Beacon

My new favorite HF antenna is the 1/4 Wave HF Vertical DX Antenna with 2 Elevated Radials. It is NOT the most portable antenna (an EFHW wins there) but it is the easiest HF antenna to construct! It is easier to construct, install, and tune than even the basic dipole antenna! It takes less than 15 minutes to build and get on the air with this HF DX antenna! No impedance transformer is required. After trimming, the antenna can directly feed 50 Ω coax. A 1:1 common-mode choke (coax choke works too) at the feedpoint is recommended but NOT absolutely required at low power levels. ...

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 ...

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. ...

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. ...

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: ...

Description We have built a Bluetooth-enabled and APRSdroid-compatible digital interface (KISS TNC) for less than 15 USD (for the fully-loaded make including cables). We call it the KISSLink v1. This digital interface can be powered from the USB 5V or the inbuilt battery. Schematic Previous Next     / [pdf] View the PDF file here. RX path simulation (AF front-end) ...

Setup: Si5351 RF generator (@ 28 MHz) ➔ GSD-Hacks-v5 digital amplifier ➔ 7th order LPF ➔ {COAX-UNDER-TEST} ➔ Digital RF power meter ➔ Dummy load Results Results at 13.8V drain: Coax Type Power Reading RG-58 (7 meters) 4.5W RG-316 (7 meters) 3.9W RG-188 (7 meters) 3.9W Results at 15V drain: Coax Type Power Reading RG-58 (7 meters) 5.4W RG-316 (7 meters) 4.7W RG-188 (7 meters) 4.7W These measurements appear to match those from Eric, WD8RIF. ...

My solar powered WSPR beacon is now active on the 12m band! Tech Stack Tech stack: Navitas 100W Solar Panel, Exide Solar Blitz 40AH battery, Skypearll Solar Charge Controller 30A, 200W 20A DC-DC CC CV Buck module (Robu) - set to output 7.5V, Waveshare ESP32-S3 Zero board, Si5351 with 0.5ppm TCXO, GSD-Hacks-v5 amplifier, DFRobot Gravity Digital 5A Relay Module Photos of components involved (for reference): ...

For HF and amateur VHF bands our WiFi VFO works great. But we didn't have a cost-effective UHF signal source until now… Design Thanks to Ismo (OH2FTG), we recently experimented with a HopeRF CMT2119A powered board called HOPERF RF module RFM119W-433S1. Here is the CMT2119A powered board in action producing a CW (OOK) signal at ~433 MHz. The stability is pretty good and a bit surprising considering that the board uses a 20ppm 26 MHz regular quartz crystal - not bad! ...