This subject has now moved to the top of the list. I have been notified that there is a good possibility of another 4 Day PSPS, starting this morning and lasting until Thursday. Basically, this is crap, and my battery charger is still in limbo!
Todd, K7TFC who likely knows as much as I do about the P3ST, since he turned it into a kit, looked at the design and offered some insight as to where to save the precious amps.
Todd's first input was RELAY's. The main IF Module uses 4 Relays on that board (below). By the time I was done I think there may be 8 or 9 Relays in total. If each relay used 10Ma for the field coil that is almost a 100Ma draw when you go to transmit where there is no draw on receive (NC contacts). The initial use of relays was based on the fact I bought them on the cheap and had a stash. But for battery operation that cheap solution is costly.
So instead of relays you have the option of a design that would use a toggle switch to power on/off various circuits. That solution would not work everywhere and thus you would have to employ Diode Steering and P Type FETS. The Diode Steering would work well with the lower-level stages and the P FET on high power RF Stages.
Another Todd suggestion (Gulp) is to switch to an LC VFO and Crystal BFO. That would really be a last effort on my part. Pox on LC VFO's. However, I could see using a Crystal BFO with a crystal switched Super VXO which could provide say 40 kHz of bandwidth on 40M. But that would have to be evaluated in terms of current draw of a Pro-Mini/Si5351 and the added circuitry for the VXO and the BFO. It is all about trade-offs.
In an effort to quantify the actual problem, I did some measuring yesterday, so now I have some sort of a baseline. My P3ST as shown on n6qw.com draws 400Ma on Receive. On Transmit without modulation the draw is 750Ma. This figure is the Relays being engaged plus those devices being run on transmit plus all of the loads like the Bias circuit. Announce "Hola" several times and the in line current meter hits 1.5 Amps. Transmitting a lot will suck the battery dry in short order.
Some ultimate goal numbers would be to draw a max of 300Ma on receive and no more than 1 Amp on transmit. I figure with a 10-AmpHour LiPO battery you could get about 8 -10 Hours of reliable operation assuming 75% listening to 25% transmitting. CW operation only, should improve those numbers.
But that notional goal would require additional changes beyond eliminating the IRF510 and eliminating relays. The Audio stage has a 2N3904 and a LM380N-8. This would have to change to say a couple of 2N3904's and earphone only operation. Some possible other changes would be to swap the IRF510 and give way to a 2N3866 or on the cheap a 2N3053. The goal is 20 Volts PTP at the output into 50 Ohms. 20 Volts PTP is 1 watt. (20^2 = 400 and that number times 2.5 = 1000 milliwatts or 1 watt.) I have run 400 Milliwatts on 40M SSB and worked out to 500 miles. So, 1 watt output does work as a rig.
Todd also suggested the use of an NVIS antenna on 40 Meters as that may prove useful during mid-day when the band appears to be asleep.
Them that know can make it go. If the power would only stay on so I could test some of these possibilities.
73's
Pete N6QW