Wednesday, March 4, 2020

New Technology for 2020 ~ The ZL2CTM Teensy 3.5 SDR Rig

ZL2CTM Teensy 3.5 SDR Rig - More!

The Teensy 3.5 and RADIG V.3 Are Alive!!!!!

 RADIG V.3 & Web SDR

3/10/2020 ~ St. Paddy's Day --a  Week Away!

So OK  a small drift into the Pasta Pete mode then back to SDR.

My XYL is part Irish (and no part Italian --if she were part Italian we'd probably would have killed each other by now) and loves her traditional Corned Beef and Cabbage St Paddy's Day dinner. 

There is a trick to cooking this meal entirely in one large pot. You must have the small white Potatoes, Cabbage Wedges, Carrots and of course the Slab of Corned Beef. Did anyone mention garlic? One year this celebration involved my cooking for 12 guests. 

For that dinner I bought a 12 pound slab of Corned Beef from Katz's Delicatessen in New York and had it air shipped to Seattle. That cost me about the price of a Ubitx V.6 with all of the bells and whistles. But hey, it was for the wifey. After dinner I looked for left overs -- there were none. It was that good.

There was a Romance Comedy movie about 25 years ago "When Harry Met Sally". Part of that movie was filmed in Katz's Deli. I have also eaten at the Deli and it is indeed superb. So if you are looking for some authentic Corned Beef --they have a website and with plastic in hand you can have "real" Corned Beef at your St Paddy's Day Dinner! There is time to order one; but the window is rapidly closing.

Funny story with that Corned Beef and New York. When the box arrived --sure enough it was one huge slab. Not wanting to screw this up, I called the Deli and asked to speak to someone about how to cook this jewel. One of the staff shared that indeed it was a good idea to cut the slab in half so it all gets cooked properly. 

The day following the dinner I called Katz's Deli and asked to speak to the manager. This grumpy, grizzly guy gets on the phone and in typical NY fashion starts off by saying "What do you want to complain about?" 

I quickly said No, I want to thank you and your staff. They were so helpful and the Corned Beef was totally consumed and nothing left -- 12 people ate 12 Pounds of Corned Beef. It was excellent! He then says --Nobody Calls to Thank Us --and hung up. Well that's NY. 

Back to SDR. ZL2CTM's winning design continues to garner excellent signal reports. So visit Charlie's you tube channel and learn how to build this amazing radio. No computer needed and if you feel the need to see your waterfall --tune in one of the web based SDR receivers. I did that just to look at the sideband suppression on the opposite side band. 

I have made about three dozen contacts so far and it has performed well. I am indeed impressed! 

Some of my future posts will be about how I stumbled through the Iowa Hills Software and the results of the filter changes. ( A note to Bob, you will probably want to tune out this part.)  

I want to test filters of various band widths such a 6 kHz (AM Receive), 2.8 kHz, 2.0 kHz and maybe even 600 Hz. Just thinking ahead -- a selector switch with four positions, and a two digit decode so  two Teensy pins could result in 4 band widths. Now how cool is that? 

Oh something else ZL2CTM shared with me during our Skype event. He asked if I had looked at the AD9833 DDS board. I said no. This is a really small DDS board and is only good to 12 MHz but just think for a minute -- those radios which use a 5 MHz VFO or PTO. 

In fact a couple of my Ten Tec Radios including a Ten Tec Omni C that has a drifty PTO. This TT radio brings the PTO signals out to a jumper on the back panel so you can fit a Remote VFO to this radio. Wow you wouldn't even have to mess with the radio. Pull the jumper plug and fit the AD9833 output into the Omni C. Charlie buys these for about $1.50 for the complete board. Amazon has them for around $4.

In doing a bit of research on the AD9833 --one homebrewer directly soldered the AD9833 to the back side of an Arduino Nano as the pins needed for the AD9833 all aligned that way. Man that was really small. He added an OLED display and in the palm of your hand a complete Frequency Generator good to 12 MHz and it would even work with your Bitx40.

2020 and yet more technology for us!

Remember scrub your hand just like a Democrat that shook hands with the emperor (with a very small e) as one precautionary preventive move in the stemming of the spread of COVID-19.

Pete N6QW

3/9/2020 ~ A Conversation with ZL2CTM

There is nothing like a bit of face to face time to clear the cloud of smoke surrounding what you are doing. Regrettably some of the smoke was from my burning parts.

Yesterday I got an email from Charlie, ZL2CTM suggesting we Skype. You have got to love this advanced technology as we were able to do just that. 

Firstly, I discovered that I had been "dabbling" with the wrong version of the Iowa Hills Software. There are several different forms (all good when used properly). Seems like I have been using the general purpose set of filter design hardware and what you really want is the Hilbert Transform (HT) Variant. 

The HT math operators have been around for a long time; but have become a staple for digital signal processing. Since we are not using DDC but the I and Q method then the In Phase (I) and the Out of Phase Quadrature (Q) signals coming from the two ADE-1 Direct Conversion receivers are separated by 90 degrees. The mathematical processing ongoing in the Teensy 3.5 recognizes and processes these 90 Degree out of phase signals using the Hilbert Transforms.

But to do this you must have the HT processing be designated in the sketch. Thus the Iowa Hills Software  generates these two sets of math operators one of which is at 45 Degrees phase added and the second is -45 Degrees phase added. Thus with the + 45 Degrees  and - 45 Degrees the span is 90 Degrees. 

This realization, a result of my conversation with ZL2CTM led me to the Hilbert Transform Software within the Iowa Hills Suite and we now have a filter that looks like what is shown below. In a contra approach to the many Commercial Box operators, I have set the bandwidth to around 2.4 kHz whereas the FLEX guys seem to like 2.8 to 3 kHz so their signals have "presence" and are not yellowie!

Now I need to collect the two sets of coefficients and embed them into a Teensy 3.5 sketch. For this 1st test run I will be using 100 coefficients and if my "dabbling" works, then I will test drive more coefficients. 

In theory more coefficients add more points to the curve and this provides a better  defined filter. The question remains. How many is enough before you reach the law of diminishing returns.

A big Thank You to ZL2CTM for suggesting we Skype -- Otherwise I would have been in the weeds for a very long time.

Stay tuned for the excitement. 

Coronavirus Tip: It is important to wash your hands in a manner just as if you were a Democrat and were forced to shake hands with the emperor (with a very small e). Special note:  it is more than just a quick rinse, it is a thorough Scrubbing!

As an aid Sing Along like Ensign Nellie Forebush in the movie South Pacific "I'm going to wash that man right out of my hands". Several chorus loops through that song is about the right length of scrubbing!

Pete N6QW

3/8/2020 ~ The 2N3866 Bi-Directional Amp!


3/6/2020 ~ 1St Contact with W7LTG, Francesca at 1314 PST on 7.204 MHz -- My report: 5X9 + with good audio ~ Running  100 Watts. I may try to work the contest this weekend. You just got to love this technology.

2nd contact with WV6PBJ, Dave at 1400 PST. We are on a roll.

Worked some of the DX Contest including a XE2, 4A7S, TI7W, KH6, TO3 (Guadeloupe), PJ4G and JA3YBK . We are indeed on a roll. I was running 600 Watts --this contest is not for the QRP kids!

I will be further testing the opposite sideband suppression. But significantly the RADIG V3 Main Board and my bi-directional 2N3866 RF Amp board are doing very well.  

BTW the RF Amp stages following the Band Pass Filter on the RADIG Board are a 2N3866 steerable amp and following that is a 2N3866 Driver Stage and the Final is the IRF510. This lash up produces in excess of 5 watts. The amplifier following the RADIG is the CCI AN762. The antenna is my inverted V with a 35 foot apex.

Ugly and Al Fresco but works!!!!!

This morning I spent some time with the Iowa Hill Software and defined a 7 Pole Chebyshev 
Band Pass Filter comprised of 127 Coefficients. This filter is only 2.4 kHz wide and looks like this. It looks like a Brick Wall.

In "diddling" with the software my first run was to set the 3 dB point on the low end to about 250 Hz and on the high end to about 2650 which effectively make the 3 dB bandwidth 2.4 kHz. At 60 dB down we are around 3.5 kHz (thus my brick wall comment). But until I actually load it into the software and test it I won't know the "real world" performance. 

This was essentially my 1st run at seriously using the Iowa Hills Software so I really may be off in the weeds. I am just at the learning stage and the seasoned pro's are likely having a good laugh. 

I have the coefficients but I think in the ZL2CTM software you have to have two sets of filter coefficients so that the other is 90 Degrees from each other. Need to study that but from what I inspected in ZL2CTM's code that appears to be the case.

I dumped the 127 coefficients into an Excel Spreadsheet but have not figured out how to make a second column where the first series of points is simply inverted. I have been doing it by hand --it may take a while to cut and paste all 127 values. But that is only half the task, as you must precede every one of the values with an identifier in the Arduino code. So that is 254 entries. It may take a day or two for me to get it all done and test drive it.

Here are the 127 coefficients:



My eyes hurt...

Pete N6QW

In unrelated news.. Mick is gone and are what people saying true that Mikey may be replaced by Nikki?
The emperor must be pissed.. Coronavirus has shown up in Florida and New Jersey and that is sure to impact his golf game! 
3/5/2020 ~ SEABEE Birthday -- 78 years ago the SEABEE's were formed ( 5 March 1942). So to all SEABEE's world wide, present and former --Happy Birthday -- Can Do!

WG5EEK posted a nice video on you tube about SDR Dongles -- again something that just showed up on my phone. 

There is some really sophisticated software floating around and one lets you have what is in essence a "super scanner" all for $20. 

There is another piece of software called SDR# that had a very nice spectrum and waterfall. 

So like "quickly" rather than slowly but surely, -- SDR is finding its way into our hobby. Most of the software is Windows based but some is also dual Windows and Linux (like Quisk). I am finding a whole new world with software that is Linux based.


[New additional video of the transmit waveform just posted.]

My initial posting of this morning described some issues I was having in making the transition from receive to transmit and back to receive. 

That configuration used a DPST relay which switched 12 Volts between receive and transmit. On receive the switched +12 VDC was only switched to the audio amp stage. On Transmit at least 4 relays were involved to add voltage to the transmit circuits and to steer signals through the bi-directional amplifier stage.

There was a considerable amount of back EMF and despite having some snubber diodes -- even the Si5351 jumped 100 Hz in the transition. NOT GOOD MY FRIEND!

The remedy was to permanently connect the 12 VDC to the audio amp stage as the muting in the software takes care of that issue. 

For the transmit side -- an old trick. The switched voltage is run through an LM317 Voltage Regulator. On the input side is a 100 NF cap and on the output side is a 1 Ufd electrolytic. From the V Output to V Adjust is a 220 Ohm Resistor. To that junction is connected 1820 Ohms to Ground comprised of a 1K and 820 Ohm in series. The LM317 Calculator says with these constants you should get around 11.5 VDC. 

Now the problem is gone and the supply to the Teensy stages is clean. No longer does the Si5351 jump in frequency as you transition. 

This is a video using my new 12 MegaPixel Camera acquired from Amazon for less than $10. There is no audio and I am using the Linux Mint shop computer with the program Cheese. 

The transmit signal is raw coming out of the bidirectional amp stage (single 2N3866). With a bit of additional filtering we should be good to go.

Don't you just love this technology -- another event in 2020. 

I am having some issues making this radio transceieve. This same Teensy 3.5 board was used previously and worked FB.

It will work receiving and like wise transmitting but upon return to receive it is like the transmitter is transmitting into the receiver. Not good.

I may have corrupted the code as there are provisions in the code to efficiently handle this transition. Another possibility is some of the relays may be hanging up. More investigation needed.

The receiver is picking up some DX --must be a contest coming up this weekend.

Just when you thought you escaped commentary on the Coronavirus, a friend sent me this calling it "The Redneck  Coronavirus Cure"

Spray in mouth liberally and often.

Might  not help, but at least you won't care!

Pete N6QW

New Technology for 2020 ~ Improvise, Adapt and Overcome

What to do during the Pandemic? This is a chance to get back on the air or to take up an interest in homebrewing your own rig. You can bui...