[RTTY] Fwd: [Elecraft] CQWW RTTY - K3 Experience

[Junior]

 Chen,
 I was ragchewing with a W7 one day who mentioned he was trying out
FSK-D mode on his K3. I am not familiar with the K3 or FSK-D.
I guess FSK-D could be the paddle configuration?
The copy was not the greatest but what I noticed was a lot of extra spaces
in between the words/print. It could have been conditons at the time causing
that.
When I listened to the diddles I heard a distinct long dash in the
diddles/shifting ( farnsworth diddles? ). That made the diddles sound like
it was slower than 45 baud. I have been listening to diddles since 1970 so
that dash stood out to the ear.
Ritty has a function called Waveform. When you invoke it all the ASCII
characters you normally don't see will print out in between the print/words
when ragchewing i.e. like CR, LF, L for letters shift in a shaded color.
Ritty was copied the long dash as a
B which is an inverted tab. 
If the signal had been strong I doubt I would got those extra spaces in
between the words.
There is a software used by some that throws in a lot letters like we use to
with the old tape headers to slip in the TD on the old machines. Ritty will
print out six or seven letter shifts with Waveform on from that software but
the diddles/shift sound normal.
I can't get a screen shot to send you as Ritty runs in DOS under Win95.
I am not knocking the K3 but only what I observed. If I could afford the top
end model I would probably purchase one. Military retired pay aint't the
greatest :(
Charles/kk5oq


-----Original Message-----
From: rtty-bounces at contesting.com [mailto:rtty-bounces at contesting.com] On
Behalf Of Kok Chen
Sent: Monday, September 29, 2008 9:27 PM
To: RTTY Reflector
Subject: [RTTY] Fwd: [Elecraft] CQWW RTTY - K3 Experience

Ah, the mystery of the 5NN unfolds (well, some of the 5NN that we saw last
weekend, anyway :-).  Read the attached posting from the Elecraft reflector.

By the way, I spend a good part of CQ WW contest SWLing and watching the
built-in RTTY decoder in the K3: the K3's built in decoder (even with the
dual passband nonsense) was throwing more errors than the particular
software modem which I was using.

For the K3 internal decoding, I was using a 400 Hz roofing filter paired
with the dual passband DSP filter, with an external crossed ellipse
indicator to help the K3 tune in an RTTY signal properly.

Without precise measurements, it is hard to tell where the built-in decoder
stands among other RTTY software and TU.  Alex VE3NEA (Mr.  
Rocky, Mr. CW Skimmer, etc) had a couple of years ago published curves for a
couple of Windows based modems on this reflector.

Although it appears to throw more errors, to measure the K3's error rate
curve precisely, I first need to build a QSE to modulate with an HF Channel
Simulator. It is something in my stack of things to do.  I have an unused
SoftRock v6.2 that I can use to generate a low level RF signal that is
modulated by an HF Channel Simulator . That way, I can feed the K3 with an
RF signal with known SNR and known and repeatable propagation model.  In
preparation for that, I have already modified my channel simulator to output
in-phase and quadrature signals for the SoftRock.

Someone with a Mac and a SoftRock QSE can eventually replicate the
experiment for the Icoms' built-in RTTY decoders, too.

The Dual Passband filter in rigs is another pet peeve of mine.  Good
software demodulators that use Matched filtering get their filters unmatched
by these "dual passband" filters.  Among others, K6STI's RITTY decoder for
example uses a Matched filtering.  Matched filters that are designed for
RTTY will result in a specific double peak response (because the baud rate
is so much lower than the RTTY shift), but when you cascade an external
filter that does not have a flat passband with a true Matched filter in a
modem, the concatenated filter is no longer matched to an RTTY keying
signal.

The only time a dual peak filter in a rig helps is if the modem itself has
the wrong filtering relative to the keying signal.

73
Chen, W7AY


> From: Arie Kleingeld PA3A <pa3a at hccnet.nl>
> Date: September 29, 2008 11:12:01 AM PDT
> To: elecraft at mailman.qth.net
> Subject: RE: [Elecraft] CQWW RTTY - K3 Experience
>
>
> I had a few spare moments this weekend and took the CW-paddle for 
> about 100 RTTY QSO's during the CQWW.
>
> Boy, that was very easy and, most of all, FUN. Only had to change my 
> routine from 5nn a4 to 5nn 14  :-)
>
> Using the CW memories made it even more easy. I think it must have 
> been a bit strange on the other side of the QSO seeing the long pause 
> after the 5nn because the "1" takes a reletive long time in CW.
> That's also why a kept going on with the 5nn instead of 599.
>
> Anyway, flawless operation and I love the rtty dual passband. Very 
> good filtering.
>
> 73,
> Arie PA3A
>
>
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