----- 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.
J
| 