More SDR Modules.

This is the second installment of the Minimalist SDR Homebrew Transceiver project. Today's "gulp from the firehose" will cover the block diagram and the USB Sound Card. To keep things from going off the rails we will be using the I and Q approach as this topology can be built Manhattan Style and needs no PCB.

Quickie review: The Analog off the air signal is down converted into two audio baseband signal streams 90 Degrees out of phase using two ADE-1 Double Balanced Mixers. The ADE-1 choice versus the commonly seen Tayloe Encoder/Decoder is to keep things minimalist. 

The ADE-1 is inherently bidirectional and the Tayloe circuit is not. Plain English, the ADE-1 can be used on receive as well as transmit. This duplicity extends to the Signal Splitter, the Band Pass Filter and the USB Sound Card. This greatly reduces the parts count and the opportunity for errors.

We will start with the I and Q outputs (I = In Phase and Q = Quadrature) from the two Direct Conversion stages which are fed to this jewel, a USB Digital Sound Card. 

Optimal Shop USB Sound Card

The "Line In" Stereo Jack is used on Receive and the I and Q Signals are fed to this jack. On Transmit the "Front Out" jack feeds the I and Q transmitted signal stream back through the ADE-1's to the Splitter which now acts as a signal Combiner and on to the Band Pass Filter. Keeping the wiring straight to these two Jacks is the Achillies heel of the project. 

The first issue stumbled upon by me was that I had QUISK set up for LSB on receive but found it transmitted on USB because of sideband inversion. My solution was to include a DPDT relay to switch the I and Q channels on transmit and problem solved. Actually, if I had invoked the RTFM process there is built into QUISK a button selection to reverse the transmitted sideband and no relay needed.

The current price of the Optimal Shop sound card is about $18 and the last one I bought was $15 -- thank you what's his name for creating a tariff war. Plain truth no US Manufacturer can supply this same unit for $15. 

Now for the "bummer part" for those who must find an excuse for not undertaking a new adventure. There is no overall schematic but instead as my usual practice where required I will supply detailed schematics of modules that are home built. The USB Sound Card is simply a plug in with the Line IN/OUT cables and a USB cable connection to the RPi5. In the QUISK software on the Sound Card selection this is identified as "CM106 Like Sound Card".

The following block diagram was developed over 5 years ago and will be updated with new block titles such as the Pi Pico in lieu of the Arduino Nano and is controlled by the RPi5 and not acting independent as shown in the diagram. 

Some other changes as 5 years ago I was not able to directly create two LO's 90 Degrees apart. The trick back then was to create an LO at 4X and then running that through a D Type Flip Flop you create two quadrature (90 Degrees Out of Phase) at 1X. The Pi Pico can do that directly at 1X. This eliminates circuitry!

Right now, in the Junk Box I have a RADIG V.3 board that will act as a test bed for this project. On that board is the Bi-Directional amp stage using two J310's (that will be changed to a BFR106), the Band Pass Filter, the Splitter, the two ADE-1's, Two Modem Transformers, the sideband switching relay and the 74AC74 D Type Flip Flop.

The D Type Flip Flop has been disabled, and I built a 1X quadrature LO using a Seed Xiao RP2040 and Si5351. This is now working on 40 Meters with the Optimal Shop USB Sound Card, the RPi5 and a USB Headset/Mic. It receives as well as transmits.

Transmit Tests ~ Needs Some Work

Haywire But Works!

I cannot overstress the importance of using this testbed as we develop the project. Right now, we have a working Transceiver albeit with some warts. With this as a starting point we can substitute modules that represent the final configuration. 

On Tune I see about 120MV PTP at the output of the J310's. This is an important data point as the BFR106 must meet or exceed that level. The J310's have some charm as its gain level is adjustable whereas the proposed BFR106 has a lot less components and a pot in the emitter leg can offer gain adjustment (I have done that on another BFR106). 

BTW at 120mv output that is 36 microwatts of power. This begs building an extra stage in the RF Chain -- more data. For those with an innate curiosity, why the 600:600 Ohm Modem Transformers. Tribal knowledge has shown that a Direct Conversion DBM can be subject to noise pickup. The Modem Transformers provide a degree of noise isolation.

Them that know can make it go. 

Just a temperature check --- everyone happy with the grocery prices? What I pay for groceries now, just for me, used to feed two people. There are no steaks or booze in those purchases. Something is terribly wrong, and I guess when you are a billionaire the price of eggs is pocket change. Toilet paper is getting there too. Maybe that is behind the push for the 51st state -- lots of trees to make cheap toilet paper.

73's

Pete N6QW

Gathering the Building Blocks -- You can build a Homebrew SDR (even Manhattan Style)

As the smoke clears with all the administrivia of the past month finally reaching an end state, I am looking to build another SDR SSB Transceiver. Only this time using a minimalist approach, and thus, the blog now becomes my documentation of progress (and failures). As I was lucky enough to build a 7 transistor SSB transceiver I proceed with great hope, and a bit of caution, to create something as simple only using SDR techniques.

So, this posting is maybe a "heads up" for those who are uninterested in such a project and now is a good time to seek out other blogs.

My process will be no different than what I regularly use and that is a modular approach. As a starter do not get your underwear in a twisted knot -- this project relies on integrated circuits, surface mount components, Arduino code, USB sound cards, a Raspberry Pi Pico and Raspberry Pi 5 SBC. Last but not least the venerable Si5351.

For those already feeling queasy at the mention of Surface Mount Devices (like ADE-1's) you have a solution as Todd, K7TFC sells mounted ADE-1's that can be integrated into Manhattan style construction.

In a nutshell, the topology will use the Raspberry Pi5 as the computer to house the software (QUISK) with the Pi Pico handling the interface to the SDR hardware, frequency generation ala Si5351 and T/R control of the main board. 

The mainboard contains two DCR's (ADE-1's), two Modem transformers, a splitter to create two RF streams on receive and one composite signal on transmit, a couple of relays, Band Pass Filter and steerable amp (BFR106). A mounted BFR106 also available from K7TFC, serves as the Rx receive amp and Tx pre-driver.

Following this lash up we need a Transmit Driver Stage and a Final RF Amp (RD16HHF1). A USB sound card (Optimal Shop now with tariffs ~ $2o) and a headset/mic with inline USB sound dongle for the mic input and sound output.

The very 1st module to acquire and most expensive is to lay your hands on a Raspberry Pi5.

Raspberry Pi 5

You will also need the fan/heatsink combo, SD card and a 5.1V / 5Amp power supply. Figure $100 for all. But you are buying a fairly sophisticated computer that is 64 Bit and good enough for Netflix streaming. So, while not in use with the SDR it can be a shack computer.

Listing of Modules

R Pi5 with Fan/Heatsink and Power Supply

R Pi Pico with Si5351

USB Sound Card

USB Headset Microphone

Transmit Driver

Transmit Final (RD16HHF1)

Main Board~ADE-1's, Relays, 2 Xmfrs, etc

Linear Amplifier Switch Box

Misc: Monitor, keyboard and mouse, QUISK

Our next blog post (separate posts) will be a block diagram and more hardware acquisition details.

Time to bail if this seems boring to you. But today's conspiracy theory is that the price of eggs has to do with Bird Flu coming from you know that foreign place offshore. But that begs the question who are the largest egg suppliers to the USA and who is getting rich with a $15/dozen carton of eggs? 

Them that know can make it go.

73's

Pete N6QW

Homebrew SDR Stuff.

Just like one guy who watches the stock market as a measure of his popularity, I watch the number of blog hits. I guess there is a very direct correlation to both metrics as low numbers say you are not appealing to your base.

So today we are not talking about Passports or White Bean Chicken Chili. But the subject is homebrew SDR's and some information from You Tube. 

In review there are two current approaches (actually there are more than two) to SDR rigs but these two seem to be the ones most favored. One is a simpler hardware approach versus the other. The 1st is the I/Q approach where analog signals off the air are converted to two audio signals 90 degrees out of phase and then a simple stereo computer sound card becomes the gateway for the digital signal processing by a computer. Fabricating an I/Q SDR involves very little hardware like two ADE-1 DBM's arranged as two direct conversion receivers and a Si5351 + Arduino generating two quadrature signals. Beyond that is a Band Pass Filter an Audio Amplifier a couple of RF Amp stages and a Final Amp and an LPF. Last but not least is a $15 USB Sound card. The I/Q can actually be built using Manhattan Style construction.

With the advent of the credit card size 64 Bit single board computers -- you now have a very small SDR transceiver as reversing the signal paths makes this small bit of hardware into a full transceiver. This is all possible because of the readily available free software suites.

I did a small project about 5 years ago that shows how simple it is to fabricate a homebrew SDR Transceiver.

Meet the Pi Pico, a later SDR generation which is currently a Receiver but likely in a cold garage somewhere it is now transmitting.

Before leaving the I/Q world, a special mention of ZL2CTM, Charlie Morris, who took a Teensy 3.5 MCU and coupled that with a SGTL 5000 plug in Audio Codec board and fabricated an SDR radio that needs no external computer. I think there are about 10 You Tube Videos on his project -- I know it works as I built two of them.

The second now even more popular method is the Direct Digital Conversion (DDC) using more advanced electronics such as Field Programmable Gate Arrays (FPGA). 

There is not much info on this homebrew SDR, but I suspect it is DDC based. Wow!

Both methods work and give you SDR without spending a King's Ransom. But the DDC because you go from an on the air Analog Signal to a Digital Signal (via an ADC) that opens the door to far more extensive signal processing using very sophisticated software. Using Thetis (a top-drawer software suite) with its noise reduction algorithm turns mush into readable signals. You have to hear to believe it.

But building a DDC type SDR almost forces you to use a factory-made circuit board as the FPGA may have upwards of 100 connection points. That 80-watt Radio Shack going out of business soldering iron you bought is incompatible with soldering the FPGA onto a PCB.

That said I know of a half dozen very sophisticated software suites that operate with a DDC type SDR and only a couple with the I/Q type SDR's. It is the software part of SDR which enables extensive upgrades without touching a soldering iron.

Them that know can make it go.

Imagine Canada as a 51st state? Conspiracy theorists suggest such an annexation move is because Canada has a National Health System and then that becomes the vehicle to "let's rid ourselves of Obama Care". 

Annexing Panama may be to gain control of who can ship through the Panama Canal. Frederick De Lesseps the builder of the Suez Canal but who failed in building a sea level Panama Canal must be rolling over in his grave. Imagine using trade to control the world -- yet another conspiracy theory. Greenland is simple -- green is the color of money -- you know bring on the green stuff and it is not vegetables.

73's

Pete N6QW

What have we become?

That is a great question, as what have we indeed become? My life has taken a turn with the passing of my XYL of 57 years. The last several years, because of her illness, have been pretty much stay at home. But now I would like to travel a bit to see the kids or maybe visit places that are on my list.

No! The Collins Museum in Cedar Rapids is not on the list -- been there and done that. Another No is Dayton and FDIM which likewise been there and done that -- what a rip off! Newington is another NO -- saw the orb and have no other desire to do so again.

I used to like to drive but now even a 300-mile trip to San Francisco sounds like a short airplane trip and that is a problem come this May. To fly in May, you either need a passport or Real ID. This is where the fun begins. There is over a month's waiting list to get either a passport or Real ID. 

I managed to schedule a passport appointment in a month from now -- but the only available location is 100 miles away. Other locations only book a 4-week period, and they are full up. My passport expired in February 2025 -- so you have to start from square one. The USPS is the agent for passports and so you pay $130 for the passport and the USPS charges you $35 just to process the paperwork. If Elon gets his way and privatizes the Postal Service -- watch that fee go to $100. 

But the real kicker is the DMV who provides the Real ID. They make it sound so simple -- all you need is a birth certificate and two utility bills that have your name and address. The DMV process has you submit the three documents via email as a pre-approval and then and only then they schedule an appointment that is about 5 weeks from now.

Now my birth certificate has a middle name, that of my paternal grandfather's name. It is an Italian thing. I hate that middle name and never use it, but it is on my certificate. My utility bills only have my 1st and last name. My submission to the DMV has been rejected several times because my utility bills lack the middle name. Now in a weird stroke of luck my driver's license has the middle name and so does my marriage certificate and DD214. I am hoping to substitute these documents in lieu of the utility bills. But there may be a situation where I will not get a Real ID and so the passport is key and while 100 miles is a far piece for a 15-minute appointment it may be the only game in town.

What have we become where something as simple as filling out a form involves hours of emailing and driving 100 miles?

The only thing that has brought a smile on my face these last couple of days is a fantasy that the Tesla stock tanks which may cause the board to dump Teflon Elon, and he goes to work for the USPS in the passport office. 

Them that know can make it go.

73's

Pete N6QW

Got to have a picture or no one reads the blog!

The Need to Measure Things. When talking antennas -- OK to say Mine is bigger than Yours!

Back in the day when ham radio was a technical hobby and not all appliance operations, hams measured things! We measured voltage, current, resistance and those with a Nano VNA a crystal filter response curve. 

There were some industry standards like the analog Simpson Model 260 or a DVM from John Fluke up there in Mount Lake Terrace in WA state. But now we use the postal or shipper services in place of test instruments. Your ICOM IC7300 is acting up -- off it goes to WA state or the Yaesu FTdx10 is wonky -- off to Southern California.

But what if you were bold and daring enough to take the case off the IC7300 and check for voltages on a terminal block -- what would you use? A more fundamental question is why you would be so emboldened?

That last question has an easy answer -- you just got fired from your tenured government job (a DOGE initiative) yesterday your 401K went in the toilet, and you just paid $15 for a dozen of eggs. So, what else could possibly go wrong? Well, I didn't mention that your mistress is pregnant -- but hey Elon has 13 kids and openly encourages more babies. 

A tour through Lauren Sanchez's Boy Friend's emporium was most revealing. There is a whole array of low-cost test instruments with good ratings from several thousand customers and some are less than $20 and even some less than $10. The very large grouping in the median are units in the $30 to $50 range and then of course the John Fluke stuff in the >$200 range.

Less than $10 with about 900 reviews 4.4 out of 5

Next is an analog meter costing less than $25 with 800 ratings for an average of 4.4 out of 5. I have one analog meter and like it because it is not always updating the LCD. This also is good for measuring DC voltages up to 1000 VDC for working on those old boat anchors.

Less than $25!

Take a tour through Amazon and you too will be amazed at the low entry cost to get a pretty good meter.

Them that know can make it go.

73's

Pete N6QW

Whole Lot of Shaking Going On. Good Thing no Eggs were involved!

With a Tip of the Cap to Jerry Lee Lewis there was indeed a whole lot of shaking going on yesterday about 10 miles from my QTH when a 4.1 earthquake abruptly interrupted my lunch. 

It was not the rolling kind of quake but rather two sharp jolts lasting but a few seconds. Is the big one coming? I was having lunch with my daughter and both our phones lit up like Christmas trees. We knew it was close but not too close as the impact was not of a magnitude to knock stuff off the shelves.

Immediately a pop screen appeared on our phones telling us what to do. The first item caused me to chuckle a bit. Imagine the event was at 1AM not 1PM and you are asleep. For many going to sleep is sleeping au natural -- naked. So, the 1st item on the list is to put on shoes (not slippers, but shoes) as there may be broken glass and you need to get out of the house -- now. There you are out in the street with no clothes on, but you do have your shoes on! A funny sight to imagine.

Now to some cooking homebrew. This was on our interrupted lunch menu yesterday -- White Bean Chicken Chili (WBCC).

WBCC with Pepper Jack Cheese

Ingredients:

1 lb of boneless, skinless Chicken breast

1 Ten ounce can of Rotel

1 Fifteen ounce can of Tomato Sauce

1 Fifteen ounce can of White Beans

1 Packet of McCormick Chili Seasoning

1 Medium Onion chopped in small pieces

4 Cloves of Garlic sliced thin

1 teaspoon of sea salt

1/2 teaspoon of Cayenne Pepper

1 Packet of Pepper Jack Cheese sliced small

3 Tablespoons of Virgin Olive Oil

The process begins by cleaning the 1 lb. chicken breast by removing any fat or shrouds of thin membrane. Cut into large pieces and place in boiling water long enough so any "pink" color is removed from the interior.

Remove the chicken from the water and cut the large chunks into small cubes about 3/4 X 3/4 of an inch. Set aside. In a two-quart saucepan place the oil, chopped onions and garlic, cooking at medium heat until limp and add the cubed chicken. Cook for about three minutes stirring constantly. Add the remaining ingredients, stir thoroughly and simmer at low heat for about 2.5 hours.

The most important step is to cook the chili the day before, refrigerating the admixture and consuming the following day. It is like a fermentation process. The next day reheat at a low temperature until hot to the taste.

Serve in bowls with the pepperjack cheese atop. Added items include Marie Calendar corn bread and a glass of red wine. Bono!

Them that know can make it go. The WBCC is in the class of a HB SDR.

Hey MAGA-O-Lytes why do jumbo eggs cost $15 a dozen?

73's

Pete N6QW

Take a breather from the Washington Mess-- buy a new radio.

It has been nearly 30 years since I laid out a wad of cash for a new radio. At that time, it was for a Ten Tec OMNI VI Option 3 Plus. There was a great deliberation about that purchase! But we have some tools today to guide us through the process.

If you use Rob Sherwood's Receiver Test Data as a guide, the very top of the list is dominated by Yaesu. The FTdx101, the FTdx10 and the FT710 seem to have some really awesome specs. Costing more than a IC7300 several Yaesu radios enjoy a good market position. 

One piece of eye candy of the FTdx10 is the 3D spectrum display, and you can have this jewel for about $1500 from DX Engineering. With that small sum for a high-performance rig, it should be a piece of cake to bamboozle the XYL that it was low in cost and therefore a real bargain.

Elecraft has a couple of radios near the top grouping like the K3S and the KX3. So that is good to see. Noteworthy is that a KX3 (a QRP Radio) costs more than an ICOM IC7300.

 

The Hermes Lite 2 with an outboard amp will set you back about the same cost as the IC 7300. But with the Thetis software you have a radio to compete with the more costly offerings!

[Read the eHam review of the HL2 here.]

All of us need a break from the brash billionaire bosom buddies* and what better way than radio shopping. A data point for you. The Omni VI Option 3 Plus radio cost $2500 in 1998. The value of a 1998 dollar in 2025 is $1.96 and that $2500 today is $4900. So, for 1/3 the price you are getting one hell of a bargain for a FTdx10. The startling fact is that the Big Dawg, the FTdx101 can be had for $4300 -- still way less than the Ten Tec priced in 2025!

Them that know can make it go.  BTW all of the named radios in today's blog have the SDR topology. SDR is upon us and the performance is the witness that you need to get onboard or get left out. Who in the world feels good or proud that you are 40 Hz low?

Absent from this post was a suggestion to scratch build an SDR as sadly there are few homebrewers left these days and from that set an even smaller number who could pull off a homebrew SDR.

73's

Pete N6QW

* I did have three more "b's" in that string, but wisdom said "keepeth thy mouth shut" as all of us rightly are frightened that the government will get us! No one is safe or immune from those who presently control the levers of power. Anyone concerned that we no longer have the freedom to express an opinion.