[Elecraft] Poor AM audio

[Ron D'Eau Claire]

Dave, you've gotten a lot of good inputs that likely addresses the problem
you noticed.

There is a couple of other sources of irritating distortion on the "short
waves" where skip reception is common when you are listening to a full
double-sideband full-carrier A.M signal that are caused by propagation
differences across the band of frequencies the A.M. signal occupies. 

One is "selective fading". Sometimes the carrier will drop out with QSB but
the sidebands will remain strong. Suddenly your A.M. signal sounds like SSB
without the local carrier injected for a few seconds. 

Another manifestation is that one side band may travel a slightly different
path through the ionosphere than the other and arrive out of phase. Phase is
extremely important to an A.M. signal and the out of phase side bands will
cause the audio to be loud but completely unintelligible for several
seconds. 

Usually you can hear these effects slowly cycle again and again. 

Using synchronous A.M. detection or receiving the A.M. station in SSB mode
completely eliminates these issues since your receiver produces a local
"carrier" to demodulate the sideband, eliminating the problem of the carrier
from the transmitter fading, and the filters cut out one sideband,
eliminating any problems with one sideband being out of phase with the
other. 

Both of those issues are a couple of the reasons why SSB became so popular,
in addition to the lack of heterodynes from A.M. carriers close in
frequency, from transmitting only one sideband, eliminating the spectrum
required for the carrier and other sideband, and the huge efficiency in
transmitters that don't have to produce the high level carrier.

73 Ron AC7AC

-----Original Message-----


I just received and assembled my K3 about a week or so ago, I only have the
2.7Khz. filter that was shipped with the kit. I love the operation on SSB
and digital modes BUT, when listening to the DX60 AM net the audio is quite
distorted. I started out with the filter set to NORMAL and then made it as
wide as possible untill the display reads 5.00. Is this normal to have the
distorted audio untill I purchase the 6.00 Khz. filter? I quess I'm
disapointed or am I doing something wrong? The operators manual does not say
any thing about the distortion, only the fidelity will be increased with the
6.00 Khz. filter.
 
Dave Purola,
N8NTA 
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