Re: [ARSCLIST] Little azimuth trick

[Mike Richter <mrichter@xxxxxxx>]

George Brock-Nannestad wrote:
> From: Patent Tactics, George Brock-Nannestad
>
> Hello,
>
> Chris @Eugene wrote
>
>
> > Hi,
> >   The normal correct procedure, according to service
> > manuals, is to adjust for maximum signal strength,
> > before "fine-tuning" with a Lissajous pattern for
> > phase relationship. It is possible to get the
> > correct Lissajous pattern at less than maximum
> > signal strength azimuth adjustment.
> >   Usually what I do is watch the signal strength
> > on an audio voltmeter or the o'scilloscope. Adjust
> > for maximum amplitude, then you can "tweak" it
> > very, very slightly for the proper Lissajous
> > pattern.
> >   Hope this helps.
> >
> > Chris
> > @eugene-audio
>
>
> ----- this is what we all do. However, Richard took the signals from the
> "edge" tracks (i.e. those almost ½ inch apart), realizing that the 1 kHz
> signals (a _low_ frequency) were in phase in all channels, and generated the
> Lissajous from these. This is a good (and novel) way to obtain precision. The
> need for obtaining a maximum amplitude reading does not arise at this low
> frequency - you cannot tilt the head so much that you get an erroneous
> "lower" maximum at this frequency, unless it is a monitoring tape at very,
> very low speed.
>
> Thank you, Richard, for this neat trick!
>
> Kind regards,
>
>
> George

Well, you *can* get an amplitude difference, but it is a cosine effect
of the misalignment. The Lissajous figure shows phase difference, a sine
effect. For any moderate alignment error, the cosine effect is likely to
be swamped by even slight amplitude variation where the phase error will
be reliable and easily read.

Mike
--
mrichter@xxxxxxx
http://www.mrichter.com/