A Crummy Commercial

Senseless Destruction but Fun: source: https://www.youtube.com/watch?v=_bdp9nk0NZk I never would have thought of this idea.  Now I have (like most experimenters) accidentally connected power backwards.  The center ground pin on a coaxial power connector was the culprit when I popped the big electrolytic in my old Koss amplified computer speakers (I should have used the wall wart !).  What an amazing stink was discovered !  Yuck, hopefully whatever gas is released doesn't cause disease :)  Now I routinely incorporate some kind of reverse polarity protection circuitry into any project. The only willful destruction of electronics that I recall participating in was using a tube tester in the Nicolet Radio Club to "supernova" the filaments of innocent vacuum tubes :)  What a waste - it got old rapidly though. Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm

I thought this was an interesting video, there are also other shorter ones from different people on Youtube. source:  https://www.youtube.com/watch?v=zhZEi7bOAjY I've mentioned de-capsulating before: https://wb9kzy.blogspot.com/2022/01/before-flash-there-was-eprom-that.html This is probably a pretty obvious idea given that the ICs are now marked with lasers, but I never thought of it. I wouldn't have had the chip power on while the laser is on but it's certainly cinematic :) I would have done the 2nd chip the opposite way, use high power at the start and then down shift the laser to lower power at the end which he sorta does for a while but then relents. It sure does beat using a Dremel tool to dig a "well" and then using red fuming nitric acid (after heating with a hot plate) to de-capsulate an IC. Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm

Yes, I do still sell the AT-121 piezo sounder on the switch and parts page (this blog is called: A Crummy Commercial for a reason :) http://wb9kzy.com/switch.htm The AT-121 is 35 cents but they do look a little grungy and have short leads - I also still sell the larger CPE-6080 piezo at $2.50 each. However one thing the AT-121 has that the CPE-6080 doesn't have is a third, blue wire - this is a feedback area of the piezo.  It's used with this type of simple circuit shown on the datasheet: I realized that I never tried this circuit - when I've used the AT-121 in my own projects I always drove it via the red and black wires by a square wave from a PIC.  The blue wire was just clipped off.  But what are the advantages of the datasheet circuit ?  The main one that comes to mind is that it is simple but also since it operates at resonance, loud.  That volume is bordering on obnoxious at 9 volts but must be ear splitting at 28 volts. So anyway I did try the circuit on...

I finally found the CQ Magazine article by W1FB from October 1997 on an antenna switch construction project.  I've mentioned it several times, for example: https://wb9kzy.blogspot.com/2022/10/dougs-desk-in-cq-magazine.html Here are the schematics: I remembered the article as using automotive relays (aka Bosch) which is correct BUT I also remembered it as employing a power saving circuit for the relays - that isn't true. So I don't know if I am thinking of a different article/author or ?? Here is a short relay power saver video: source:  https://www.youtube.com/watch?v=CqLfx7yIhIE It shows the concept of bridging a series resistor with an electrolytic cap - this allows the relay to pull in but the relay current decreases as the cap is charged. I don't know what to say about my memory though :( Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm

I saw this on Ebay: Source:  https://www.ebay.com/itm/287339757881 It's a small, notecard sized display - E-paper like the various E-book readers.  The virtue of E-paper is that it requires no power to keep alive.  Indeed these Ebay displays are powered by NFC (near field communication) like the smart credit cards.  So it doesn't need a power supply, just an NFC signal to upload the image you want to display.  Then the image persists even if there is no signal present.  This NFC signal probably comes from an app for an NFC enabled phone, which I now have !  But it could come from something like an Arduino with an NFC shield. But you are probably thinking: can't you just write (or use a computer printer) a message or image on regular paper or card stock - that doesn't require any keep-alive power, right ?  That's certainly true, as I said, it's almost irresistible :( I was thinking of E-paper for a clock display but there are two problems, this NF...

In the olden days of the 20th century Morse code keys were so common and cheap that you could do stuff like this: source on page 38:  https://www.worldradiohistory.com/Archive-Radio-TV-Experimenter/Radio-TV-Experimenter-1967-08-09.pdf BTW, I don't know what they are talking about at the end: "since most keys have both a make and a break contact" - I've never seen this - keys are single-pole-single-throw AFAIN.  I think the only way I could sanction this project is using one of those cheap keys with a plastic base like this one that came with the Knight-kit LC-1 CPO: Now Digi-Key doesn't sell keys (if they ever did).  They *might* sell you Fahnestock clips: (the key relay uses two Fahnestock clips) at $3.54 each in quantity 1000 and they have to be special ordered ! Yeah, I don't think I'm going to go into the key as relay kit business anytime soon ! Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm

I got a couple of goodies in the mail on Saturday, first another breadboard (they are always handy but I probably overpaid at $7.37 delivered with tax): It wasn't new though, one of the rubber feet is missing: I will add a ground plane like I did here with the new one I bought from the same Ebay seller: https://wb9kzy.blogspot.com/2025/02/a-quick-project-for-cleared-bench.html That seller also had this: An actual new-in-box Oak Hills Research wattmeter meter (only) - not bad for $7.37 delivered with tax.  I didn't ask where it came from but the docs for the wattmeter are on the internet so it shouldn't be too hard to brew up a home made copy.  The enclosure will be a little more challenging though. Finally, I saw this when I went out for the mail (and got the above Ebay items) on Saturday: Saturday wasn't that great  a day The snow recedes and reveals the secrets of what perished during the hard winter !  At least it was only a road sign, not my mailbox :) Best Regar...

I saw this in the daily ad from Electronic Goldmine: $20 for a Germanium diode is a little high but the name Hoffman reminded me of this ad: Here is a Hoffman Solar radio KP706 for $289 on Ebay (and the solar cells don't work !) source:  https://www.ebay.com/itm/177777411535 The inflated price of the KP706: More info on the KP706 here: https://solarmuseum.org/cells/hoffman-rp-706-solar-radio/ Here is a picture of Les Hoffman of Hoffman Radio: source:  https://www.ebay.com/itm/306751529317 Basically everything associated with Hoffman is high in price :) Here is the wiki for Les Hoffman: https://en.wikipedia.org/wiki/Les_Hoffman And what could be done with that $20 diode in a $289 radio ?  Maybe as a detector replacement ?  Here is the Beitman 1960 schematic: It's a nice radio but of a pretty standard design, I'll keep both my $20 and $289 in my pocket :) Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm  

I became aware of an adjustable voltage regulator IC, the LM338K, which is a 5 amp adjustable regulator in a TO-3 can: Yikes, over $100 ?   The LM338T is the same part in a TO-220 package: The only reason I can see for offering the part in the expensive package is that the TO-3 steel case is probably hermetically sealed (hermeticity requires metal, glass or ceramic) - this is important in certain commercial and military applications.  I suspect that these are for repair / spares only - although it's surprising that they still offer the chip at all in this package.  The TO-220 packaged chip would be fine for me :) Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm  

I saw this part mentioned on the GQRP email list (I gotta renew my membership one of these days !): Had never heard of it before, apparently it is quiet enough for radio use.  Not super cheap but reasonable: And it should also plug in for a 78L05 (ground in the middle pinout not necessarily space wise) but not sure on how the Recom compares as far as power goes.  While it only has a 500 mA rating the 7805 needs a big heatsink to handle a full 1 A current, over 7 watts.  This might be a candidate for an emergency USB charger from a 12V source: https://wb9kzy.blogspot.com/2025/05/charge.html The 9 volt version also looks interesting for use with transistor radios during a power outage.  No power event today but the internet was out for almost 1/2 hour - as long as the temperature stays below freezing the power should be relatively secure - it's that ice on the trees plus wind that causes problems.  Best Regards, Chuck, WB9KZY http://wb9kzy.com/ham.htm  

Waiting on 4 USPS packages: I was *supposed* to get the last item on Wednesday - what a lot of bunk: "Held at Post Office, At Customer Request"   It is some boards for kits, why would I delay delivery ?  I suspect they just forgot to deliver it and that was the closest excuse on the system ?  Note that I did get one piece of junk mail on Wednesday.   The first item (which was fulfilled by Amazon)  arrived on the Island Wednesday but the USPS doesn't deliver until the next day.  Wouldn't any other business deliver the same day ?  I realize it's the winter ferry schedule but still, it never used to be this way. The Digikey item is also for a kit order - BTW, Digikey also baked in a extra day before sending the order: "unavoidable delay" So I guess I shouldn't complain about the USPS delays if even Digikey now has feet of clay :( Update: the Amazon package and the "held at customer request" package did show up:  But 9:55a ?   I didn't ...

The Jaycar Short Circuits transmitter was blogged on here previously: https://wb9kzy.blogspot.com/2025/12/jaycar-am-morse-code-transmitter.html I mentioned the damped sine wave output and after a little looking I finally figured out why the circuit acted that way.  The ferrite rod used was from an AM/FM tuner by Oak, bought at Olson Electronics last century.  The connections I made to the smaller winding (L2) were intermittent and were apparently shorted in the circuit  So I tried replacing the ferrite rod with the coil from an old GE radio.  There is no secondary winding (in effect L2 is replaced by a short) so there is no feedback to sustain oscillation, the output waveforms: the flip flop output is in yellow When the flip flop connection to the base of Q3 goes low, the coil energy is dissipated in the tank circuit resulting in the damped sine wave. the signal (blue trace) is a damped sine wave with a frequency of about 1.3 MHz  And I purposely excluded t...

In the olden days of the 20th century, headphones were sometimes called: cans.  Well here is a 21st century version of high impedance cans (really can, a single element): It uses the headband from a defunct Gemini headphone - the dynamic elements and padding were removed.  Cable ties were then used to attach the Altoids round tin lids (actual cans).  Then a piezo telephone sounder, a CPE-6080, was wired to a 3.5 mm jack.  Then a standard 3.5 mm cable can be used to connect to a radio.  I did try these with the Elecraft K2 headphone jack and they are usable although not super comfortable.  I could add another piezo to the other can in the future but for now this is it. I also tried it with the old crystal set but no luck, the antennas currently in place are too small to be of use or some connection has broken over the winter - I'll try them again in the spring when antenna time returns. High impedance ?  Yes, although there is a peaky response: the CPE-...