Archive for category Amateur Radio
Wouxun KG-UV3D: Improved Knob Index
Posted by Ed in Amateur Radio, Machine Shop, Recumbent Bicycling on 12-September-2012
After Raj thoroughly shamed me for slobbering white glop on the KG-UV3D’s volume / power knob, I hereby repent…
Clamp a cutoff chunk of 3/16 =0.1875 inch diameter brass tubing in the lathe and file down one side to put the flat 0.150 inch from the far side, so that the knob is a tight slip fit. If you happen to have some solid rod, that would work just as well. In this case, the file pushed the paper-thin brass remnant into the tubing and I didn’t bother to clean it out:
KG-UV3D knob with fixture
Clean the white glop off the knob, jam the knob on the fixture, clamp the fixture in the Sherline’s vise, use laser targeting to center the spindle on the notch adjacent to the minuscule pip on the knob:
Laser aligning to knob feature
Drill a 2 mm recess that en passant obliterates the pip:
Drilling index recess
Fill it with some light gray paint that just happens to be on the shelf:
Knob with filled index mark
And, by gosh, it really does dress up the radio! [grin]
Wouxun KG-UV3D with improved knob
While I had the Sherline set up, I did the knob for the other radio, too.
Thanks, Raj… I needed that!
KG-UV3D GPS+Voice Interface: APRS Bicycle Mobile
Posted by Ed in Amateur Radio, Electronics Workbench, Home Ec, Machine Shop, Recumbent Bicycling on 11-September-2012
Wouxun KG-UV3D with GPS-audio interface
Both of the GPS+voice interfaces for the Wouxun KG-UV3D radios have been working fine for a while, so I should show the whole installation in all its gory detail.
If you haven’t been following the story, the Big Idea boils down to an amateur radio HT wearing a backpack that replaces its battery, combines the audio output of a Byonics TinyTrak3+ GPS encoder with our voice audio for transmission, and routes received audio to an earbud. Setting the radios to the APRS standard frequency (144.39 MHz) routes our GPS position points to the global packet database and, with 100 Hz tone squelch, we can use the radios as tactical intercoms without listening to all much of the data traffic.
The local APRS network wizards approved our use of voice on the data channel, seeing as how we’re transmitting brief voice messages using low power through bad antennas from generally terrible locations. This wouldn’t work well in a dense urban environment with more APRS traffic; you’d need one of the newfangled radios that can switch frequencies for packet and voice transmissions.
So, with that in mind, making it work required a lot of parts…
Tour Easy – KG-UV3D GPS interface
A water bottle holder attaches to the seat base rail with a machined circumferential clamp. Inside the holder, a bike seat wedge pack contains the radio with its GPS+voice interface box and provides a bit of cushioning; a chunk of closed-cell foam on the bottom mostly makes me feel good.
The flat 5 A·h Li-ion battery pack on the rack provides power for the radio; it’s intended for a DVD player and has a 9 V output that’s a trifle hot for the Wouxun radios. Some Genuine Velcro self-adhesive strips hold the packs to the racks and have survived surprisingly well.
Just out of the picture to the left of the battery pack sits a Byonics GPS2 receiver puck atop a fender washer glued to the rack, with a black serial cable passing across the rack and down to the radio bag.
A dual-band mobile antenna screws into the homebrew mount attached to the upper seat rail with another circumferential clamp. It’s on the left side of the rail, just barely out of the way of our helmets, and, yes, the radiating section of the antenna sits too close to our heads. The overly long coax cable has its excess coiled and strapped to the front of the rack; I pretend that’s an inductor to choke RF off the shield braid. The cable terminates in a PL-259 UHF plug, with an adapter to the radio’s reverse-polarity SMA socket.
The push-to-talk button on the left handgrip isn’t quite visible in the picture. That cable runs down the handlebar, along the upper frame tube, under the seat, and emerges just in front of the radio bag, where it terminates in a 3.5 mm audio plug.
The white USB cable from the helmet carries the boom mic and earbud audio over the top of the seat, knots around the top frame bar, and continues down to the radio. USB cables aren’t intended for this service and fail every few years, but they’re cheap and work well enough. The USB connector separates easily, which prevents us from being firmly secured to a dropped bike during a crash. I’d like much more supple cables, a trait that’s simply not in the USB cable repertoire. This is not a digital USB connection: I’m just using a cheap & readily available cable.
All cables converge on the bag holding the radio:
Tour Easy – KG-UV3D + GPS interface – detail
Now you can see why I put that dab of white on the top of the knob!
The bag on my bike hasn’t accumulated quite so much crud, because it’s only a few months old, but it’s just as crowded:
KG-UV3D + GPS interface on Tour Easy – top view
This whole “bicycle mobile APRS system”, to abuse a term, slowly grew from a voice-only interface for our ICOM IC-Z1A radios. Improving (and replacing!) one piece at a time occasionally produced horrible compatibility problems, while showing why commercial solutions justify owning metalworking tools, PCB design software, and a 3D printer.
I long ago lost track of the number of Quality Shop Time hours devoted to all this, which may be the whole point…
In other news, the 3D-printed fairing mounts, blinky light mounts, and helmet mirror mounts continue to work fine; I’m absurdly proud of the mirrors. Mary likes her colorful homebrew seat cover that replaced a worn-out black OEM cover for a minute fraction of the price.
Wouxun KG-UV3D Volume Knob: More Black on Black
Posted by Ed in Amateur Radio, Machine Shop, Recumbent Bicycling on 7-September-2012
The volume / on-off control knob on our Wouxun KG-UV3D radios has the most minute raised dot you can imagine to mark its orientation. Yes, it’s another subtle black-on-black control! See if you can spot the dot:
Wouxun KG-UV3D – volume knob marking
The radio lives in a small pack attached to the back of the seat frame: we turn it with a fingertip and adjust the volume by touch; the dot is just barely perceptible to my finger. Nevertheless, WIBNI (Would It Be Nice If) you could look at the knob from a distance and determine whether the radio was turned on?
A dab of typewriter (remember typewriters?) correction fluid later:
Wouxun KG-UV3D – garish knob marking
Not elegant and sure to wear off after a while, but the smudge should remain visible forever.
Updating An Old Bike
Posted by Ed in Amateur Radio, Machine Shop, Recumbent Bicycling on 3-September-2012
Rollfast bike with Aztek brake pads
Our Larval Engineer acquired a free bicycle to get around at school: a Rollfast “girl’s bike” dating back to 1972 with 105 miles on the odometer. She completely dismantled it, cleaned everything, reassembled it in reverse order, and added a rear rack & panniers. Having touched every part of the bike, she’s now in a much better position to fix whatever may go wrong in the future.
It was an inexpensive bike to start with and we left everything as-is, with the exception of the brake pads. You’re supposed to bend the brake arms to align the pads with the rims, a technique which I didn’t like even back in the day. So we swapped the OEM pads with worn-but-serviceable Aztek pads sporting spherical washers:
They’re way grippier than the old pads, even on those chromed-steel rims. I had a bike with steel rims and old pads; given the slightest hint of water, it didn’t stop for squat. With any luck, the Azteks will at least slow this one down.
Although she wanted to take the Tour Easy, the bike must live outside under the apartment stairs all year and, frankly, that’d kill the recumbent in short order. Forgive me for being a domineering parent; when she has a good place to store a spendy bike, it’s hers for the taking.
We haven’t figured out how to mount the GPS/APRS tracker + radio and antenna. The evidence suggests she prefers to travel incognito from now on…
Wouxun KG-UV3D Battery Contact Locations
Posted by Ed in Amateur Radio, Electronics Workbench, Machine Shop on 28-August-2012
Having gone to great pains to put the center of the contact studs on the GPS+voice case exactly at the center of the screws on the back of the radio:
HT-GPS Case – Wouxun KG-UV3D rear view
I now discover why Wouxun used 7 mm square pads on the batteries: the springy contacts hit the pack so far off-center from the studs that they very nearly miss the heads on the 4-40 brass screws I’m using as contacts. This family portrait shows the radio, the battery pack, and the GPS+voice case:
Wouxun KG-UV3D – battery contact locations – GPS case
The lines on the masking tape highlight where the spring contacts touch the case and barely kiss the screw heads:
KG-UV3D contact marks on GPS case
Squinting at the marks on the battery case contacts (you can’t see it in the pictures), the contact line is maybe 2.5 mm beyond the centerline of the square pads. How this worked on the first case I built, I have no clue. For this version, I deliberately filed the heads a bit less and recessed them into the case a bit more; obviously, that was the wrong thing to do, as the connection was intermittent at best.
For the purposes of getting things working, I wrapped snippets of copper mesh tape (from NASA, according to the surplus blurb, with conductive adhesive) around thin chunks of conductive foam, then put them over the studs. The scars in the plastic came from an abortive attempt to get the springs far enough into the case surface to kiss the very edge of the studs:
Copper mesh on GPS case contacts
There’s no point in having a contact patch on the near side of the radio springs, because nothing ever touches there. So the right thing to do is simply move the contact studs to the far side by 3 mm, centering them around the actual contact point. That means changing the PCB layout by the same amount. That’s easy enough to do, but … drat!
When I took the case apart to boost the mic gain, I replaced those neatly filed studs with unfiled pan head 4-40 brass screws from the same parts stock. The heads were tall enough to touch the radio spring contacts closer to their centers and make perfect contact. Not elegant, but better than that copper braid tape.
The one thing I do not like about the Wouxun battery packs: the radio contact pads are flush with the pack surface, so there’s absolutely no protection against casual shorts when the pack isn’t on the radio. The packs also sport four bare round contacts on their outer surface that mate with the charger, two of which make direct contact with the battery; those sit inside a shallow molded recess that helps prevent inadvertent shorts.
I assume there’s a protective circuit inside the pack that turns off the current on a dead short, but I am most assuredly not going to test that assumption. When the packs aren’t on the radio (which they never will be, effective immediately), they sport a strip of tape across those radio contact pads.
TinyTrak3+ Trimpots: Not All Are Created Equal
Posted by Ed in Amateur Radio, Electronics Workbench, Machine Shop, Recumbent Bicycling on 23-August-2012
I designed the GPS+Audio case around the TinyTrak3+ board in my radio, which has two square, blue-plastic trimpots. The case worked fine for that board. Then I printed the case for the next bike and that TT3+ didn’t slide neatly into place:
TinyTrak3+ trimpot overhang
Turns out that one of the three TT3+ boards uses plastic trimpots and the other two have metal trimpots bent to fit the existing holes (so they’re not a drop-in replacement), with a very slight overhang beyond the edge of the PCB.
So I attacked the case with some riffler files and carved a notch above the PCB slot. No pictures of that, lest you think I’m a butcher of lovely 3D printed objects. Next time: build the notch into the case’s solid model.
Most likely, this is the only instance of those pots causing anyone a problem…
Wouxun KG-UV3D Audio Levels
Posted by Ed in Amateur Radio, Electronics Workbench, Recumbent Bicycling on 22-August-2012
Wouxun KG-UV3D with GPS-audio interface
The Wouxun KG-UV3D is advertised as a “dual band” radio, but it has only one hardware receiver: in TDR mode (there is no explanation of what TDR means, so there may not be an English equivalent; I suspect it’s not Time Domain Reflectometry) with two frequencies / channels displayed, the first to receive a transmission produces audio output until that signal stops, regardless of what happens on the other frequency / channel. In contrast, the ICOM Z1A and W32A radios we were using had two hardware receivers and the audio output was the sum of the two signals, with independent volume controls.
That wouldn’t matter, except that I monitor the E911 dispatch channel while riding, so that I know when an emergency vehicle will be coming along my route: distracted drivers are bad enough, but a distracted driver dodging an ambulance is really bad. The E911 transmitters have punchy audio compared to anything else, so it’d be nice to turn down the dispatcher’s level compared to the relatively quiet voice + APRS signals on the other channel.
No can do.
The KG-UV3D also requires much higher audio on the mic input than the Z1A for the equivalent output. Contrary to that schematic, I’m now running the op amp gain at about 4.5 (13 dB) instead of 1.6 (4 dB): it’s a 100 kΩ feedback resistor. That puts it on a par with the E911 audio, but it’s still somewhat quiet.
The TinyTrak3+ board produces audio tones through a 4-bit binary resistor network that feeds into a 220 kΩ resistor in series with the 10 kΩ trimpot that sets its output level. Cranking that pot all the way up produces roughly the same volume as the +13 dB helmet mic audio. If I increase the mic gain any further, however, I should also increase the TT3+ audio output, which means reducing the 220 kΩ resistor on the TT3+ board. The TT3+ doc advises:
Some mobile radios require more audio drive than TinyTrak3 puts out. If audio levels are too low, even with the R6 pot set to maximum, consider replacing the 220K R5 with a 100K resistor or shorting jumper. This should allow for about double the audio range.
Dunno if that means another 3 or 6 dB or what, but it might come in handy.
However, increasing the mic gain has the disadvantage of causing more wind noise: it’s always there and high mic gain makes it much worse. The foam balls over the mics work well, but the voice volume drops off dramatically as the mouth-to-mic distance increase; about half an inch is a good distance. So there’s an upper limit on mic gain.
I’ve also increased the earphone attenuation, with a 150 Ω resistor in series with the earbud, to give the receiver volume control more useful range.
It’s workable as it stands and the many APRS receivers have no trouble decoding the packets, so all this is in the nature of fine tuning. I do miss the dual audio outputs, though…
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