Re: #uBITX Firmware KD8CEC - IF-Shift etc. #ubitx

Tim Gorman
 

Allard,

I don't think I agree with you. PBT and "clariier" are two different
things.

A "clarifer" or incremental tuning control is only useful for tuning an
off-frequency signal. The BFO must be at the suppressed carrier
frequency for proper detection of a SSB signal. If you deviate from that
frequency then the detected audio becomes distorted, the old "donald
duck" sound spoken of by the old-timers. One of my first
ham-band receivers was an old RME-4350, 1950's vintage. It had a "BFO"
control which was really useful on SSB because in a round-table not all
transmitters could be set to the exact same frequency - resolution of
1kc was pretty good! The BFO could be used to tune everyone in properly,
in essence it was what is today called an "receiver incremental tuning"
control.

Passband tuning (or IF Shift) does not impact the relationship of the
BFO to the suppressed carrier at all. You could do the IF Shift by
changing CLK1 in order to shift where the signal impacts the 12Mhz
passband of the SSB filter but CLK0 would still have to maintain the
same relationship to CLK2 in order to demodulate the signal properly.

tim ab0wr

On Sun, 11 Mar 2018 01:09:24 +0100
"Allard PE1NWL" <@pe1nwl> wrote:

Jerry,

I believe it works in a similar way as the PBT (or "clarifier")
function in the Raduino v2 software for Bitx40.
https://github.com/amunters/bitx40-raduino-v2/blob/master/PBT.png
It allows the user to slightly shift the BFO frequency from the
frontpanel (only during RX of course).
It's not IF shift in its true sense, but the behaviour is quite
similar. I have the impression that not many BitX40 builders actually
installed this mod, which has always surprised me as I personally
find it a very useful feature.

73 Allard PE1NWL

On Sun, March 11, 2018 00:52, Jerry Gaffke via Groups.Io wrote:
OK, so IF-Shift is just a BFO offset (relative to the crystal filter
passband) 
that is for receive only, the transmit BFO offset generally stays
put. Makes sense.

I went off into the weeds there because Gerald's original query
stated that
 In LSB I can adjust the received sound with the IF-Shift with a
very pleasing effect, but this does not work the same with USB.
Sounded like there was something more going on.
But could be just that the code didn't quite handle the USB case
correctly.

Yes, eventually I'll move on to try some of the newer software.
But for now have my hands full with other projects.

Jerry  

On Sat, Mar 10, 2018 at 02:49 pm, Mike Woods wrote:


Most commercial rigs have an IF Shift or Passband Tuning (PBT)
control. 
This control can help with removal of QRM on receive ( e.g.by (
http://e.g.by ) eliminating a strong carrier or another station on
the edge
of the passband by shifting the passband up or down by a few 100
Hz. It can also compensate for a poorly adjusted frequency
response on a signal that is being received (too bassy or too
trebly).  
Ian’s software implements just such a control.  It functions in
a similar
manner to the BFO calibration routine, in fact, but unlike the
calibration
function, it should only operate on RX. This was the bug - it
didn’t turn
off on TX.  I checked on my uBITx and found the same problem here.
 
If you haven’t tried the KD8CEC firmware you should.  It has a
number of
other worthwhile software features!
 


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