A view of the middle of the Very Large Array of the National Radio Astronomy Observatory:
A view of our back yard, one foggy morning:
Coincidence? Ha!
Category: Amateur Radio
Using and building radio gadgetry
The signal from the Baofeng UV-5R HT tucked behind the seat of my Tour Easy became exceedingly choppy on recent rides. Here’s an earlier version to give you an idea of the situation:
Of course, it worked perfectly in the garage and only failed while on a ride. The clue turned out to be having it fail more on rough roads and crappy scab patches (courtesy of NSYDOT) than on relatively smooth asphalt.
That led me to wiggle of All The Cables while crouched beside the bike in the garage, listening to another HT, and watching the transmit LED. After about five minutes of this, I found wiggling the 3.5 mm connector between the cable from the PTT button on the handlebar and the radio blinked the transmit LED: ah-HA!
The connector had worked itself loose from the straps holding the radio pack in place, pulled some slack in the cable, and was bouncing around in mid-air. A wrap of duct tape now holds the connector halves together, the upper loop passes around the Velco-ish strap, and the lower loop (from the PTT button) goes through the bottom of the repurposed bottle holder:
No trouble on the next two rides, so we’ll call it fixed.
Protip: it’s always the connector.
The audio output wire from the Baofeng UV-5R to my bike helmet headset adapter broke after a year and a half, far longer than I expected:
It’s the green one, over on the left, pulled out of the heatstink tubing that should have provided some strain relief, having broken at the solder joint to the resistor.
A quick & easy fix, after which I reapplied even more tape to hold everything in place.
Maybe it’ll last two years this time around …
Following a linkie I can no longer find led me to retrieve the Tektronix Circuit Computer in my Box o’ Slide Rules:
I’m pretty sure it came from Mad Phil’s collection. One can line up the discolored parts of the decks under their cutout windows to restore it to its previous alignment; most likely it sat at the end of a row of books (remember books?) on his reference shelf.
The reverse side lists the equations it can solve, plus pictorial help for the puzzled:
Some searching reveals the original version had three aluminum disks, shaped and milled and photo-printed, with a honkin’ hex nut holding the cursor in place. The one I have seems like laser-printed card stock between plastic laminating film; they don’t make ’em like that any more, either.
TEK PN 003-023 (the paper edition) runs about thirty bucks (modulo the occasional outlier) on eBay, so we’re not dealing in priceless antiquity here. The manual is readily available as a PDF, with photos in the back.
Some doodling produced key measurements:
All the dimensions are hard inches, of course.
Each log decade spans 18°, with the Inductive Frequency scale at 36° for the square root required to calculate circuit resonance.
Generating the log scales requires handling all possible combinations of:
- Scales increase clockwise
- Scales increase counterclockwise
- Ticks point outward
- Ticks point inward
- Text reads from center
- Text reads from rim
I used the 1×100 tick on the outer scale of each deck as the 0° reference for the other scales on that deck. The 0° tick appears at the far right of plots & engravings & suchlike.
The L/R Time Constant (tau = τ) pointer on the top deck and the corresponding τL scale on the bottom deck has (what seems like) an arbitrary -150° offset from the 0° reference.
The Inductive Frequency scale has an offset of 2π, the log of which is 0.79818 = 14.37°.
The risetime calculations have a factor of 2.197, offsetting those pointers from their corresponding τ pointer by 0.342 = log(2.197) = 6.15°.
A fair bit of effort produced a GCMC program creating a full-size check plot of the bottom deck on the MPCNC:
By the conservation of perversity, the image is rotated 90° to put the 1 H tick straight up.
The 3018 can’t handle a 7.75 inch = 196 mm disk, but a CD-size (120 mm OD) engraving came out OK on white plastic filled with black crayon:
The millimeter scale over on the right shows the letters stand a bit under 1 mm tall. And, yes, the middle scale should read upside-down.
Properly filling the engraved lines remains an ongoing experiment. More downforce on the diamond or more passes through the G-Code should produce deeper trenches, perhaps with correspondingly higher ridges along the sides. Sanding & polishing the plastic without removing the ink seems tedious.
The Great Dragorn of Kismet observes I have a gift for picking projects at the cutting edge of consumer demand.
More doodles while figuring the GCMC code produced a summary of the scale offsets:
Musings on the parameters of each scale:
How to draw decades of tick marks:
It turned out easier to build vectors of tick mark values and their corresponding lengths, with another list of ticks to be labeled, than to figure out how to automate those values.
More on all this to come …
The PTT switch on Mary’s Tour Easy became intermittent:
It’s been sitting there for least five years, as witnessed by the sun-yellowed hot melt glue blob, which is pretty good service from a switch intended for indoor use. The 3D printed button never fell off and, in fact, was difficult to remove, so that worked well.
I took it apart and cleaned the contacts, but to no avail, so her bike now sports a new switch with a similar rounded dome:
I clipped the wires a bit beyond the terminals and soldered the new switch in place, so it’s the same cable as before.
Now, to see how long this one lasts …
The Baofeng UV-5R radios on our bikes seem absurdly sensitive to intermodulation interference, particularly on rides across the Walkway Over the Hudson, which has a glorious view of the repeaters and paging transmitters atop Illinois Mountain:
A better view of the assortment on the right:
And on the left:
Not shown: the Sheriff’s Office transmitter behind us on the left and the Vassar Brothers Hospital / MidHudson pagers on either side at eye level. There’s plenty of RFI boresighted on the Walkway.
Anyhow, none of the Baofeng squelch settings had any effect, which turned out to be a known problem. The default range VHF covered a whopping 6 dB and the UHF wasn’t much better at 18 dB, both at very low RF power levels.
We use the radios in simplex mode, generally within line of sight, so I changed the Service Settings to get really aggressive squelch:
I have no way to calibrate the new signal levels, but I’d previously cranked the squelch up to 9 (it doesn’t go any higher) and, left unchanged, the new level makes all the previous interference Go Away™. Another ride over the Walkway with the squelch set to 4 also passed in blissful silence.
If the BF-F9 levels mean anything on a UV-5R, that’s about -100 dBm, 20 dB over the previous -120 dBm at squelch = 9.
The new squelch levels may be too tight for any other use, which doesn’t matter for these radios. As of now, our rides are quiet.
[Update: Setting the squelch to 5 may be necessary for the Walkway, as we both heard a few squawks and bleeps while riding eastbound on a Monday afternoon. ]
I bought a pair of third-party 3800 mA·h batteries for the Baofeng UV-5RE Plus (whatever that means) radios on our bikes. Oddly, the packs carry the same “Model BL-5” identification as 1800 mA·h batteries shipped with the radio:
The obviously mislabeled “Baofeng” battery eliminator also sported a 3800 mA·h label:
I conjured a “test fixture” from a clamp, copper sheet, and copper tape snippets:
Which produced interesting results:
The 250 mA load = 15 hour rate seemed reasonable to simulate radios spending most of their time in power-save mode, but the packs still delivered only 2.8 A·h.
The packs also claim an unnaturally precise 28.12 W·h, but they’re still underperformers at 20 W·h:
Anyhow, I can run the radios for a week without (worrying about) running out of juice during a ride.
The Smell of Molten Projects in the Morning 