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Improves uBITX receive performance by CEC Firmware V1.07 (include example of the ATT feature)

Improves uBITX receive performance by CEC Firmware V1.07 
(include example of the ATT feature)

This document is for uBITX users and students.

Version 1.07 firmware can be downloaded from the link below.

I implemented IF-Shift while creating Version 1.01.
The idea of implementing IF-Shift started with a suggestion from a friend with a great idea.

As you all know, IF-Shift is used for ambient noise.
For a description of IF-Shift, see the link below.

I received good ratings from amateur radio friends from all over the world.

I'm not talking about IF-Shift right now.
This is because it is possible to improve the reception performance and implement the RF Gain Control for Receive (ATT) in the same way as IF-Shift.

uBITX has two filters using crystals.
(two red square)

Anyone thinks that 12Mhz will be much sharper?

I returned the VNA to test the receiver performance of uBITX and brought my favorite equipment.

12Mhz filter part.
I respect the developer who created uBITX.
I was able to remove noise by shifting the signal to one side as it passed through this filter.

The video below is a test image of IF-Shift when releasing Version 1.06. You can see that the signal passes through the above filter only.

Anyway, when I did the above IF-Shift experiment, I experimented on 45Mhz.
That's what I'm talking about today.
It's a 45Mhz filter.
(It is the image which made the bandwidth more than three times wider than the above figure.)

1. The curve is smooth.
2. The peak point is near 45Mhz.
 (Version 1.061, which retained the original source code and method, is slightly lower than 45Mhz.)

I have created a function that can shift when passing through that filter.

in the code above, increase the frequency before passing through the filter, and then pass it down.
In the case of LSB, the frequency decreases by Clock 1.

And I saved the Adjust value in eeprom so that it is always available.

-------------------- TEST ------------------------------

The reason I brought the above old equipment was to do the following tests.
The reason why I use the instrument in this post is because the reception ratio is quite subjective, so I need to confirm it more objectively.
In the following post I will improve receive without instruments.
I will post this article and write soon.

1.Upload the original firmware.

2.Connect uBITX to the instrument.
  (RF and AF)

3.Because the instrument does not support SSB, it generates a signal below 1Khz.
0.04332v was measured at -95.0 dbm input.

4.Upload Version1.07 firmware to uBITX.

The measurement results from the instrument are the same as when the original firmware was uploaded.

5.Now I enter the ATT menu to reduce the RF Gain (for Receive).

Default Value is 0

Turn the dial to increase the ATT value.
Originally, as the ATT value increases, the reception tone should decrease but it will increase. This is lucky for you. Because your uBITX can get better.

The maximum increase was about 80 to 100.
at 80, a maximum of 0.07020 was measured.

This is probably the situation below.
(Below I have added a value to the graph to help you understand it.
The values are exaggerated for understanding. Please use it for reference only.)

[before IF Tune Applied]

Your uBITX is ready for the best performance.
'I am annoying to use uBITX so I always have to turn 80 on the ATT menu!' -> It is a wrong idea. The ATT function applies only to receive. If you save the Tune value as shown below, your SSB transmmit performance may be slightly improved.
(In CW mode, only receive performance is improved)

Then run uBITX Manager.
(IF Tune is supported from Version 1.02)

Check 'Enabled IF1 Calibration Value'
Then enter 80 in the IF1 (45Mhz) Calibration field.
(Firmware Version 1.071 will add the option to use IF-Tune and ATT in the opposite direction.  For people using modified filters or using DIY uBITX)

Write to uBITX.
(If you are using uBITX Manager for the first time, please refer to the article on uBITX Manager in other articles of my blog.)

Reboot uBITX.
Calibration values are applied so you can feel that reception is improved no matter what frequency you are going to.

Now let's see if the ATT function works properly.

Enter ATT Menu

Try increasing the ATT value.
As the ATT value increases, the reception ratio decreases.
ATT value 0 is the best receive condition.

 When ATT value exceeds 200, almost no signal is heard.

This is probably the situation below.
(Below I have added a value to the graph to help you understand it.
The values are exaggerated for understanding. Please use it for reference only.)

[After IF Tune Applied]

Added comment
If you have done this in the LSB, it may not have a big effect when you enter USB mode.
If you subtract 30 from the measured value at LSB, both LSB and USB will be satisfied.
But I do not recommend this method. 
because At the 1.7x beta is over, I will make sure that I get the best performance on both LSB and USB.

If you have followed this method, just enter the measured value from the LSB. Updating Version 1.71 may have increased USB reception performance.

This is the experiment I've done so far.

Using this function, John (VK2ETA) created AGC.
When I apply S.Meter in my firmware I am going to apply John's code.
Thanks to John for discussing this feature.


  1. Good Morning Ian
    Many thanks for the new version which is in many points again a lot improved! I was testing your software with the new calibration feature last night and have seen exactly what you are describing in the article above, by ear the signal decreased in strength before increasing again, but it was not clear to me if I heard it correct. So, your explanations are very helpful to me. And it will be nice to have the s-meter included in a coming version.
    Vy 73, Gerald - HB9CEY

    1. Thanks for your attention.
      Now I am going to support third party hardware, including S.Meter.
      Ian KD8CEC

  2. Hello Ian
    I am trying to set up CAT with the N1MM Logger+ using the FT817 settings but the program always looses the connection after a few seconds. Did you test this program as well and could give me a hint on how to configure the connection?
    73, Gerald

    1. Gerald.
      I have not tried N1MM Logger + yet, so I'll try and tell you soon.
      I do not know for certain, but I guess it would be arduino reset problem.
      I'll test it as soon as possible.
      Ian KD8CEC

    2. Gerald
      I have tested the N1MM Logger now.
      Perhaps my guess is right. See the link below

      However, in my case, I did not take any action and could use it.

      Radio : FT-817 (Select)
      Speed : 38400 (Select)

      DTR : Always Off
      RTS : Always Off
      Radio Polling Rate : 100% Slower

      The rest was in the default setting.
      If this setting does not work well, you can fix the Arduino Reset Problem.

      Ian KD8CEC

  3. Hi Ian,
    I have installed the new 1.061 release and now USB and LSB are reversed. I listen LSB station with USB and viceversa.
    What can I do?
    Thank you in advance.

    Paolo IW6BET

    1. Paolo
      Do not worry.
      1. If you upload this firmware, calibration will not be changed.
      2. Perhaps your uBITX is likely to have a fairly wrong Calibration value.
      3. In particular, it sounds like the LSB and USB have changed since the BFO Calibration was set to zero.
      4. Maybe the same thing happens if you upload the original (factory built) firmware.
      5. The solution is simple.
      Enter the BFO setup menu, set the value to 11996500, then increment or decrement.
      Then the sound quality will be better and the LSB and USB will match.

      6. If the frequency is slightly wrong, go to Master Calibration and set the value in the range of 14 ~ 18.

      7.Please reboot uBITX for every setting above.

    2. For the first, thank you for the fast reply. Unfortunatly nothing is changed: I have set the BFO (Set the BFO) to 11996500 and reboot uBITX, but the problem remain.
      Is there a kind of reset to the factory values?


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