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February 2, 2024. I saved the best for the last in this series. The Digital LO!

It is a mystery to me why so many home brewer's  shy away from the Digital LO. Putting the transition off to some future date only makes it more difficult. Yet, it is a fact that is in fact a fact!


Optionally there are so many more things that you can do with a Digital LO, perhaps only limited by your imagination.  You have to learn stuff to do the digital trip. BUT if you want to be a homebrewer or even properly use your $30 Nano VNA or $50 Tiny SA you have to learn a lot of stuff. 
 
The biggest Plus factor with the Digital LO is the Frequency Stability (No Drift) matched by the Frequency Accuracy of the Display. True your LC VFO can put a rig on the air, but likely it drifts and you do need something more than a cardboard scale for a frequency readout. 
 
I reflect back to when I went to real estate agent licensing school so I could learn about real estate for my own personal investments. The guy teaching the class emphasized the importance of how to answer questions. Often asked was: Does the roof leak? The response: Not too much or only in really hard rains! From the mouths of the die hard Analog LC VFO guys on VFO drift: Only when it drifts and not too much! They must have gone to Analog LC VFO school!
 
Here is a list of some of the advantages: 
   
  •   Frequency Accuracy (you are not 20Hz off)
  •   Frequency Stability
  •   A/B VFO's at a flick of a switch.
  •   Band changing is simplified
  •   Built in Tune Tones
  •   Monitoring of factors such as Heat and SWR
  •   S Meter Functionality and Display
  •   Keypad Selection and Tuning
  •   Quadrature Outputs for SDR applications 
  •   Simultaneously produce the LO and BFO
 
 
Here are some examples of displays ranging from the 16X2 LCD, to OLED's, to the more exotic and large 3 Inch Color TFT's.
 
 

 

 
 

 


1 inch Square Color Display


Level Shifting for the ILI9341 Display


A Whopping Three Inch Color TFT!

Less Than 1 Inch High OLED

But the latest buzz is the Seed Xiao RP2040 which is about the size of my fat finger thumbnail and has but 14 pins. In size, about 1/2 the size of the Arduino Nano and 2/3 the size of the Pro-Mini.

But the real clout is in the processor speed at 133 MHz and the storage is 2MB. Translated for you Analog LC VFO guys -- it has a lot of compute power and is fast enough to do the Fast Fourier Transforms and play with Hilbert Transforms that are the heart of the SDR signal processing.

With help from K7TFC I have a sketch working to  replace the Arduino in many of my projects. So, while many have turned their noses up at the Arduino, the technology and the Digital LO has made some giant leaps beyond what Massimo Banzi envisioned. 
 
The cost is another factor as the Seeed Xiao is in the $5 range so a lot more capability for about the same price as a Nano. If you want a copy of the Xiao, RP2040 sketch then email me at my QRZ.com address

Xiao RP2040 with  the Si5351

Here with a 16X2 Juliano Blue LCD


Now the Xiao will program with the Arduino IDE and once I learned the few tricks needed to make it play, it was fairly easy to port over my older Arduino sketches. Because of the Pin limitations (14)  it is easier to use LCD's or OLED displays. But I see no reason why you can't drive a 16X4 or 20X4 with the Xiao.


20X4 LCD. BTW the Front Panel is 1/8 Inch Plywood.
 
These last several weeks have been a fun trip as I could draw upon my many past projects to share with you some Tribal Knowledge. That was a minimum effort as all of the source material is in the existing project folders. 
 
That  said my caretaker duties at the XYL's Board and Care Facility continue and that does not leave much time for new development work. That is regrettable as there are so many things I would like to take on -- just no time. 
 
Lots of really new technology stuff popping up daily and for those who do have time, I wonder why you do not move into 2024?
 
 73's
Pete N6QW

PS: But who is keeping track? So far the two most popular posts of this recent series are the CW Transceiver and yesterday's Low Pass Filter. The Least Popular was the Double Balanced Mixer. I am not sure what to make of that data. But maybe the homebrewer community doesn't like triple wound ferrite cores but single winding units are OK. Also strange, one of my higher rated You Tube videos, in terms of views, is how to construct a DBM with Ferrite Cores.  It must have something to do with the flaky/shaky Banggood (love that name) Capacitor Assortments.

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