[Milsurplus] LM freq meter calibration book accuracy

[John Vendely]

A good point.  Aside from frequency measurements, a decent heterodyne 
detector can be quite useful, even in troubleshooting later model 
synthesized equipment, e.g. TMC, Manson, etc.  Of course, a heterodyne 
frequency meter is of no value in making precise frequency measurements 
on such equipment.  But these old synthesized equipments require a good 
deal of tweaking and fussing around to get them really working 
correctly.  A freq meter used as a heterodyne detector is a useful tool 
for quickly analyzing (by ear) short-term stability and close-in 
noise/spurious problems while making adjustments.

A comment about the inherent accuracy of these remarkable instruments.  
I have observed the tendency of some frequency meters to weakly 
"injection-lock" if coupled too tightly to the signal source being 
measured.  This can give the illusion of greater frequency stability 
than the instrument is actually capable of.  I've seen this occur in 
both LMs and BC-221s. Fortunately, it's an easy problem to avoid, and 
not all of them do it anyway.  In some cases, it can actually be used to 
advantage.

As a side note, the BFO of some R-390As can exhibit very weak injection 
locking to the IF.  Not all R-390As will do this, of course.  But I've 
always wondered if this might have given rise to some of the wild 
stories of R-390As maintaining absolute zero beat with test signals for 
hours on end...

73,

John K9WT

On 7/28/2013 8:28 AM, J. Forster wrote:
> Not so obsolete functionally. There are very few currenht boxes that can
> act as a signal generator and receiver around today.
>
> YMMV,
>
> -John
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>> A