|[AMRadio] New analog phone bandwidth petition|
ne1s at securespeed.us
Sun May 15 16:47:24 EDT 2016
On 5/15/16 2:29 PM, manualman at juno.com wrote:
> The only reason I can think of to not limit the bandwidth is that it
> typically makes one sound better (for whatever that's worth).
How about these reasons:
(1) It's another -unnecessary- restriction on our freedoms which we
should not tolerate.
(2) It's an attempt to fix something that's not broke.
(3) It's something that the FCC will not have the resources, and
possibly not even the desire, to enforce.
(4) Some stock commercially-manufactured amateur transmitters of
days-gone-by may not be able to meet that specification and therefore
would become illegal. For example, I recently "swept" 3 different
Central Electronics 20A exciters in good operating condition (and
recently properly-aligned), and measure relative output vs. frequency
for both the desired and undesired sideband in the SSB mode. None of
them would meet the 8Kc @ 20dB spec EVEN IN SSB modes. This is because
at audio frequencies above 3.5 Kc or so, the passive audio phasing
network can't maintain it's +/- 45 degree phase relationship between the
two audio channels which is necessary for cancellation of the undesired
sideband, and hence those frequencies make it into the undesired
sideband with minimal attenuation. The only way to meet this spec would
be to severely restrict the audio bandwidth by making modifications to
the speech amp or adding some sort of filter. (I did the latter to one
of mine, as it's a rig I use regularly on those occasions I operate SSB,
and I choose to occupy a channel width that's appropriate for the mode).
Probably several other good reasons exist, but that's just off the top
of my head.
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