[Elecraft] AM receive band width

[Erik N Basilier]

> AM audio much more understandable (pleasant) on the FM filter, the extra 1
> KHz helps.
>

To those who feel that AM reception with the 6 kHz filter is not very 
understandable:

I had that same impression the first day or so after assembling my K3. Then 
I discovered that, with my small hi-fi speakers, excessive bass was the 
culprit. It appears that broadcast AM transmissions are balanced to sound 
pleasant with a wider receiver passband. The 6 kHz filter removes some 
highs, so to restore balance some of the lows need to be cut. This was 
easily achieved with the K3's receive equalizer. Of course, if you are using 
a speaker designed for communications, this is not likely to be needed. 
Anyway with the equalizer cutting off frequencies below 200 Hz or so, and 
some attenuation at 400 Hz, I found AM receive quality on voice to leave 
little room for improvement, and better than good SSB (assuming no ESSB). 
For music the FM filter would be a significant improvement of course, but 
when I listen to SW broadcasts, music is not generally what I am looking 
for, so I haven't been able to justify a 13 kHz filter.

Incidentally, I find a similar situation with the surround sound system in 
my living room. When the tuner is set to AM, I need to adjust controls to 
cut some bass, probably because the manufacturer takes pride in a deep bass 
response. The car radio and small portable radios don't seem to have that 
problem, perhaps because the manufacturers expect the products to be 
actually used for AM, and of course in many cases less bass means lower cost 
of manufacturing.

73,
Erik K7TV