Germanium diodes are a staple of electronics. It appears as the detector in both radio and television, the tone chain of musical instrument amp, and plenty of other places. This part offers a low voltage drop, low capacitance, and relatively high speed. They used to be cheap and everywhere, and still have plenty of uses - especially for experimenters.
Unfortunately, germanium diodes aren’t common these days, and aren’t made in any great quantities. There’s also the online hysteria surrounding the part, where unscrupulous sellers are more than happy to label a schottky diode as germanium. While these are fine for detectors in radio, they aren’t germanium and if you’re expecting the properties of germanium, you won’t get it.
However…
The USSR made germanium parts right up until the end. There’s still millions of germanium diodes out there from this era, and, while even those are starting to get harder to get, you can still get them relatively easy from online sellers and auction sites. These diodes are perfectly good germanium parts, and came in many different styles and ratings. For most experimental purposes, there’s no difference between parts, and this isn’t going to discuss that. There is, however, a singular difference between Western and Soviet parts.
Here’s an old GE 1N60 diode. This image came from…the Internet. Somewhere, I’m sorry I don’t remember where.
Note that the package states the cathode, i.e. negative-most terminal, is denoted by the band, or the bar on the graphic symbol (the diode symbol) printed on the glass. In this case, the cathode is pointed towards the left. This is the way Western diodes are marked, and is the way pretty much every diode made today is marked. There are some exceptions, but there’s almost always some identifier to indicate what’s what.
Here’s a bunch of diodes.
I’m going to test these parts. We have, from top to bottom:
A traditional 1N34A glass diode.
An unknown germanium - this may be a 1N60.
A Soviet type D9A.
All of them have well denoted bands. I’m going to toss in a 1N4007 Si rectifier diode (not shown) as well, just for comparison.
Here’s the parts as viewed through a magnifying glass. Of particular note is the Soviet part - you can clearly see the flying lead and the point of contact on the germanium crystal.
1N34A
Unknown germanium
Soviet D9A
Testing the diodes
What’s the purpose here? Well…the Soviet part has something interesting about it. If you’re familiar with how the diode works, you’ve already noted the issue.
Let’s test the parts, I’m going to be using my old reliable, a meter I purchased many many years ago. It has a diode function that tells you the voltage drop across the diode’s junction.
For diodes, these are the “perfect” theoretical voltage drops across a junction:
Silicon: 0.7VDC
Germanium: 0.3VDC
In reality, it’s closer to 0.5VDC and 0.23VDC, respectively. Let’s test the parts on the bench. First one is the silicon diode, for comparison.
Note the negative lead of the meter is on the banded side of the diode, so we know that’s the cathode. We see the expected 0.5xxVDC drop of the junction.
Here’s the 1N34A:
That’s in line with the expected drop.
Here’s the unknown germanium:
Again, the expected drop.
Here’s the Soviet D9A:
It’s correct, that’s zero. There’s no drop across this device, indicating the unit isn’t conducting. It’s connected correctly, isn’t it?
No - Soviet diodes put their bands on the anode. That is, they are marked completely backwards from what we accept as diode marking. Here’s the device properly biased:
There’s the expected drop. Completely backwards from what we expected.
Why is this important?
Soviet germanium diodes are the most common Ge diode available at this time, so they show up in a lot of places. Radio kits, fuzz boxes for guitars, small signal rectification circuits - anywhere a diode with it’s properties are needed. For a radio kit, it’s not really terribly important which side of the information you recover from the carrier, but if you’re trying to rectify a signal it’s very important. You need to make sure you install them correctly, and if you follow “accepted” conventions you’re not going to accomplish that goal.
Measure your part - that’s the best way to verify what you have.
Recently, a forum buddy and I talked about capacitor measurement and devices to do such work. I decided, since I have a number of devices and access to a calibrated measurement device, to check a number of parts to see how well each device matches.
Why are we testing capacitance meters?
Simply put, there are many out there on the market under $100, and I have a number of them. I wanted to both know how these performed, and I told the forum I’d see which one performed the best. Thus, the testing.
Introduction and the devices themselves.
The reference device is an Agilent E4980A. This is a thousands-of-dollars instrument that tells you nearly everything you could need to know about capacitors. It’s calibrated, and has compensated kelvin clips for the measurement end. There are no pictures of this device in situ because, while the facility it’s in says I’m free to use it, they asked that no pictures be taken inside the facility. Sure thing, no prob. You can find pictures of this device online.
For this testing, I wasn’t worried about marked value vs. actual value, although that was recorded for posterity. All of the parts save one is NOS or RFE. These parts were chosen to be representative of the components you would find inside of an older device, especially the kind that typically graces my bench.
Capacitance meters were chosen based on the fact that you can get them, or their re-badged cousins easily at a show or online. Those devices are:
A generic L/C meter from an online shop. No name.
A FNIRSI LC1020E.
A B&K Precision Model 830 Autoranging Capacitance Meter.
A NIU M-Tester from Dayton 2016.
The leads in the picture were used for all devices except the m-tester, which needed the jig clips shown. These were made by me the night before testing using stock from my parts bins.
The parts that we’re testing.
Components were either things I had in storage, things I had bought for projects, or components removed from devices. All save the new one on the top left were suspect, leakage/etc. did not factor in to my testing.
They are, from left to right, top to bottom:
A Supertech wet, 100μF, new.
A GI 50μF dry, NOS.
A Mallory dry, 20μF, RFE
A Good*All wax paper 0.25μF, RFE.
A Bumblebee dry paper, 0.047μF, RFE.
A Solar postage stamp, 100pF, RFE.
A Sangamo Silver Mica dogbone, 1nF, new.
A Aerovox postage stamp, 6300pF, NOS.
A CornellDublier postage stamp, 10000pF, RFE.
A Bumblebee paper in oil, 0.022μF, blue wire lead, RFE. (Leaks oil.)
A Bumblebee paper in oil, 0.022uF, bare wire lead, RFE. (no leaks yet!)
A Sprague wet, 15μF, RFE.
A GI encapsulated paper, 0.033μF, RFE.
New = new part purchased within the last few years.
NOS = an old part, otherwise unused.
RFE = Removed From Equipment.
wet = wet electrolytic
dry = dry electrolytic
The rest should be self explanatory.
The postage stamps are presumed to be mica, but it’s hard to tell. Paper was packaged that way, so no assumptions are being made to their construction.
The testing methodology and notes.
Testing was simply connecting the unknown, adjusting the frequency (if possible,) and recording the value. Test frequencies used were:
120Hz - All electrolytics
1KHz - All others
The reason for this is these meters use a component of measurement called reactance. This is basically resistance of the part, with a phase angle. Geometry students will know that as a phasor, a complex number with an imaginary √-1 component. This complex number is a resistance value and an angle, -90° for a perfect capacitor.
You can’t measure DC resistance of a capacitor because it holds a static charge on it’s plates, and presents an open to your meter. AC, however, “goes through a capacitor like piss through a tin horn,” according to my first electronics instructor, Mr. Norman. This complex number is why you have a capacitor on motors. Not only does the capacitor help provide a kick to start the motor (the storage capacity of the device,) but the capacitance tries to drag the opposite force of the motor’s inductance back to zero where you only pay for the actual power used, not the power represented by the complex number. It’s basically black magic with some science added for flavor.
Regardless, data was recorded from all devices and compared to the reference unit. I originally thought that the venerable B&K 830 would provide the best measurement, as it was a fairly expensive instrument sold to industry, but that was not the case. I’m assuming this is because it doesn’t change the measurement frequency, but tries to use a best approximation for everything.
The FNIRSI device, however, came within 0.5% of the Agilent reference except on a very small value part, of which is probably due to capacitance of the leads…1 part in 100 is 1%, so any small deviation is going to show up. It’s far better than you’d need as a hobbyist and shows how far we’ve come in tech. The M-Tester and the B&K 830 kind of went around themselves competing for 2nd place, but the M-Tester offers other component tests and is really good enough for most stuff. It’s a fairly valuable device on my bench.
I realized after the fact that the FNIRSI device came with kelvin clips - I’ll re-run the test at a later date and publish new data.
The blue generic device came in third. It’s not terribly accurate, but it did the job. If you needed something and were working on old equipment, this device would satisfy your needs.
Conclusions.
The FNIRSI LC1020E, at about $80, is a superb value and will get you industrial bench performance at a hobby price. This is without using the compensated clips, so you get an instrument with leads you can reliably expect to provide good data, assuming you can set it up. The device does far more than this, and offers a staggering amount of data on the parts.
The M-Tester is a good, quick way to check all common parts, including common semiconductors. While not as accurate, they’re cheap, good enough, and should be in your travel bag if you do electronics of any sort.
The B&K 830 is meh. These still show up on the secondary market, but really don’t do anything that modern devices can’t. They are fairly rugged and can be powered from the line, so if you need a good-enough device with those parameters this is your man.
The generic one is nah. If you can get one for a couple bucks at a show, sure. It’s good to have a 4th opinion. Otherwise? Pass.
If you hit Projects recently, you may have noticed the site running slow or not responding.
I can’t be certain, but I think that had something to do with the comments. I decided to re-open them for a while with “hold for approval” selected and some basic keyword filtering to reduce the adult spam. That immediately gained me a list of spam in Cyrillic that, when translated, was more-or-less meaningless, as well as the expected adult website spam. But site performance also started to suffer with random timeouts, poor image retrieval, and just overall slow times. The host’s site tools would similarly time out.
Commenting on boards such as mine is highly weaponized. I expected nothing - and got it. Comments closed, some code was modified to remove the ability to get into the comment form or feed, and that was that.
But, site performance came back pretty much within an hour or two of doing that.
What did I find?
After the two brain cells I have left managed to connect “Site performance better” + “Right after comments closed” = 4, I pulled the logs for the last few weeks. I found what I was looking for:
14.184.185.155 - - [18/Mar/2026:06:02:01 -0400] "GET /projects/index.php/2026/01/15/the-sabtronics-2010a-dvm-part-1-checkout-and-observations/comments/ HTTP/1.1" 200 5646 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.64 Safari/537.36"
Just page after page after page of bots like Claude, SEMrush, Petalbot, and countries like Egypt, Viet Nam, China, and Germany slamming the site trying to retrieve the comments feeds on both the production and (now turned off) dev site I was using to test new themes. Once I turned that feed off and removed the dev site, a few more 404s and then the storm was gone.
Analysis and thoughts on the spammers and slammers.
You’ll notice some familiar names in there. Claude, is of course, Anthropic’s AI bot, and it was a very bad actor. I’m considering blocking this one via IP and name just because they are hard on things. SEMRush is SEO, so someone is indexing my site with that. I saw Huawei’s bot, Meta’s bot, ByteDance’s bot, and others, all slamming to get those comments. Same posts, over and over and over. I haven’t even located the comment posters yet, there’s so much noise.
The minute they (comments) were gone, it stopped and performance was back. Would that have eventually slowed as these bots finally filled their need for new URL indexing, or would they have assumed that a comments feed might get comments so it needs to be checked over and over? I have no idea, but regardless of that, comments were not useful on this page and they are gone. Because of the way this blogging platform works, you’ll see “🐗❤️” instead, which just takes you to the post from the main feed, or the top of the post when viewing a single post.
As always, if you’d like to comment on something, please use either Mastodon or the Telegram feeds: Channel Feed and Chat Channel - anyone can join the feed, it generally follows here but I do post one-off shots of things I’m working with or find interesting. The chat feed is by approval, but I generally won’t disapprove unless the person is spamming.
If you want to follow what’s going on here, there’s now a telegram channel. It will generally follow the blog, with perhaps a few more messages about events here and there, as well as pictures of things I see while out and about that could be of interest to the channel but don’t warrant a full post.
Check it out: https://t.me/wereboarprojects. You will, of course, need Telegram but you can preview the feed without joining.
There’s also a chat channel: https://t.me/wereboar_projects_chat - it’s open to all but new members must be approved. This is just to prevent spambots.
Early boar ticket prices end March 1st, after that the price goes from $26 to $30. This ticket gets you in for all three days - May 15th, 16th and 17th. Ordering now also gives the post office plenty of time to deliver to you.
If you’d like to comment on a post, please do so - click the link at the bottom of each post that has the word comment in it.
You’ll need a name, and will have to answer a simple question to submit your comment. After that, I’ve set it up so that they are hidden until I can review them - while this won’t stop the spammers, you won’t see it until I make sure it’s not spam. I’ll try and look at any posted comments a couple times a week.
Let me know what you think about the work I’m doing, if you like it (or don’t like it, I’ll take constructive criticism,) or even if you’d like to see more of something I’ve posted. Keep it clean, things that are obviously spam, bait, and profanity won’t be visible.
They’re closed again. Strange Russian spam that I couldn’t figure out what they were posting for, and posts that mention sites that only talk about fans…there’s nothing of use here. Please use mastodon to comment, or join the telegram channels.
There was also the oddity of poor performance shortly after I re-opened the comments, all of which vanished the moment I closed them and removed the links from pages. I have to wonder if someone was slamming the site trying to post comments only to be rejected due to the simple keyword filtering I installed. I’ll know more when I do forensics on the logs.
One of the things that has been suggested to me is a quick way to find all of the major projects that have appeared on this blog. The easiest way for me to do this would be as you see it here: a single post, similar to hamfest pictures, that collects all of the major device projects that have appeared here.
This hub contains all the the things I am currently working on, or have completed. New projects that are still underway generally appear at the bottom of the post, and the post will grow as more are added. The only things that are not here is a few small things that I did for other people, or the home automation stuff. You can find the latter in a new category on the sidebar aptly labeled “Automation”.
There’s a permanent link on the sidebar that will bring you directly to this hub post.
Click on the title of each item to be taken to that project’s hub.
If you’ve been here before, you’ve probably noticed something different.
There’s a new theme set for the page.
Why? Well - as the world becomes more mobile, the site needs be mobile friendly. While I liked the simplicity of the previous theme, it didn’t react well to mobile and made viewing on your phone difficult. This template is reactive, and shows the site better to both desktop and mobile. I’ll make a few small changes, like the top image, but overall I like this. It’s clean, the colors are calm and pleasing, and it does react well to mobile. I’m still playing with some things, so there’s a few placeholders. I’m also going to try and update Flatpress to a newer version, but that’s going to be in a testing directory - you shouldn’t see any “the way this works” changes until I’m satisfied that the system is operational.
If you’re not seeing a new theme, ctrl+F5 should clear your cache and reload fresh.
I recently undertook a task to clean up and optimize images here on Projects, both for size and content. Some of the images were simply enormous, and some were showing stuff not relevant to the task at hand. You don’t need to have 5MB of image downloaded just to show you my bench with a single part on it. It can be much smaller. I also wanted to name things with a more universal convention.
That has been, more or less, completed. There’s a few images hanging out in hamfest folders that could be touched again, but for the most part they’re fine. And a couple I missed in QA…
Enter part 2.
Flatpress has a plugin that allows the pages to present a set of metadata that makes it more friendly towards searching. I’ve decided to (slowly) go through the pages here, add descriptions and keywords, and hopefully make the site easier to find what you’re looking for. This is probably going to take a while, but you shouldn’t see any interruptions on the front end of the site. I’m going to be working forwards from 2021, with 2026 already fully metadata’d.
Thank you for visiting Projects. I hope you’ve found something of interest here.
Progress:
2026: Done
2025: Done, and found some missing images.
2024: Done, and found some missing images.
2023: Done, and found some missing images.
2022: Done
2021: Done
This project is pretty much done. I’m going to set the search engines loose on the site in the coming weeks, hopefully more links to the site should show up and provide easier searching.
While still about 4 months away, there’s no better time to get your ticket as you can get the early boar price of $26, mailed to you at no extra charge. This is good for all three days - May 15th, 16th and 17th.
Ticket prices increase March 1st, so there’s no time like the present to get one if you plan on attending. Get your ticket here: https://hamvention.org/purchase-tickets/
