Dennis,
First a clarification - if the band is below 15 meters, RTTY is LSB and
RTTY REV is USB.
You don't have to worry about that on bands above 15 meters because the
K2 automatically makes the corrective swap, but when aligning the
filters, use a band below 15 meters so as not to mix the sidebands.
Secondly, since you run out of range when aligning the 400 Hz filter
width at 1000 Hz, your BFO range is not correct (too high) on the low
frequency side. That can usually be corrected by adding a small value
capacitor (10 pF to 22 pF) between the junction of the crystals and C174
and ground - a capacitor between pins 6 and 3 of U11 is a good place to
insert it. Check the BFO range against the manual range limits after
adding the capacitor and adjust the capacitor value as required.
Once you have the BFO range corrected, you will have to re-align *all*
your filters - SSB, CW and RTTY. You can refer to the filter alignment
information on my website www.w3fpr.com - see part 3 of the K2 Dial
Calibration article.
The RTTY FL1 settings should be OP1 width, and the BFO settings should
normally be the same as used for SSB LSB and USB. That filter will be
the one normally used and works well with a full waterfall display.
The problem comes in when a strong signal comes into the filter passband
and activates the AGC such that the K2 receiver gain is reduced. All
signals in the passband will be reduced because of the AGC action.
The solution to that problem is to use a narrowed bandwidth (to get the
strong signal out of the passband). That is the purpose of the narrow
RTTY and RTTY REV filters.
To accomplish that, I normally set FL2 to 1000 Hz, FL3 to 700 Hz and FL4
to 400 Hz. Those are the widths that I use, you are free to make your
own choices on your desired filter widths.
For the BFO frequencies of these narrow filters, the RTTY filters will
be in the vicinity of 4912.xx and the RTTY REV filters will be in the
vicinity of 4914.xx.
Yes, use Spectrogram to set all the filters. The settings in the manual
for SSB and CW will produce a workable set of filters, but they will not
likely be optimum.
One note on the SSB filters, be aware of the actual width of the SSB
FL2, FL3 and FL4 filters. Many K2s in the serial number range near
yours have varactors that make those filters much wider than indicated
by the display on the K2. Make FL2 about 200 Hz more narrow than the
FL1 OP1 width, FL3 about 200 Hz more narrow than FL2 and FL4 about 200
Hz even more narrow. Observing the actual filter width with Spectrogram
will produce usable filters for reducing QRM from an interfering SSB
signal on the high frequency side. The low frequency slope of the SSB
filters should be placed close to the 300 Hz point on the Spectrogram
display although the FL4 may be placed a bit higher (between 400 and 500
Hz). That will produce a set of SSB filters that can be progressively
narrowed to maintain communications in the presence of interfering
strong signals slightly off frequency.
Now, if you followed all of that, you know as much as I do about
aligning the K2 filters.
73,
Don W3FPR
On 2/19/2014 10:01 PM, Dennis Moore wrote:
I'm trying to get my K2 (SN 5711) working on digital modes, initially
just WSPR. I have the fixed audio output wired to pin 5 of the Mic
header, going to a Signalink USB which is working fine. Audio in/out,
keying, all just fine. If I transmit on WSPR my signal is being heard
on 80m whether I'm in RTTY or RTTY REV. That in itself seems odd. I'm
not able to decode any signals even though I can hear them. I'm having
a hard time wrapping my brain around RTTY, RTTY REV, and when to use
which mode. Also have questions about setting up the filters using
Spectrogram. I've got the manual and I've searched the web for answers
which probably just added to the confusion.
First issue: RTTY & REV as it applies to USB/LSB
On 80m, mode RTTY, am I transmitting on LSB or USB?
If RTTY is LSB, when I switch to REV am I then transmitting on USB?
Is that true on all bands? I read about sidebands switching above 17m
on the K2. What exactly does that mean, and what effect does that have
on which sideband I'm transmitting on? When would I use RTTY vs RTTY
REV? If digital modes normally use USB, shouldn't I always be set to
RTTY REV?
Second issue: Setting up filters
I read Don's advice regarding setting up filters for JT65 but it
wasn't clear to me about BF2, BF3, BF4. Don said to center the filter
at 1000 Hz, and that the high value should be used for RTTY REV and
the low value should be used for RTTY. Say I have a filter setting of
700 Hz. In Spectrogram I see a 700 Hz wide noise signal, do I center
the peak of that signal on 1000 Hz? I know that if I adjust the BF
value to center on 1000 Hz at 4912.85 that I can keep adjusting the
value until my noise disappears outside the filter and then will
reappear and I can center it again on a value of 4914.74. Should this
high value should be used when I'm setting the filter for RTTY or RTTY
REV?
Third issue: BF4 running out of range
As I'm trying to adjust the center of the signal at 1000 Hz the filter
seems to run out of tuning range right before I get it centered, and
the value of the BF jumps from it's low value to it's high value.
I know that a lot of this is pretty basic but I'm just trying to get
my thoughts on this straight. It seemed to be a lot easier getting my
K3 up on WSPR but I think getting this K2/10 is just the thing for
weak signal digital work.
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
