[HBR] HBR's in 2014?

[Brian Burns]

Hello Tim,

~ When I compare what I hear on the air with my novice days, is that the SWL
stations are mostly gone from the ham bands!!! This is a good thing!

When I started in 1953 the 40 meter novice band was from 7175 to 7200---25
kHz wide! That was about the bandwidth of my ARC-5 receiver, and all my
tuning was just to adjust the pitch of the signal I wanted to listen to!
When I got my General Class later that year, I immediately went to 7010,
that being the only crystal available to me at the time. It was a lot
clearer down there!

~ With regards to selectivity... what makes some crystal filters ring like a
machine gun hitting a bell, is that they have a lot of group delay variation
inside the passband. This is especially typical of "brick wall"
8-pole-or-more filters folks so longingly buy for their rigs based purely on
numerical specs, without knowing how bad they sound in real life.

Very interesting!

~ Better filter designs move the group delay variations outside the passband
and give up some of the wall steepness, reducing the ringing. Many modern
DSP rigs have well designed CW filters.

But DSP is cheating! 

Cheers,

Brian


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