K2 drifting?

[NR5A]

I started noticing a problem tonite with my K2 drifting slowly down in freq.
I mostly run PSK31 with it and tonite I was chasing the stations I worked
down in freq. I was accused of running Drake equiment? hi

Anyway I'm wondering what in the world should I check or do??

Jerry - NR5A - South Dakota


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[Rich Lentz]

I observed the same problem when I use any of the filters (XFIL) other than
the main one OP1.  The narrower filters can be slightly off frequency but
you always transmit with OP1.  Thus you will be slightly off frequency when
you transmit at what you hear for the other parties frequency. His PSK
program will use AFC to find your signal and transmit at that frequency.
Thus the next time you will transmit lower because your AFC is also
tracking. Cure - If you use narrow filters then SHUT OFF AFC in the PSK
program (it's near impossible to get the narrower filters of the K2 within 1
Hz.)

Rich
KE0X

-

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[Rich Lentz]

The RTTY or Digital filters are available on the newer versions of
"firmware" and allow a complete set of filters tuned and setup specifically
for RTTY or digital modes, however they must be enabled.  The manual
explains this Or if you have an older K2 with an upgraded MCU then you need
to look at the newer manual.

The major point is that -  1. it is almost impossible to get any of the
narrower filters within 1 Hz of the main (OP1) filter that is used for
transmit in all cases regardless of which filter is selected. 2. The PSK
program will transmit a tone equal to what the PSK program thinks is the
received signal frequency - however, that is off frequency by 1 to as much
as 20/30 Hz. from the actual received frequency when ANY filter is used
other than OP1 because the K2 switches to OP1 in transmit. (The offset can
be observed by tuning in a solid carrier and switching filters.)  3. If the
other Party has AFC turned on then he will now transmit at that new
frequency and thus the drift or actually frequency starts walking up/down
the band.  

If you don't have AFC turned on then you will continue to transmit at the
same frequency, unless you reset the signal to the new frequency. If at
least one of the two parties involved does not have AFC turned on then Drift
is less likely to happen.

There is a small amount of drift in the K2 (less with the Temp Stabilizing
MOD) from cold start for about 15 - 30 Minutes. Thus the above discussion
assumes that 1. you have the temp stabilizing mod installed and 2. the rig
has been on for about 30 minutes.

Rich


----------

Oh, good point.  I forgot to mention that I was using  FL4 which was
specifically set up for 1000 Hz center frequency and 700 Hz bandwidth.  

I thought that FL4 was specifically set up for digital modes.  Does that
mean "other" digital modes like RTTY and that PSK31 should be run with
OP1 instead?

Mark, NK8Q


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[Mark J. Schreiner]

Hi Rich,

Thanks for the detailed description.  I think I'm getting it now.  Sometimes I'm a bit slow, sometimes I'm a bit fast, I guess I have a high amount of jitter on my clock (sorry, it is a work related joke, and probably a poor one at that).  

Now, I think I only have three more questions (for now) based on your description.  What is the mod that you are referring to?  I have a nearly brand new K2 (S/N 4786), so is the mod already implemented by Elecraft in my kit or is it yet another mod I should do?  In my case the radio was on for well over one hour, so it should have been nice & stable.  

Next question is once the filter calibrations & settings are done I understand how it could be off by as little as 1 Hz or as much as 20 Hz from OP1.  Is this value consistent once things are set or does it vary each time the filter is switched in/out?  If for example the K2 is done being set up and FL4 is activated (which mine is and is set for 1000 Hz center frequency and 700 Hz BW), it may be say 5 Hz low.  If I switch it to OP1 it should be right on with Tx & Rx, if I switch to FL2, FL3 or FL4 it could be off by as little as 1 Hz or as much as 20 Hz, but will FL4 always be off by 5 Hz (unless I change filter calibration settings)?

Final question for now is related to the DSP filter I just installed.  I set up DSP filters which I still need to play with to get a feeling for, but essentially expect them to act as a brick wall for signals outside their parameters.  While I know they are audio and not IF filters so if I have a very strong station nearby while I'm using OP1 on Tx & Rx and a very narrow DSP filter I may not get the best function out of the filtering.  So, I would then use a combination of FL2/FL3/FL4 as appropriate and then add DSP as well.  Oh, the question is if I use OP1 for Tx & Rx and a narrow DSP filter I don't think the DSP will change the frequency at all like the FL2 - FL4 filters would, is that correct?  So, assuming that is the case, maybe I always want to use OP1 and the desired DSP filter and then just add FL2 to FL4 as needed.  I guess I just have to play with it and see what works best for me in given circumstances.  

72/73,

Mark, NK8Q

>From: Rich Lentz <[hidden email]>
>Date: Mon May 02 13:03:56 CDT 2005
>To: [hidden email]
>Cc: 'NR5A' <[hidden email]>, 'Elecraft Reflector' <[hidden email]>
>Subject: RE: [Elecraft] K2 drifting?

>The RTTY or Digital filters are available on the newer versions of
>"firmware" and allow a complete set of filters tuned and setup specifically
>for RTTY or digital modes, however they must be enabled.  The manual
>explains this Or if you have an older K2 with an upgraded MCU then you need
>to look at the newer manual.
>
>The major point is that -  1. it is almost impossible to get any of the
>narrower filters within 1 Hz of the main (OP1) filter that is used for
>transmit in all cases regardless of which filter is selected. 2. The PSK
>program will transmit a tone equal to what the PSK program thinks is the
>received signal frequency - however, that is off frequency by 1 to as much
>as 20/30 Hz. from the actual received frequency when ANY filter is used
>other than OP1 because the K2 switches to OP1 in transmit. (The offset can
>be observed by tuning in a solid carrier and switching filters.)  3. If the
>other Party has AFC turned on then he will now transmit at that new
>frequency and thus the drift or actually frequency starts walking up/down
>the band.  
>
>If you don't have AFC turned on then you will continue to transmit at the
>same frequency, unless you reset the signal to the new frequency. If at
>least one of the two parties involved does not have AFC turned on then Drift
>is less likely to happen.
>
>There is a small amount of drift in the K2 (less with the Temp Stabilizing
>MOD) from cold start for about 15 - 30 Minutes. Thus the above discussion
>assumes that 1. you have the temp stabilizing mod installed and 2. the rig
>has been on for about 30 minutes.
>
>Rich
>
>
>----------
>
>Oh, good point.  I forgot to mention that I was using  FL4 which was
>specifically set up for 1000 Hz center frequency and 700 Hz bandwidth.  
>
>I thought that FL4 was specifically set up for digital modes.  Does that
>mean "other" digital modes like RTTY and that PSK31 should be run with
>OP1 instead?
>
>Mark, NK8Q

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[Rich Lentz]

K2 Temperature Compensated PLL Reference Upgrade - Only needed for K2 SN
less than 3446 - you do not need it.

It has been my experience that the offset remains the same - this is related
to your calibration for the XFIL's.

Do not have the DSP filter - perhaps Lyle can answer that question.

Rich



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[KK7P]

> if I have a very strong station nearby while I'm using
> OP1 on Tx & Rx and a very narrow  DSP filter I may not
> get the best function out of the filtering.

The AGC would see the wider bandwidth while the computer running PSK31
or whatever mode you are using would see the narrow bandwidth, so there
could be some pumping due to AGC depending on QRM/QRN.

 > the question is if I use OP1 for Tx & Rx and a narrow
> DSP filter I don't think the DSP will change the frequency at
 > all like the FL2 - FL4 filters would, is that correct?

That is correct.  The DSP doesn't alter the frequencies.

73,

Lyle KK7P

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