Posted by
David Woolley (E.L) on
Jan 13, 2008; 10:49am
URL: http://elecraft.85.s1.nabble.com/New-K3-SN-207-built-but-question-on-AM-Filter-tp458592p458593.html
Paul Webb wrote:
> now when i select SSB and tune to a AM signal i can alter the
] bandwidth to anything up to 6KHz, when i switch to AM i can only adjust
] the bandwidth up to 3KHz , the audio sounds like it is a 3KHz filter
] too, what am i doing wrong since i cant set the 6KHz bandwidth in AM.
> any ideas???
The basic reason has already been explained, however, there are very few
cases were exceeding 3kHz audio bandwidth is useful. HF broadcast
stations use 5kHz channelling, which would only allow them 2.5kHz with
brick wall filtering at both transmit and receive ends, although they
probably do expect to suffer significant adjacent channel interference.
MF broadcast stations use 9kHz channelling in Europe and 10kHz in the
USA, but I suspect that adjacent channel interference is less
acceptable. As they were designed to be received with LC IF filters,
with poor shape factors, I suspect they don't even make use of the full
channel, and if they did, they would probably be required to have
filters which put the adjacent channel into the filter stop band.
[ Note: excessively long lines re-wrapped. See RFC 1855. (Probably using
yahoo.) ]
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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