Zero effort 2.4GHz CW beacon with switchable frequency - Page 1
Forum section: electronics / rf-microwave

author: RoGeorge
author_rank: Super Contributor
timestamp: January 31, 2024, 02:19:58 am
content: Have you ever needed a constant carrier signal in the 2.4GHz band? Well, if you happen to have a wireless mouse, chances are the mouse has a test mode in which it emits a continuous carrier (for EMI tests and such).To enter the test mode, turn on the power switch while keeping pressed all 3 main buttons, left+middle/wheel+right. For the one I have, it is enough to keep pressed the left button and the wheel while turning on the power switch. No USB receiver and no pairing is required for test mode.Once in test mode, at each new click the CW will jump to another frequency. Mine cycles with R-click between 2405, 2448 and 2472 MHz.Different models might use other frequencies, and other buttons, e.g. for Telink TLSR8510/TLSR8513 datasheet, p22 of 35:http://wiki.telink-semi.cn/doc/ds/DS_TLSR8510%26TLSR8513-E_Datasheet%20for%20Telink%20TLSR8510%26TLSR8513.pdfto enter test mode:QuoteTurn the power switch off then on again to return the mouse to its normal working mode.Attached, the 3 spectral lines memorized in red after cycling through each CW test frequency. Live averaged spectrum in green. Captured with a PlutoSDR usingSATSAGENsoftware.

author: ataradov
author_rank: Super Contributor
timestamp: January 31, 2024, 02:28:49 am
content: A few of our customers used a similar "hack" to get a tunable 2.4 GHz CW generator. Atmel ZigBee radio ICs have a CW test mode, so they just used those ICs as a tunable PLL. And those ICs were cheaper than standalone PLLs and had better performance in most cases.

author: RoGeorge
author_rank: Super Contributor
timestamp: January 31, 2024, 03:13:15 am
content: Also nRF24L01+ (which is dirt cheap) has a CW mode, with programmable CW frequency and amplitude. Used that a couple of times, mostly as a quick sanity check for SDR + Rx antenna + cable integrity. Though, it will take some time to wire, to power and to program a chip.The funny part about the wireless mouse is that it's already sitting on the workbench, and it only takes two seconds to put it in CW mode.

author: Seint
author_rank: Newbie
timestamp: February 19, 2024, 10:41:32 pm
content: Quote from: RoGeorge on January 31, 2024, 03:13:15 amHi,I need a cheap tuneable 2.4-2.5GHz CW generator, can you help with building one? I can pay for the project, please let me know if we can work on it.I'm an RF engineer but have almost zero software knowledge.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 20, 2024, 12:28:49 am
content: There are ready made modules with nRF24L01+ and a PCB antenna. Some modules also have an UFL connector, for an external antenna if needed. Note that there are some nRF24L01 (without the + at the end). I've tested the CW mode only on the nRF24L01+).Then, you'll need a microcontroller to talk with the nRF chip. Most common and cheapest would be an Arduino Nano board. Can be bought ready made from any maker's shop, ebay, etc. Probably they are at mouser or Digikey, too, but I never searched.Both modules come with 0.1'' pins. Wire them together with some DuPont wires, or solder them on a test board, and that's it.For the software part, the CW mode for the nRF chip is documented in its manual, so there are plenty of ready made Arduino examples to put the nRF24L01+ in CW mode. Connect the Arduino to a PC, download the demo, and it should work. For a ready made program, search for 'nRF24L01 continuous carrier Arduino'. Random example:https://forum.arduino.cc/t/nrf24l01-arduino-trying-to-get-constant-carrier-wave-output-for-testing/322112/13In case you never used an Arduino before, there are step by step instructions online, either written or on youtube. The idea is to download the Arduino IDEhttps://www.arduino.cc/en/softwareplug the USB cable, then follow the instructions found online for how to download a "sketch". Arduino calls programs "sketches", though the Arduino "sketches" are plain C/C++.Since the examples for putting the nRF chip in CW mode are anly a few lines and already written by others, no software knowledge is required. Copy paste an online example into the Arduino IDE, set the proper Arduino model and COM port, then upload the sketch into the Arduino Nano board. The IDE will also compile the C/C++ code before uploading the binary.You can ask here, or in the programming section in case the online tutorials are not clear, or if it doesn't work.Good luck with the project.