LNA

Idea Ismo recently shared the https://github.com/CoolNamesAllTaken/adsbee project, which is very interesting. Challenges The ADS-B (Automatic Dependent Surveillance-Broadcast) system uses a data rate of 1 Mbit/s (1 megabit per second) for aircraft position and identification transmissions on 1090 MHz. Unfortunately, this is too fast for HOPERF CMT2300A and related transceiver chips. This led us to consider the following VFM ADS-B RX chain. Architecture Here is a simple ADS-B receiver chain. Antenna (a simple dipole / ground-plane antenna / PCB antenna) ➔ Zeenko LNA ➔ ADS-B Bandpass SAW Filter ➔ 100 pF (DC block) ➔ (Optional digitally controlled RF attenuator for AGC loop) ➔ Fast Schottky detector diode (BAT68 SOT-23) ➔ RC filter (10 kΩ, 10-33 pF) ➔ MCP6567 SOIC-8 comparator with output pull-up ➔ MCU GPIO (RP2350 PIO controlled). ...

Related articles: Proper Single Transistor LNA for HF A Sustainable Radio Design? Design We are finally going to build a QSD RX! Here is the rough schematic I am thinking about: References MC1496 Information HSDAOH on RP2350 (see internal_adc section) This way we can continue using RP2350 instead of moving to something like STM32H5 immediately PicoRX Simulations (also for DSP code)

Note: This HF LNA design is inspired by PY2OHH designs and mcHF work. Previous article: Single Transistor LNA for HF - it cut a corner when it came to output impedance matching ;) Design The idea that a single-transistor preamp with 10 dB gain is more than enough for HF comes from Gajendra Kumar (VU2BGS). As a new "designer," I am often overwhelmed by the available design paths, so guidance from an elmer is crucial. ...

Instead of punching islands or using commercial pads (islands) or making traditional pads myself, I simply make use of small pieces of single-sided PCBs to create the pads / islands easily for my boards. The Technique This technique has a huge advantage over the punched islands or scored and divided boards techniques as it keeps the bottom ground plane perfectly 100% intact! Also, it is almost a tool-free process to create the pads by breaking or cutting the single-sided PCBs. Single-sided prototyping boards also happen to be very reasonably priced. ...

Circuit: DDX-Commercial-7 Antenna: Small jumper cable attached Initial Results 10m: 36 dB on WSJT-X audio meter, on quiet and also with nearby beacon on !!! 12m: 36 dB on audio meter, on quiet and also with nearby beacon on !!! 15m: 46 dB on audio meter on quiet, 65 dB with nearby beacon on - OK 20m: 44 dB on quiet, 65 dB with beacon on - OK 40m: 40 dB on quiet, 60 dB with beacon on - OK ...

Note: This HF LNA design is inspired by Charlie Morris ZL2CTM's prior work. Design The idea that a single-transistor preamp with 10 dB gain is more than enough for HF comes from Gajendra Kumar (VU2BGS). As a new "designer," I am often overwhelmed by the different possible design paths, so guidance from an elmer is crucial. It seems even MMBT2222A should work for building a HF LNA! ...