[RTTY] Upside down

[Robert Chudek - K0RC]

Hello Gary,

There are a number of different situations which will cause you do 
decode "garbage" characters.

I happened to be in the middle of one of your attempts to decode an East 
Coast station on 20m this afternoon (20:03z). In this case, there was 
nothing wrong with his TX signal. He was transmitting right side up, at 
the proper speed, and zero beat on your signal. And I'm confident there 
really wasn't anything wrong with either of your stations... I was 
printing both of you perfect.

That said, your signal coming from near the polar region into the 
continental US (at that time) had a lot of flutter and distortion due to 
ionospheric conditions. I suspect the same distortion was being applied 
to the East Coast signal as it traveled up to your QTH. There is not 
much you can do to correct this type of anomaly. In this case, selecting 
a different "profile" in MMTTY might help somewhat. Other times it's 
better to send a message after a couple of attempts, like "pse try 
later". As a point of reference, here have been times when signals from 
Asiatic Russia are +10 dB/S-9 here and I cannot decode them.

The second part of  your message asks about the REV button in MMTTY. 
Yes, if you click that button your receive decoder will flip the 
incoming mark and space tones. IF the transmitting station is indeed 
transmitting "upside down", you should begin to print normal text. The 
button is instantaneous and you can determine within a few seconds 
whether someone is transmitting reversed or not. Be aware that REV 
button does not affect your (or his) TX signal. Asking him to use the 
REV button would not change anything on your end. If you find a station 
who is transmitting reversed, most modern transceivers have a menu 
selection to flip the TX tones to the correct configuration. Some 
software allows you to do this as well, the EXTFSK driver (if it is 
being used) with MMTTY is one example.

I did not encounter any signals this weekend that were transmitting 
reverse. If there were any, I didn't hear them. But that last station 
trying to work you many have been an exception. I did hear a few 
stations that were transmitting faster than 45.45 bauds this weekend. 
This is a third possibility that can create garbage receive on your end. 
In this particular case today (20:03z), the TX station was at the 
correct speed.

All these different aspects of RTTY signals and timing of the data bits 
can accumulate (be additive, like feed line loss) to create a problem 
for your decoder. As you go down to the 40m, 80m, and 160m bands the 
distortions and "hits" from noise become even more problematic.

By the way... I think I worked EVERY transceiver that was ever shipped 
to Alaska! You guys were hogging 20m from end to end! I just need to get 
one of you in the log on 80m RTTY and I'll have all 50 on that band.

73 de Bob - KØRC in MN




On 2/13/2011 11:23 PM, Gary AL9A wrote:
> During the contest I was repeatedly called by some poor soul whose entire
> string was nothing but garbage.  I knew it was the same station each time
> because in the middle of each garbage string were the characters ...s901...
> I could not decode anything and even though I sent several messages stating
> that I could not decode the station calling me he kept calling over and
> over.  This happened several times during the contest and right at the end
> he was the last station that tried to work me.
>
> Being a bit slow on the draw sometimes it finally dawned on me too late that
> the guy might be sending upside down.  By that time though it was all
> history and I couldn't verify my suspicion.  I don't think I've ever run
> across an upside down signal before so I'm not sure what I should have done.
> If I hit the REV button in MMTTY would it then decode his signal?  If he was
> indeed upside down, how could he copy my call and exchange?  If this happens
> again should I tell to other the op to hit his REV button to see if it
> corrects the garbage?  What's the best way to handle this?
>
> 73,
> Gary AL9A
>
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