Agreed!!!!!! But why would or should an AFSK signal have humm or hiss?
Most TNC's (or soundcards) do not have adequate control on the output to
reduce their level to properly feed a mike input. Oh yes, one can turn the
level down, but this is not necessarily correct. Especially when the output
circuit of a sound card is configured for a line level or speaker level
condition. The S/n ratio is destroyed. This is the reason for humm and
hiss. It's not the TNC's fault, it's not the soundcard fault, it's not the
radio's fault, it is the way one has elected to connect the systems.
Correctly, the TNC or soundcard should feed the line level input on the
radios and thus the levels are such that one will have enhanced or
acceptable S/n ratio and thus the hiss problem is eliminated. I find all
too often where one has elected to feed the signal into the mike input,
primarily as a matter of convenience, and then turn the levels down to make
it work. As to humm, most often ground loops or RF in the shack is the
basic cause. Again, it is an interface issue. My computer with its
soundcard, my TNC connected to the computer, the transceiver and the legal
limit amp sit on the same desk. No humm, no RF an no problem using FSK or
AFSK with either of the 2 trancerivers on any band, 160M - 10M.
In looking at my configuration with a spectrum analyzer, using the sound
card outputs direct to the radio, line in and line outs, there is absolutely
no humm observed. The S/n ratio of the system is better than 55dB. As to
audio generated hiss, the mike level gain is turned all the way down and
thus there is no hiss from the un-used mike stages. I don't use
transformers or any other interface either. I've found these to be prone to
introduction of humm. Correct configuration is the solution.
FSK is nice as long as one wishes to use 180 Hz shift which is standard in
most radios. But some modes use 200Hz shift. Oh most TNC's will deal with
the difference but for the purist, either 180 Hz shift is correct or 200 Hz
shift is correct. Not both. With most radios today you have a choice of one
FSK shift, not both. With AFSK, either can be correctly generated. This
may be the basic reason for moving away from true FSK.
As to CW, RTTY and etc being a dying mode, it's dying because it's not being
fed with new technology to support such. Here's an interesting observation,
with CW and RTTY being considered as dying, I'm seeing a insurgence of AM
operations on all of the HF bands. There's lots of folks that are
discovering and returning to the "better sounding audio" mode of operation.
Most all of today's new transceivers support that mode while only a few
years ago the AM mode was not present on any of them.
----- Original Message -----
From: "Roger Borowski" <K9RB@bellsouth.net>
Sent: Friday, April 04, 2003 7:35 AM
Subject: Re: [TenTec] Fw: Orion & FSK/AFSK
> Agreed! And...if you're AFSK signal has hum, hiss, and /or feedback
> distortion from RF introduced into the audio, it makes it so much more
> difficult to copy on the receiving end. Anybody who operates RTTY has
> experienced attempts to copy a S9 RTTY signal and not get enough clean
> readout to figure out the other stations callsign unless listening over
> numerous attempts and piecing it together. This is AFSK.....never happens
> with FSK! TS-950SDX and some other fine rigs use true FSK but they seem to
> be a dying breed with all the sound card emulation's of RTTY today forcing
> manufacturers towards what is easy and less expensive to implement. Lets
> face it, CW and RTTY are slowly dying, as some of us old timers are also,
> but the newly designed rigs of today are also helping with the demise of
> these modes, not mentioning brand names but some with poor keying and
> prominent key-clicks, others lacking provisions for FSK. Frustrations set
> for newcomers trying these modes, only to have them soon give up and go
> to the PC's and microphones. Old timers see that things don't work as
> as they once did and many also go in different directions. Sometimes newer
> is not necessarily better. Thats what is sad.
> ----- Original Message -----
> From: "Robert & Linda McGraw K4TAX" <RMcGraw@blomand.net>
> To: <firstname.lastname@example.org>
> Sent: Friday, April 04, 2003 7:37 AM
> Subject: Re: [TenTec] Fw: Orion & FSK/AFSK
> > I've used both FSK and AFSK over the years with various radios. I've
> > to one solid conclusion..........if you can't hear'em, you can't
> > 73
> > Bob, K4TAX
> > ----- Original Message -----
> > From: "Jim Reid" <email@example.com>
> > To: <firstname.lastname@example.org>
> > Sent: Thursday, April 03, 2003 10:44 PM
> > Subject: Re: [TenTec] Fw: Orion
> > >
> > > > Seems like Kenwood and ICOM are the only ones that care
> > > > about fsk. Yaesu does the keyed afsk way.
> > > > This issue may hold me back from ordering one.
> > >
> > > What a shame!
> > >
> > > Oh well, just means someone else will get his/her's earlier!
> > >
> > > 73, Jim KH7M
> > >
> > >
> > > _______________________________________________
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> > >
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