开云体育

My Mouser order got here this morning with new 390pF caps for the LPF in my 20m QCX, and I'm glad to report that - after three weeks of reading the reflector and faffing with the inductors, my meter, and everything else - my unit is putting out almost exactly the full rated power! My power output at 14V is now closer to 4.2W instead of the previous 2.2W.

With that sorted out, I'm trying to figure out a portable power solution less bulky than my 7.5Ah SLA; being a broke student and a habitual cheapskate I'd rather not splurge on RC batteries. I've got 4 good NiMH AA cells in a drawer, though, and an 8-cell AA holder to boot, so I'm thinking of ordering a fresh 4-pack of NiMHs and running my rig off 8 in series - the supply voltage should peak at around 12V, average off at 9.6 and fall to about 7.2 at the lowest.

Is anyone else running their QCX off such a low-voltage power source? Is there anything in particular I should do or know? (I'm not too concerned about the low power output. Longer battery life!)

Also - during some limited testing I've done with batteries below about 11.5V, I've had some small but annoying problems with the sidetone: upon keying, there's a short delay until the sidetone starts playing. At about 15WPM the delay is long enough that dits don't produce any sidetone at all, almost like sending with a Pixie! The delay gets shorter as I send a string of dahs (holding the paddle down) but then goes back to its original length in the inter-character interval. Has anyone else had this problem at low supply voltages? I can live with it, but...

Seth

See if you can acquire a used gel cell. Hospitals are known to recycle them when they have plenty of life, sometimes folk bring them to ham club meetings to give away, or cheap at a hamfest. Rig will operate for countless hours on a small gel cell. Pc backups use gel cells.

Curt

Hi Seth,

If you'd like to use just 4 NiMH AA cells then you might try the Ikea Ladda cells (basically eneloop pro cells, 2450 mAh, 4 for <$10) paired with the DC-DC boost converted designed by DK3IT for his .? This will bump you up to 12V for at least a few hours, given the low consumption of the QCX.?

DC-DC filtered boost converter

Ikea Ladda AA batteries

Hi Seth
I'm running my 40m QCX off 8V with a solid 1W output and no problems.? I fired it up like that first time, partly to reduce the chances of damage if I'd made a build error, now because I'm still playing around with antennas and the GPS connection.? I might well keep to 1W anyway!
From the power graphs on page 129 of the excellent QCX manual I can see that you might expect around about the same 1W from 8V on 20m if you short circuit the "idiot diode".? Page 3 of the manual gives a recommended power supply range of 7V - 15V so I think you should be fine with 8 AAs.
I've not experienced any delay in the sidetone - have you sorted that one now?
72
Rod
G0VKX

If you just want a low cost power supply, you can get 3 18650 e-cig batteries and get a 12v supply out of that.? 3s battery packs are a couple bucks, and it should be easy to find chargers and cells on a college campus.