[GreenKeys] Mod 28 Gearing

[Ralph Mowery]

I am going to wild guess on that.  

Someone explained a while back in this conversation that the 7.42 instead of
just 7.00 was because of the machinery .  

My guess for the 7.5 is when the computers came out that they could generate
the 7.5 a lot easier than the 7.42.  I know the UART chips often had a
choice of 1, 1.5 or 2 stop bits. You may see that in some of the computer
'glass teletype' programs. 

On the ham bands instead of hams using the 170 Hz shift some were using 200
hz shift as some of the old telephone modems use 200 hz shift.  When feeding
audio tones into a SSB transceiver, the frequency of the tones is not that
important as long as they are separated by the required amount.  The 200 hz
was usually close enough to work for most.

Ralph ku4pt


-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Steve Garrison
Sent: Monday, August 12, 2019 10:34 AM
To: 'John, W9DDD'; greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] Mod 28 Gearing

Thanks John, great information to have!

I'm still puzzled as why there was more than one "standard."

Especially the 7.00.  And the 7.42 & 7.50 are so close (0.08") why bother?

Steve G./N4TTY