[GreenKeys] HAL ST-6 Manual needed

[Nick England]

I know that Collins S-line transmitters (and I'm sure others) use a keyed
audio tone to generate CW. In an SSB transmitter, any RF signals at the
transmitting frequency must be generated by audio tones. Otherwise it isn't
an SSB transmitter.

I may be dense, but I fail to see any difference between SSB AFSK and "true
FSK" (assuming a single TTY signal). Isn't the output of the transmitter
exactly the same? In either case, the output alternates between two signals
170 Hz apart. Using FSK vs AFSK might change the reading on your frequency
dial, but that is trivial.

With "true FSK" you can use class C amplifier stages in the transmitter
chain vs linear amplifier stages found in an SSB rig, so the "true FSK"
transmitter can be more efficient, but that means you need a separate
transmitter for RTTY and another one for SSB voice.

AM transmitters with FSK have a separate FSK keyer that mixes the shift
pair with the VFO/crystal to generate the transmitted signal - the audio
modulator is turned off. Back in the olden days I think AFSK on AM was used
mainly at UHF where equipment wasn't accurate/stable enough for FSK.

n.b. One advantage of AFSK SSB is that you can run multiple tone pairs for
frequency-division multiplex of multiple TTY signals, but hams don't do
that...

Cheers
Nick England K4NYW
www.navy-radio.com

On Thu, Oct 20, 2016 at 10:03 AM, Ralph Mowery <rmowery28146 at earthlink.net>
wrote:

> I have not checked into it, but have read that some rigs generate the CW
> signal by using an internal audio generator that is fed into the ssb
> modulator.  While this will in effect generate a CW signal it makes me
> wonder how many rigs do this and if something similar to it is done when
> the
> rigs that have a RTTY position on the mode switch are generating true FSK
> by
> actually generating a carrier and shifting it or the simulated FSK from the
> audio.
>
> KU4PT
>
>
> > -----Original Message-----
> > From: GreenKeys [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of
> > Kevin H. Phillips
> > Sent: Thursday, October 20, 2016 6:44 AM
> > To: greenkeys at mailman.qth.net
> > Subject: Re: [GreenKeys] HAL ST-6 Manual needed
> >
> > You can contact Mark Prather, WB9HFK, at HAL: mprather at halcomm.com
> >
> >
> > I just got a manual for a CWR-6850 Telereader I acquired from a local
> > ham friend who is "thinning his herd".  Very nice device, by the way.
> > It is fully self-contained; no demodulator required.  I am looking
> > forwarding to coupling that with the ICOM IC-761 I also picked up to
> > finally do some true FSK RTTY as opposed to the "keyed AFSK" my Yaesu
> > FT-1000D does.
> >
>
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