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