[Elecraft] IF Shift vs. Passband Tuning?

[Don Wilhelm]

Jeff,

As far as I know, IF shift and Passbasnd Tuning are the same thing - just
different names for the advertizing hype folks to enjoy.

The major benefit of Passband tuning is that an interfering signal can be
moved off the edge of that reciever passband without changing the pitch of
the received signal.  IMHO, the same thing can be accomplished by reducing
the receiver bandwidth - it matters not whether it is CW or SSB.  If the
offending signal is on the low side of the wanted signal, it will be
necessary to reduce the low frequency content on the wanted signal - OTOH
with a voice signal, there will be a lot of information (intelligibility)
lost if the passband does not contain energy in the 300 to 500 Hz range, so
cutting the low frequency offending signal will result in a loss of
intelligibility for the wanted signal.  Cutting the high frequency end is
quite feasible, and can be accomplished easily by using the variable
bandwidth filter provided in the base K2.  I can set the normal IF filters
to a bandwidth of 1600 Hz and still maintain intelligibility for the male
voice (the female voice begins to loose intelligibility at a bandwidth of
1800 Hz or less).  Set the low frequency corner of the passband at 300 Hz
and accept whatever the high froequency end may be - this is not passband
tuning, but is reduction of the high frequency end of the received signal,
and I find it as useful (if not more useful) than true passband tuning.

I normall set the SSB IF filters to OP1 for the FL1 position, then 300 Hz
less for the FL2 position - note that the numbers displayed on the K2 may
not be a good indication of the actual bandwidth for wide filter settings,
use Spectrogram to determine the actual filter width.  With a 2300 (or 2400
Hz) OP1 bandwidth, I set Spectrogram markers at 300 and 2600 Hz then center
the passband between those markers.  Then FL2 thru FL4 are set to
progressively more narrow bandwidths - FL2 = 2200 Hz, FL3 = 1900 Hz, FL4 =
1600 Hz.  The important thing is to keep he low frequency corner of the
bandpass  at 300 Hz to maintain good intelligiblilty.  Be aware that the
filter bandwidths indicated by the K2 may be substantially different than
what is indicated by the K2 display - use Spectrogram to determine the
actual filter bandwidth - If the K2 indicates 2200 kHz for the filter
bandwidth, it may acually be 2600 Hz wide and quite ragged in the passband -
sett it for the actual width as observed o the Spectrogram display.

OK, all the above is valid for SSB - for CW, I find it sufficient to simply
switch to a more narrow IF filter - if you center the passband at your
chosen sidetine pitch, bothe the low and high requencies will be reduced by
switching to a more narrow filter.


73,
Don W3FPR


> -----Original Message-----
> Are IF shift and passband tuning (PBT) the same thing?  I assume
> that they produce the same effect.  I have a Ten-Tec Argonaut V
> that has PBT, but I have never used that feature, thus I don't
> miss it on my K2.  I guess I just don't grasp what PBT would do
> for me that I can't do with RIT and the variable width DSP filter
> of the Argonaut V.  However, I'm a CW op; someone commented that
> IF shift is more useful on SSB than on CW.  Why is that?
>
> Thanks, 73 & 72,
> Jeff
> WB5GWB
> Long Island, NY
>