Hand Crank Generator
Tested on W6/NC-190
No Batteries Required
A potato powered radio was the most ridiculous way I could put my QRP Power Board to the test, but a hand crank generator was also high on the list of strange power sources for a SOTA activation. Luckily, an early generation K-TOR "Pocket Socket" popped up on Craigslist for $20!
The Pocket Socket has a standard wall outlet, but outputs 120V DC and can produce 10W if you're determined. I tapped into the motor's rectified output and fed this to the buck-boost on the QRP Power Board.
Summit: W6/NC-190 (Marsh Benchmark)
Date: April 23, 2022
Route: Hike from Morgan Territory Staging Area
Equipment: QCX-Mini, 49:1 matching unit, 45' wire, Pocket Socket hand crank generator, 120mF capacitor bank, and QRP Power Board.
YouTube channel "ham_bitious" (AA6XA and KN6REU) posted a video from the day!
The Activation (Marsh Benchmark, W6/NC-190)
After a fun meet and greet with the NorCal SOTA group, I joined KE6MT, AA6XA, AB6D and K3GX for a hike up Marsh Benchmark. Nice day, and a nice hike through the lush hills. After some HF contacts and S2S with AJ6X and KM6ELO on nearby Mt. Diablo, I set up the QCX-mini and the Pocket Socket.
The QCX-mini is pretty lean on RX current, has an efficient power amplifier, and tolerates a wide input voltage range - so it is a good candidate for unstable power sources like the hand crank. I started out turning the crank, while Rex KE6MT ran the radio. Light cranking was good enough to keep the radio alive during RX, but it got noticeably tougher to keep spinning once the radio keyed up - a good sign, since the power radiated from the antenna needs to come from somewhere. Rex finished his 4th CW contact on 30m moments before my arm fell off, and then he was kind enough to turn the crank while I completed a contact with AB6SO.
I noted that the potato battery was significantly less efficient than just eating the potatoes and pedaling a generator. I didn't plan my carboloading properly for this hike, so I stopped at McDonalds on the way home to catch up on potato calories (french fries).
Disassembled View
Two stages of gears keep the motor spinning at a high speed. There is some unpleasant grease inside.
Circuit Board Inside Crank
The Pocket Socket outputs 120V DC. This is fine for many devices like cell phone chargers, which can just as easily run their PFC input stages from DC. The Pocket Socket's hand crank is connected to a couple stages of gearing, then a 3 phase brushless motor, then a rectifier, and then a boost converter.
I tapped into the output of the rectifier, which gives ~18V at a "fast" cranking speed. The QRP Power Board regulates the 0-18V input to 12.3V for the QCX-Mini, which gets the full 5W out. I borrowed a capacitor bank from the potato project since the power ripple of hand cranking provided too unstable an output voltage while transmitting. The capacitor provides a few seconds of hold-up while in RX.
