It is possible to use regulator chips (LM2940 family) that need only a
half volt head room. Later Scouts did that, I don't know about earlier
ones. The frequency modulation at 12 volts is a hint that some other
radios have the same problem. The main regulator in my home brew station
supply regulates down to 0.02 volts drop in the regulator. It should be
possible to use a variation on it (mine uses TL431A and N type MOSFETs)
using LM4140 and P type MOSFETs to regulate in the positive line. I've
sketched out that circuit but not tried the positive line regulator. The
regulator in my power is in the negative side which has several
benefits. But the LM2940 family ought to do well enough.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson. Reproduction by
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