[UK-CONTEST] RTTY operation (was ARRL Contests)

[David, G3YYD]

I have always wondered why FSK is used when AFSK is so much more 
flexible and simpler to implement. I have used AFSK since the early 
1970s. I have never had anyone complain about my transmitted signal. 
Recently I listened on my FT1000MP to my K3 on AFSK and could not detect 
any problems at all even at very low levels. I suspect that many of the 
wide RTTY signals are FSK generated as they will not have the filtering 
that is available on AFSK.

When using AFSK:  RUN net off and AFC on is the configuration - ensures 
auto track off QRG callers without TX moving. When on S&P net on and AFC 
off is how I operate - net on insures where you RX you TX.

David G3YYD

Chris Tran ZL1CT wrote:
> Hi Steve et al
>
> I think it is OK for our particular set-up to have AFC on when 'running' - I 
> probably need to explain more -  myself and Ken ZL4NR had quite a learning 
> curve about this - so much so that I'm putting a webpage on my website about 
> it, with some screenshots. None of the existing internet help pages were 
> sufficiently specific to our set-up.
>
> For RTTY, ZM4A is running N1MM contest logging software, which controls the 
> MMTTY datamodes software, which in turn controls the MicroKeyer II router 
> software, which then controls the MicroKeyer II via a virtual COM port. The 
> MicroKeyer then keys the FSK socket at the back of the FT-1000 MkV.  The 
> true FSK this generates means that our RTTY *transmitted* mark and space 
> frequencies do not change unless the FT-1000 VFO dial is changed - either 
> manually by the operator or by the software via the CAT control (which N1MM 
> might be able to do, but we don't really want)  For this reason it is OK to 
> use the MMTTY 'AFC' facility and/or the RIT as you suggested, to tune in 
> stations that are calling when running. Personally I think the RIT method is 
> better than the AFC method.
>
> On AFSK the situation is very different - the software can easily vary the 
> audio tones that are sent to the Mic socket on RTTY transmit, hence varying 
> the RTTY transmitted frequencies, so with AFC and NET both 'on' the 
> possibility of following another station up or down the band is real.
>
> The advantage of true FSK is that it is difficult to have a poor transmitted 
> RTTY signal, whereas with AFSK it is easy to overdrive the Mic input stages. 
> However, our initial impression is that true FSK has the disadvantage that 
> when S&P, you have to carefully tune in every station you wish to call (with 
> our AFC off) to be accurately netted (you could argue that their AFC would 
> find us but if we're in a pile-up I guess not)   Standing by to be corrected 
> by experienced RTTY ops. !
>
> Good luck with GB5CC - I had great fun operating GB5CC last year - hope to 
> work you with my new callsign ZL4CT or as ZL1CT. Not sure yet if I'm in the 
> VK/ZL team but I'll be QRV anyway.
>
> 73
> Chris
> ZL1CT/GM3WOJ 
>
> _______________________________________________
> UK-Contest mailing list
> UK-Contest at contesting.com
> http://lists.contesting.com/mailman/listinfo/uk-contest
>