David:
VA7JBE is right about the LiFePO4 battery. It is a much better and safer choice. Li ion batteries tend to catch fire too easily.
He also found a good PA project. But it is not quite in the portable category. Note the caveats in the story. They are hard-learned and true lessons.
The original BITX40 puts out ca. 5W with a total power consumption of about 11W on transmit (guess). Adding a 20W PA will increase that input power to
about 45W on transmit. Which is why some people go to Class D amplifiers. That's a good load for any small battery.
I am also leery of switching power converters because of their noise. Often it is hard to get rid of.
Another thing to think of is the antenna. This is not a small item.
Try out your configuration at home first and figure what out what works. That is the best way. Then you can decide (or work) on its portability.
There are a lot of examples around of early and late portables of small rigs and the associated gear. Usually they were (and are) for CW.
Portability and voice communications is almost a contradiction in terms. But it can be done. Think it through and experiment to see what works.
All this being said, why not make a portable rig?...as long as it isn't a backpack rig.
73
john
AD5YE
