old git, you're only 4-5 years younger than I ;-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
              AGW proponents are like watermelons...
             GREEN on the outside, RED on the inside.

Yes, we still used them at Semco (capacitors) for the oscillator in the precision reference. Up to the day they closed! which would be like 2 years now..

I think I may have some lying around the house.

Is there anything in there about the pet anteater?

I remember those!

Had some oscillating at around 600MHz in some gear back in the '60s.

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)