On Jul 26, 2011, at 9:27 AM, Tom Osborne wrote:
> I wouldn't try to use the 'hole' in between the two traces :-) Not unless
> you have a narrow enough filter to filter out their mark and space tones.
Heh, heh :-)
Speaking of spectrum holes... those of us who had used waterfall tuning used to
have a free run with split DX.
All you had to do is to zero beat the station that the DX is working -- that
takes a second or two at most, especially if your modem implements something
like the "click buffer" in cocoaModem, where you can print the past signal of a
station after they have already stopped transmitting.
It used to take a while before the old fashioned knob twiddlers find where the
DX is listening to, especially if the DX is working a station they can barely
hear (but sticks out like a sore thumb on a waterfall).
Back then, working split RTTY was like shooting fish in a barrel if you use a
waterfall based receiver (especially if you have the second receiver parked at
the DX's signal).
That was 5 years or 6 years ago. Over time, there has been more waterfall
tuners (I suspect it is the Flex guys). Nowadays, the QSX gets piled on almost
instantly.
A better technique nowadays is to find a hole right next to the previous QSX
once the old QSX becomes congested.
Now, if you know that the DX is also using waterfall tuning (for example, the
VP2MUM and 9X0TL operations), then the "best" technique is a little different.
In this case, you have to guess the bandwidth that the DX is using. In the
case of DL2RUM operating, you know that he uses a K3 (not a SDR) and his
waterfall range is limited to about 2 kHz. By watching the stations that he
answers, you can pretty quickly find the lower and upper bound of his
waterfall. In this case, finding the cleanest part of the spectrum that he
watches becomes the key. Especially if you have a puny signal.
You can readily tell if the DX is using a waterfall by seeing him jump around
very often.
Another interesting trick to crack a pileup is to perfectly "straddle" an RTTY
signal with another RTTY signal. Place your mark tone (or space tone) right
smack in the middle of the other guy's shift. If the DX tunes to you, one of
the QRM tones will be right in middle between your mark and space, and with
most RTTY filtering (either with matched filters or the "dual-peak" filters)
the QRM will be depressed by many dB, thus giving you a better chance to print
cleanly. The same is true if the DX tunes over to the other chap of course --
his print will be clean and you will barely QRM him. But, in a pileup, there
is likely to be more that one station at the other frequency, QRMing one
another.
73
Chen, W7AY
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