[Elecraft] The K2 and RTTY

[sheajohnw at aol.com]

I have made several thousand RTTY Contest QSOs using the K2/100.  It is 
AFSK only.  My TX power out is about 90 watts usually into a low 
Diamond verticle antenna rated for 200 watts.  Receive works OK for me 
considering the limitations of the antenna.  Transmit works well for me 
on search and pounce.  I leave the fan speed set high during contests.  
The limitation of my antenna have kept my rate at 100 - 200 QSOs per 
contest.  If I had better antennas, a higher S&P QSO rate might result 
in over heating.

I have tried running mode but find that the rig starts to get 
unacceptably hot after several minutes of CQing.  During very good band 
conditions, my hourly S&P rate was high enough to damage the 40M and 
20M matching components in the Diamond antenna.  I now must restrict 
the Diamond antenna to 80M and 15M use and use a low Alpha Delta DX-CC 
fan dipole for 40M and 20M.

I set the K2 AGC off and control RX signal strength into the computer 
sound card using RF gain.  AGC off prevents pumping that can depress 
weak signals when a strong signal comes onto the passband.  Under 
crowded conditions, I use AFil to narrow bandwidth with 1000 Hz being 
used as my center frequency.  RTTY AFil is set to opt1 with the strong 
right third of the filter passband aligned with 1000 HZ.  I always try 
to TX at 1000 HZ to keep the TX signal strength consistent.  I use 
narrowed CW filters centered on 1000 Hz when needed.

Reducing RF gain is more beneficial for copying weak signals that using 
narrow DSP filters.  Problems copying weak signals appear to be more 
related to the background noise level than adjacent signal 
interference.  The narrow DSP filters work FB to eliminate unwanted 
signals within a wider passband with the AGC off to prevent signal 
strength depression by the AGC.  I avoid XFil because I find the small 
frequency shift annoying on digital modes when switching between the 
XFil used on RX and the Opt1 fil always used on TX.

I hope to make the following future changes:
-higher and better antennas to improve my QSO rate,
-an external amplifier so that I can use lower power on the K2/100 to 
enable run mode without significant heating,
-an external muffin fan to improve K2 cooling efficiency.

I have never had a heating problem using typically lower power PSK31.  
AGC pumping can be challenging on PSK 31 because of the narrow signal 
and closeness of adjacent signals.

HTH 73 de KB1IKD

 
Lee Buller wrote: 
 
> > > Well, I am getting back into RTTY and PSK31 after a couple of 
years away from the modes. I have my IC756PROII set up for AFSK and 
going to FSK using MMTTY on RTTY (only) 
> > What I "hate" about the PROII is when you are using RTTY I have to 
use AFSK Keying and the receiver's bandpass is less that ideal. This is 
why I am going to FSK so I can used the great filters on the PROII. 
> > Well, I never thought about using the K2/100 as an RTTY rig. I know 
it has RTTY filters...but I am sure it does not use FSK, but uses AFSK 
through the RTTY Filters? Right? 
> > Could somebody who has used the K2 on RTTY and PSK31 eludicate me 
on their experience with the rig and the mode? 
> > Lee - K0WA 
> > 
> 
>In our day and age it seems that Common Sense is in short supply. If 
you don't have any Common Sense - get some Common Sense and use it. If 
you can't find any Common Sense, ask for help from somebody who has 
some Common Sense. Is Common Sense devine? 
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