[Elecraft] Sideband reversal

Mon Jan 28 11:58:11 2002

The answer to why the touch-tone pad is arranged the opposite of a
calculator is that the early touch-tone keypads and Telco tone receivers
could not keep up with the key punches by people trained to use
calculator keypads.  Bell Labs decided to arrange the keypad the
opposite of the adding machine so that users would enter the keystrokes
more slowly.

Rod KI7ZI

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Steve Lawrence
Sent: Monday, January 28, 2002 8:43 AM
To: [email protected]
Cc: [email protected]
Subject: RE: [Elecraft] Sideband reversal

Wow!  You've answered one of lifes mysterious questions I've always 
wondered about:  why LSB below 20, USB above?  Somehow, I'm not
surprised 
at the outcome.  It's sort of like the question:  Why are calculator 
keypads (specifically the numbers) arranged bottom to top and telephones

arranged top to bottom?  (I'm still looking for the answer to this
one.... 
but like the USB/LSB convention its probably some stupid early technical

problem that's no longer an issue either.)

Steve

"Ron D' Eau Claire" <[email protected]>
Sent by: [email protected]
01/28/2002 11:29 AM
Please respond to rondec

        To:     <[email protected]>
        cc: 
        Subject:        RE: [Elecraft] Sideband reversal

> The Swan-350 (and possibly other swan rigs) reversed sidebands between

> upper and lower bands.  It was an analog rig, so there were backward
> scales on the
> dial for the reversed bands. In fact I think this is how the
convention 
of
> using LSB below 20m, and USB for 20m and up got started.

The early "low cost" commercial SSB filters used an i-f of 9 MHz. With
simple, single conversion designs that resulted on the output sideband 
being
the lower one on bands below that frequency and on the upper side for 
those
above.

The 'convention' has gotten so ingrained that I was "reading the mail"
on 
40
SSB one day and heard some ops telling two others who were on USB that 
they
were transmitting "illegally" since the FCC required lower sideband on
40 and below and upper on 20 and up. Not true at all, of course. The
choice 
of
sidebands is just a long-standing convention based on what was 
'convenient'
for the manufacturers.

Ron AC7AC
K2 # 1289

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