> Most HF users want AM and ESSB (occupied bandwidth greater than required
> for
> communications quality - 2.6 to 2.8 KHz) banned. Unfortunately,
> certain special interest groups continue to drive the debate.
Hi.
There are also a lot of radio amateurs that are concerned about the fact
that such restrictions in bandwidth will harm the experimenting part and
freedom within amateur radio. Radio amateurs has always been experimenting
with different microphones etc. trying to make it sound as good as possible.
That is a part of what amateur radio is all about (for some). Implementing
strict commercial bandwidth limitations within amateur radio is not a good
idea.
My view is that as long as we try to make our transmitted signals as "clean"
and splatter-free as possible there should be no problems.
When i tune across the bands I see a lot of distorted splatter stations on
the spectrum scope on my IC-756pro3, especially on 20m. This is because a
lot of radio amateurs use way too much microphone gain (high ALC-action)
and/or compression/processing resulting in very wide occupied transmitter
bandwidth. This is also consistent with the findings of SM5BSZ, Leif
Asbrink. Check his articles here:
http://www.nitehawk.com/sm5bsz/dynrange/alc.htm
http://www.nabble.com/file/p17066871/russian%2Bstation%2Bsplatter%2B1.jpg
wide splatter station on 20m
My experience is that all these splatter stations are a lot bigger problem
than if someone transmits with 3,0kHz or 4,0kHz in SSB. If one shall focus
on bandwidth, one must go for the area where something should be done. Maybe
a lot more education is needed for new radio amateurs (during licensing)
regarding ALC-settings and checking transmitted signals on a spectrum scope
to avoid splatter.
Some improvements has been done in recent years since many radios now uses
Digital Phase Shift Network modulation in SSB (DPSN). This also gives better
opposite sideband suppression. The transmitted signals are more "brick wall"
than on some older equiptment I think.
Going from 2,8kHz to 4,0kHz TX bandwidth on the Omni VII does not create a
very wide signal as long as it is clean and not distorted. Too much
ALC-action will create splatter regardless of IF-filter bandwidth.
http://www.nabble.com/file/p17066871/Omni%2BVII%2Bwith%2B4kHz.jpg
the Omni VII with 4kHz SSB TX
There are also facts like some radio amateurs have problems with hearing
loss, cutting away the audio to a narrow range (200-2800Hz) will make it
difficult to read for some people. The area between 100Hz and 4kHz are the
most important for the human ear. This can be confirmed by several
scientists working with speech intelligibility research :
http://www.polycom.com/common/documents/whitepapers/effect_of_bandwidth_on_speech_intelligibility_2.pdf
That is why I hope such bandwidth limitations within amateur radio never
will be implemented.
Best regards
LA4AMA
Roar
--
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Sent from the Elecraft mailing list archive at Nabble.com.
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