[TenTec] Further Orion Sub Receiver

[Grant Youngman]

> I'd prefer it the way it was done for almost a century, and 
> it worked that way in V1, so it's clearly a degradation.

I'd offer the following recent paper by Dallas Lankford as interesting
reading.  While it addresses specifically AM distortion caused by fading,
there are some other useful points.  If you're not into formulae, scan for
the conclusions peppered throughout the document.

One of those, in particular, is that (approximated to the 2nd harmonic),
distortion in a square law detector is actually lower when a steady state AM
signal is tuned to remove most of one sideband than when the carrier is
centered in the passband.  Centered, the percent harmonic distorion is
approximately 6.25*m**2 and shifted to remove most of one sideband it is
approximately 1.5625*m**2, where m is the modulation index.

This doesn't exactly "rest the case" because measured results were somewhat
different (for reasons the author may still be investigating), but the paper
does rightly point out that there are more serious forms of distortion to
worry about than that which might be caused in a real radio from shifting
the passband. The benefits of "offset tuning" an AM signal to reduce fading
distortion is pretty well known to serious SWLers.

Maybe it's something worth measuring.

The paper can be found here -- http://tinyurl.com/fxp6a

Grant/NQ5T