[Elecraft] [K3] Rx/Tx equalization

[Jack Smith]

True story related to your comment below ... I worked my way through law 
school in the 1970's as a transmitter engineer at a 50 KW AM directional 
station in the Detroit market. The studio was 15 miles from the 
transmitter, connected by main and backup broadcast quality telephone 
lines.

One afternoon I'm watching the meters and listening to the monitor 
speaker when I hear a series of beeps, sounds like a string of Morse 
dots and then the main telco line goes dead. Switch to the backup line 
and let the Chief Engineer know.  A half hour or so later, same thing 
happens to the backup line, so crossing my fingers, I switched back to 
the main and it was working.

Later  that day, the jocks started complaining that the audio sounded 
muddy. All the guys at the transmitter thought it sounded fine to them. 
For those who have not worked in this environment, a 50 KW transmitter 
room is not silent, as it has several multi-horsepower blowers to keep 
the transmitter cool. And, the monitor speaker was not what one would 
use for serious audio reference.

We then ran a sweep of the lines that night and sure enough, instead of 
the 15 KHz response the station paid for, the line cut off around 3.5 
KHz. Both of them.

It turns out that the beeps were the pair identification tones  the  
telco splicers use when working on cables and what they had done was add 
loading coils to the program lines, converting them to a standard toll 
grade quality line.

That experience taught me my ears are not a precision calibrated 
instrument and that I should have more faith in spectrum analyzers.

Jack K8ZOA

> With ANY audio adjustments, the final test is what it SOUNDS like. 
> Good operators ALWAYS get reports from good ears on the other end of 
> the QSO after they've done the first round of tweaking. The 
> broadcast guys tweak and listen, tweak and listen, tweak and listen. 
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