Substitute for a Germanium Diode - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: June 29, 2020, 09:00:33 am
content: I recently discovered a circuit for testing the output of low power RC drown transmitters in the UHF band.testing that the antenna was in tune.the circuit called for agermanium diode! this is not the first time I have come across this in an RF sniffer circuit.So where do you get a germanium diode? not a shockley diode.where can you salvagegenuine germanium diodesin today's electronics?are there any old or used consumer electronics that guarantee to have genuine germanium diodes in them?vs waiting weeks for a package to arrive that maybe or may not be more shockley diodes.as Jaycar do not seem to stock them ether.

author: RoGeorge
author_rank: Super Contributor
timestamp: June 29, 2020, 09:14:34 am
content: Almost any diode will work, Ge or not.

author: jonovid
author_rank: Super Contributor
timestamp: June 29, 2020, 09:26:14 am
content: the RF sniffer circuit I was looking atits says VHF but I may try to make it work on UHF

author: David Hess
author_rank: Super Contributor
timestamp: June 29, 2020, 05:06:35 pm
content: Low barrier schottky diodes make pretty good replacements for germanium diodes. Look for parts with low capacitance and low forward voltage drop.The alternative I have used in the past to increase the sensitivity of silicon diodes when doing direct detection is to use two diodes in a bridge configuration with the RF applied to one side of the bridge and the other decoupled to ground with a capacitor. This compensates for the forward voltage drop of the diodes.Another thing I would try now is to use 2N3904 base-emitter junctions as diodes since they have better conductance and are faster than common silicon switching diodes.

author: bob91343
author_rank: Super Contributor
timestamp: June 29, 2020, 07:56:18 pm
content: Germanium diodes are still available. You can use 1N34 and 1N270 for instance. I have a drawer full of them and use them to replace burned out diodes in power meters, probes, etc.

author: notsob
author_rank: Frequent Contributor
timestamp: June 29, 2020, 09:23:08 pm
content: Try Aztronics in Adelaide aztronics.com.auThey once supplied the AHARS (Adelaide Hills Amateur Radio Society) VHF Antenna analyser kit. I have purchased 1N34A germanium diodes from them a long time ago. Their stock list has "please call" against 1N34A.May be worth a try

author: profdc9
author_rank: Frequent Contributor
timestamp: July 03, 2020, 02:58:52 pm
content: If you want a source of a large number of cheap schottky diodes, the diodes called "1N60" or "1N60P" on ebay/aliexpress can usually be had for 100 for 1.50 USD. I have bought large numbers of these for projects on occasion.

author: @rt
author_rank: Super Contributor
timestamp: July 04, 2020, 08:09:45 am
content: I’ve made several working crystal radios with them, so I assume they are the real thing.https://www.ebay.com.au/itm/10-PCS-GERMANIUM-DIODE-1N34A-DO-7-1N34-IN34A-S/192345843160?hash=item2cc8b4a5d8:g:F5sAAOSwuUlb1mCq

author: cdev
author_rank: Super Contributor
timestamp: July 08, 2020, 02:17:58 am
content: Diodes wont conduct unless the voltage is its junction voltage, silicon is (usually) around twice as high as germanium. For that reason a germanium diode makes a better RF detector, IMHO. An 1N34A will usually do.Quote from: RoGeorge on June 29, 2020, 09:14:34 am

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 08, 2020, 05:48:43 am
content: RB751S40T1G, RB751V40T1G, SDMK0340L-7-F look good.Tim

author: RadioNerd
author_rank: Regular Contributor
timestamp: July 10, 2020, 09:56:18 am
content: Depending on the desired power level I can recommend SMS7621 and SMS7630 schottky Diodes (digikey/mouser etc have them). They are pretty sensitive detector diodes more than fast enough for UHF work.

author: cdev
author_rank: Super Contributor
timestamp: July 10, 2020, 12:04:13 pm
content: Why use these newer diodes preferentially as I have a bunch of 1n34s now? Is there a reason they are better?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 10, 2020, 01:14:24 pm
content: Point-contact diodes have quite high ESR due to the, well, point contact. Small junction area. Same thing that gives them low capacitance, but which planar diodes can improve upon in all respects.If you don't happen to need performance factors in that range, no, absolutely nothing wrong with them.Tim

author: cdev
author_rank: Super Contributor
timestamp: July 10, 2020, 02:15:11 pm
content: Do any other diodes have a lower voltage drop? (and act as a more ideal 'detector'?)

author: Grandchuck
author_rank: Super Contributor
timestamp: July 10, 2020, 02:55:17 pm
content: "Infineon RF Schottky diodes are silicon low barrier N-type devices and, unlike other solutions available in the market, they come with various junction diode configurations which can be used for very sensitive power detector circuits, in sampling circuits or in mixer circuits. The very low barrier height and very small forward voltage, along with low junction capacitance, make this series of devices excellent choice as detector functions at frequencies as high as 24 GHz"Google will turn up lots of info about Shottkys

author: ignilux
author_rank: Unknown
timestamp: July 10, 2020, 07:39:45 pm
content: Speaking of "ideal detectors", you might find this oldHP app noteon zero bias schottky diodes interesting.

author: grouchobyte
author_rank: Regular Contributor
timestamp: July 10, 2020, 11:11:27 pm
content: I use these all the time for this. Cheap and not overkillhttps://docs.broadcom.com/doc/AV02-1320ENBob

author: djidji
author_rank: Newbie
timestamp: August 04, 2020, 12:49:19 am
content: Quote from: cdev on July 10, 2020, 02:15:11 pm1N21D

author: bob91343
author_rank: Super Contributor
timestamp: August 04, 2020, 03:52:20 am
content: An amazing guy.https://en.wikipedia.org/wiki/Walter_H._Schottky