[GreenKeys] HAL ST-6 Manual needed

Sat Oct 22 14:43:42 EDT 2016

The audio tone method of generating CW or FSK is fairly common on SSB 
rigs. I do have a few comments and questions however. First, it is very 
important that the tones used to produce an output from an SSB 
transmitter be pure, clean, and delivered to the balanced modulator at 
the correct level. Any distortion or stray sounds with them will create 
unwanted outputs. Another issue is the continuity of the carrier when 
using tones into an SSB transmitter. With a "direct" FSK modulator, the 
carrier never drops until transmission is ended, it just shifts 
frequency. With tones into an SSB transmitter, there will be no carrier 
in the tiny instant when one tone ends and the other begins. It might 
seem inconsequential, but if the break of one tone  and the beginning of 
the other was really sharp, it could produce "key clicks".  If the two 
tones overrode each other in the transition, distortions and mixing of 
them could produce other unwanted outputs. To avoid these problems, I am 
thinking the audio oscillator should run constantly and care should be 
taken to not shift it's frequency too sharply. Regarding amplifier class 
of operation, some rigs change the biasing on the driver and final to 
class "C" when the mode is CW, FM, or FSK to increase efficiency and 
take it easier on the power supply. Most sideband rigs take advantage of 
the lower duty cycle of SSB  on the power supply. Many that have 
marginal power supplies will set far lower limits on power and loading 
for AM transmission, and if they don't change class, may also restrict 
FM and FSK.

     Bruce Gentry  KA2IVY

On 10/20/16 10:42 AM, Nick England wrote:
> 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 <http://www.navy-radio.com>
>
> On Thu, Oct 20, 2016 at 10:03 AM, Ralph Mowery 
> <rmowery28146 at earthlink.net <mailto: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
>     <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 <mailto: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 <mailto: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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