[Elecraft] Sideband reversal

Mon Jan 28 13:36:12 2002

Hello Steve,

	FYI, the numbers on the phone are done differently than on
calculators and computers on purpose. It stems back to when the phones
were all using machanical relays that could easily jamb if the numbers
were entered too fast. In thier infinate wisdom the phone people
realised that accountants and others that were proficient with the
keypads would boggle the system, so they put the numbers opposite to
slow things down. This is similar to the reason that we have qwerty
keyboards. The qwerty system was designed for machanical typewriters
because they would also jamb if a person typed too fast. There are much
more effecient ways to set up a keyboard. I hope this solves the
longtime mystery for you.

Mike
KB1DXC

-----Original Message-----
From: Steve Lawrence [mailto:[email protected]]
Sent: Monday, January 28, 2002 11:43 AM
To: [email protected]
Cc: [email protected]
Subject: RE: [Elecraft] Sideband reversal

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

arranged top to bottom?  (I'm still looking for the answer to this
one....=20
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

=20
        To:     <[email protected]>
        cc:=20
        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=20
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=20
being
the lower one on bands below that frequency and on the upper side for=20
those
above.

The 'convention' has gotten so ingrained that I was "reading the mail"
on=20
40
SSB one day and heard some ops telling two others who were on USB that=20
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=20
'convenient'
for the manufacturers.

Ron AC7AC
K2 # 1289

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