K2 CW Filter Loss

[Lemkes]

I keep forgetting to use "Plain Text":
Don,
  Thanks for the analysis.  I will send you the Spectrogram plots.  We have
family visiting this weekend, but I can get back to the K2 on Sunday evening
or on Monday.
  I did look at the 1 microvolt signal with Spectrogram.  As I remember, the
peak did indeed not drop with narrowing bandwidths, which I thought curious
(but didn't pursue).  The noise level was pushed down off the bottom of the
display, so I'll have to adjust the scale to get it all back on the screen.
  When performing the MDS measurement using a DVM on AC volts at the phone
jack I get:
       OP1 2.4 kHz   S+N= 3.15 VAC       N=0.1 VAC
         F1  1.2 kHz   S+N= 1.14 VAC       N=0.065 VAC
        F2  0.80kHz   S+N= 0.80 VAC       N=0.060
        F3  0.40kHz   S+N= 0.535 VAC      N=0.057
So, I am running into a "noise floor" that seems to be coming from a
combination of the product detector/mixer and the audio amp.  When I use the
built-in amplification in the DSP or use an external audio amp, I can gain
another couple dBm of MDS across all bandwidths.  Oh, the Preamp is on, and
the AGC is off.  RF gain full on, and audio gain at least at 3 PM to full
on, no load on the phone jack other than the DVM.
  The Spectrogram plots should be more revealing.  Vic, K2VCO also suggested
(as you did earlier) that I take a hard look at T7.
  More later.  73, Dick, AD7AF

Dick and Marty Lemke
PO Box 1038
Ocean Park, WA 98640
Tel. [phone]
www.lemkestudios.com

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Tom Skinner-3]

This is probably a stupid question - the answer to which I should probably
know - but I just can't see it.

I have (I think) properly adjusted my K2 (4991) using Spectogram.

If I tune in a CW signal with the mode switch in U or L, and then mode to C,
the signal shifts about 600 Hz.  

Why would the frequency where the signal appears to be shift?

TIA,

Tom, KJ3D
Curious in Virginia




_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Don Wilhelm-3]

Tom,

It should shift exactly by the amount of your sidetone pitch.  That is the
way the CW offset works - there is no offset on LSB or USB, but CW is offset
so you can read the frequency of the signal on the K2 display, but be able
to hear it by placing the BFO off to one side or the other by the amount of
the sidetone pitch.

The K2 always displays the frequency of the carrier.  If you want to figure
it out, you might relate it easiest to a direct conversion receiver -
listening to SSB, you can hear the voice if the receiver is tuned to the
suppressed carrier frequency, but in CW if you tune to the carrier
frequency, the signal would be 'heard' at zero Hz.  The receiver must be
tuned off to the side of the signal to hear it at a sidetone pitch.  The K2
does that automatically (and is a superhet instead of a DC receiver), but
the principle is the same.

73,
Don W3FPR

> -----Original Message-----
>
> This is probably a stupid question - the answer to which I should probably
> know - but I just can't see it.
>
> I have (I think) properly adjusted my K2 (4991) using Spectogram.
>
> If I tune in a CW signal with the mode switch in U or L, and then
> mode to C,
> the signal shifts about 600 Hz.
>
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

[Tom Skinner-3]

To all who replied - thank you.

I guess I probably knew this, but just couldn't quite get my aging head
around it.  I think I was considering the CW filters as just an extension of
the SSB filters without realizing that in changing to CW I was shifting the
passband from the carrier frequency by the amount of my sidetone.  

I guess if I set my sidetone to 0 Hz, there would be no shift - and that
makes everything make sense.

73,

Tom

From: Don Wilhelm [mailto:[hidden email]]

Tom,

It should shift exactly by the amount of your sidetone pitch.  That is the
way the CW offset works - there is no offset on LSB or USB, but CW is offset
so you can read the frequency of the signal on the K2 display, but be able
to hear it by placing the BFO off to one side or the other by the amount of
the sidetone pitch...

73,
Don W3FPR

> -----Original Message-----
>
> This is probably a stupid question - the answer to which I should probably
> know - but I just can't see it.
>
> I have (I think) properly adjusted my K2 (4991) using Spectogram.
>
> If I tune in a CW signal with the mode switch in U or L, and then
> mode to C,
> the signal shifts about 600 Hz.
>
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com