And then there is my 60's vintage Collins KWM2 which makes CW by
keying an internal audio oscillator...
Do AFSK exciters key between two
steadily running oscillators, with some sort of dead space
between tones, or do they shift one oscillator? Because of the
narrow audio bandwidth of SSB, many people do not realize the
need for the audio to be as distortion free as possible when
it reaches the balanced modulator(s). A major advantage of
true FSK is that it can be amplified by class "C", a lot more
efficient.
Bruce Gentry, KA2IVY
On 2/4/22 13:24, Paul Kasley wrote:
Distortion products. Feeding audio tones into the mic jack of
an SSB tx can result in splatter due to overdrive, and there
will normally be some level of spurs generated by
non-linearities in the signal chain. Plus any junk on the
input signal itself gets translated to the RF.
Directly shifting a carrier oscillator eliminates the audio
chain and is essentially CW.
-w9ts
On 2/4/2022 10:55, Ralph Mowery
wrote:
The
only thing I can think of is that AFSK is usually easily
to hook up.
I
really hate the term AFSK unless used in an AM or FM
transmitter. The results of feeding a single audio tone
one at a time as in RTTY into the SSB transmitter is
still FSK .
I
have not checked the FCC rules lately, but below 10
meters true AFSK (as in AM of FM) is not legal.
Ralph
ku4pt
Me and a ham club buddy were
discussing this yesterday, so I'll throw the question
to the wolves; in regards to RTTY, is there any
benefit to doing true FSK on a modern radio vs AFSK?
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