Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
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:
Walkway Over The Hudson – Illinois Mountain Antennas
A better view of the assortment on the right:
Illinois Mountain – North Antennas
And on the left:
Illinois Mountain – South Antennas
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:
Baofeng UV-5R – Improved Squelch Settings
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. ]
While packing the vacuum tube LEDs for the HV Open Mad Science Fair, I noticed the knockoff Arduino Nano inside one had come unstuck from the base. It seems the double-stick foam tape I’d used had lost its sticky:
Vacuum Tube LEDs – unstuck foam tape
Replacing it with my now-standard black 3M outdoor rated tape ought to solve the problem forever more.
For whatever it’s worth, the SK6812 RGBW LEDs have had exactly zero failures in the last two years or so; I finally turned off the test fixture.
Before reassembling the light, I plugged the USB cable into the bench supply and watched the Nano reset erratically. Careful poking showed the USB cable was intermittent, so I carved it up:
Failed USB cable – autopsy
As far as I can tell, the black wire (supply common) was cut mostly all the way through, with just a few strands remaining, before I peeled the insulation back.
A closer look at the solder joints doesn’t inspire much confidence in their QC:
Failed USB cable – solder joints
If those pads tarnished along with their solder blobs, the overmolded plastic isn’t the right stuff for the job. If they started life like that … ick.
I must up my cable spend, although I have no confidence doing so will improve the quality.
I’ve finally had it beaten into my head: any public exhibition requires paper handouts, if only for younger folks who are too shy to ask questions. Paper may seem obsolete, but it serves as a physical reminder long after the sensory overload of a busy event fades away.
Hence, I made up cards describing my exhibits at the HV Open Mad Science Fair, each sporting a QR code aimed at far more background information than anybody should care about:
Because I planned to take my collection along to HV Open’s Mad Science Fair, I finally used a Round Tuit for some adhesive action.
The general plan was to punch a ring from double-sided tape, thusly:
Astable – Radome adhesive – poor surface
The OD required touching up the edge of a brass tube punch I’d made a while ago:
Astable – Radome adhesive – punch sharpening
It worked exactly as expected:
Astable – Radome adhesive – punching
Unfortunately, the 3D printed spider’s “spherical” socket has such a rough surface that the adhesive had too few contact points to hold the ball in place.
My fallback has become 3M outdoor-rated double-stick foam tape, so:
Astable – Radome adhesive – 3M foam tape
This leaves a small black ring visible between ball and socket. Recessing the foam tape by half its thickness should improve its ahem optics, although it’s probably not worth the effort with black PETG.
The battery pack on my ancient Dell E1405 laptop finally died, so I tore it apart to see what horrors might lurk within:
Dell UG679 Lithium Battery – teardown
The case snaps apart without too much effort, although the delicate single-use latches won’t survive the operation. These certainly didn’t, which didn’t bother me at all, as I already had a replacement battery on order.
One of the cells (in the front) seems to have leaked ever so slightly inside its wrapper:
Dell UG679 Lithium Battery – leaky cell
The three cells in that 3P section seem to have failed open: they pass no current at all.
The other pair of 3P slices, charged at 4.2 V with a 700 mA current limit until the current dropped under 10 mA, still have some life:
Dell UG679 3P sections
Perhaps recycling individual cells into LED glowies would be nice, as they have enough capacity remaining to run an Arduino for quite a while, and a 1S USB charger would make for a self-contained package.
The Smell of Molten Projects in the Morning 