Archive for category Amateur Radio
Separately charging all four cells from the Baofeng BL-5 packs covered the Electronics Bench with wires:
The cell sits on a ceramic tile as a nod to fire safety, although I doubt it makes any difference.
The discharge tests showed two nearly identical pairs:
Surprisingly, cells A and B (upper traces) were deaders in the original packs. Cells C and D (lower traces) were more-or-less fully charged, but now have a lower terminal voltage and slightly lower capacity. I have no explanation for that, nor for the voltage undulations.
The rebuilt packs pair up A+B and C+D.
Reassembling pairs into the pack shell and resoldering all the leads produces a good pack:
I later added a snippet of heavy manila paper under the nickel tape bent around the edge of the pack as a third level of insulation, in the interest of having the nickel tape not produce a dead short between the isolated – terminal and the + cell case.
Memo to Self: tape the long wiggly leads from the protection PCB to the radio contacts (at the left side) before soldering the PCB to the cell terminals, because an inadvertent short will convert the 8205A battery protection IC into a Light-Emitting IC, at least for a moment, and subsequently release the Acrid Smell of Electrical Death. A handful of charge PCBs are en route halfway around the planet, from which I intend to liberate one IC for this board; with luck, I didn’t incinerate anything else.
The pack works fine in the radio, as does the APRS interface:
Unfortunately, two APRS iGates vanished in the last year, leaving poor coverage south of Poughkeepsie.
The TinyTrak3 on the Wouxun adapter wasn’t working, showing a dim red Power LED to indicate it wasn’t getting enough juice. A bit of tracing showed my adapter board provided just over 5 V to the poor thing, not the nearly 9 V it should be getting, which led me to believe the transistor switching the supply had failed. A bit more tracing, however, revealed the true problem:
The schmutz on the black cap matches up with a crater in the rear of the (originally not so) brown cap.
The Little Box o’ SMD Caps revealed two nearly identical sets of 33 μF caps, one with a 6 V rating, the other with 16 V rating. Yup, when I added that cap in the hopes of reducing RFI troubles, I soldered the wrong one onto the PCB: it’s my fault!
The poor thing lasted for over six years with just under 9 V applied to it, so I can’t complain.
I removed the corpse and reassembled the box without the additional cap (and without the terminals contacting the back of the Wouxun, because reasons). If RFI turns out to be a problem, I’ll take another look at the situation.
My carefully contrived plug plates for Wouxun radios:
… of course don’t fit the Baofeng radio. This being in the nature of a final fix, I chopped off enough protrusions to make the remainder fit snugly into the recess.
The case containing the TinyTrak3 GPS board and the APRS-voice adapter PCB of course doesn’t fit in place of the Baofeng battery pack, so I replaced the battery contact studs with simple 4-40 screws to prevent heartache & confusion.
Based on one ride, both Baofeng batteries have very little capacity left after several years on the shelf, which comes as absolutely no surprise whatsoever.
As part of some protracted flailing around while trying to get GNU Radio running on a Raspberry Pi 3, I discovered Raspbian defaults to a 100 MB swap file, rather than a swap partition, and everything I thought I knew about swap management seems inoperative. The key hint came from some notes on
/etc/dphys-swapfile config file to set
CONF_SWAPFACTOR=2 for a 2 GB swap file = twice the size of the Pi’s 1 GB memory.
Start it up:
sudo dphys-swapfile swapoff sudo dphys-swapfile setup sudo dphys-swapfile swapon
And verify it worked:
cat /proc/meminfo MemTotal: 949580 kB MemFree: 194560 kB MemAvailable: 594460 kB Buffers: 85684 kB Cached: 377276 kB SwapCached: 0 kB Active: 600332 kB Inactive: 104668 kB Active(anon): 250408 kB Inactive(anon): 20688 kB Active(file): 349924 kB Inactive(file): 83980 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 1918972 kB SwapFree: 1918972 kB Dirty: 40 kB Writeback: 0 kB AnonPages: 242072 kB Mapped: 136072 kB Shmem: 29060 kB Slab: 33992 kB SReclaimable: 22104 kB SUnreclaim: 11888 kB KernelStack: 1728 kB PageTables: 3488 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 2393760 kB Committed_AS: 947048 kB VmallocTotal: 1114112 kB VmallocUsed: 0 kB VmallocChunk: 0 kB CmaTotal: 8192 kB CmaFree: 6796 kB
Then it became possible to continue flailing …
Rather than bestir myself to measure the Test Signal Source on the Ham-It-Up upconverter:
The 74LVC2G14 Schmitt-Trigger Inverter datasheet supplies useful parameters:
All of which come together and produce a waveform (clicky for more dots):
Which suggests the Test Signal ticks along at tens-of-MHz, rather than the tens-of-kHz I expected from the birdies in the filtered 60 kHz preamp response.
Of course, hell hath no fury like that of an unjustified assumption, so actually measuring the waveform would verify the cap value and similar details.
The dotted line comes from WWVB’s 1 Hz PWM (-ish) modulation: yeah, it works!
Well, not quite all the hash. Enabling the SDR’s hardware AGC and zooming out a bit reveals some strong birdies:
The big spike over on the left at 125.000 MHz comes from the Ham-It-Up local oscillator. A series of harmonics starting suspiciously close to 125.032768 kHz produces the one at 125.066 MHz, just to the right of the WWVB signal, which leads me to suspect a rogue RTC in the attic.
There is, in fact, a free running “Test Signal Source” on the Ham-It-Up board:
Although I have nary a clue about that bad boy’s frequency, measuring it and cutting the inverter’s power trace / grounding the cap may be in order.
The SDR’s AGC contributes about 30 dB of gain, compresses the hottest signals at -25 dB, and raises those harmonics out of the grass, so it’s not an unalloyed benefit. Manually cranking on 10 dB seems better:
The bump in the middle shows the WWVB preamp’s 2 kHz bandwidth around the 60 kHz filter output, so the receiver isn’t horribly compressed. The carrier rises 30 dB over that lump, in reasonable agreement with the manual measurements over a much narrower bandwidth:
With all that in mind, a bit of careful tweaking produces a nice picture:
I love it when a plan comes together …
Radio communication between our bikes failed on the way back from a grocery ride and the problem turned out to be a failed radio:
The Wouxun KG-UV3D radio seems jammed firmly somewhere in its power-up sequence, doesn’t respond to any buttons, and has no hard-reset switch. On the other paw, it’s been in constant (and rugged!) use for almost exactly five years, so I suppose it doesn’t owe me much of anything.
The new radio, another KG-UV3D from PowerWerx, has marginally different spacing around the screw attaching the plug cover preventing the previous screw from fitting, so I kludged up a screw from a 2 mm socket-head screw, a 2.5 mm (yes) washer, and a pair of 2 mm nuts:
Which looks a bit odd, but holds the plug adapter plate firmly in place:
I suppose when the radio on my bike fails, I must rebuild both APRS + voice interfaces for Yet Another Radio, because the Wouxuns will be completely unobtainable.
The weather abruptly became too cold for riding, at least for sissies such as we, but maybe we’ll get out later in the month …