[RTTY] K3 reduced-bandwidth RTTY analysis

[Kok Chen]

On Mar 22, 2013, at 1:31 PM, Joe Subich, W4TV wrote:

> Similarly, even ARRL (most specifically W3IZ's review in the current
> issue of QST) do not make the slightest mention of signal purity issues
> like the absolutely horrible transmit phase noise spectrum of the new
> FT-3000.

As bad as the FT-dx3000, its transmit phase noise (about -100 dBc at a 1 kHz offset) is still nowhere close to the interference from an (continuous phase) FSK signal, whose keying sidebands are in the region of -60 dBc at the same 1 kHz offset from one of the FSK tones.

You might be confusing the transmit phase noise with the poor reciprocal mixing (-82 dBc at 2 kHz offset) in the FT-dx3000.  The latter only affects the owner, not the other occupants of the band.  But even that number is still dominated by FSK keyclicks from a signal that is 2 kHz offset away (although not by much).

One way to look at it is that if you receive with an FT-dx3000, you probably won't be able to tell if the other people are filtering their RTTY signals :-).

73
Chen, W7AY