Dick, I have to agree with Joe on this.....they have a problem. I first noticed
it last August and sent along the information to NJ1Q several times. I still
have the screen captures from RTTY, PSK and MFSK on different bands
and the signals are pretty bad. I can send them if you're interested.
Ron K0IDT
----- Original Message -----
From: "Dick Kriss" <aa5vu@arrl.net>
To: "RTTY Reflector" <rtty@contesting.com>; "Joe Subich W4TV" <lists@subich.com>
Cc: "Joe Carcia, NJ1Q" <nj1q@arrl.org>
Sent: Tuesday, January 29, 2013 8:48 PM
Subject: Re: [RTTY] Bad AFSK
Joe Subich, W4TV
It was pretty obvious you were talking about a W1AW with the "terrible" AFSK signal.
There are no W1AW RTTY bulletins on Tuesdays so I listened to the early BPSK-31
bulletin on 14.095 and on 18.102.5 using a Kenwood TS-590S with a direct USB interface
to fldigi-3.21.67 on an iMac with OS X 10.8.2. The W1AW signal was on frequency on
both bands with solid print, clean looking BPSK-31 signals with none of the harmonics
or birdies you mentioned.
I am aware of the W1AW setup with Icom transmitters and the station manager tries very
hard to be sure each band dedicated transmitter is correctly adjusted with no ALC
showing. The Station Manager uses a custom interface hard wired to the digital ports
on the rear - not via the Mic connector as implied in your message.
I think you owe the Joe Carcia, NJ1Q, the W1AW Station Manager and this reflector a
retracton for your public comments about the "terrible" W1AW signal and your statement
"….One simply *can not* run "all sliders to the max" and "all knobs to the right" with
AFSK."
You may want to check your setup for local interference causing the harmonics and
birdies you observed. There was no evidence of harmonics or birdies on the early
29-Jan-2013 PSK-31 bulletin.
Dick AA5VU
Date: Tue, 29 Jan 2013 10:38:45 -0500
From: Joe Subich, W4TV <lists@subich.com>
To: MMTTY@yahoogroups.com, RTTY <rtty@contesting.com>
Subject: [RTTY] Bad AFSK
Message-ID: <5107ED05.6010405@subich.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Elecraft have taken the lead on FSK bandwidth - thanks to W7AY, K0SM
and W0YK among others. Lets hope other manufacturers follow quickly.
Yesterday evening as I was looking for some RTTY activity to try the
new Elecraft "narrow FSK filter", I stumbled across another terrible
AFSK signal. It just happens to belong to a well known club so I
won't give the call here but I have contacted the trustee.
However, I've posted a screen capture from my P3 that clearly shows
what happens when over driving the mic input of an SSB transmitter at:
http://www.subich.com/BAD_AFSK.jpg (the last spike at about 14.0972
is a local birdie).
Note this transmitter has not only "second harmonic" energy at
+1 KHz/340 Hz shift and "fourth harmonic" energy at +2 KHz/680 Hz
shift, it also shows insufficient opposite sideband suppression (or
possibly IMD in the PA - it's impossible to tell which).
One simply *can not* run "all sliders to the max" and "all knobs to
the right" with AFSK. Any manufacturer or individual who says to
do so is giving you bad advice. Again, unless you have the tools
to make absolutely sure you are generating clean AFSK, *use FSK*,
the clicks are far less objectionable than 2nd/3rd audio harmonics
that are suppressed by -18 and -15 dB respectively. This capture
was made during a fade - signal levels were generally much higher
and even the spurious signals were well above -73 dBm (S9+).
73,
... Joe, W4TV
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