Evan, Thanks for the explanation about the Antuino plot scan display.

Here is a note about my final calibration steps... (This is a follow-up of my post # 105935, above.)
I was not satisfied with the results of the Frequency calibration. Zerobeat requires a relatively strong signal, in order to hear the low frequency audio tone as zerobeat is approached. Also, when using the Setup mode (in the "yellow box" on KD8CEC v1.2 or v2), the resolution is poor. The best I could do was around +/- 200 Hz off frequency... and that required a strong stable signal. I used an HF broadcast station. But, in my location, it is rare to have good propagation and signal quality.

What worked for me was... (These steps assume that the BFO calibration is right. See my post above, about that.)
1. Tune in to HF broadcast station, on an expected frequency. The signal was too weak to hear program audio. However, there was a good beat note on either side of center (switching between LSB and USB).z
2. Monitor the receiver audio output on a spectrum analyzer, with frequency markings.
3. Tune below center freq. by 1 KHz, in USB mode (note beat note frequency on analyzer).
4. Tune above center freq. by 1 KHz, in LSB mode (note beat note frequency on analyzer).
??? If the radio calibration is true, the beat not frequency will be the same in both LSB and USB. (If different, note the difference.)
5. Connect the radio to the AJ6CU uBitx Settings Editor, and go to the calibration tab.
??? Write down the Master Calibration number.
??? Edit the number shown by adding or subtracting one or two thousand.
??? (As you narrow the frequency error, you can make smaller changes in the Cal number.)
6. Write? to the radio, and reboot it.
7. Go back to steps 2 and 3. Note how much the beatnote frequency changed, and in which direction.
8. Repeat steps 5, 6, 7 until the frequency is right. It is possible to get within 1 or 2 cycles by this method.

Also check the receiver passband with the audio analyzer, after the center frequency is calibrated. The strength of the beat note should drop off rapidly at about 3 Khz either side of center (in LSB or USB).

By manually adjusting the Master Cal numbers, using the AJ6CU settings editor as above, there is much better resolution, than by using a zerobeat procedure (even the one included in the Settings Editor "Calibration Wizard"). Also, when the Settings Editor is connected, the receiver noise level increases. So, except for steps 5 and 6, disconnect the radio from the computer when using a weak signal.

I'm sure others have used a similar method. But perhaps sharing what I did will be helpful to someone.

开云体育

Evan, I get what you are going for— that it might be coupling between the loops, however take a look at this post

Gordon,

Can you remove the long jumper runs for this last test and just jump across D15 and D19?? This would be to eliminate any bypassing of the filters through the jumpers.

73
Evan
AC9TU

Very Differrent Result -- OUTPUT DIODES from other filters also now connected.


1.? The 21 MHz signal still goes directly through the upper LPF to the antenna
2.? The HV voltage supply is connected (but I have not measured whether it is working properly and this is crucial!)
3.? The input diodes fromthe OTHER LPFs are now connected
4.? And new here, the OUTPUT diodes from the OTHER LPFs are now additionally connected.

AND WE HAVE HARMONICS --



Here is the schematic that I think applies:



And here is a photograph of the actual soldering:




SO NOW there are lots of questions:

1.? Is the HV power supply working?
2.? Are the switching diodes all reverse biased (every one of those should be reverse biased?
3.? How does this happen, since all of the other filters' cutoff frequencies are WAY LOWER ANYWAY!!? Even if one of the other filters were TURNED ON, it should not be passing 42 MHz nor? 63MHz.
4.? Are the back-biased diodes somehow creating the harmonics???


Anyone got ideas or explanations???? ?I'm all ears as I work toward the next experiment, whatever it is.

73
Gordon KX4Z

NEW EXPERIMENTS TONIGHT
1.? Now the "input switching diodes"? sides of the low pass filters were reconnected, in addition to the HV voltage power supply, and the ISOLATED highest low pass filtter is still used to directly take the output of the amplifer and go to the output.
2.? See photo of the SCHEMATIC, the photo of the soldering, and the photo of the output spectrum
3.? The 2nd harmonic is now about -42.5dBc,, the 3rd harmonic is still way way down.? ?Having the INPUT diodes connected -- but no connection from the OUTPUTS to anywhere, didn't make a terribly large bit of difference.










73
Gordon KX4Z

Sale pending?

Selling my ubitxv6. It's a neat radio, just above my ability. It works fine, I bought the basic kit and added my own case ( it's ugly) the only thing that was wrong with it is the volume knob broke off the board and had to be replaced. I'm thinking $110 shipped OBO. US only. I still need to find a box and packing materials so don't expect me to mail it out within a day.

It works for me but it's still clunky.? There is still a 30 second delay until it sends your reply to a CQ and that results in repeat transmissions.? It looks like there will be a proper update soon.

I also made the changes to index.html with C type comments and it didn't help.
I then tried html style comments and that caused the the window to not properly launch.
Anyone get this to work?
--
73
??? Bob? KD8CGH

Basic answer is that the 5351 has higher phase noise (jitter).
ITs adequate for HF use but at higher frequencies where the ambient
and galactic noise are lower it handicaps the receiver performance.
This is old news.

The Si570 is roughly 10x lower jitter ans as a result less phase noise.

Compared to a good crystal or VFO they are an order of magnitude nosier.
The price paid for stability and digital tuning.

--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.

Dave,

The difference is in how the Antuino works and measures frequencies.? ?In the case where you are measuring the passband of the filter, the Antunio has control of the stimulus frequency, stepping it through the range specified.? Since it is a narrow frequency, the width of the receiving filter is not an issue as the input is very narrow.? When used as a spectrum analyzer, the width of the input filter does affect the measured response.? As I had stated before, the resolution bandwidth (RBW) of the Antunio used as a spectrum analyzer is 3KHz.? This will widen the perceived signal as you scan the frequency range.

73
Evan
AC9TU

开云体育

Great news !!

Evan,
Thanks for the updated diagrams.
I'm still puzzled by the wide BFO signal as plotted on my Antuino (in my previous post).
But the main thing is that the radio seems to be working, now. (Thank you all.)

Dave WD8AJQ,
Thank you for suggesting CHu Canada.
Unfortunately, I tuned to those frequencies and heard nothing. After a little reading, it seems that the CHu transmitters are relatively low power (compared to WWV) and located farther away, in eastern Canada. Since they are not received well in western Canada, they are not of much help in Alaska. But I was not aware of this station before, and I appreciate the information.

By the way, I just updated my QRZ.com page. The biography section mentions my Bible based website. Since it is largely text, I think you would find it very accessible.
73
DaveW

All this work is open source, including the board designs. github in my sig below is where all the repositories are. At the moment, I still consider the boards pre-beta. I am hoping that I am getting to a point where the designs are stable. Currently, the Pico based board is re-spinning because of display headers pin connections were incorrect. It is also (fingers crossed) the first board that will have a TX/RX external signal that can trigger a RX/TX switch or perhaps an amp.

At this point, my plan is to have JLCPCB pre-mount the SMT devices on a small number of "beta" boards. That will just leave the various sockets and headers for folks to assemble themselves. Probably start with the Pico beause it is so inexpensive.? But probably will not get to this point until after the holidays. Will look for volunteers then. This is a hobby for me. If the boards are any good (I am a software guy, not a hardware designer), perhaps one of the various vendors here will take the boards on and offer them.

73
Mark

--
AJ6CU/7
KD8CEC 2.0, Nextion Screens,? and open source uBITX Raduino boards for Arduino IOT, BLE, RP2040, Teensy 4.0, and Raspberry Pi Pico
https://github.com/aj6cu

Mark,

The boards and display looks Beautiful!!!!!!.

73
David
ac9xh

Mark,

Do you have a website with this listed?

Also? when you get some complete assemblies ready email me . Im in for at least one.

73
David
ac9xh