[MRCA] [ARC5] Vintage test equipment?

[J. Forster]

Leaving the generator fixed and tuning the receiver was probably a lot
faster and easier than retuning the generator a few kHz, which would have
required setting the BC-221 on the new frequency, then tuning the
generator for zero beat.

Much easier, absent a sweep setup, just to rock the receiver a bit.

-John

====================



> In reviewing the alignment procedures and maintenance practices, etc.
> for the SCR-274-N and ARC-5 equipment, I'm curious what test equipment
> they (the military) had at the time and, in fact, used for the
> aforementioned?  I know that the early scopes were present, although not
> "calibrated" as we know it today.  I also know the BC-221 and LM were
> readily available, of course.  Also, fairly accurate voltage measuring
> equipment, to include, I believe, VTVMs (which would provide high
> impedance measurements).  I suppose that the standard 20k/v multimeters
> would obviously have been available. Finally, signal generators, too.
> The thing is, accuracy and precision is my real question.  I don't think
> that the military had quite the PMEL functions available today.  How
> good were the test sets out in the field?  Boiling it all down, I read
> the procedure in the maintenance manuals for the above radio sets, in
> particular the receivers and their alignment and test. _If I'm
> interpreting things correctly_, the procedure for measuring receiver
> bandwidth was one where, instead of setting up a reference on the
> desired frequency and moving a calibrated signal generator up and down
> or sweeping the bandpass, they (Navy and Army) used a method whereby the
> signal generator was set on frequency and the receiver was tuned above
> and below the set frequency (or was it the reverse?)  Anyway, by
> increasing the signal generator levels in discrete steps up to values
> representing from 6db (2x) to +60db (1000x) from the reference, the
> receiver (or generator?) was off-tuned until receiver output was seen to
> drop to the original set level.  Of course, the method does work, no
> question, and by using fairly accurate (and measurable at the time) high
> levels, the results could be considered good.
>
> Does this seem reasonable to all of you?  Again, other then the LM and
> the BC-221, what other "standard" RF and measurement test gear was in
> use from '42 thru '45?
>
> Inquiring minds ask.......
>
> Jeep K3HVG
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