[BC] Weston VU Meters

[Bob Foxworth]

> Doug is correct. It did require a 3900 ohm series resistor and it did
> have to bridge a loaded 600 ohm line. What is interesting, CBS, which
we
> all know stands for Can't Be Standard, unlike, NBC and then ABC didn't
> use 600 ohm lines, they use 150 ohm. They still used the VI meters,
but
> did some interfacing to accommodate the standard.
>
> LB
>
> schleutker at schleutker.net wrote:
>
> >>Many of the older rack mounted meters had switches that inserted
> >>resistors. It appeared to me that "Volume Units" had different
> >>meanings depending on what fed it.
> >>
> >>
> >>
> >A 'standard' VU meter had defined meter ballistics that were only
valid under certain conditions.
> >I may be a bit hazy on this part, but I believe the meter required a
3900 ohm series resistor and had to bridge a loaded 600 ohm  (maybe it
was 500 ohm) line.    Anybody with a better memory who could clear the
haze?
> >
> >Douglas E. Schleutker


I can add a bit to this. My recollection of the internal impedance of
a standard VU meter was it being 3600 ohms. When this was
put in series with a 3900 ohm external resistor, the bridging
impedance across the terminated 600 ohm line was 7500 ohms.
Then the 3600 + (600/2) matched 3900 ohms. This external
resistor provided the proper meter pointer damping.

I am hazy on this but I think the meter read 0 VU at a +4 dBm
level when the fixed 3900 was used. This could be replaced
with a Daven step attenuator which may have been 7500 to 3600
ohms. The line went to center and in and the meter went to
center and out.  When I got into radio in the 60's I really splurged
and bought a Simpson 4 inch VU meter with two 47 bulbs for
illumination, and one of the Daven step attenuators. I think it
ranged from +2 to maybe +20-ish? These things cost as I
recall about $60 each which is what I made in a couple of
days but I was 22 and single and had little else to worry about
in life, and thought it was really cool to have pro equipment
like this. I had them until the mid-80's, all mounted on a 5-1/4
panel, along with a 600/600 non-detent Tee pot   What fun...

Bought all that stuff at Harvey Radio on west 45th street,
cash, over the counter.

When I first started in NYC radio they gave us a thick printed
set of documents with all this stuff printed on it. Wish I had
kept it.

- Bob Foxworth



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