[Elecraft] Filter Challenged...I'm so confused

Sat Mar 8 12:02:01 2003

Sometimes I am dense<G>.. 

When I answered this question yesterday I failed to mention that what
you are describing is CORRECT in other rigs. In the K2, the Local
Oscillator frequency is shifted automatically by the firmware when you
change the BFO frequency to compensate! 

I'm so used to that "effect" that I forget it's there. Lou, W7HV brought
that to my attention this morning. Thanks Lou! 

In an "ordinary" rig, you would be shifting the pitch of the SSB signal
by simply moving the BFO, but not in the K2. There used to be an
excellent write up on the Elecraft reflector by Wayne on how the K2's
system works called "The Mechanics of CAL FIL" that goes into great
detail. I might still be there, but for me finding something under the
"Builder's Resources" on the web site is harder than fining a 1/4 watt
resistor in the bottom of my junk box. 

You aren't the first op to spot that behavior and question it <G>.

Ron AC7AC
K2 # 1289

-----Original Message-----
From: Wallace, Andy [mailto:[email protected]] 
Sent: Friday, March 07, 2003 9:33 AM
To: '[email protected]'; [email protected]
Subject: RE: [Elecraft] Filter Challenged...I'm so confused

> -----Original Message-----
> From: Ron D'Eau Claire [mailto:[email protected]]
> 
> One reason for using the OPT1 filter in SSB for FL2 or 3 or 4 is to 
> produce the equivalent of "passband tuning". You can define different 
> BFO frequencies in FL2 or 3 or 4 that will "shift" the passband of the

> filter to higher or lower frequencies.

But if you do this, will you be transmitting on the correct 
frequency with FL2-4 shifted as you describe? Or will the received
signal (using FL2-4) BFO shift -- to do "passband tuning" in 
effect -- cause you to tune in the received station at a 
frequency different from where your K2 will transmit, using FL1 
in the transmit path?

I hope you understand what I'm asking. I don't have a KSB2 (yet) so I
can't experiment. 

Andy