[BC] Positive peaks.

[Grady Moates]

> What most likely kicked off the MW-1 was not the positive peaks
> but lots of low frequency audio (<50 Hz. in the spot)
>
> Proof of the MW-1 showed it would overload on 20 Hz. 100% mod.

    Quite a few older, low-to-medium power tube AM rigs had
this problem, too.  The 2 uF Modulation coupling cap was
resonant with the modulation reactor at about 25 Hz.  These
boxes had about a 2 dB bump at 25 Hz in them.

    Even with a 50 Hz high-pass, these transmitter would have
a lot of bounce caused by kick-drum transients.  I found that
adding an 8 uF cap in parallel with the 2 uF cap made the
problem go completely away, as long as the 50 Hz high-pass
in the processing was in-circuit.

    That allowed the audio to be turned up 1.5 dB or more.

    It's surprising, even today, how much audio quality
improvement can be achieved with simple power supply mods.