[Elecraft] Can't calibrate K2 narrow RTTY filters to 2.2KHz (hightones)

[Don Wilhelm]

Guido,

The BFO RANGE is not sufficient to set the BFO far enough from the carrier
and permit a tone of 2295 Hz on both sidebands.  You will need a minimum
range of 4590 Hz (and likely at least 500 Hz more will be required for a
comfortable margin).  Your range is only 4180 Hz.

You could try increasing the BFO range or reset all the RTTY BFOs to center
the filters at 1125/1295 rather than 2125/2295.  This will require tuning
the RTTY signal offset by 1 kHz and most sound card programs will properly
handle that - if you are using a hardware TNC that requires the 'real'
2125/2295 audio tones, you will have to increase the BFO range further.

73,
Don W3FPR

----- Original Message ----- 

> As I wrote in my last message, on K2 #4334 I was not able to calibrate the
> narrow filters on RTTY normal to center high tones (about 2.2KHz): I reach
> about 1.6KHz and then the BFO resets to the intial frequency.
> It happened only on RTTY normal (LSB), on RTTY reverse (USB) I was able to
> calibrate correctly the filters to match the 2125/2295Hz tones.
> During the BFO calibration,  I had to add 68pF and 100pF in parallel with
> C174 and C173 to have the correct BFO range (4916.77 KHz - 4912.59 KHz),
do
> you think that I can't calibrate the filters because the BFO limits are
not
> yet enough (too high or too low)?
> Any suggestion?