On May 8, 2005, at 2:10 AM, Leigh L Klotz, Jr. wrote:
I have enough BFO range as described in the manual and am able to
reach 4912.97 on the low end. Unfortunately, while that is low
enough for me to center the RTTY filters on 1000Hz for one of the
sidebands, it is not for the other.
I ran into this problem, too, when I tried to configure the RTTY
filters to center on 1500 Hz.
I did some searching and saw some posts from 2003 that said that
being able to reach RTTY filter frequencies of 2200Hz was often
possible only on one sideband, but I am not able to hit even my
target 1000Hz mark.
It's easy, really.
First, figure out which sideband you're having trouble with (remember
that the sideband used flips above 20 MHz). Normally, for 20m, you'd
use the LSB side for RTTY, and the USB side for RTTY-REVERSE (which
you'd commonly use for PSK)
I had trouble with the RTTY side. My BFO bottomed out at 4912.64 --
which was low enough for the CW filters at 600 Hz.
Are other K2s able to center RTTY filters on 1000Hz on both
sidebands? Would this small cap Bill suggests help mine without
affecting stability?
Yes. I'd try about 2 pf or so.
The 3 pf cap I used moved the low end down about 800 Hz without
affecting the high end.
Of course, increasing the BFO range means that the BFO adjustment
steps are a little wider, so don't increase the BFO range much more
than you have to.
It looks like I need a 250Hz-300Hz move down on the low end. I
don't know if that is reasonable and an effect of the wider KSB2,
or if I have some other, undiagnosed problem.
One concern I would have is the use of 1000 Hz signals with the OP1
filter. One reason RTTY pitches AFSK signals so high is so that the
harmonics of the audio signal fall outside the SSB filter passband.
If you are using the OP1 filter in FL1 for RTTY mode, this is the
filter you'll be transmitting with.
For my filters, 1500 Hz is plenty high to kill any second harmonic,
whereas the standard frequencies of 2125, 2295 were high enough that
my filters might actually attenuate it a bit.
Bill Coleman, AA4LR, PP-ASEL Mail: [EMAIL PROTECTED]
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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