[RTTY] Fw: ARLB006 NTIA: No Objection to Additional Data Modes on60 Meters

[Kok Chen]

On Mar 29, 2012, at 6:31 PM, Ron Kolarik wrote:

> Uhh, doesn't the K3 use a 15khz IF? If you use the FSK keying input on it
> you're just generating 2 audio tones in DSP....AFSK controlled by the
> firmware.

Yes, mathematically, some of the newer rigs (not just the K3) generate an RTTY signal at a lower tone pair (just like AFSK RTTY on SSB rigs) before shifting it up to RF frequencies.  

Except that the mixer image of the 15 kHz intermediate frequency is further away than in the audio case (for example, 30 kHz instead of 4 kHz) and pose a smaller problem.  Non-zero however, since the 15 kHz intermediate frequency still has to be heterodyned up to RF frequencies using old fashioned scalar mixers). 

In addition, extra sideband suppression in DSP rigs result through generating In-phase/Quadrature (I/Q) schemes instead of passing scalar analog signals through SSB filters to suppress the RTTY sidebands.

73
Chen, W7AY