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This is an early design sketch of VHF (2m - 145 MHz) APRS beacons that are small and can be placed in vehicles like ambulances or fire trucks. Key Points Si5351 module powered by the usual 25 or 26 MHz 0.5 ppm TCXO. Si5351 generates 145 MHz Two-Tone APRS RF output directly! Using an Si5351 for APRS (Automatic Packet Reporting System) transmission via FSK (Frequency Shift Keying) allows us to generate highly accurate AX.25 packets directly at the RF frequency (e.g., 144.390 MHz), eliminating the need for a separate modulator and VCO.Since APRS typically uses AFSK (Audio Frequency Shift Keying) fed into an FM transmitter, generating FSK with an Si5351 means directly shifting the carrier frequency or the VFO instead of modulating an audio tone. ...

This is an early design sketch of a UHF (70cm - 440 MHz) WSPR beacon. This design comes from Ismo (OH2FTG). Key Points 10 MHz OCXO TCXO powering the Si5351 module instead of the usual 25 or 26 MHz 0.5 ppm TCXO. Si5351 generates 217 MHz output, which we double to ~434Mhz using the https://techlib.com/files/diodedbl.pdf technique. Use 440 MHz SAW filter at the output (from LCSC) ONSEMI MMBD701LT1G RF Schottky diodes - locally available ...

I learned about the Sub-1€ TRX challenge from Ismo (OH2FTG) - thank you (maybe for getting me addicted?). The constraints Sub-1€ TRX, with LCSC parts. This excludes the PCB, so it can be 10x10 2-layer or 5x5 4-layer. My Design WIRELESS WL4456 (TX) and WIRELESS WL550 (RX) pair - 17 cents T/R switch: TECH PUBLIC TPAS169-73LF - 16 cents 13.56 MHz crystals (HY13560M49SBSMDOB1R30 / 8DSC135G0012L) - 5 cents * 2 MCU: PY32F002AL15S6TU SOP-8 from Puya - ~11 cents ...

The constraints 5V (~500mA) power from mobile phone 1W RF output required Very compact with less "moving" parts 14 MHz capable The design We use INNOTION YG401530VB MMIC in this design. 100n Si5351 CLK 0 --||----+---------+ | MMIC | | IN | | | | OUT +----||---- RF OUT ---- LPF ---- 50R dummy load +----+----+ 100nF | 10uH RFC | |---100n---GND | +5V Note: No explicit 'special' matching required it seems ;) This seems to be an extremely broadband circuit which should cover all HF! Results 10 dBm from Si5351 and 13.8 dB gain of the INNOTION MMIC gives ~9.8Vpp output theoretically. ...

Disclaimer: This post reflects my personal experience with a merchant operating on Shopify. It is not an allegation that Shopify intentionally supports fraudulent merchants. Rather, it is a critique of the incentives and customer experience I encountered. Recently I purchased from a merchant running on Shopify. The store looked legitimate, accepted payment without issue, and presented itself professionally. Unfortunately, that was where the positive experience ended. The merchant failed to deliver what was promised. Attempts to resolve the matter directly went nowhere, so I tried contacting Shopify expecting that a platform of its scale would at least investigate. ...

The constraints 5V (~500mA) power from phone 1W RF output required Very compact with less "moving" parts 14 MHz capable The design We purposefully utilize "high Rds" EPC GaN parts with very low Qgs. Simulation Results Power consumption: Around 300mA @ 5V. pout: AVG(v(out)*i(r3))=1.0606 FROM 5e-05 TO 0.0001 pin: AVG(-5*i(v3))=1.38209 FROM 5e-05 TO 0.0001 isupply: AVG(-i(v3))=0.276418 FROM 5e-05 TO 0.0001 eff: pout/pin*100=76.7393 Cost Cost: < 500 INR. ...

The old hack Sometime around 2015-2016, I had to connect two rooms that were separated by a balcony. The simple answer was obvious: run an Ethernet cable through the balcony and plug it into the router on the other side. It worked. It was cheap, fast enough, and did not need any special equipment. For a while, it felt like the sort of practical fix that makes home networking fun. ...

Related work Baby QRO Switching RF amplifier for HF Digitally Adjustable RF PA Supply A new generation of the Baby-QRO switching amplifier targets 25W to 50W of RF output for FT8 and other FSK modes. While it can do 100W, it becomes more of a thermal engineering project then ;) It is designed to operate with a Bare DDX-Commercial transceiver board and has an inbuilt T/R switch. Design 3D render: ...

Related work Baby QRO Switching RF amplifier for HF A new generation of the Baby-QRO switching amplifier targets 25W to 50W of RF output for FT8 and other FSK modes. Goal The Baby-QRO amplifier already has a very useful RF power control knob: the PA drain voltage. A bench supply works for experiments, but it is not the right answer for a digital beacon or transmitter stack. We want the MCU controller to set the PA voltage, and therefore the RF output power, in software. ...

Photographers often say: The best camera is the one you have with you. DDX-UNO ("Digital Pixie") applies the same philosophy to amateur radio. The best HF transceiver isn't necessarily the most powerful one. It's the one you remembered to bring. Most HF stations remain at home. Portable radios often require batteries, coax cables, antenna tuners, protective cases, and a backpack full of accessories. The result is that many operators leave their radios behind. ...