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RE: Software Defined Radio (SDR) Experiment Board

Fruitpunch12 — Tue, 16 Dec 2025 01:39:04 GMT

Hi Shabaz, thank you for the schematic since I am new to RF and hobby radio I have a few questions about the schematic design. First I see you used a 7805 voltage regulator for the power source, can I make my own voltage regulator with power mosfets to preform the same function? I also see you said you used a sd5400 which is quad n channel fet array. I also wanted to ask if I can use something like 4 RFP30N06LE's in parallel. I read that I could replace the dual channel op amp for something else so I might try a design with an NE5532 or TDA2822 in kicad.

I'm just using your schematics as a template for a quadrature demodulator and wanted to know if some of these changes make sense with what your original plan with this project was since I am new to RF circuits as a whole. I plan on using this design for a SDR based transceiver using a teensy 4.1 micro controller for the ADC conversion and I/Q signal processing since I've seen some projects already using it for an SDR set up. Just wanted to ask some of those questions.

RE: Software Defined Radio (SDR) Experiment Board

Jan Cumps — Sun, 03 Dec 2023 12:44:56 GMT

SDR trolling is a thing now:

Source: https://youtu.be/h-fKtt7nRSg?si=UprlB7hwqozUFfD3

RE: Software Defined Radio (SDR) Experiment Board

Observer — Wed, 08 Jun 2022 17:55:15 GMT

I am a QSD fanatic !

From where I can buy the board?

Also, can the 7474 be configured as a simple squarewave driver to the mixer ?

RE: FPGA: a quadrature oscillator with rotary encoder control

dougw — Fri, 22 Oct 2021 14:19:56 GMT

Would a PSoC 4 have enough programmable fabric and speed to implement this function?

RE: FPGA: a quadrature oscillator with rotary encoder control

Jan Cumps — Thu, 21 Oct 2021 22:19:52 GMT

It works on the Zynq too, but strange enough,

only if I place the 3 individual blocks on the block diagram, and combine them there.

If I put the wrapped design on the block diagram, it doesn't work.

I'll retry from fresh tomorrow.

This is how it looks like now (+ action video):

[View:/resized-image/__size/620x244/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0475cec6-bcd1-411e-8318-0674368ec63d/5224.contentimage_5F00_216673.png:620:244]

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=6278227959001:740:466]

edit: it works with the wrapper too. I made a typo and had assigned the reset of the quad generator to a rotary encoder pin.

fixed and all ok now:

[View:/resized-image/__size/609x485/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0475cec6-bcd1-411e-8318-0674368ec63d/0456.contentimage_5F00_216675.png:609:485]

RE: FPGA: a quadrature oscillator with rotary encoder control

Jan Cumps — Thu, 21 Oct 2021 20:30:42 GMT

I'm trying if the exact same design runs on the Zynq.

[View:/resized-image/__size/620x229/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0475cec6-bcd1-411e-8318-0674368ec63d/8688.contentimage_5F00_216672.png:620:229]

VHDL is unchanged. The clock and nReset come from the ARM µcontrollers this time

RE: FPGA: a quadrature oscillator with rotary encoder control

shabaz — Thu, 21 Oct 2021 18:38:58 GMT

Hi Jan,

This is great, fantastic work, I'm looking forward to trying it. I'm also going to print out the VHDL and try to follow it and learn..

I attempted a slightly similar idea and barely got the encoder functioning enough to control an output, but I was concerned I didn't know what the VHDL was creating in some places, and aborted until I understood it some more, so looking at your VHDL will help loads.

RE: FPGA: a quadrature oscillator with rotary encoder control

Jan Cumps — Thu, 21 Oct 2021 18:29:33 GMT

It works

[View:/resized-image/__size/620x388/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0475cec6-bcd1-411e-8318-0674368ec63d/0211.contentimage_5F00_216667.png:620:388]

I had 1 error: the nReset pin was not in my constraint file. So it was always 0 and the circuit constantly in reset.

I changed the constraint file (also moved the clk_out to a PMOD pin named clock)

[embed:dc8ab71f-3b98-42d9-b0f6-e21e02a0f8e2:3ef06e6b-9b7d-4651-b12d-db8be7f5e991:type=text&text=net+nReset_in+++++++++++++++++++loc%3Dk15%3B%0Anet+clk_out+++++++++++++++++++++loc%3Dt7%3B]

and the image with the pins in the post above.

[View:/resized-image/__size/286x96/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-0475cec6-bcd1-411e-8318-0674368ec63d/4024.contentimage_5F00_216668.png:286:96]

RE: FPGA: a quadrature oscillator with rotary encoder control

DAB — Wed, 20 Oct 2021 20:12:30 GMT

Nice post Jan.

DAB

RE: Software Defined Radio (SDR) Experiment Board

Jan Cumps — Sun, 17 Oct 2021 20:23:25 GMT

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=6277585064001:740:466]

Note to self: FPGA design quadrature_oscillator_advanced

bypass quad generator, get clock at PMODB[0]

Clocks.fclk0_mhz = 100

oscillator_register.write(0x0, 18)

RE: Software Defined Radio (SDR) Experiment Board

rsjawale24 — Sun, 17 Oct 2021 07:09:31 GMT

This is an interesting project. This got me thinking. How to make a SDR that can send data to PC using USB so that it can be used with GNU radio? I have no knowledge about drivers so that the custom SDR could be detected by GNU radio

RE: Software Defined Radio (SDR) Experiment Board

shabaz — Sun, 17 Oct 2021 02:12:56 GMT

This took quite a few evenings! a lot longer than expected, but finally I have a functioning frequency synth, it uses an off-the-shelf Si5351A board, and a Pi Pico, plus rotary encoder and display.

Now the dilemma, should this synthesizer be a separate PCB, or should the SDR Experiment Board be modified and physically extended (say twice the size, I want to space things out).

Here it is receiving a French radio station (I still need to change the code so that the displayed frequency is 1/4 of the generated signal, and compensate for offset set in the PC SDR software).

Keeping with the experimenter theme, this is using Python on the Pi Pico so that code can be easily modified, and the ready-made Si5351A board means no tiny parts to solder.

The Si5351a board in the photo is an Adafruit model, but lower-cost boards from China are compatible too (I tried it). That's important, because the Si5351A chip is becoming hard to find due to the semiconductor shortages, whereas the China version is using a different chip (which happens to be compatible) which hopefully remains available.

[View:/resized-image/__size/883x552/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-3d95cdde-5ebc-4fdd-803b-cb3caeff70ed/2146.contentimage_5F00_216647.jpg:883:552]

[View:/resized-image/__size/656x412/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-3d95cdde-5ebc-4fdd-803b-cb3caeff70ed/0083.contentimage_5F00_216648.jpg:656:412]

RE: Software Defined Radio (SDR) Experiment Board

Jan Cumps — Fri, 01 Oct 2021 18:08:16 GMT

Radio China International

7.35292 MHz, AM, 8 KHz bandwidth, 12.9K as midpoint, Youssef filter because [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-3d95cdde-5ebc-4fdd-803b-cb3caeff70ed/4075.contentimage_5F00_1.png:16:16]

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=6275113863001:740:466]

RE: Software Defined Radio (SDR) Experiment Board

Jan Cumps — Fri, 01 Oct 2021 13:12:03 GMT

I've temporary replaced the local oscillator by this FPGA design. It allows me to scan the frequency range automatically.

[View:https://players.brightcove.net/1362235890001/NkxiVJdjx_default/index.html?videoId=6275072946001:740:466]

[View:/resized-image/__size/620x301/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-3d95cdde-5ebc-4fdd-803b-cb3caeff70ed/0456.contentimage_5F00_216553.png:620:301]

RE: Software Defined Radio (SDR) Experiment Board

Jan Cumps — Thu, 30 Sep 2021 19:36:42 GMT

Nothing yet, but searching ...

[View:https://www.youtube.com/watch?v=s6ebdXs1rvA:1110:699]

The circuit definitely works.