A few months ago in a little consignment shop in our locality, I stumbled across something I’d never seen before. Stamped as “The Standard Desk Calcumeter,” it appeared to be some sort of calculating device. Since I have an odd fascination for such things, and since the price tag on it was only $12, I snatched it up. A little research confirmed that it was a cleverly-designed mechanical adding machine, where the digits were entered using the tip of a stylus on the rotating disks visible through the front plate. The Reset wheel on the far right side provided a quick and easy way to reset all the wheels to zero.
When I first obtained it, this machine was a bit on the grubby side, and the reset wheel was very difficult to turn. It was apparent that it had not been used in many years (unsurprisingly). It would be a bit of a restoration project.
If you’ve been geeking out for a couple decades, chances are you at least saw the Radio Shack ProbeScope at some point in time.
I bought one back in the late ’90s and found it to be fairly handy for a number of things. Its sampling rate, as I recall, was 4MHz, meaning you could use it to at least detect the presence of RF in a circuit. I also used it to help me debug the code I wrote to emulate serial communications in the microcontroller for my Digital Setting Circles project.
The ProbeScope included a floppy disk with software on it for both DOS and Windows that allowed you to view the waveforms on your PC by connecting the ProbeScope to the PC’s serial port. Alas, the software was written back in the 16-bit days and won’t run on the 64-bit operating systems on most modern PCs. Plus, who has a floppy drive to read that disk anymore? But if you’ve read any of my other blog posts, you know I have a habit of finding ways to revive old but still useful technology that’s long since been left behind.
This is a little tidbit I stumbled across while reading KE7X’s “The Elecraft KX3 – Portable” manual. I was interested in adding a PTT switch of some sort to go with the lightweight computer headset I intended to use for portable operation with my Elecraft KX3. It’s possible to use the XMIT button on the front panel for PTT, but I wanted something a little more convenient.
A KX3 menu setting, a simple momentary SPST pushbutton switch, and a repurposed ballpoint pen housing ended up doing the trick. I think the picture below is worth a thousand words:
After having not touched the bluetooth-serial interface I built for over a year, I pulled it out of the drawer recently and found it to be dead–specifically, the BT2S module. Seeing that a replacement was going to be $17.95 plus shipping, I began looking for alternatives. I selected the BT2S specifically because it worked at +5V voltage levels. There are a number of similar-looking modules on eBay that sell for much less, but they all use +3.3V supply and logic levels (search for HC-06 on eBay and you’ll see what I’m talking about). Could my circuit be converted to run at 3.3V?
It turns out the answer is yes. I was able to modify the circuit to operate at 3.3V by replacing the MAX232 chip with a MAX3232, the 78L05 voltage regulator with a 78L33 3.3V regulator, and the BT2S with one of the HC-06 bluetooth slave modules available from Amazon, eBay, and several other sources. No changes to the circuit board are needed. I’ve added details on the changes to the project page.
Did I mention that I just received my new Elecraft KX3 (#5522) ham transceiver? Wonderful rig (but more on that in another post). The KX3 ships with your choice of a USB cable or a serial cable for interfacing with your PC. With either of these cables, you can use Elecraft’s KX3 Utility software to update the KX3’s firmware, or you can otherwise control the rig with suitable software (say, Ham Radio Deluxe) running on your PC. At any rate, I received the USB cable with my KX3.
I’m interested to see if I can rig up a bluetooth connection between my KX3 and my Android tablet, though, and it seemed that a good place to start would be to fabricate a serial cable, to which I could ultimately connect a serial-to-bluetooth adapter of some sort. Here’s how I did it.
Tonight I played in my first Spartan Sprint in quite some time, and it was a great night for it. I just yesterday finished adding an in-ground mounting hole for my 20-ft telescoping fiberglass pole that I plan to erect temporarily as a support for my Norcal Doublet antenna. My half-size G5RV mounted along the side of the house just wasn’t cutting it, and the wind took it down the other day anyway, so it was time for something new.
I finally finished the Survivor. Truthfully, I thought I finished it over two weeks ago, but I didn’t take it to the field with me for QRP to the Field this year like I planned because, well, my plans changed. I still went out for QRPTTF, though, which is what counts. I picked up the Survivor again when I got back, ostensibly to make sure it was all ready for use. And it’s a good thing I did–it was definitely not working right.
In a previous post I told you about my purchase of the Survivor 75-meter SSB/CW rig from Hendricks QRP Kits. I’m taking a “build a little, test a little” approach to building this kit, having a great time and learning a bunch of stuff. I’ve been making some notes and adding them to my site. If you’re interested, here’s the main page for those notes. So far I’ve built up the voltage regulation, VFO, BFO, TX/RX switching, tune mode oscillator, and the balanced modulator. My goal is to have this thing completed and ready for QRP to the Field on April 27th. If this is the kind of thing that interests you, check back every few days for updates.
So, it’s been quite a while since I did any significant electronics construction. The reason is probably that it’s been a while since a new kit has come along that interested me enough to want to build it. Sure, there are plenty of ham radio kits out there, but I’ve built plenty of CW transceivers and really don’t feel like I need another one. But when Doug, KI6DS announced a new SSB/CW transceiver kit over at QrpKits.com earlier this year, my interest peaked. Dubbed the “Survivor,” it’s a fairly compact but usable rig for the trail. I decided to take the plunge and placed my order, and I’ve just begun the building process. I’m documenting the build as I go, trying to learn a few things about its design along the way. You can follow along if you’re interested:
The kit is much simpler than the serial version–the pull-up resistors were eliminated, the oscillator replaced by a crystal, and a MAX232 chip is no longer needed. The board and encoders are powered by the USB port, too, so no external power supply is needed. The kit includes all the components, including the programmed PIC chip, but does not include the TTL-232-5V cable. The cable must be purchased separately and is readily available from Mouser and Digikey, for about $20 plus shipping.
This kit should work great if you want to run your digital setting circles straight through the USB port of your laptop. However, if your goal is to use a bluetooth connection between your computer/PDA/smartphone and the board, then the serial version of the kit is the one you want to use. Furthermore, this USB version really isn’t adaptable for use with a smartphone or PDA–the TTL-232 USB cable needs to plug in to a PC in order to work.