[RTTY] ST0R RTTY Statistics

[Larry]

I did RTTY from XV this year and it was interesting. I was running  with 
MMTTY.
The signal display often looked like a DC signal on a scope with a slight 
ripple
for several kHz making the display nearly useless as a tuning aid. The 
stronger
signals would usually pop out while tuning across the pile but not always.

I was only able to manage about 10% RTTY QSOs from XV. I had hoped to get
the percentage closer to 25%.  Low power and only a vertical didn't help. I 
often
called CQ with no response.

The discussion here is interesting and I will have to look at the 
possibilities for next year's
trip to XV.

73, Larry  W6NWS
----- Original Message ----- 
From: "Kok Chen" <chen at mac.com>
To: "RTTY Reflector" <rtty at contesting.com>
Sent: Thursday, August 11, 2011 12:09 PM
Subject: Re: [RTTY] ST0R RTTY Statistics


>
> On Aug 11, 2011, at 8:02 AM, Joe Subich, W4TV wrote:
>
>> With nearly three times as many CW QSOs as RTTY (Digital) QSOs and
>> five phone QSOs for every two RTTY QSOs, there is still a long way
>> to go before major DXpeditions are giving RTTY more than "lip
>> service."
>
> I suspect this will improve as DXpeditions adopt better tuning techniques 
> for RTTY.  IMHO.
>
> With CW, you can listen for signals and decode a signal that are a full 
> kHz away (guys like N5KO use the filters in their own brains for CW; 
> Trey's advice to me was to call away from a CW pile if I know that he is 
> the op at the DX end).
>
> With voice, you make use of the "cocktail party effect" (the term is 
> actually used in technical papers, see also here 
> http://en.wikipedia.org/wiki/Cocktail_party_effect).
>
> You cannot do either in RTTY if you are tuning with a VFO knob.
>
> If the pile is heavy on the previous RTTY QSX, it could take a bit of 
> waiting for a call to appear cleanly on the DX's screen, or for a really 
> large signal to override everyones power combined (like the FM "capture 
> effect," but with one station against the power of many stations combined, 
> versus one station against one other station), or having to retune slowly 
> using the VFO knob.  None of this is especially fast.
>
> If the DX uses an RTTY skimmer, or a waterfall with memory, they could 
> find a station far away from the pile to work.  Just find the first 
> station that is in the clear within a 20 kHz (or however wide the receiver 
> can tune) passband to work next.
>
> You can imagine that for CW, you are instantaneously working with a 2 
> dimensional field (time and frequency).  With a traditional way of tuning 
> RTTY, it is one dimensional (time only).  But you gain back the advantage 
> compared to CW when you use a skimmer or memory-buffered waterfall tuning 
> (standard waterfalls won't give you that of course).
>
> All digital modes are machine decoded today anyway, so you might as well 
> take advantage of that fact to pull out one signal from among many 
> signals.  (Whether you prefer to call it RTTY or something else -- the 
> technology today that people use for keyboard modes is far different from 
> the "RTTY" that was used with mechanical teletypes; the only similarity to 
> real steam powered RTTY is the use of two FSK carriers, a shift of 170 Hz 
> and a baud rate of 45.45 Hz.  And if you don't write your own software to 
> do the demodulation, that distinction between the different digital 
> modulation modes is blurred even further.)
>
> Bear in mind that dynamic range is not so big a problem if you are the DX. 
> They can polish off all the large signals first before working their way 
> to the weaker ones.  The limitation of being able to concurrently decode 
> RTTY signals whose signal strengths are separated by "only" 10 or 15 S 
> units is not a problem.  At some point, that weak signal that is barely 
> above the noise floor is going to be within 10 S units of the loudest 
> signal present at the time.
>
> Once a DXpedition adopts wideband, agile tuning for RTTY, we too would 
> have to change our pileup busting behavior.  The key is to look for an 
> empty hole, no matter how far away from the previous QSX it is.  That has 
> already been shown to be true with 9X0TL.  In Tom's Quicktime video, you 
> can also watch 9X0TL clear out the strongest signals first but eventually 
> get to the weak ones.
>
> I don't myself really look forward to that progress (where the DX can pick 
> you off quickly as long as you are above the FSK decoding threshold with 
> respect to their noise floor).  Working DX becomes "shooting fish in the 
> barrel" and the challenge goes away.  How hard anyway is it to find an 
> empty bandpass to transmit.  He eventually finds you.
>
> BTW, the above scheme also applies to working a DX that is "begging" in an 
> almost empty subband where you have no idea what his QSX is.  Today, you 
> have to wait for him to slowly tune across you while you are calling.  If 
> you are weak, he will usually miss you completely if he is not a seasoned 
> RTTY operator (this happens to me so often that I prefer to let the DX 
> find a strong station first and then call next at that frequency; the 
> strong station acts as a beacon for the inexperienced RTTY op to hone in 
> on).  With a skimmer or waterfall at his end, he will notice you the 
> instant you transmit.
>
> The skimmer allows inexperienced ops to be pretty much as effective as the 
> experienced ops -- is that what we want eventually?  (Even a child can use 
> a cell phone.)
>
> 73
> Chen, W7AY
>
> _______________________________________________
> RTTY mailing list
> RTTY at contesting.com
> http://lists.contesting.com/mailman/listinfo/rtty
>