Rectify 500MHz Small Signal

There are zero-bias diodes available up to at least Xband (10GHz). They have a sensitivity of in the order of -55dBm

I recently got some for 30 bucks each.

Rene

On a sunny day (Mon, 28 Sep 2009 17:46:39 -0700) it happened Joerg wrote in :

UJTs were very available. I have used them for H and V oscillator in a vidicon camera I designed in 1968. Also used those in thyristor drive circuits, in large quantities, same time.

Tunnel diodes were also available, but have not used them. Worked with some equipment that had them in it. In some of the Ampex quadruplex videotape recorders the FM modulator was a tunnel diode. UJTs are cool.

Thanks, John! That's a decent price. And thanks for the SASE offer, but maybe I'll combine that with a beer at Zeitgeist when I get down there :-)

As a kid I grew up in Europe and back then such exotic parts were very hard to find over there, even at hamfests.

tunnel diode.

Well, yeah, but you probably lived in the Netherlands as a kid. You guys had dump handelaars and all sorts of electronics places. UJTs were unobtanium in Germany. Once in a while we'd mount a car and head over the border. But since I was a kid back then and didn't have my own car I'd have to hitch a ride. We usually split the cost for gas and then it was affordable for everyone, but you needed a whole day.

Later I lived in Zuid Limburg and with a stiff bicycle ride you could haul stuff home from the surplus dealer in Margraten. Wrecked many baggage racks that way, plus some chains, axles and so on. And found out the hard way that bicycle brakes don't work so good with 50 pounds of stuff on the back.

as

IEEE

Well, drop in. We have a zillion exotic parts in stock. And the quality of Z's burgers has improved radically lately. Only biker bar I know of with Chimay on tap.

We were lucky. Tons of exotic surplus gear, lots of old teevees, Allied and Lafayette and Fair Radio Sales mail-order available to anyone, local distributors for over-the-counter transistors and

John

Try Skyworks. Similar parts for under a buck.

John

On a sunny day (Tue, 29 Sep 2009 09:34:08 -0700) it happened Joerg wrote in :

Still widely available, I used the 2N2646:

I like PUTs for things like laser interlocks. Unlike ICs, I know exactly how they'll behave in fault conditions, which matters a lot. Relays are good too.

Cheers

Phil Hobbs

as

IEEE

Still not as good as now. I just bought an excellent-condition HP 8568B spectrum analyzer for $900. About 2 cents on the dollar. So far this year I've bought test equipment that would have cost way over $100000 new, for probably $4k altogether. Amazing.

Cheers

Phil Hobbs

Burgers and Chimay on tap? My kind of bar, have to get down there.

Same here, fixing stuff. Provided more learning experience than many university courses. And some money or beer, you didn't have to wait until 21 for that in Europe :-)

Also Digikey. Even the places John mentioned probably didn't have quite that selection. Nowadays you can buy a xxGHz BJT for a buck. Which BTW can also be used to gussy up a transition by a lot. OTOH the dire parts situation back then taught me lots of tricks and most of all, discrete design. Opamps of known origin cost several Dollars. You could get opamps of not so noble origin ("Fell off the truck" brands) for under a buck but that was really frustrating because you never knew what deficiency they'd exhibit. So I stuck with transistors because they worked. You just had to stay away from those bag-o-ten "Universal NPN transistors".

Thanks. AFAICT the 2646 has long since been obsoleted, maybe still considered by boutique mfgs. When I was young I was always told "We can order it but that'll really cost ya". I didn't know you could still get the 6027 although the fact that it was never migrated to SMT doesn't bode well for its future.

Personally I have never seen a design that contained a UJT, this technology may have played chicken and egg for too long.

diodes, as

IEEE

engineers

them

and

switching.

And I'm looking at, theoretically, a quarter million dollars worth of sampling heads over there on my shelf. This is an amazing time to start a niche business, or even an exotic hobby.

John

Didn't in New Orleans, either!

John

diodes, as

IEEE

engineers

loved

them

and

switching.

DC

Funny you should mention that. ;)

Cheers

Phil Hobbs

For my purposes the two-BJT SCR works fine too. Doesn't have to be fast, just very reliable and predictable.

Cheers

Phil Hobbs

diodes, as

IEEE

engineers

loved

them

and

switching.

DC

Is there anything available at reasonable cost that does zippy sampling without needing a Goliath of a scope attached to it?

If I need a crowbar or something to that effect I usually take a regular SCR, a TL431, a transistor and some resistors. You can make that go off at rather precise levels. Impressed a client quite a bit who was used to the regular sloppy crowbars. I told them mine would trigger between 3.6V and 3.7V. "Really?" ... "Yeah". It triggered at precisely 3.65V :-)

Thanks John, we then took some M/A-Com parts. It was to be mounted into a waveguide in the DO119 case. I'll have a look at skyworks for next time. They deliver through BFI Optilas and possibly digikey.

Rene