Why Bloody PP3s?

So many designs, projects etc, are powered by the poxy 9v PP3 battery! Why? They have sod all capacity, and cost a fortune! Yes, I know they are conveniently sized and shaped, but half the things I see powered by them could just as well be designed to run on a pair of AA's at little more space and a fraction of the cost.

Earlier today, simply because I came across the detector innards from a previous version in a box, I knocked up a Field Strength Meter, using the meter movement from a defunct chinese cheapo multimeter, and the first 3D printed box Alex at work made for me. A spare telescopic antenna fitted, and its a conveniently handy sized device. But, its rather insensitive due to the meter movement I used, so really needs an amplifier. Hence the above rant - all the designs use a PP3! Im looking for a design now that uses 3v so I can power it from a couple of AA's,

The remaining seven Low Battery Warning modules are now built, and offered for sale. One initially failed testing, this turned out to be the collector pin of the optocoupler that had failed to solder properly. All of them switch to alarm state between about 19.9-20.5v. Not bad for the component tolerances.

Ive offered these for sale on the Clansman Field facebook page, at £10 each. For every one sold, im putting £4 into the coffers for our charity fundraising!

https://fundraise.cancerresearchuk.org/page/bob-and-martins-hadrians-wall-challange2019