Posted by
Don Wilhelm-4 on
Oct 02, 2010; 4:00am
URL: http://elecraft.85.s1.nabble.com/K2-Heat-On-Digital-Modes-tp5572168p5593581.html
Jon,
The default BFO frequencies for the RTTY filter set will not be optimum
for your K2, you will have to optimize them the same as you must do for
SSB and CW if you are to achieve decent filters. A note of interest -
due to the varactors that were supplied with K2s over the past year, the
wide (greater than 1.00) filter widths are much greater than that
indicated by the K2 display. The "cure" is to use Spectrogram (or other
audio spectrum analyzer) to measure the actual width of the filters for
SSB and possibly for RTTY.
I suggest you use Spectrogram to set the filters. RTTY is not much
different than either the SSB or the CW filters. See part 3 of the K2
Dial Calibration article on my website www.w3fpr.com for information
about using Spectrogram for filter alignment.
Set FL1 to the OP1 filter since the OP1 filter will be always be used
for transmit. Set the BFOs for FL1 the same as you have for SSB - yes,
RTTY should be the same as LSB and RTTYr should be the same as USB. The
low frequency -3dB corner of the filter passband should ce located at
300 Hz. That will provide you with a full width filter for use with
most PSK31 applications.
I usually set FL2 at a 1.00 kHz bandwidth, FL3 at 0.70, and FL4 at
0.40. You may vary those if you prefer different widths.
Whatever your chosen widths, set the BFOs for those filters to center on
1000 Hz. Use Spectrogram to see the filter passband and where it is
positioned.
Those settings will give you narrow filters for PSK31 when there are
strong signals nearby and good narrow filters for RTTY (set the RTTY
application to use 915 Hz as the mark frequency). When using the narrow
filters, tune the desired signal to the vicinity of 1000 Hz on the
waterfall display using the K2 VFO.
If you have the KDSP2 installed, you must change the DSP RTTY filter AF2
through AF4 center frequencies to center on 1000 Hz to agree with the IF
filter frequencies. Leave the AF1 setting at LO PASS.
On the RTTY power question, that recommendation you referenced is for
the base K2 without the KPA100. With the KPA100, you can operate
continuously at 35 watts, or for 1 to 2 minute periods at 70 watts with
no harm.
73,
Don W3FPR
On 10/1/2010 11:20 PM, Jon Perelstein wrote:
> I'm having a problem with the BFO settings for RTTY. The outputs on the
> different filters are centered at significantly different places in the
> waterfall. For R-Reverse, they're as follows:
>
> Filter Width Center on Waterfall
> ------- -------- ---------------------------
> FL1 2.5 KHz 1.1 KHz
> FL2 1.3 KHz 2.0 KHz
> FL3 0.6 KHz 1.6 KHz
> FL4 0.3 KHz 1.1 KHz
>
>
> Thus, a station centered at 1.0 KHz on my waterfall when using FL1 is not
> visible in the waterfall when using FL2 or FL3, but is again visible when using
> FL4.
>
> My understanding from the main K2 manual is that R-Normal is LSB, and R-Reverse
> is USB. Based on that, I used the KSB2 LSB BFO settings for R-Normal and the
> KSB2 USB BFO settings for R-Reverse. The settings for R-Reverse were:
>
> Filter Width BFO
> ------- -------- ---------
> FL1 Op1 4916.3
> FL2 1.40 4916.1
> FL3 0.70 4915.5
> FL4 0.20 4914.7
>
> These R-Reverse BFO settings are the same as I have set with USB.
>
> By comparison, for USB, using the same BFO settings, I get all four filters
> centered at about 1.1 KHz. A station at 1.0 KHz on my waterfall is visible on
> FL1, FL2, FL3, and FL4.
>
> I took the measurements with a straight stereo cable from the headphone out to
> the line in on my computer. I also re-did them with a SignaLink USB and got the
> same results. Similarly, I tried both fldigi and DM-780 as my software and got
> the same results.
>
> What am I doing wrong? I didn't find anything in either the K2 Operating Guide
> or the KSB2 Operating Guide for any BFO calibrations related to the RTTY mode.
>
> By the way, I re-did the KPA-100 bias adjustment on my rig and it was pretty
> close to correct to begin with. I did notice that the K2 Operating Guide
> recommends against transmitting at more than 10w for more than 1-2 minutes at a
> time for continuous duty cycle RTTY/data modes.
>
> As always, thanks for your help,
>
> Jon
> KB1QBZ
>
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