[Elecraft] KSB2 bandwidth - 1.9 kHz?

[John, KI6WX]

When I designed the filter bandwidth options, I made a number of
measurements in both transmit and receive.  In transmit, the bandwidth was
very close to the nominal values (measured with an audio signal generator
driving the audio input of the K2 with the ALC disabled).

In receive, the 2nd Xtal Filter can effect the measured bandwidth using
Spectrogram, especially if your K2 doesn't have the 2nd Xtal Filter
Flattening Mod.  For independently testing the SSB filter, I recommend
bypassing the 2nd Xtal Filter with 0.1uF capacitors as described in my note
on the KSB2.  With the 2nd Xtal Filter bypassed, both the transmit and
receive results were nearly identical.

Your 2.5 kHz SSB filter could have a narrower response if the motional
inductances of the Xtals are not well matched.  This parameter is not
measured by Elecraft and it possible to get a set of Xtals that don't work
well at this bandwidth (they will work fine at the standard Elecraft
bandwidth).  I would recommend using Spectrogram to measure the bandwidth
with the 2nd Xtal Filter bypassed as described in my note.  If your
bandwidth is significantly narrower than 2.5 kHz (or you see more than 4 dB
of ripple in the passband), you may want to order another set of Xtal's from
Elecraft to replace those in your filter.

-John
 KI6WX

----- Original Message ----- 
From: "Baker" <baker@nildram.co.uk>

I have installed the capacitor values for a 2.5kHz B/W. On air reports
show TX B/W of 2.2 to 2.3kHz. That suits me fine.
On receive both LSB & USB responses are symmetrical, but start to roll
off at 2kHz and are 10dB down at 2.5kHz (2nd Xtal filter ?).