Topics

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

ge_clipboard
 

Hello Ian and All

The sound of SSB signals with my uBITX are very strong on the high side. 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. And I have noticed, that using the IF-Shift, does also influence the TX signal where the output is becoming a DSB signal with lots of power in the other sideband. I have also tried to adjust the BFO, but without positive results.

Would it be possible to have the IF-Shift function just with the RX and leave the TX on its own? What am I doing wrong?

Best 73, Gerald - HB9CEY

Rod Davis
 

Hi All,

Doesn't that mean that your transmitted audio (prior to IF shift) was also on the high side?

Rod KM6SN

On 03/10/2018 09:15 AM, ge_clipboard wrote:
Hello Ian and All

The sound of SSB signals with my uBITX are very strong on the high side. 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. And I have noticed, that using the IF-Shift, does also influence the TX signal where the output is becoming a DSB signal with lots of power in the other sideband. I have also tried to adjust the BFO, but without positive results.

Would it be possible to have the IF-Shift function just with the RX and leave the TX on its own? What am I doing wrong?

Best 73, Gerald - HB9CEY


Jerry Gaffke
 

A straightforward implementation of an SSB transmitter would be to have a sharp crystal filter,
let's assume nice even numbers of 2khz wide between 11.999000 and 12.001000 mhz.
Also a BFO that is 500 hz beyond the edge of the crystal filter, the frequency of the BFO
is the frequency of the suppressed carrier of the transmitted (or received) SSB signal. 

To create an upper sideband signal, we might use the filter to allow through only the stuff that 
is between 500 hz and 2500 hz above the carrier.  So the BFO should be at 11.998500 mhz,
and the audio frequencies that get through are between 500 and 2500 hz.

To create a lower sideband signal, we use the filter to allow through only the stuff that
is between 500 hz and 2500 hz below the carrier.  So the BFO should be at 12.001500 mhz.

The critical issue for Gerald is likely the 3000 hz difference (in this case) between the
11.998500 mhz and the 12.001500 mhz BFO.  This needs to be adjustable somehow
to account for variations in filter width and different preferences regarding how far the BFO
should be from the filter passband.  (The further the BFO is from the filter passband,
the more high frequency content the audio will have.)  

On the uBitx, the LSB/USB selection is carried out by moving the second local oscillator
between 33 and 57 mhz, the BFO is always on the low side of the 12 mhz crystal filter.
So a little bit harder to think about than the "straightforward implementation" presented above.

A fix for the code as shipped from HFSignals would be to modify the code here: 
     https://github.com/afarhan/ubitx
such that this value in ubitx_20.ino  can be varied within the configuration menu 
    #define SECOND_OSC_USB (56995000l)

Procedure would be to adjust the BFO using the existing configuration routines for best audio
for LSB reception, then adjust SECOND_OSC_USB for best audio on USB reception.
When transmitting, everything just runs backwards and all those relationships still apply,
so audio allowed through the 12mhz filter should be identical.

Jerry, KE7ER



On Sat, Mar 10, 2018 at 09:15 am, ge_clipboard wrote:

The sound of SSB signals with my uBITX are very strong on the high side. 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. And I have noticed, that using the IF-Shift, does also influence the TX signal where the output is becoming a DSB signal with lots of power in the other sideband. I have also tried to adjust the BFO, but without positive results.

Would it be possible to have the IF-Shift function just with the RX and leave the TX on its own? What am I doing wrong?

Mike Woods
 

Jerry

The IF Shift function should only be applied during RX, but it sounds like it is being applied during TX in error in KD8CEC's sketch.  Probably a bug.

However, the op shouldn't be using the IF Shift permanently, he may not have used the BFO calibration function to fix the shift for LSB & USB for the correct passband.

Mike ZL1AXG

On 11/03/18 7:25 AM, Jerry Gaffke via Groups.Io wrote:

A straightforward implementation of an SSB transmitter would be to have a sharp crystal filter,
let's assume nice even numbers of 2khz wide between 11.999000 and 12.001000 mhz.
Also a BFO that is 500 hz beyond the edge of the crystal filter, the frequency of the BFO
is the frequency of the suppressed carrier of the transmitted (or received) SSB signal. 

To create an upper sideband signal, we might use the filter to allow through only the stuff that 
is between 500 hz and 2500 hz above the carrier.  So the BFO should be at 11.998500 mhz,
and the audio frequencies that get through are between 500 and 2500 hz.

To create a lower sideband signal, we use the filter to allow through only the stuff that
is between 500 hz and 2500 hz below the carrier.  So the BFO should be at 12.001500 mhz.

The critical issue for Gerald is likely the 3000 hz difference (in this case) between the
11.998500 mhz and the 12.001500 mhz BFO.  This needs to be adjustable somehow
to account for variations in filter width and different preferences regarding how far the BFO
should be from the filter passband.  (The further the BFO is from the filter passband,
the more high frequency content the audio will have.)  

On the uBitx, the LSB/USB selection is carried out by moving the second local oscillator
between 33 and 57 mhz, the BFO is always on the low side of the 12 mhz crystal filter.
So a little bit harder to think about than the "straightforward implementation" presented above.

A fix for the code as shipped from HFSignals would be to modify the code here: 
     https://github.com/afarhan/ubitx
such that this value in ubitx_20.ino  can be varied within the configuration menu 
    #define SECOND_OSC_USB (56995000l)

Procedure would be to adjust the BFO using the existing configuration routines for best audio
for LSB reception, then adjust SECOND_OSC_USB for best audio on USB reception.
When transmitting, everything just runs backwards and all those relationships still apply,
so audio allowed through the 12mhz filter should be identical.

Jerry, KE7ER



On Sat, Mar 10, 2018 at 09:15 am, ge_clipboard wrote:

The sound of SSB signals with my uBITX are very strong on the high side. 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. And I have noticed, that using the IF-Shift, does also influence the TX signal where the output is becoming a DSB signal with lots of power in the other sideband. I have also tried to adjust the BFO, but without positive results.

Would it be possible to have the IF-Shift function just with the RX and leave the TX on its own? What am I doing wrong?


--
Mike Woods
mhwoods@...

Ian Lee
 

Gerald

Thanks for feedback.

Errors that apply IF-Shift on TX will be corrected soon and will be included in the next version.
If you test a bit more about IF Shift, we can improve it.

Ian KD8CEC

2018-03-11 2:15 GMT+09:00 ge_clipboard <clipboard@...>:


Hello Ian and All

The sound of SSB signals with my uBITX are very strong on the high side. 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. And I have noticed, that using the IF-Shift, does also influence the TX signal where the output is becoming a DSB signal with lots of power in the other sideband. I have also tried to adjust the BFO, but without positive results.

Would it be possible to have the IF-Shift function just with the RX and leave the TX on its own? What am I doing wrong?

Best 73, Gerald - HB9CEY






--
Best 73
KD8CEC / Ph.D ian lee
kd8cec@...
www.hamskey.com (my blog)

Jerry Gaffke
 

I think I was wrong in my previous post, shifting the value of SECOND_OSC_USB won't help.
The audio frequencies through the crystal filter should be strictly a matter of where the BFO is relative to 
the crystal filter passband.  I can't explain why USB audio would be different than LSB audio.

I'm not quite sure what you mean by "IF Shift function".
Can you give an example?

Jerry


On Sat, Mar 10, 2018 at 11:59 am, Mike Woods wrote:
The IF Shift function should only be applied during RX, but it sounds like it is being applied during TX in error in KD8CEC's sketch.  Probably a bug.

However, the op shouldn't be using the IF Shift permanently, he may not have used the BFO calibration function to fix the shift for LSB & USB for the correct passband.

Jerry Gaffke
 

Though Ian has responded, he seems to know what's going on here.


On Sat, Mar 10, 2018 at 12:54 pm, Jerry Gaffke wrote:
I think I was wrong in my previous post, shifting the value of SECOND_OSC_USB won't help.
The audio frequencies through the crystal filter should be strictly a matter of where the BFO is relative to 
the crystal filter passband.  I can't explain why USB audio would be different than LSB audio.

I'm not quite sure what you mean by "IF Shift function".
Can you give an example?

Ian Lee
 

Jerry.

I programmed something similar to what you said. I just added another setting instead of a constant(SECOND_OSC_USB).

The code is shown below.

    if (isUSB){
      si5351bx_setfreq(2, SECOND_OSC_USB - usbCarrier + f  + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_USB);
    }
    else{
      si5351bx_setfreq(2, SECOND_OSC_LSB + usbCarrier + f + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_LSB);
    }

Also, I would like to ask you an opinion, but now I am using the hotspot in the place where the internet is not available, so I can not use it long. 

I temporarily shifted the usbCarrier (BFO Setting value) when IF-Shift was applied.
I thought IF-Shift was a temporary function that only used for a while, so I could not satisfy both LSB and USB.
The IF-Shift value can be set to + or -, so can set the desired value according to the using mode.

Ian KD8CEC



2018-03-11 5:54 GMT+09:00 Jerry Gaffke via Groups.Io <jgaffke@...>:

I think I was wrong in my previous post, shifting the value of SECOND_OSC_USB won't help.
The audio frequencies through the crystal filter should be strictly a matter of where the BFO is relative to 
the crystal filter passband.  I can't explain why USB audio would be different than LSB audio.

I'm not quite sure what you mean by "IF Shift function".
Can you give an example?

Jerry

On Sat, Mar 10, 2018 at 11:59 am, Mike Woods wrote:
The IF Shift function should only be applied during RX, but it sounds like it is being applied during TX in error in KD8CEC's sketch.  Probably a bug.

However, the op shouldn't be using the IF Shift permanently, he may not have used the BFO calibration function to fix the shift for LSB & USB for the correct passband.



--
Best 73
KD8CEC / Ph.D ian lee
kd8cec@...
www.hamskey.com (my blog)

Jerry Gaffke
 

I think my first post on this thread was simply incorrect.
I don't think adjusting  SECOND_OSC_USB  would fix anything.
Unless perhaps we are somehow running up against the edges of the 45mhz filter.
But then I could be wrong, I don't really understand this one yet.

I haven't messed with your code, but do plan to.
Hope to have a full digital station going, using a RasberryPi.

And hope to take a look at your code soon and give some intelligent feedback.
For now, here's some poorly thought out unintelligent feedback:

Perhaps a temporary shift of the BFO relative to the crystal filter passband 
would be a good idea.  Allows an easy zero beat of an AM station such as WWV
when calibrating the rig, for example.  Or could be used to "clarify" the reception of some ham
with a deep voice (has mostly low audio frequencies, perhaps) who has a transmitter tuned
to match it.  Other than that, I'm not sure why any sort of temporary shift would be wanted.

How does this IF-Shift feature get used?
Exactly what does IF-Shift do?

Jerry


On Sat, Mar 10, 2018 at 01:31 pm, Ian Lee wrote:
Jerry.
 
I programmed something similar to what you said. I just added another setting instead of a constant(SECOND_OSC_USB).
 
The code is shown below.
 
    if (isUSB){
      si5351bx_setfreq(2, SECOND_OSC_USB - usbCarrier + f  + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_USB);
    }
    else{
      si5351bx_setfreq(2, SECOND_OSC_LSB + usbCarrier + f + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_LSB);
    }
 
Also, I would like to ask you an opinion, but now I am using the hotspot in the place where the internet is not available, so I can not use it long. 

I temporarily shifted the usbCarrier (BFO Setting value) when IF-Shift was applied.
I thought IF-Shift was a temporary function that only used for a while, so I could not satisfy both LSB and USB.
The IF-Shift value can be set to + or -, so can set the desired value according to the using mode.
 
Ian KD8CEC
 

Mike Woods
 

Jerry 

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 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!

73 Mike ZL1AXG


On Sun, 11 Mar 2018 at 11:32 AM, Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
I think my first post on this thread was simply incorrect.
I don't think adjusting  SECOND_OSC_USB  would fix anything.
Unless perhaps we are somehow running up against the edges of the 45mhz filter.
But then I could be wrong, I don't really understand this one yet.

I haven't messed with your code, but do plan to.
Hope to have a full digital station going, using a RasberryPi.

And hope to take a look at your code soon and give some intelligent feedback.
For now, here's some poorly thought out unintelligent feedback:

Perhaps a temporary shift of the BFO relative to the crystal filter passband 
would be a good idea.  Allows an easy zero beat of an AM station such as WWV
when calibrating the rig, for example.  Or could be used to "clarify" the reception of some ham
with a deep voice (has mostly low audio frequencies, perhaps) who has a transmitter tuned
to match it.  Other than that, I'm not sure why any sort of temporary shift would be wanted.

How does this IF-Shift feature get used?
Exactly what does IF-Shift do?

Jerry


On Sat, Mar 10, 2018 at 01:31 pm, Ian Lee wrote:
Jerry.
 
I programmed something similar to what you said. I just added another setting instead of a constant(SECOND_OSC_USB).
 
The code is shown below.
 
    if (isUSB){
      si5351bx_setfreq(2, SECOND_OSC_USB - usbCarrier + f  + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_USB);
    }
    else{
      si5351bx_setfreq(2, SECOND_OSC_LSB + usbCarrier + f + (isIFShift ? ifShiftValue : 0));
      si5351bx_setfreq(1, SECOND_OSC_LSB);
    }
 
Also, I would like to ask you an opinion, but now I am using the hotspot in the place where the internet is not available, so I can not use it long. 

I temporarily shifted the usbCarrier (BFO Setting value) when IF-Shift was applied.
I thought IF-Shift was a temporary function that only used for a while, so I could not satisfy both LSB and USB.
The IF-Shift value can be set to + or -, so can set the desired value according to the using mode.
 
Ian KD8CEC
 

Jerry Gaffke
 

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 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!
 

ge_clipboard
 


Hi All

Many thanks for all the response concerning the BFO adjustement and about using the IF-shift. I have been playing around with the BFO setting while monitoring myself on another transceiver but as I’m not getting there where I really would like to, I returned to the factory settings. Leastening to the transmitted LSB and USB on another transceiver was never symetric, maybe the steps to set the bfo are not fine enough to do this or I am making something wrong.

Yes, the IF-shift is often a very helpfull feature within crowded bands and as Mike pointed out, it is also nice to be able to adjust the sound of a ssb signal on receive. So, if this could be corrected in the software would be very fine.

Another point I’ve noticed today while using CW, dx-cluster and CAT to jump to a anounced station... When the CWL-, CWU-feature is enabled, then the frequency is not spot on but offset by the amount of the CW-Tone. 

Nevertheless, this little rig is a joy to play with, especially with all the added features by Ian‘s software.

Vy 73, Gerald - HB9CEY 


Allard PE1NWL
 

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!
 

Tim Gorman
 

I wonder if we need to define some terms here. Passband tuning and IF
Shift typically move the *filter*, not the carrier. The carrier will
remained tuned to the same frequency when adjusting this. For instance,
if you use IF Shift when listening to a CW signal the tone of the CW
signal should not change. You can move the filter bandwidth up or down
to eliminate an interfering carrier that is close to the desired
frequency.

What you are describing is more like an Incremental Tuning, e.g. RIT or
XIT. When you move the BFO you move the carrier frequency, not the
filter bandwidth.

Ideally the BFO would be set to replicate the suppressed carrier
frequency. The filter then determines what is heard.

The ubitx uses a 12Mhz crystal filter. I don't know its bandwidth or
what the actual absolute frequencies are. I haven't had a chance to run
a spectrum analyzer against mine. Let's assume it has a 2400hz
bandwidth and goes from 12,000,300hz to 12,002,700hz.

If you want to listen to a signal at 10Mhz then CLK2 should be tuned to
55Mhz to generate the 45Mhz signal the first IF needs.

CLK1 should then be set to generate a 12Mhz signal, i.e. 33Mhz. For an
USB signal we should then see frequencies of 12Mhz to 12.003Mhz (or
whatever the transmitted bandwidth is, e.g. 0-3000hz). You will then see
frequencies of 12.0003Mhz to 12.0027Mhz out of the filter.

This is how an ideal receiver would work.

When you are talking about adjusting the BFO I assume you are talking
about adjusting CLK1. If you adjust CLK1 to move the actual suppressed
carrier frequency somewhere else in the filter bandwidth then your
frequency indication is going to be off. What should be a 10Mhz signal
is going to look like something else.

This will cause an asymmetric USB and LSB response and frequency
indication.

If you want to change the BFO frequency on the fly then it should be
understood as being an incremental tuning so you can remember what the
base frequency should be.

Now each filter is probably going to have a different actual physical,
absolute bandpass. The BFO will have to be adjusted to allow for this
but the frequency indication needs to be adjusted as well to match. It
should be a fixed reference, not a variable one.

Your transmitted frequency has to be offset from the CW-tone if it is
to be zero beat with the received signal. If it isn't then you'll never
be zero beat. I'm assuming that the CWL and CWU frequencies are
indicating a frequency CW-tone away from the actual transmitting
frequency. That may be because your receive BFO frequency isn't set to
indicate actual carrier frequency.

I didn't mean for this to get so complicated but it isn't an easy
subject.

tim ab0wr


On Sun, 11 Mar 2018 01:08:55 +0100
"ge_clipboard" <clipboard@...> wrote:

Hi All

Many thanks for all the response concerning the BFO adjustement and
about using the IF-shift. I have been playing around with the BFO
setting while monitoring myself on another transceiver but as I’m not
getting there where I really would like to, I returned to the factory
settings. Leastening to the transmitted LSB and USB on another
transceiver was never symetric, maybe the steps to set the bfo are
not fine enough to do this or I am making something wrong.

Yes, the IF-shift is often a very helpfull feature within crowded
bands and as Mike pointed out, it is also nice to be able to adjust
the sound of a ssb signal on receive. So, if this could be corrected
in the software would be very fine.

Another point I’ve noticed today while using CW, dx-cluster and CAT
to jump to a anounced station... When the CWL-, CWU-feature is
enabled, then the frequency is not spot on but offset by the amount
of the CW-Tone.

Nevertheless, this little rig is a joy to play with, especially with
all the added features by Ian‘s software.

Vy 73, Gerald - HB9CEY

W2CTX
 

Yes I was confused a while back when Ian announced his IF shift.  The code
looked just like our RIT.  Our RIT displays the freq on bottom line and the
line above displays the plus/minus offset as you move the encoder.

rOn




From: Tim Gorman <tgorman2@...>
To: BITX20@groups.io
Sent: Saturday, March 10, 2018 8:24 PM
Subject: Re: [BITX20] #uBITX Firmware KD8CEC - IF-Shift etc.

I wonder if we need to define some terms here. Passband tuning and IF
Shift typically move the *filter*, not the carrier. The carrier will
remained tuned to the same frequency when adjusting this. For instance,
if you use IF Shift when listening to a CW signal the tone of the CW
signal should not change. You can move the filter bandwidth up or down
to eliminate an interfering carrier that is close to the desired
frequency.

What you are describing is more like an Incremental Tuning, e.g. RIT or
XIT. When you move the BFO you move the carrier frequency, not the
filter bandwidth.

Ideally the BFO would be set to replicate the suppressed carrier
frequency. The filter then determines what is heard.

The ubitx uses a 12Mhz crystal filter. I don't know its bandwidth or
what the actual absolute frequencies are. I haven't had a chance to run
a spectrum analyzer against mine. Let's assume it has a 2400hz
bandwidth and goes from 12,000,300hz to 12,002,700hz.

If you want to listen to a signal at 10Mhz then CLK2 should be tuned to
55Mhz to generate the 45Mhz signal the first IF needs.

CLK1 should then be set to generate a 12Mhz signal, i.e. 33Mhz. For an
USB signal we should then see frequencies of 12Mhz to 12.003Mhz (or
whatever the transmitted bandwidth is, e.g. 0-3000hz). You will then see
frequencies of 12.0003Mhz to 12.0027Mhz out of the filter.

This is how an ideal receiver would work.

When you are talking about adjusting the BFO I assume you are talking
about adjusting CLK1. If you adjust CLK1 to move the actual suppressed
carrier frequency somewhere else in the filter bandwidth then your
frequency indication is going to be off. What should be a 10Mhz signal
is going to look like something else.

This will cause an asymmetric USB and LSB response and frequency
indication.

If you want to change the BFO frequency on the fly then it should be
understood as being an incremental tuning so you can remember what the
base frequency should be.

Now each filter is probably going to have a different actual physical,
absolute bandpass. The BFO will have to be adjusted to allow for this
but the frequency indication needs to be adjusted as well to match. It
should be a fixed reference, not a variable one.

Your transmitted frequency has to be offset from the CW-tone if it is
to be zero beat with the received signal. If it isn't then you'll never
be zero beat. I'm assuming that the CWL and CWU frequencies are
indicating a frequency CW-tone away from the actual transmitting
frequency. That may be because your receive BFO frequency isn't set to
indicate actual carrier frequency.

I didn't mean for this to get so complicated but it isn't an easy
subject.

tim ab0wr


On Sun, 11 Mar 2018 01:08:55 +0100
"ge_clipboard" <clipboard@...> wrote:

> Hi All
>
> Many thanks for all the response concerning the BFO adjustement and
> about using the IF-shift. I have been playing around with the BFO
> setting while monitoring myself on another transceiver but as I’m not
> getting there where I really would like to, I returned to the factory
> settings. Leastening to the transmitted LSB and USB on another
> transceiver was never symetric, maybe the steps to set the bfo are
> not fine enough to do this or I am making something wrong.
>
> Yes, the IF-shift is often a very helpfull feature within crowded
> bands and as Mike pointed out, it is also nice to be able to adjust
> the sound of a ssb signal on receive. So, if this could be corrected
> in the software would be very fine.
>
> Another point I’ve noticed today while using CW, dx-cluster and CAT
> to jump to a anounced station... When the CWL-, CWU-feature is
> enabled, then the frequency is not spot on but offset by the amount
> of the CW-Tone.
>
> Nevertheless, this little rig is a joy to play with, especially with
> all the added features by Ian‘s software.
>
> Vy 73, Gerald - HB9CEY
>





Vince Vielhaber
 

IF Shift is supposed to shift the signal thru the passband without changing the frequency. So if you're listening to 3930 and there are signals on 3928 (it happens daily) at the same time, you can use the IF Shift to move the signals on 3928 out of the passband. If affects the sound of the desired signal like a tone control but that's a side effect of the action.

Vince.

On 03/10/2018 09:02 PM, Ronald Pfeiffer via Groups.Io wrote:
Yes I was confused a while back when Ian announced his IF shift. The code
looked just like our RIT. Our RIT displays the freq on bottom line and the
line above displays the plus/minus offset as you move the encoder.

rOn



------------------------------------------------------------------------
*From:* Tim Gorman <tgorman2@...>
*To:* BITX20@groups.io
*Sent:* Saturday, March 10, 2018 8:24 PM
*Subject:* Re: [BITX20] #uBITX Firmware KD8CEC - IF-Shift etc.

I wonder if we need to define some terms here. Passband tuning and IF
Shift typically move the *filter*, not the carrier. The carrier will
remained tuned to the same frequency when adjusting this. For instance,
if you use IF Shift when listening to a CW signal the tone of the CW
signal should not change. You can move the filter bandwidth up or down
to eliminate an interfering carrier that is close to the desired
frequency.

What you are describing is more like an Incremental Tuning, e.g. RIT or
XIT. When you move the BFO you move the carrier frequency, not the
filter bandwidth.

Ideally the BFO would be set to replicate the suppressed carrier
frequency. The filter then determines what is heard.

The ubitx uses a 12Mhz crystal filter. I don't know its bandwidth or
what the actual absolute frequencies are. I haven't had a chance to run
a spectrum analyzer against mine. Let's assume it has a 2400hz
bandwidth and goes from 12,000,300hz to 12,002,700hz.

If you want to listen to a signal at 10Mhz then CLK2 should be tuned to
55Mhz to generate the 45Mhz signal the first IF needs.

CLK1 should then be set to generate a 12Mhz signal, i.e. 33Mhz. For an
USB signal we should then see frequencies of 12Mhz to 12.003Mhz (or
whatever the transmitted bandwidth is, e.g. 0-3000hz). You will then see
frequencies of 12.0003Mhz to 12.0027Mhz out of the filter.

This is how an ideal receiver would work.

When you are talking about adjusting the BFO I assume you are talking
about adjusting CLK1. If you adjust CLK1 to move the actual suppressed
carrier frequency somewhere else in the filter bandwidth then your
frequency indication is going to be off. What should be a 10Mhz signal
is going to look like something else.

This will cause an asymmetric USB and LSB response and frequency
indication.

If you want to change the BFO frequency on the fly then it should be
understood as being an incremental tuning so you can remember what the
base frequency should be.

Now each filter is probably going to have a different actual physical,
absolute bandpass. The BFO will have to be adjusted to allow for this
but the frequency indication needs to be adjusted as well to match. It
should be a fixed reference, not a variable one.

Your transmitted frequency has to be offset from the CW-tone if it is
to be zero beat with the received signal. If it isn't then you'll never
be zero beat. I'm assuming that the CWL and CWU frequencies are
indicating a frequency CW-tone away from the actual transmitting
frequency. That may be because your receive BFO frequency isn't set to
indicate actual carrier frequency.

I didn't mean for this to get so complicated but it isn't an easy
subject.

tim ab0wr


On Sun, 11 Mar 2018 01:08:55 +0100
"ge_clipboard" <clipboard@... <mailto:clipboard@...>> wrote:

Hi All

Many thanks for all the response concerning the BFO adjustement and
about using the IF-shift. I have been playing around with the BFO
setting while monitoring myself on another transceiver but as I’m not
getting there where I really would like to, I returned to the factory
settings. Leastening to the transmitted LSB and USB on another
transceiver was never symetric, maybe the steps to set the bfo are
not fine enough to do this or I am making something wrong.

Yes, the IF-shift is often a very helpfull feature within crowded
bands and as Mike pointed out, it is also nice to be able to adjust
the sound of a ssb signal on receive. So, if this could be corrected
in the software would be very fine.

Another point I’ve noticed today while using CW, dx-cluster and CAT
to jump to a anounced station... When the CWL-, CWU-feature is
enabled, then the frequency is not spot on but offset by the amount
of the CW-Tone.

Nevertheless, this little rig is a joy to play with, especially with
all the added features by Ian‘s software.

Vy 73, Gerald - HB9CEY




Jim Sheldon
 

Tim the only problem I have with your explanation is on the CW offset. The transmitted CW signal MUST be exactly on the frequency shown on the LCD and the RECEIVER must be offset by the sidetone value to properly zerobeat the other signal. If you shift the transmitter frequency, when you have the other station tuned on your receiver to the same tone as your sidetone frequency, but offset your transmitter, you will be transmitting either lower or higher than his signal depending on whether you are receiving that signal in USB or LSB (CW or CWR).

Do not shift the transmitter, shift the receiver and leave the transmitted CW carrier on the display frequency if you want the offset to be proper. You might accidentally be transmitting out of band if you were tuned to a station almost on the band edge and your transmitter was offset by the sidetone value.

Ran into this problem ourselves when Ron, W2CTX and I were hashing out how CW was supposed to work a while back.

Jim Sheldon, W0EB

------ Original Message ------
From: "Tim Gorman" <tgorman2@...>
To: BITX20@groups.io
Sent: 3/10/2018 7:24:00 PM
Subject: Re: [BITX20] #uBITX Firmware KD8CEC - IF-Shift etc.



Your transmitted frequency has to be offset from the CW-tone if it is
to be zero beat with the received signal. If it isn't then you'll never
be zero beat. I'm assuming that the CWL and CWU frequencies are
indicating a frequency CW-tone away from the actual transmitting
frequency. That may be because your receive BFO frequency isn't set to
indicate actual carrier frequency.

I didn't mean for this to get so complicated but it isn't an easy
subject.

tim ab0wr

Jerry Gaffke
 

I think Gerald's complaint about USB sounding different than LSB winds up being due to
a USB signal going through the 45mhz filter a few khz away from where an LSB signal does. 
Gerald was using Ian's code which I have not yet looked over.
I assume Ian borrowed numbers from the original uBitx code.
Here's my argument:

The original uBitx code has the BFO at
    #define INIT_USB_FREQ   (11996500l)
and uses these frequencies for clk1:
    #define SECOND_OSC_USB (56995000l)
    #define SECOND_OSC_LSB (32995000l)

The 12mhz filter is passing audio between roughly 500 and 2500 hz in its upper sideband,
so the 12mhz filter is probably centered around 11996500 + (500+2500)/2 = 1199800 hz.

With a clk1 for USB of 56995000 hz, the center of that upper sideband in the 45mhz filter
would be 56995000-11998000 = 44997000 hz
With clk1 for LSB of 32995000 hz, the center of that lower sideband in the 45mhz filter
would be 32995000+11998000 = 44993000 hz.

That's a 4khz difference in where the center of the sideband of interest got placed
within the 45mhz crystal filter passband. 

Assuming the the 45mhz crystal filter is truly centered at 44.995mhz as the notes in the code suggest,
then I figure that values of 56993000 hz and 32997000 hz should be optimal for clk1.

If the 45mhz crystal filter sweeps out to be somewhere else, then add the difference to those two figures.
For example, if the center is found to be at 44.997mhz (so 2khz higher) then the two figures for clk1
should be 56995000 hz and 32999000 hz.


Regarding Tim's writup:

> When you are talking about adjusting the BFO I assume you are talking about adjusting CLK1.

No, we are talking about adjusting the BFO.
When adjusting the BFO, we should move the VFO to get us back to the displayed frequency.
The display shows the frequency of the suppressed carrier, always easy enough to compute:
    For USB, it's   VFO-(clk1-BFO)
    For LSB, it's   VFO+(clk1-BFO) 
where VFO is clk2, and BFO is clk0.

RIT allows a different VFO setting on receive than transmit.
This IF-Shift thing apparently allows a different BFO setting (with attendant VFO correction) on receive than transmit.

So IF-Shift will change what part of the sideband the 12mhz filter will capture (and thus capture a different range of audio frequencies) 
but does not change the frequency of the suppressed carrier that we are tuned to.

CW is a bit different, but easy enough.

Jerry, KE7ER 

Tim Gorman
 

Vince,

If you are listening to a CW signal then moving the IF Shift doesn't
change the tone of the CW signal at all. You are just moving the
passband. That can change the sound of a SSB signal because you are
removing some of the received audio along with the interfering signal.
Just like cutting the highs or lows with a treble/bass tone control.

tim ab0wr

On Sat, 10 Mar 2018 21:07:17 -0500
"Vince Vielhaber" <vev@...> wrote:

IF Shift is supposed to shift the signal thru the passband without
changing the frequency. So if you're listening to 3930 and there are
signals on 3928 (it happens daily) at the same time, you can use the
IF Shift to move the signals on 3928 out of the passband. If affects
the sound of the desired signal like a tone control but that's a side
effect of the action.

Vince.



On 03/10/2018 09:02 PM, Ronald Pfeiffer via Groups.Io wrote:
Yes I was confused a while back when Ian announced his IF shift.
The code looked just like our RIT. Our RIT displays the freq on
bottom line and the line above displays the plus/minus offset as
you move the encoder.

rOn



------------------------------------------------------------------------
*From:* Tim Gorman <tgorman2@...>
*To:* BITX20@groups.io
*Sent:* Saturday, March 10, 2018 8:24 PM
*Subject:* Re: [BITX20] #uBITX Firmware KD8CEC - IF-Shift etc.

I wonder if we need to define some terms here. Passband tuning and
IF Shift typically move the *filter*, not the carrier. The carrier
will remained tuned to the same frequency when adjusting this. For
instance, if you use IF Shift when listening to a CW signal the
tone of the CW signal should not change. You can move the filter
bandwidth up or down to eliminate an interfering carrier that is
close to the desired frequency.

What you are describing is more like an Incremental Tuning, e.g.
RIT or XIT. When you move the BFO you move the carrier frequency,
not the filter bandwidth.

Ideally the BFO would be set to replicate the suppressed carrier
frequency. The filter then determines what is heard.

The ubitx uses a 12Mhz crystal filter. I don't know its bandwidth or
what the actual absolute frequencies are. I haven't had a chance to
run a spectrum analyzer against mine. Let's assume it has a 2400hz
bandwidth and goes from 12,000,300hz to 12,002,700hz.

If you want to listen to a signal at 10Mhz then CLK2 should be
tuned to 55Mhz to generate the 45Mhz signal the first IF needs.

CLK1 should then be set to generate a 12Mhz signal, i.e. 33Mhz. For
an USB signal we should then see frequencies of 12Mhz to 12.003Mhz
(or whatever the transmitted bandwidth is, e.g. 0-3000hz). You will
then see frequencies of 12.0003Mhz to 12.0027Mhz out of the filter.

This is how an ideal receiver would work.

When you are talking about adjusting the BFO I assume you are
talking about adjusting CLK1. If you adjust CLK1 to move the actual
suppressed carrier frequency somewhere else in the filter bandwidth
then your frequency indication is going to be off. What should be a
10Mhz signal is going to look like something else.

This will cause an asymmetric USB and LSB response and frequency
indication.

If you want to change the BFO frequency on the fly then it should be
understood as being an incremental tuning so you can remember what
the base frequency should be.

Now each filter is probably going to have a different actual
physical, absolute bandpass. The BFO will have to be adjusted to
allow for this but the frequency indication needs to be adjusted as
well to match. It should be a fixed reference, not a variable one.

Your transmitted frequency has to be offset from the CW-tone if it
is to be zero beat with the received signal. If it isn't then
you'll never be zero beat. I'm assuming that the CWL and CWU
frequencies are indicating a frequency CW-tone away from the actual
transmitting frequency. That may be because your receive BFO
frequency isn't set to indicate actual carrier frequency.

I didn't mean for this to get so complicated but it isn't an easy
subject.

tim ab0wr


On Sun, 11 Mar 2018 01:08:55 +0100
"ge_clipboard" <clipboard@... <mailto:clipboard@...>>
wrote:
Hi All

Many thanks for all the response concerning the BFO adjustement and
about using the IF-shift. I have been playing around with the BFO
setting while monitoring myself on another transceiver but as I’m
not getting there where I really would like to, I returned to the
factory settings. Leastening to the transmitted LSB and USB on
another transceiver was never symetric, maybe the steps to set the
bfo are not fine enough to do this or I am making something wrong.

Yes, the IF-shift is often a very helpfull feature within crowded
bands and as Mike pointed out, it is also nice to be able to adjust
the sound of a ssb signal on receive. So, if this could be
corrected in the software would be very fine.

Another point I’ve noticed today while using CW, dx-cluster and CAT
to jump to a anounced station... When the CWL-, CWU-feature is
enabled, then the frequency is not spot on but offset by the amount
of the CW-Tone.

Nevertheless, this little rig is a joy to play with, especially
with all the added features by Ian‘s software.

Vy 73, Gerald - HB9CEY




Jerry Gaffke
 

It was getting late when I pressed send, a couple minor errors crept in:

>  The 12mhz filter is passing audio between roughly 500 and 2500 hz in its upper sideband,
>  so the 12mhz filter is probably centered around 11996500 + (500+2500)/2 = 1199800 hz.
>
>  With a clk1 for USB of 56995000 hz, the center of that upper sideband in the 45mhz filter
>  would be 56995000-11998000 = 44997000 hz
>  With clk1 for LSB of 32995000 hz, the center of that lower sideband in the 45mhz filter
>  would be 32995000+11998000 = 44993000 hz.

When I say "upper sideband in the 45mhz filter", I'm talking about the upper sideband
of the original signal.   Should rewrite those last few lines with a few more words:

  With a clk1 for USB of 56995000 hz, the center of that sideband within the 45mhz filter
  (now below the carrier due to sideband inversion from the high side VFO)
  would be 56995000-11998000 = 44997000 hz
  With clk1 for LSB of 32995000 hz, the center of that sideband within the 45mhz filter
  (now above the carrier due to sideband inversion from the high side VFO)
  would be 32995000+11998000 = 44993000 hz.


And I flipped the arithmetic at the wrong spot in these formulas:

>  The display shows the frequency of the suppressed carrier, always easy enough to compute:
>      For USB, it's   VFO-(clk1-BFO)
>      For LSB, it's   VFO-(clk1+BFO) 

Those two formulas should read:
 
     For USB, it's   VFO-(clk1-BFO)
     For LSB, it's   VFO-(clk1+BFO) 


Jerry, KE7ER


On Sat, Mar 10, 2018 at 11:36 pm, Jerry Gaffke wrote:
I think Gerald's complaint about USB sounding different than LSB winds up being due to
a USB signal going through the 45mhz filter a few khz away from where an LSB signal does. 
Gerald was using Ian's code which I have not yet looked over.
I assume Ian borrowed numbers from the original uBitx code.
Here's my argument:

The original uBitx code has the BFO at
    #define INIT_USB_FREQ   (11996500l)
and uses these frequencies for clk1:
    #define SECOND_OSC_USB (56995000l)
    #define SECOND_OSC_LSB (32995000l)

The 12mhz filter is passing audio between roughly 500 and 2500 hz in its upper sideband,
so the 12mhz filter is probably centered around 11996500 + (500+2500)/2 = 1199800 hz.

With a clk1 for USB of 56995000 hz, the center of that upper sideband in the 45mhz filter
would be 56995000-11998000 = 44997000 hz
With clk1 for LSB of 32995000 hz, the center of that lower sideband in the 45mhz filter
would be 32995000+11998000 = 44993000 hz.

That's a 4khz difference in where the center of the sideband of interest got placed
within the 45mhz crystal filter passband. 

Assuming the the 45mhz crystal filter is truly centered at 44.995mhz as the notes in the code suggest,
then I figure that values of 56993000 hz and 32997000 hz should be optimal for clk1.

If the 45mhz crystal filter sweeps out to be somewhere else, then add the difference to those two figures.
For example, if the center is found to be at 44.997mhz (so 2khz higher) then the two figures for clk1
should be 56995000 hz and 32999000 hz.


Regarding Tim's writup:

> When you are talking about adjusting the BFO I assume you are talking about adjusting CLK1.

No, we are talking about adjusting the BFO.
When adjusting the BFO, we should move the VFO to get us back to the displayed frequency.
The display shows the frequency of the suppressed carrier, always easy enough to compute:
    For USB, it's   VFO-(clk1-BFO)
    For LSB, it's   VFO+(clk1-BFO) 
where VFO is clk2, and BFO is clk0.

RIT allows a different VFO setting on receive than transmit.
This IF-Shift thing apparently allows a different BFO setting (with attendant VFO correction) on receive than transmit.

So IF-Shift will change what part of the sideband the 12mhz filter will capture (and thus capture a different range of audio frequencies) 
but does not change the frequency of the suppressed carrier that we are tuned to.

CW is a bit different, but easy enough.

Jerry, KE7ER