[Boatanchors] IN34A 1N60 detector diode question

Kees & Sandy windy10605 at juno.com
Tue Apr 5 13:51:53 EDT 2011


I have recently done a considerable amount of work looking into Germanium diodes and Schottky diodes as detectors for a mWattmeter design I'm doing. I didn't want to use the relatively costly AD8307 Log Amp detectors. The key is that Germanium diodes will detect very low levels without requiring forward biasing. The most sensitive and readily available Germanium ones I found are 1N270 and 1N277. Get the kind that are marked with the number or by colored bands. The ones which are not marked or only indicate "cathode" are iffy at best (I have many, many as a result of testing, if you want to see). 
The Schottky diodes are excellent (actually slightly better than the Germanium diodes) but WILL require a little forward bias (5uA is OK.....yes, that's microamps) to get them to the low sensitivity levels. The Schottky diodes also come in matched pairs which I needed for Forward/Reverse and for temperature compensation consistency. 
73 Kees K5BCQ   

---------- Original Message ----------
From: Al Klase <al at ar88.net>
To: boatanchors at mailman.qth.net
Subject: Re: [Boatanchors] IN34A 1N60 detector diode question
Date: Tue, 05 Apr 2011 12:40:29 -0400

Hi Greg,

We went 'round and 'round with this in the crystal radio community.  It 
turns out that parts numbers have very little meaning.  Dump out your 
germanium drawer, and sort for the best performing units.  Some of the 
later small glass diodes from the orient, like the ones Radio Shack used 
to sell are statistically better.  Schottkeys may have an edge under 
special circumstances, but the impedance matching needs to be just so.

More than you wanted to know about this on Ben Tongue's (Think 
Blonder-Tongue) site:  http://www.bentongue.com/xtalset/xtalset.html

Al

On 4/5/2011 12:10 PM, Greg Mijal wrote:
> Hi what do you think is the most sensitive diode for the detection of AM signals in the receiver?
> This question is not limited to the 1N34/1N60 diodes.  I'm interested in the Schottkey types and anything else out there that is VERY sensitive.
> Thanks
> Please no $50 a pop wonders.  I'm trying to fill a parts drawer with improved diodes.
> Greg
> WA7LYO
> Kinston NC
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-- 
Al Klase - N3FRQ
http://www.skywaves.ar88.net/

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