On Oct 9, 2005, at 1:43 PM, Charlie, W0YG wrote:
Since the ability to set filters when using the RTTY mode is
different than LSB/USB if used for AFSK, what center frequency do
you use? Perhaps I should rephrase this. When setting filters in
the RTTY mode (the K2 defaults to the SSB filters when in RTTY mode
unless RTTY filters are set) do you use 1000 Hz as the center
frequency?
I went through this a few months ago. Initially, I set things up for
the Low Tones (1275 / 1445). However, when I went to reprogram the
KDSP2 filter, I found that it would only move to center frequencies
that were multiples of 100. This made it impossible to set the filter
in the center (1360).
Now, you must know that I have my K2/100 modified with the KI6WX
"1.9" kHz filter. It's really like the old stock filter - about 2 kHz
wide, but with less passband ripple. If you have a wider filter, you
might consider using higher frequencies. This places the second
harmonic higher in the passband, outside the filter range.
After some consideration of the problem, I ended up picking 1500 Hz
as my center frequency, and placing my tones at 1415 and 1585. The
next problem I had is that I could center the adjustable bandwidth
filter on both modes (RTTY and RTTY REV). This was solved by modding
the BFO to increase the range. Adjusting the BFO range is kinda
tricky. As you increase the range, the steps the BFO move become
courser, so there's more opportunity for slight frequency variations
as you change filters or switch modes. I managed to increase the
range just enough to get all the passbands centered on 1500 Hz.
That's all you want -- just enough range to get those frequencies
set. For this reason, using a frequency like 1500 Hz may be better
than trying to use the standard high tones.
The adjustable bandwidth filter is a real benefit on RTTY. With just
a few adjustments, you can get some really nice filters set up for
digital use -- something that would have cost a lot of money in other
rigs.
For RTTY, I use the progression OP1, 1.0 kHz, .5 kHz and .3 kHz. OP1
is good for scanning the bands, 1.0 is good for tuning in a crowded
band, and .5 kHz pretty much is single-signal. .3 is kinda narrow for
RTTY, and it will clip some of the signal -- but it does work great
for PSK31.
For CW, I use the odd progression of 1.0 kHz, .4 kHz, .16 kHz and
OP1. I don't like tuning around the CW bands with OP1 unless it is
really vacant, like up on 10 or 15 meters these days.
About the only downside of running RTTY with the K2/100 is that you
can only use about 20-35 watts. The KPA100 will get HOT very quickly.
PA efficiency gets really poor at this level.
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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