K2 and RTTY - a few questions

[Andreas (KU7T)]

Hi,

 

I literally worked my first RTTY QSOs ever last weekend in the WPX RTTY
contest. Was a lot of fun.  A few question come up.  I have aligned my
filters according to the well written document of Don, W3FPR at
http://www.mail-archive.com/elecraft@.../msg103915.html.  And I
seemed to have done it right, because switching through the filters does not
move the signal, just tightens the roll off.

 

Question 1: My frequency is 1000Hz off compared to what DX cluster spots
show.  When I see  a spot at 14.077 it, is for at 14.078. This must have to
do with the fact that the filters centers at 1000Hz, but is there a way to
compensate somewhere for this? Would be nice to be able to use the band map
of my contest program to jump to stations I would like to work.

 

Question 2: I noticed that 15m and up, I had to put both MTTY and the K2 in
RTTY reverse.  Is this correct? I happen to remember that the switch to USB
from LSB happens on 20m. Now I am wondering if this is something special for
RTTY or not.

 

Thanks

Andy,

KU7T

 

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[Don Wilhelm-4]

Andy,

It all depends on the software application are you using for RTTY? You
are using MMTTY which displays the frequency the K2 is tuned to (without
the audio offset considered).

With the RTTY filters, just like the SSB filters, the K2 dial indicates
the suppressed carrier frequency, and you are sending AFSK tones
centered around 1000 Hz.  That means your actual signal is 1000 Hz away
from the K2 dial indication.  The cluster spots are giving the actual
signal frequency.

If you were using a software application with a waterfall display (such
as Fldigi or HRD/DM780) you would see the actual signal at 1000 Hz on
the waterfall, and if you have the K2 to application set up right, the
actual frequency would be displayed on the waterfall.

As far as having to switch to RTTYrev for 15 meters and above, I thought
the K2 automatically compensated for th sideband switch.  It does that
for SSB, but I don't know about RTTY, I have never checked.  The K does
remember the mode on a per band basis, so once you are set up, it should
be transparent for operation.  The mixing scheme changes at 15 meters,
not 20.

73,
Don W3FPR

On 2/11/2013 11:54 PM, Andy, KU7T wrote:

> I literally worked my first RTTY QSOs ever last weekend in the WPX RTTY
> contest. Was a lot of fun.  A few question come up.  I have aligned my
> filters according to the well written document of Don, W3FPR at
> http://www.mail-archive.com/elecraft@.../msg103915.html.  And I
> seemed to have done it right, because switching through the filters does not
> move the signal, just tightens the roll off.
>
>  
>
> Question 1: My frequency is 1000Hz off compared to what DX cluster spots
> show.  When I see  a spot at 14.077 it, is for at 14.078. This must have to
> do with the fact that the filters centers at 1000Hz, but is there a way to
> compensate somewhere for this? Would be nice to be able to use the band map
> of my contest program to jump to stations I would like to work.
>
>  
>
> Question 2: I noticed that 15m and up, I had to put both MTTY and the K2 in
> RTTY reverse.  Is this correct? I happen to remember that the switch to USB
> from LSB happens on 20m. Now I am wondering if this is something special for
> RTTY or not.
>
>

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[Bill Coleman-2]

On Feb 11, 2013, at 11:54 PM, "Andy, KU7T" <[hidden email]> wrote:

> Question 1: My frequency is 1000Hz off compared to what DX cluster spots
> show.  When I see  a spot at 14.077 it, is for at 14.078. This must have to
> do with the fact that the filters centers at 1000Hz, but is there a way to
> compensate somewhere for this? Would be nice to be able to use the band map
> of my contest program to jump to stations I would like to work.

If you use the N!MM contesting software, you can program an offset. Generally, the frequency of the spot should be the Mark frequency, so your offset should be the value of your mark frequency.

> Question 2: I noticed that 15m and up, I had to put both MTTY and the K2 in
> RTTY reverse.  Is this correct? I happen to remember that the switch to USB
> from LSB happens on 20m. Now I am wondering if this is something special for
> RTTY or not.

I would double-check that you have the sidebands correct on your RTTY mode BFO settings. It sounds to me like you have both sides tuned to the same sideband. Member RTTY and RTTY REV should correspond to LSB and USB, respectively, much like the CW and CW REV modes.

The K2 does an internal inversion on 15m and up, but it picks the opposite sideband, so it all comes out the same. However, you've got to have the BFO settings right.

I've got a blog posting about how I set up my K2/100 filters here:
http://boringhamradiopart.blogspot.com/2010/02/configuring-elecraft-k2-crystal-filters.html

There's several tips in this posting. Note that I opted for a RTTY center frequency of 1500 Hz, which required a slight modification to the BFO oscillator to get enough range. It's in the article.

The K2/100 works pretty well on RTTY. My only complaint is that the transmitter gain varies wildly from band to band, so you have to carefully adjust the audio input level when you change bands.

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
           -- Wilbur Wright, 1901

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[Bill Coleman-2]

On Feb 12, 2013, at 7:59 AM, Don Wilhelm <[hidden email]> wrote:

> As far as having to switch to RTTYrev for 15 meters and above, I thought the K2 automatically compensated for th sideband switch.  It does that for SSB, but I don't know about RTTY, I have never checked.  The K does remember the mode on a per band basis, so once you are set up, it should be transparent for operation.  The mixing scheme changes at 15 meters, not 20.

It does it correctly, as you suggested. I think this fellow may have his BFO settings incorrect for RTTY REV.

Bill Coleman, AA4LR, PP-ASEL        Mail: [hidden email]
Web: http://boringhamradiopart.blogspot.com
Quote: "Not within a thousand years will man ever fly!"
           -- Wilbur Wright, 1901

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