Software Defined Radios for 2020

Some new technology to add to the new technology for 2020.

2-3-2020 Photos of the day..

First we have a photo of Virginia Hall (from Baltimore), a famous WWII Spy working for the Brits and later the OSS. Here we see her pounding brass on a Paraset.

That must be a British version of the GN82 hand crank generator. Notably she had a wooden leg, a result of a self inflicted gunshot wound. She passed in 1982.

Our next photo has a deep meaning...

Maybe this was about their voting for the emperor (with the small e)

After connecting power of the wrong polarity to a circuit how many have said what is on this T Shirt. 

I didn't do that but did put a Teensy 3.5 into a socket, one pin over, and did see a ball of flame come out of the top of the chip. Luckily I had two Teensy 3.5's (now only one). Even more lucky it was not the Teensy 4.0!


2-1-2020 TEENSY 3.5 ala ZL2CTM, Working Again; But needs further evaluation. 

[My plan is get a Teensy 3.5 working and then transition to the Teensy 4.0 MCU. Keep in mind the Teensy 3.5 build is modeled almost entirely after the work done by Charlie, ZL2CTM who has done all of the heavy lifting. My contribution is to routinely solder my fingers together --twice today.]

The Codec Board is the key interface tool.

The trick with this board is the interconnections to pins 11, 12, 13 and 14. These are the Line In / Line Out pins. I have terminated these connections into 3.5 mm stereo jacks one for Line In and the other for Line Out. Short jumpers connect from these two sets of jacks over the board to another set of similar jacks and an all important DPDT relay. 

(Notice I used a mailing envelope as a scratch pad to draw out the interconnections.)

This relay (as I found out in the RADIG V1) switches the I and Q channels on transmit. Yes friend this is also done on the Soft Rock V6.3 and the Ensemble. What I have yet to determine is the polarity ( I and Q) on my RADIG Board. So there may yet be some wire switching to be done.

I was listening to 40 Meters early this evening as the band was dying out --so must await more testing tomorrow when signals are bit stronger. I may call this the PlankSDR since it is mounted on a chunk of plank.

When you know stuff and have a junk box full of built modules, then you can do stuff in about a half a day!

Note the microphone (an electret) plugs into Pins 15 & 16. I may jury rig something so I can have a very low level transmitted signal to evaluate opposite sideband suppression and if I have all the wiring in the correct order.

Stay tuned.

Coronavirus may be a solution not a problem. Just saying!

Pete N6QW



If You Don't Want To Know Stuff, Then You Must Be A Republican U S Senator. But If You Know Stuff, You Can Do Stuff. 

Have started my Teensy 4.0 Trek by resurrecting my ZL2CTM Teensy 3.5 SDR using the RADIG V2 homebrew SDR Board. (

This approach will enable me to get a working system wherein I can later swap in the Teensy 4.0 and Codec Board as I would know that the remainder of the circuitry is working properly. I have a couple of Teensy 3.5's and so if I smoke something, it won't be the newest Teensy 4.0.

I think I discovered a wiring error in my original ZL2CTM Teensy 3.5 / Codec Board. That might account for a couple of strange observations I had when I was putting it on the air.  Nothing like putting something away and then taking a look with a fresh pair of eyes.

Pete N6QW

1-30-2020 --- My Teensy 4.0 and Codec Boards arrived yesterday!

But I am resisting taking them out of the box and powering them "ON" until I better understand the interconnects and any special application considerations. 

I thought initially I might create a sketch just to drive a Si5351 as a single output. A friend has shared code with me to create the quadrature signals directly. I will get it to work first with a single output and fully understand its capabilities and short comings before heading off to quadrature outputs. Am really trying to avoid smoking my 1st Teensy 4.0.

Do know it has a smaller foot print than the 3.5 or 3.6 -- so that makes physical construction a bit easier. One of my first tasks will be to install Male pin headers on the Teensy 4.0 and then matching Female sockets on the Codec Board. I think they are 14 pins --I have 16 pin types so probably will get the proper size. 

There are some other preparations needed if the Teensy 4.0 is operated with a separate power supply other than being plugged into  USB all of the time. I thinks I saw some notes about adding a SD card. Lots to absorb before the first smoke test. Patience grasshopper!

Stay tuned!

Pete N6QW

1-29-2020 --- Some Noodling Thoughts about using the Teensy 4.0.

On the screen above is a prototype noodling exercise of how a 4X20 LCD might appear using the Teensy 4.0 in a Homebrew SDR Rig. The actual hardware  generating this is a Teensy 3.5 that was used with ZL2CTM's SDR project. I had to keep my hands busy with something, as I await a Teensy 4.0 to arrive from Oregon.

Typically if you use just a single output (versus the quadrature output of the Si5351) and then further run that through the 74AC74 -- you have two unused outputs of the Si5351. Assuming you use CLK0 as the LO (at 4X) to drive the dual flip flop, then CLK1 and CLK2 are idle. 

Thence in a flash of brilliance I said why not program fixed frequencies into these clocks. Therefore  by flipping a switch you could shift to the FT-8 frequency (or WSPR) and also make it shift to USB. A DPDT relay could easily switch the Clocks going into the 74AC74. With a bit more code work you could even make VFO B tunable versus fixed. 

So in the display above -- VFO A is tunable and VFO B is set to the FT-8 frequency using CLK2. Those wishing to really extend the envelope could make a VFO C that would boot up on WSPR. You could even have "enable code" so only when you selected the other VFO's would that clock be active. 

Lots of possibilities that come from a bit of noodling. Keep in mind I am a brute force homebrewer and those even mildly more proficient in software development than me would suggest writing code so that no switches were involved and it was simple menu selections using the encoder push button. So noted -- but when your are few cornflakes short of a bowl, like I am, then you resort to "kludge" approaches to achieve a desired end. Works for me!

Stay tuned for more misadventures from N6QW as he steers a Teensy 4.0 into a mushroom cloud of smoke.

Pete N6QW


Firstly, you all are encouraged to visit the N2CQR Up on Bill's blog is a video of an LT SPICE simulation of a DSB signal. I didn't know you could do that with this program -- but I followed the video and was able to do it. 

This is a new capability for me and the bonus --you get to see a FFT display of the resultant output. This is more new technology to use in 2020!

The two spikes about mid-center of the photo below are the USB and LSB signals. If you add a DC Offset in the simulation factors you will see a third spike in the middle which is the Carrier. The stuff on the display toward the right hand side of the photo -- gives good cause for Filtering in our rigs! 
What I have not explored is how you look at the output of say a 1st stage audio amp to see the FFT spectrum. The video covers two voltage sources in a mixer stage. Some link must be made to see an output of say the audio amp as a voltage source. I just could not push enough buttons fast enough to do that so RTFM is in order.

New Technology for 2020

PJRC (up there in Oregon) has recently unveiled a new Teensy known as the Teensy 4.0. This is a smoking MCU board operating at 600 MHz and there is a matching CODEC Board so a homebrew SDR using something other than a Raspberry Pi is here!

Charlie Morris, ZL2CTM has done a lot of pioneering work with the Teensy series in a homebrew SDR transceiver and even the uBitix V6 can now be fitted with a  Teensy 4.0 in lieu of the Nano. That almost seems like shipping coal to Newcastle --true faster and more umphf -- but it still is a hardware defined analog radio. 

Hans Summers' QSX when it hits your mailbox I believe is using a Teensy. I suspect it won't be too long before Hans will be shipping product.

[A correction here. Hans is not using a Teensy but another processor so that was an inaccurate statement on my part (Thanks, Ben!). I also do not have any real knowledge about when the QSX is being released to production. I along with a lot of other hams are wishing and hoping  that it is soon.]

After a download of an ancillary program (from PJRC) you can program the Teensy 4.0 just like a standard Arduino using the Arduino IDE. The ancillary program has internal libraries that facilitate their use in SDR. 

You should also visit Iowa Hills Software to get the free software that enables you to build Digital Low Pass, High Pass and Band Pass Filters. Data from the Iowa Hills Software filter output coefficients is simply embedded in your IDE sketch.

An interesting note here as the Teensy 4.0 can be had for less than a $20 (less than what the Teensy 3.5 and 3.6 cost)  and the matching CODEC Board is about $15 --so with shipping two $20's should get you both. I mention this in light of the abundance of new technology hitting us in 2020 that won't break the bank. Think if the Teensy 4.0 purchase is a light meal for two at McDonald's.

I am getting a strong urge to use the Teensy 4.0 in a SDR transceiver but a lot more noodling ahead before anything concrete would happen. Stay Tuned to this space.

Just so you don't think this project has died...

 73's (From the Left Coast Wonderland!)
Pete, N6QW

Popular posts from this blog

21st Century Homebrew SDR SSB Transceiver Project

New Technology for 2020 ~ SDR RADIG #2 Part II

New Technology for 2020 ~ The Phasing Transmitter