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Re: OT, but fairly basic question- rf detectors

Joe Na
 

John,

?? The 1n21B is an OLD diode! That style is what we used to call a 'Microwave' diode back when I was a kid in the early 1960s and it was OLD even then. In fact those are the first self-contained diodes ever built. They were developed during WW II and they talk about them in the MIT Radiation lab books that describe electronics developments made during the war. It's a silicon diode and you're right it does use a cat whisker! The screw moves the whisker around on the crystal for the best contact and they're then potted with wax so don't move the screw unless you have to and unless you know what you're doing. I have no idea how high the 1N21s go in frequency or how good they are relative to newer diodes but I strongly suspect that the newer diodes are much better!

--- On Tue, 9/22/09, John Griessen <john@...> wrote:

From: John Griessen <john@...>
Subject: Re: [hp_agilent_equipment] Re: OT, but fairly basic question- rf detectors
To: hp_agilent_equipment@...
Date: Tuesday, September 22, 2009, 5:22 PM






?





Alan Melia wrote:

I have collected

a number of Marconi, GR and, and HP diode detectors most would be overkill
as they are rated to 10GHz or higher.


fredschneider2001 wrote:

> Here is some info about those things. Very easy to make when it's under 1GHz.



> . mcmaster. ca/~elmer101/ sqlaw/sqlaw. html



Alan or anyone,



How do you identify which of the old detector diodes go up to 2.4GHz?



That's the frequency where

I want to do some relative measurements to select good antenna layouts for

peak power transfer with milliwatt chip radios. I'll be teeing off of

a folded dipole antenna fed to a dummy load of 200 Ohms, (the antenna impedance),

to go to the detector.



One old diode I have is a gold plated cylindrical can with ceramic middle

and a gold pin on the other end marked 1N21B and "microwave" and uA surrounded by a square.

The diode has an adjusting screw on the flange end of the cylinder can!

Does that mean cat whisker connection?

That one is part of a X485B detector mount that attaches to 1cm X 3cm waveguide.



I have some other diodes like it from slotted lines. How do you tell how fast they are?



John Griessen
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