[GreenKeys] Frequency diversity radioteletype experiments

[Nick England]

 FWIW, Late-40s/early-50's US Navy FSK transmitters and FSK adapters all
included that 200Hz phase modulation

Nick England K4NYW
Chapel Hill NC
www.navy-radio.com


On Tue, Oct 13, 2026 at 1:29 AM Jim Haynes via GreenKeys <
greenkeys at mailman.qth.net> wrote:

> Here's something that I believe is not well known
>
> \bibitem[Davey3]{davey3} J. R. Davey and A. L. Matte {\it Frequency Shift
> Telegraphy -- Radio and Wire Applications.} AIEE Transactions \bf 66\rm,
> 1947, p. 479.  Also in Bell System Technical Journal \bf 27\rm, April
> 1948, p. 265.
>
> the FSK tones might be phase or
> amplitude modulated at a frequency of 200 Hz or so.  The purpose of
> this is to widen the spectrum of each tone, in hopes of avoiding
> the effects of frequency-selective fading.  The experts seem to agree
> that this technique is inferior to dual diversity reception,
> but may be helpful where diversity reception is not possible.
> (perhaps on shipboard where there is no space for widely-spaced
> antennas)
>
>         ---
>
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