⚠️ WARNING: This page is obsolete
Articles typically receive this designation when the technology they describe is no longer relevant, code
provided is later deemed to be of poor quality, or the topics discussed are better presented in future
articles. Articles like this are retained for the sake of preservation, but their content should be
critically assessed.
Two hours after getting home from work I’m already basking in the newfound carefreeness thanks to the successful completion of my thesis defense (and graduation requirements). Yesterday I went to SkyCraft, early this morning I posted a schematic diagram of a basic circuit concept for a radio/microphone interface box with tone generating functions, and this afternoon I finished its assembly. It’s hacked together, I know, but it’s just a prototype. What does it do? It’s complicated. It’s basically just an exercise in microchip programming.
Future Scott reacts to this in August, 2019 (10 years later)
LOL! That's a pipette box! A chip socket was sunk into a plastic enclosure somehow! And that "regulated power supply" is an LM7805 on non-metallic perfboard screwed to two Jenga blocks!
Here’s the little setup with the main control unit and a DC to DC regulated power supply / serial microchip programmer I made.
Here’s the main control box. Notice the “2-way lighted switches” which I described in the previous entry. I found that proper grounding (floating pin prevention) was critical to their proper function. I’m still new to these chips, so I’m learning, but I’m making progress!
Getting a little artsy with my photographs now… this is the core of the device. It’s a picaxe 14m!
This is a 5v regulated power supply I built. The headphone adapter is for easy connection to the serial port. It has a power switch and a program/run switch (allowing use of pin 13, serial out) while still “connected” to the PC.
I’ve slightly improved the connection between my radio’s coax cable to the J-pole antenna I made.
I’m able to get pretty good signals from this antenna, but it’s probably not likely to do much to my assembly skills (and lack of tuning), and more likely due to the fact that I have an unobstructed view of middle/southern Orlando from the 3rd story of my apartment balcony. I could probably wire up a rubber duck on a stick and get good results with that location! I’ll miss my reception when I move.
After a few weeks of using InkScape, slowly working through documentation, tutorials, and practicing drawing random objects, I think I’m finally getting the feel of designing images in InkScape, and am growing to appreciate the depth of its usefulness. I’d love to have some great diagrams to include in potential publications. For example, I want a diagram to show how the autonomic nervous system innervates the mouse heart, but no such diagram exists! Here’s one for humans but it’s major overkill, shows every organ (I only want the heart), and doesn’t go into detail as to what the nerves do when they reach the heart (something I’m researching). Also, mouse brains are very different in shape from human brains, and there aren’t any good pictures of the ventral side of a mouse brain. So, I found the best one I could and re-created it with InkScape.
I used an existing image as a reference, made half a brain, and can mirror it when I’m done. It looks pretty good, right?
I’m posting this information hoping that someone else in a position similar to mine can benefit from the experience I gained through trial and error while trying to rapidly design and develop professional-looking QSL cards at low risk. I Googled around for this information, but didn’t find anything too helpful, so I figured I’d come up with something on my own and share my story.
QSL cards are like postcards which amateur radio operators often mail to one another after making long distance contacts.__ In addition to providing tangible proof of the communication, they’re cool mementos to tote around to remember who you’ve made contact with over the years. QSL cards display information bout the contact (time, date, call sign, frequency, signal report, etc.) and sometimes contain extra pictures/graphics which make them unique and appealing.
Once I got a HF rig for my apartment (a Century 21 CW-only HF rig which puts out ~30 watts), I started making contacts and getting QSL cards myself, so I wanted to send some nice ones in return. Being a poor college student (and a graduate student at that), I was extremely cash-limited, and didn’t want to sit around for weeks while my cards were professionally printed. This post describes how I created nice looking QSL cards in a few hours, for less than $0.25 each!
Step 1: Design the cards with the correct dimensions. The most cost-effective way to print nice digital images is my local Target (a store with a 1-hr photo lab which accepts JPEGs as the image source for $0.20 cents a picture), but the snag was that they only print 4’’ x 6’’. QSL cards need to be 3.5’’ by 5.25’’. I used Inkscape to create an image exactly 4’’ by 6’’, and inside of it I drew a border 3.5’’ by 5.25’’. Everything outside that border I made black. I designed my QSL card _inside _that border, such that when the images would be printed I could trim-off the black border and have a perfect 3.5’’ by 5.25’’ QSL card.
Step 2: Print the reverse side on full-size label paper. All I needed was some framed boxes for QSL information, so I quickly sketched up the design in Inkscape and saved it in the same format as before (4’’ by 6’’). I left a LOT of white space around the edges so it’s very forgiving down the line. I then printed the design on full-page label paper (full-sheet stickers, available at most office stores cheaply in the printer paper section), placing 4 “backs” per page.
Here’s what the adhesive paper looked like after printing:
Step 3: Attach backings to QSL cards. This part is easy if you have a paper cutter. I purchased mine ~5yrs ago and I *LOVE* it. It’s almost as useful as my soldering iron. Seriously, so convenient. I wouldn’t dream of doing this with scissors! Anyhow, roughly cut the sticker paper into quarters.
Next, peel and stick on the backs of cards. Don’t worry about overhang, we’ll take care of that later…
Step 4: Trim the edges. Make sure you do this step _after _applying the sticker. This was the secret that I wish I realized a while ago. If you trim first, sticker placement is critical and difficult. If you place the sticker _before _you trim, you get perfect edges every time.
How nice does that look? If you did your math correctly, your new dimensions should be exactly 3.5’’ by 5.25’'.
Step 5: fill-out information. I decided to use a metallic Sharpie to write the name of the call sign I send this to on the front of my card. How cool does that look? This is what the front/back of this card looks like after filling it out.
I hope this information helps you. If you print your own QSL cards using this (or a similar) method, let me know about it! I have to say, for ~5 / $1, these don’t look to bad. It’s especially useful if you only want to print a few cards! Good luck.
– Scott, AJ4VD
⚠️ Check out my newer ECG designs:
I’ve been working on a homemade ECG machine over the last month. This is the most basic circuit I’m currently using, designed using two quad op-amps. I’ve produced some surprisingly good ECG traces and even identified an arrhythmic heartbeat. Currently the device is limited because you have to be attached to your computer, I’m working toward making it a mobile device (powered by a 9V battery) which records voltage data to a minidisc recorder . There’s one problem - I need to optimally adjust the gain, but how if I cannot see the trace of the wave on a monitor? I could a VU meter to monitor the output… My minidisc recorder can take mic-in and echo it the line-out at the same time, so I’ll just put the VU meter on the line-out and it shouldn’t affect my trace. The result is that I can walk around for 24 hours, recording my ECG, with a device I hope to get down to the size of a cell phone. (Maybe a 1990s cell phone?)
Here’s a simple LED-based digital VU meter circuit I found, along with some sample images of its (bread-boarded) construction. I have all the parts at home I think, so it should be straightforward to make. The pain now is the electrodes (which are still the junky ones made from scissor-cut aluminum cans), and I think I might splurge and buy some actual disposable ECG electrodes. I think the total cost of my device as it stands is about $4, so I don’t want to spend more than I have to on electrodes.
In other news it appears I’ve been accepted into dental school. I got a voicemail this morning at 8am, another one at 12:30pm, and apparently one on my parents’ answering machine (I listed them as an alternate number), then they sent me an email! Naturally it was the email I noticed first. Here’s a snapshot from my inbox, phone call 1 and phone call 2.
