Archive for category Amateur Radio
One of the battery packs powering the GPS+audio interface on our bikes has completely failed, with zero volts at the output and no charge indication. The other five chug along as well as can be expected:
The push-to-test button on Pack 4 has become increasingly erratic over the last few months, rendering the charge status LEDs mostly useless, so it has two curves: the lower capacity came directly from the bike, the higher hot off the charger.
For reference, here’s what they looked like in May 2012:
And right after they arrived:
Given their nearly constant use and charge cycling, I’m impressed.
Those Lenmar DVDU923 packs look similar, at twice the no-name 2010 price. So it goes…
The DCRT folks held a “soft opening” last week at the bridge over Rt 55 completing the rail trail from Hopewell Junction to the Walkway Over the Hudson; the Hudson Valley Rail Trail continues westward to Lloyd. I hadn’t actually planned to ride the whole thing, but Monday was a lovely day and, hey, why not?
So here’s what a pleasant, mostly off-road 36 mile ride looks like:
Hadn’t realized it was Columbus Day until well into the ride, which accounted for a Hudson River crossing at 3 mph embedded in a solid 1.5 mile scrum. Being no fool, I returned over the Poughkeepsie (a.k.a. Mid Hudson) Bridge.
Back in the day, you wrapped with cork tape and had to worry about the direction on each side. Silicone tape fuses into a solid mass and the orientation shouldn’t matter; that’s a Good Thing, because I’m not sure what direction would be correct in this situation.
The yellow section covers the SRAM twist grip, which means it has a moving joint at each end. I suspect the tape will pull back from the larger part of the grip and form an unsightly lump just behind it.
It’s certainly much grippier than I expected…
The first two charges for those Baofeng BL-5 batteries show that the actual capacity isn’t quite up to the 1800 mA·h spec:
The (meager) instructions say that the batteries will reach “full capacity” after three charges. Unless there’s a miracle waiting in the wings for that third charge, I very much doubt that they’ll get any better than the 1400 to 1500 mA·h you see in that graph. Note that the two batteries have quite different capacities and that the capacity for Pack B decreased on the second charge (purple vs. green trace).
Compare that with the Wouxun batteries (plotted with Gnuplot, rather than a screen grab):
Those are all at 250 mA, which is certainly less than the peak current and probably more than the average current. It’s close enough for now, anyway, and shows that the Wouxun batteries actually live up to their spec.
Huh. Who’d’a thunk it?
It looks like the blinky lights should go into power-save mode under 7 V, because there just isn’t that much capacity left when the cells start rolling over the edge of the cliff.
After I mentioned I was thinking of repurposing the nearly unused lithium-ion batteries from the Wouxun KG-UV3D radios for a blinky light, Dragorn of Kismet introduced me to his Baofeng UV-5 radio. The radio itself seems to be the worst amateur radio you’d be willing to use, but when seen as a standardized battery and drop-in charger with a free radio and antenna tossed into the deal, it’s not all that bad:
The Wouxun and Baofeng 7.4 V batteries allegedly have similar capacities: 1700 vs 1800 mA·h. The Baofeng also has a 3800 (or 3600) mA·h pack that extends well below the base of the radio (not all large packs seem to be compatible with the UV-5RE radios I got); that would be roughly equivalent to the larger packs that power the Wouxun / APRS / voice gadgetry on the bike.
The Baofeng battery pack is smaller and has features that seem less likely to misbehave on a bike.
It has a latching tab with a ramp and a positive notch, with ridges around the edge that engage the radio shell:
The radio body (which is what I must duplicate) has a movable latch tab above the battery contact pins, so the latch holds the battery into the compartment. The spring-loaded pin pairs are wired in parallel, presumably for redundant contact with each battery terminal:
The battery terminal pads are reasonably well protected by the tab:
The battery slides into the radio compartment and latches with a snap. Two holes on the battery base engage a pair of pegs on the radio case:
The holes are rounded rectangles and the pegs have one corner sliced off. The pegs seem entirely too fragile and not well suited for 3D printing, so some metalwork may be in order. The pegs must resist only pulling forces perpendicular to the case back, not sliding forces, and the case constrains side-to-side motion.
The two square posts (with two others not shown) form the “feet” that support the radio when it’s standing on the desk or in the charger.
Now, to doodle up the dimensions and measure the actual capacity.
Speaking of capacity, BL-5 batteries on eBay range from $23 for “genuine Baofeng” that may or may not actually have that name on the label, all the way down to $8 for the usual no-name equivalent.
The first Wouxun (evidently pronounced “ocean”) KG-UV3D HT spent a month or two in my bike, lashed to a kludged version of the APRS+voice interface box and powered by its own lithium-ion pack. After I got the circuit worked out and built a duplicate, I picked up a second HT for Mary’s bike; as a result, that battery pack never got much use.
A pair of discharge tests shows the difference:
The 2011-03 battery has almost exactly the rated 1.7 A·h capacity, at least if you’re willing to run it down to 6 V, and the 2012-06 pack delivers 1.9 A·h. Electronic gadgets measure state-of-charge using the battery voltage, so the older pack “looks” like it has much less capacity: it runs about 100 mV lower than the newer pack out to 1.2 A·h, then falls off the cliff. Looks to me like one of the two cells inside is fading faster than the other; so it goes.
I’m still thinking of using these to power some LED taillights, because they have a nice form factor and built-in latches:
If you happen to own an MFJ-260B dummy load and it’s giving you weird SWR values, take the cover off and roll the power resistor in its mounting clips:
My buddy Aitch discovered that oxide / corrosion / dirt buildup between the resistor and the clips can produce absolutely baffling results, even while passing enough current to warm up the element, far more power than you’d think would burn away any crud.