Hi Jeff,
>Bottom line: limiting after preemphasis results in a reduction in the
>noise-limited dynamic range at higher frequencies; that's a natural
>byproduct of a process which originated in the user's radio. The
repeater,
>following the same preemphasis/deemphasis curve as the user's radio,
has no
>further affect. Any variation or degradation in frequency response,
S/N,
>THD, etc. as the audio passes through the repeater is solely due to
>imperfections in the design, implementation, or medium, not the
>preemphasis/deemphasis process within the repeater since the two are
>receiprocol.
How true.
Beyond that, our long-held view here is that the major bad guy
(especially in linked systems, where there is a series of them) is the
post-clipper ('splatter') filter. If they're all first-order filters,
you'll lose 6 dB at the high end (3 kHz) for each one you go through.
No wonder some systems sound muddy.
And no wonder the no-emphasis repeater builders have had success with
their technique.
When you take discriminator audio, run it through your own clipper and
brick-wall filter, and feed it into the modulator, you bypass a lot of
original audio circuitry. The explanation seems to be, "de-emphasis and
pre-emphasis is bad because when I got rid of it, my system sounded
better." But it wasn't the de-emph and pre-emph, it was the OEM clipper
and filter.
You can make a good argument for replacing OEM audio circuitry,
including the squelch. But doing it for each port on a multiport
controller is probably too expensive for most of the market.
73,
Bob
________________________________________________________________________
AOL now offers free email to everyone. Find out more about what's free
from AOL at AOL.com.
