[GreenKeys] FSK shifts

[Russ Miller]

It was about 1968 when 170 Hz narrow shift became popular.  If you go back
to RTTY Journal during that period, you will see the slogan "Broad minded?,
Try narrow shift!"

Why is narrow shift preferred?

Here are some of the reasons: - narrow shift maes copy better with QRM.
Period, end of discussion.

Why technically? The ability to use a 500 Hz filter greatly improves the
signal to noise ratio and helps eliminate adjacent station interference.

73
Russ WA3FRP



On Sun, Aug 22, 2021 at 9:33 AM Steve Garrison <steve.n4tty at gmail.com>
wrote:

> Maybe because the FCC seems to be narrow banding everything?  Just my
> guess.
>
> Steve G./N4TTY
>
> -----Original Message-----
> From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net>
> On Behalf Of Duncan Brown
> Sent: Sunday, August 22, 2021 8:47 AM
> To: Green Keys <greenkeys at mailman.qth.net>
> Subject: [GreenKeys] FSK shifts
>
> I was surprised to learn that KPH is running 170Hz shift on RTTY and that
> is now the standard for commercial RTTY/SITOR/NAVTEX.
>
> 850Hz shift was the standard shift for a long time and gives some
> diversity assistance in TUs that can copy with just one tone. Hams using
> 850 Hz shift got some flack from CW operators because of their "wide"
> signal among the narrow CW signals.  That, plus the (once) crowded CW
> bands, forced the change to amateur RTTY switching to 170 Hz. (More stable
> TX & RX made narrower shifts more practical, but didn't require it.)
>
> Other than narrower transmitter bandwidth, is there any advantage to 170
> Hz shift over 850 Hz? When & why did the commercials change to 170 Hz? With
> assigned channels, they would not have the QRM problems that we have on the
> Ham bands.
>
> Thanks,
>
> Duncan
> K2OEQ
>
>
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