On 2015-01-30 6:29 PM, Fred Jensen wrote:
Ummmm ... I've never understood the infatuation with FSK over AFSK,
especially for someone just trying RTTY out for the first time. If
the sound card produces clean audio [pure sine wave sans noise], and
most newer ones do these days, the result at RF is essentially the
same, with less equipment.
That *ASS-U-MEs* that the person hooking up and configuring the AFSK
knows what they are doing. Given the number to particularly gross
AFSK signals on the air today, that assumption is not a good one.
The manufacturer of one "inexpensive" amateur sound interface even
instructs its users to run the Windows sliders at maximum (it needs
that because its internal VOX is not sensitive enough otherwise) but
that drives the poorly filtered and unregulated DAC into distortion.
Couple that with improper grounding and overdriving mic preamps in
many rigs and you have a recipe for garbage - before even considering
all the "windows noises", streaming audio, and open mic stuff that
gets on the air ... none of which happen with FSK.
While it may be true that a proper AFSK signal is cleaner than FSK in
many rigs (the K3 FSK is exceptionally clean - as clean as the filtered
AFSK), it takes very little to make AFSK absolute garbage - most users
can't mess up FSK any more than the manufacturer's design.
73,
... Joe, W4TV
On 2015-01-30 6:29 PM, Fred Jensen wrote:
Ummmm ... I've never understood the infatuation with FSK over AFSK,
especially for someone just trying RTTY out for the first time. If the
sound card produces clean audio [pure sine wave sans noise], and most
newer ones do these days, the result at RF is essentially the same, with
less equipment. The K3 also has a shaping filter when running AFSK that
makes AFSK cleaner than FSK, or so I've read.
My "radio laptop" is a fairly new [1 yr] quad-core Acer running Windows
7. On the spectrum analyzer, any undesirable products other than the
single tones are lost in the minuscule noise on the baseline.
There can be other reasons for running FSK with the extra interface
equipment which usually offers other features beside FSK, but for
someone just trying out RTTY, "less is definitely more." There is a
steady stream of traffic on this list from people trying to get
MicroHam, SignalLink, or other interfaces working, so it's definitely
not a piece of cake. MMTTY is tough enough for a newbie.
The K3 does have a potential "gotcha" which is easy to avoid if you know
about it. The RF Power is controlled by a closed-loop ALC system. The
power knob sets the "requested" power, the loop then adjusts the drive
to make that power. Consequently, you cannot adjust the output power
with the MIC/LINE IN front panel gain control. Adjust the MIC/LINE IN
control for 4 solid ALC bars with the 5th just flickering when sending
idles [diddles]. Then set the desired power with the PWR knob.
There's almost no conversational RTTY anymore, it's pretty much all
contesting.
73,
Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org
On 1/29/2015 5:15 PM, RIchard Williams wrote:
Though AFSK will work, I think you will be a lot happier with using FSK.
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