Date: Thu, 14 Apr 2005 09:01:16 -0400

Author: "J. Terrence Klopcic"

Subject: Re: Diode for CENCO microwave set-up

Post:

Chuck,

I would really (really) like to get a few 1N23s. I routinely use the old
Cenco 3-cm microwave apparata for hands-on lab exams. But I have no back-up
units and no way to fix one that dies - an invitation to a downer experience
for some unlucky student.

I'll be glad to reciprocate in any way I can.

Thanks.

Terry

J. Terrence Klopcic
Director of Laboratories
Departments of Physics and Mathematics
Kenyon College
Gambier, OH 43022

----- Original Message -----
From: "Chuck"
To:
Sent: Wednesday, April 13, 2005 9:38 PM
Subject: RE: Diode for CENCO microwave set-up


> I still have some of the 1N23 (9Ghz) series diodes in my junque box. If
you
> want a couple, send my your address and I'll send them to you to play
with.
> Standard terms, once you have them you have to keep them. No returns...
>
> I also have a few 1N3655 series diodes in the same style case. I believe
> they run at about 3 Ghz. I can send you a couple to try out as well if
you
> would like them.
>
> cheers,
> chuck...
>
>
> -----Original Message-----
> From: owner-tap-l@listproc.appstate.edu
> [mailto:owner-tap-l@listproc.appstate.edu] On Behalf Of Stan Dodds
> Sent: Wednesday, April 13, 2005 1:37 PM
> To: tap-l@listproc.appstate.edu
> Subject: Re: Diode for CENCO microwave set-up
>
> Microwave detector diodes are actually rather specialized. They are
> designed for very small capacitance, so that they have high reactance
> at microwave frequencies, and small gap so they can detect weak
> signals. The package is similarly designed for very small stray
> capacitance and inductance.
>
> The 1N23B is (I think) a point-contact type diode. These consist of a
> very thin tungsten wire pushed against an n-type semiconductor surface.
> A substantial current is passed through the contact, forming a tiny
> p-type region within the n-type substrate. The resulting p-n junction
> does the rectification. These are not wonderful as diodes: There is
> relatively large reverse leakage current and reverse breakdown may be
> only a few volts, but they do detect much higher frequencies than the
> usual signal diodes.
>
> Schottky Barrier detectors are used in more modern devices. The
> principle is much the same, but a thin-film metal contact replaces the
> tungsten wire to form the rectifying junction. Their advantage is lower
> resistance and hence lower noise. They can be used interchangeably with
> point-contact devices in detector applications such as yours.
>
> The biggest problem will be to find someone who supplies a diode in the
> proper type of package. I guess that you have a cartridge-type, which
> looks a little like a fuse with a pin on one end and a flange or pin on
> the other. That used to be standard, but now it's surface mount
> packages intended for stripline or coax systems. Your best bet is to
> contact some old microwave spectroscopist at your university to find a
> left-over. Failing that, you might find someone who still sells
> waveguide microwave gear at X band (10 GHz), where these diodes were
> used heavily.
>
> Happy hunting.
>
> Stan
>
>
> On Apr 13, 2005, at 10:32 AM, trappe@physics.utexas.edu wrote:
>
> > That number sure sounds familiar. If its what I think it is, the
> > notation
> > "microwaave crystal diode" is just an apparatus manual explanation of
> > its
> > purpose, and is not its general intended use, ie, I don't think it was
> > specialized for microwave frequencies.
> >
> > I recall that most numbers like 1N23B were simple diodes rated at
> > about 100 to
> > 400 volts, and a few hundred miliamps current, at best. I suspect
> > that their
> > working frequency was very broad range, so they would be a common
> > substitute
> > for many different circuits. I'd bet that any "older" physics or
> > electronics
> > group has one stuck away in miscellaneous diode drawers. I'd also bet
> > that an
> > ARRL manual would have full specs on it, including its markings/color
> > coding.
> > Karl
> >
> > Quoting Dale Stille :
> >
> >>
> >> Tappers,
> >>
> >> I have already contacted Dan about this, but for those of you who are
> >> interested, the demonstration apparatus manual list the diode in the
> >> receiver as a 1N23B microwave crystal diode.
> >>
> >> Later,
> >> Dale Stille, IRS
> >> U of Iowa
> >>
> >> On Wed, 13 Apr 2005, Papp, James J wrote:
> >>
> >>> Did you ever get any help with this issue? Diodes are readily
> >>> available in
> >> many many types.
> >>> Can you provide me with more information about the unit, or any
> >>> markings on
> >> the diode? Old equipment manuals often have the circuit diagram and
> >> part
> >> numbers incorporated into them, if you can find the manuals at all.
> >> Even if
> >> you only know the voltage and current requirements of the diode, that
> >> can be
> >> enough to start repairing it.
> >>>
> >>> Anyway, good luck
> >>>
> >>> Jim Papp
> >>>
> >>> -----Original Message-----
> >>> From: Daniel A Margulies [mailto:danimal@Glue.umd.edu]
> >>> Sent: Monday, April 04, 2005 9:29 AM
> >>> To: tap-l@listproc.appstate.edu
> >>> Subject: Diode for CENCO microwave set-up
> >>>
> >>>
> >>> Greetings,
> >>>
> >>> We have an old CENCO 12cm microwave transmitter setup, and the diode
> >>> on
> >>> the receiver just blew. Does anyone know where I can find a
> >>> replacement
> >>> diode? I called Sargent-Welch, but they just laughed. Ah well.
> >>>
> >>> Dan Margulies
> >>> University of Maryland, College Park
> >>> Physics Lecture Demonstration
> >>> 301.405.5995
> >>>
> >>> ----------------------------
> >>>
> >>> "The law in its majestic equality, forbids the rich as well as the
> >>> poor
> >>> to sleep under bridges, to beg in the streets, and to steal bread."
> >>>
> >>> Anatole France
> >>>
> >>>
> >>
> >
>
>
From cbettis@unlserve.unl.edu Thu Apr 14 09:10:20 2005

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