[GreenKeys] True FSK vs AFSK

Paul Kasley w9ts at comcast.net
Fri Feb 4 13:24:32 EST 2022


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
>
> *From:*greenkeys-bounces at mailman.qth.net 
> [mailto:greenkeys-bounces at mailman.qth.net] *On Behalf Of *Jeff G
> *Sent:* Friday, February 04, 2022 11:36 AM
> *To:* GreenKeys at mailman.qth.net
> *Subject:* [GreenKeys] True FSK vs AFSK
>
> 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?
>
> Jeff KC3GJX
>
>
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