The resolution of the display is 1kHz, the accuracy of the tuning is
typically
within 100 Hz or so either way. So if the set does drift/age "the
wrong way" by
only a few Hz, the display suggests a 1kHz error - because that is its
resolution.


To avoid the effect you are seeing, when we aligned the radios we set
the
oscillators 50Hz or so higher than they should have been, and this had
the
effect of landing the display the right side of 9/0 boundary when
tuning in
synchronous modes.


However the design of the set, particularly the clever (cheap) way the
inserted
carriers are generated adds to the possibility of that effect.


Basically there's probably nowt wrong with it as we say in Derbyshire.


The growling effect I first heard when doing the final alignment and
testing in
the early days of '150 production. I spent a few days trying to stop
it but
failed. The designer, JT, wasn't particularly interested. I found that
it would
happen only with weak signals - 1 to 5 microvolts if I remember
correctly. Not
much of a problem in practice. If that is what your set is doing, once
again -
nowt wrong with it.


If the growling instability is more noticeable than that, there may be
a fault.
Just had a thought - make sure there is no mains power supply or
computer
monitor near the set and throwing alternating magnetic fields at it.


Standard text ...


Our public liability insurance premium in respect of our sales
to the USA and Canada is no longer worth paying compared
to the volume of goods we sell there. As a result, regrettably,
we can't sell goods or services to that part of the world. If you
know anyone outside NA we can deal with them.


----------------------------------------------------------------
Best regards


Tony Mikol,


Workshop, Lowe Electronics Ltd.
Chesterfield Rd
Matlock +44 (0)1629 832374
Derbyshire DE4 5LE fax 580020