[BC] Scope for Mod Monitor...

[Burt I. Weiner]

R,

Yes, for negative peaks it's very easy to see carrier cutoff.  If you 
want to set your modulation for +120% or the maximum 125% positive 
peaks, a scope won't cut it.  Tone maybe yes, program, no.  The FCC 
looks for excessive (AM) negative peaks with a scope.

Burt

At 09:38 AM 7/19/2006, you wrote:
>From: Robert Meuser <Robertm at broadcast.net>
>Subject: Re: [BC] Modulation Monitors...
>To: "Broadcasters' Mailing List" <broadcast at radiolists.net>
>Message-ID: <44BDE0FD.1090303 at broadcast.net>
>Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
>Must disagree, Burt.
>
>The FCC uses a scope for both AM and FM modulation measurements. The
>original discussion was limited to AM operation where a scope is the
>best way to check modulation. I agree that positive modulation  is a
>little more difficult to observe but then I know of no station that
>observes the positive modulation rule.  Harold stated a while back on
>one of the lists that from his records no station has ever been cited
>for positive over mod.  I know of major stations in the top groups that
>will not accept equipment that does not do at least 145% positive mod. I
>have never accepted at TX that does less than 165% positive mod and have
>never run a TX at anything less than 150%. My antenna systems are
>contractually speced for 200% mod with continuous tone bursts.
>
>R
>
>
>Burt I. Weiner wrote:
>
> > Any station that does not have a properly working modulation monitor
> > for their transmitter/s is fooling themselves and whoever is
> > responsible should have their head examined.  If you think the
> > bargraphs on the front of the transmitter are going to tell you what's
> > happening, you're wrong.  A scope is fine to a point but it won't tell
> > you if you're modulating 115, 120 or 125 percent positive peaks under
> > dynamic program conditions.  You cannot resolve modulation close
> > enough with a scope under program conditions.
> >
> > Burt

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at earthlink.net
K6OQK