Generating 5v from 4 batteries

[Melanie]

So, you don't like the simplicity of that idea....

One Transistor (BC639 as an example), one 5.6v Zener and a 22K Resistor... ten cents...

[BobP]

Thanks for the replies. Unfortunately the simple diode solution is no use! The Tx and Rx modules need a solid 5v. Any less and their range falls dramatically.

It seems the easiest solution is to power it from 3 cells use a step up regulator and take a hit on the slightly reduced battery life.

But thanks again for everyone’s help.
Bob