[Elecraft] To PLL mod or not

[k6se@juno.com]

Mike, VP8NO wrote:

"Altering the main tuning, either by intent or VCO drift, will move a
signal within the passband of the filter, it has to, how could one move
on to another signal otherwise.
----------
True.
==========

"With respect to zero beat or your desired sidetone.  VCO drift will also
alter the side tone frequency, as in normal tuning, but not the
relationship between the BFO and the filter."
----------
I believe what Mike meant to say is, "VCO drift will also alter the pitch
of the received signal."  Sidetone frequency can only be changed by the
ST P menu.
==========

"We are dealing with two separate issues here, hence the need for two
cures.

1.  To remove the necessity of retuning [the VFO knob] to keep the signal
within a narrow filter."
----------
True if only VFO drift is the problem.  Not true if BFO drift is the
problem.
==========

"2.  To remove the problem of BFO drift causing a change in side tone
frequency whilst keeping a signal within a narrow filter."
----------
BFO drift does not cause a change in sidetone frequency.  It causes the
filter passband to drift away from the sidetone frequency.  The result of
this is that, when the signal is tuned in for max strength (max reading
on the S-meter), it is not within the filter passband and therefore
cannot be heard or is heard very weakly, just like any other signal
outside of the passband.
==========

"It has to be looked at both ways, whatever effects receive will also
effect transmit, that is the transmit signal will also drift."
----------
True for VFO drift, but not true for BFO drift.

73, de Earl, K6SE