[BC] Scope for Mod Monitor...

[Robert Meuser]

The FCC measure ALL modulation with a scope. This includes FM. Jeff W 
and Willie have both offered valid ways to set positive mod using a 
scope although negative peaks are all that really matters..

R

Burt I. Weiner wrote:

> 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
>
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