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Re: LF: Ampliphase

To: [email protected]
Subject: Re: LF: Ampliphase
From: "John Rabson" <[email protected]>
Date: Fri, 1 Feb 2002 09:24:22 -0000
References: <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: <[email protected]>
----- Original Message -----
From: "Dave Pick" <[email protected]>

... 4.5KHz cutoff filters that the EBU compliant broadcasters used.
What was the specification of those filters? When I was involved in starting
up University Radio Essex, a licensed station, in 1970 we were given a
specification which required the modulation to be 40dB down at 4.5 kHz from
the carrier. We dutifully complied with a filter that would do this with 80%
modulation with a sine wave.

When the Men from the Ministry did their tests, they used a classical music
feed at 30% modulation! The transmitter (a rebuilt KW Vanguard) would have
managed that with only a little tailoring of the microphone amplifier.

73 de
John Rabson G3PAI

PS (off topic) does anyone from that establishment in those days recall a
piece of doggerel that started "The chief defect of Shirley Thing"? If you
do, please e-mail me direct. Many thanks.

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