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

[Tom Wylie]

Personally I think that running with AFC on is bad practise as your 
signal will wobble up and down the band.   In major contests its very 
hard when changing bands or QSYing for a mult, to re-find a clear 
frequency on 14Mhz for example - sometimes impossible.   That would only 
be harder if people kept allowing their frequency to wander.

Even when running people drift in and out of your passband with their 
AFC on.   Would that be tolerated during CQWW CW or SSB, I think not..

This is one reason why I TX on VFO B and RX on VFO A so that I can net 
my RX on another signal, but keep my TX frequency fixed.   In fact more 
often than not I will have my VFO lock on.    If others cannot net on 
me, then its a bad day and they really shouldn't be there if they cannot 
manipulate their equipment so to minimise QRM.

Now where's my flameproof suit?

Tom
GM4FDM





Ian White GM3SEK wrote:
> David, G3YYD wrote:
>
>   
>> Chris Tran ZL1CT wrote:
>>     
>
>   
>>> 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. !
>>>
>>>       
>
>   
>> 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.
>>
>>     
>
> Both Chris and David make valid points.  FSK has no user settings so the 
> signal quality is always the same; but that quality depends on the rig. 
> Sudden frequency shifts produce similar key-clicks to unfiltered CW 
> keying (which is why I always felt a bit nervous about FSK in the 
> FT-1000).  AFSK can manage these problems in software, so in some rigs 
> it can produce a cleaner signal than the hardware FSK... but the user 
> has to adjust the drive level into the rig, so AFSK can also be truly 
> awful.
>
> Coming back to the business about AFC and NET: when it's so easy to tune 
> in an FSK signal, who really needs them? For RTTY I keep both of them 
> permanently switched off.
>
> The FFT spectrum display in MMTTY makes it very easy to tune an RTTY 
> signal. Just drop the two tones onto the two yellow bars  (or anywhere 
> reasonably close) and MMTTY will start decoding.
>
> Another advantage of the FFT display is that it's like having a little 
> panadaptor permanently on-screen. It helps you find clear frequency 
> slots and keep aware of nearby QRM. Keying sidebands spilling into your 
> slot are clearly visible, and so are the extra 170Hz sidebands from 
> overdriven AFSK. The two yellow bars in the FFT are separated by exactly 
> 170Hz, and in heavy QRM that's a big help in sorting out which pairs of 
> tones belong together.
>
> The traditional "crossed bananas" display does nothing that isn't done 
> better by the FFT, so I keep that switched off.
>
>
> Having said all that, apologies for the config trouble in the very first 
> QSO last night (that was the logger, not MMTTY). Also apologies for the 
> hang-up later on, when I discovered I'd kicked the keyboard lead out of 
> its socket. What with one thing and another, it never felt comfortable, 
> but 76 turns out not too bad.
>
>
>   

-- 
Men are like fine wine.   They start out
as grapes, and it's up to women
to stomp the crap out of them until
they turn into something acceptable
to have dinner with!



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