[Elecraft] Filter Calibrate Question

[Don Wilhelm]

John,

If you haven't done so already, I suggest that you take a look at Step 3 of
the K2 Dial Calibration article on my website www.qsl.net/w3fpr.  It has
information on filter alignment that you may find helpful - there are also
links to other sources of help.

When you align the SSB filters, keep in mind the width of the passband and
the audio spectrum that you want to hear (through that passband) - for the
stock OP1 filter, the passband is about 2 kHz wide, so if you set
Spectrogram markers at 300 and 2300 Hz, then set the BFO to center the
filter passband between those markers - similarly for a 1600 Hz filter, set
markers at 300 and 1900 Hz and center the passband between those markers
(use the actual displayed passband width as displayed on Spectrogram - the
indicated widths displayed on the K2 are only approximations).  The idea is
that you retain the low frequency content of a voice signal and drop off the
higher frequencies as you narrow the bandwidth - that has worked for me and
several other folks that I have assisted in setting the filters.

Changing the BFO will result in a frequency change because the received
frequency is calculated as VFO - BFO (with an additional offset equal to the
sidetone pitch setting in CW mode).

If you still have trouble, send me a note off-reflector and I will see if I
can help more.

73,
Don W3FPR

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

> Once again the mysteries of filter calibration escape me.
>
> Looking at Spectrogram, I see that my CW filters are close.  I use OPT1,
> 1000, 500, 250.  A tone at 600Hz on OPT1 is at that same place +/- 20 Hz.
> for each of the other filters.
>
> Sideband is different.  I noticed last night that in filters 3 and 4 that
> the LSB signal moved and I have to tune about 100 Hz. lower to tune it in.
> To check, I tuned in, on LSB, the audio tone from my Fort Smith QRP Group
> Frequency standard to 600 Hz..  (The same holds for USB, but in the
opposite
> direction.)
>