Related articles: Proper Single Transistor LNA for HF A Sustainable Radio Design? We are finally going to build a QSD RX! Here is the rough schematic I am thinking about: References: https://www.n6qw.com/MC1496.html https://github.com/steve-m/hsdaoh-rp2350 (see internal_adc section) This way we can continue using RP2350 instead of moving to something like STM32H5 immediately https://github.com/dawsonjon/PicoRX/tree/master/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 ;) 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 having guidance from an elmer becomes crucial. ...
Future radio receiver design ideas (from Ismo, Pete and other folks): Antenna ➔ (BPF) ➔ BFR93A based pre-amp from mcHF project ➔ MC1496 (Mixer) ➔ 455 kHz IF ➔ Ceramic filter SMD (HCI) ➔ 'IF amplifier' (20-40 dB gain?) ➔ Overclocked Pico 2's ADC (3+ MSPS) ➔ Digital down-conversion and processing in digital domain ➔ Expose the processed audio samples over USB (Pico 2 acts as a sound card). Benefits: This enables reception of SSB and CW signals! The 455 kHz IF with digital processing gives us the best of both analog selectivity (ceramic filter) and digital flexibility. ...
For HF and amateur VHF bands our WiFi VFO works great. But we didn't have a cost-effective UHF signal source until now… 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! ...
Shipping hardware internationally is a hard, labor intensive, and overall a frustrating process - especially more so these days. Here is our plan to supply the DDX to customers: Make the hardware files free / low-cost. The users will be able to order fully assembled boards from JLCPCB or other vendors on their own. Required a small licensing fee for the software firmware part. This is how we get to keep the hobby self-sustaining! ...
Circuit: DDX-Commercial-7 Antenna: Small jumper cable attached 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. 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 having guidance from an elmer becomes crucial. It seems even MMBT2222A should work for building a HF LNA! ...
We make heavy use of https://github.com/kholia/Easy-Digital-Beacons-v1 for testing RF amplifiers. This single board is a versatile WiFi VFO and FT8 / FT4 / WSPR beacon. You can also use our CW-SigGen project to generate a suitable test signal.
My homebrewed PA0FRI Active Antenna is working well from a very physically constrained location. 3D render: Schematic: Results: The antenna is connected to a RSP1 Clone SDR which is running custom FT8-band-hopping software. I am using a SOLID 4-Way 5-2400 MHz RF splitter to connect multiple SDRs to the same active antenna. NB: Plug in 75-ohms dummy loads (terminators) on the unused ports of the RF splitter - MX-282 / MX-280 75-ohms dummy loads work fine. ...
Sometimes we all need a bit of QRO - Life's too short for QRP sometimes. So we give you the Baby-QRO switching amplifier! This Baby-QRO switching RF amplifier design is inspired by the wonderful Single NXP MRF-101 Eval Board project by Jim Veatch. Thank you Jim! Instead of using the expensive MRF101 MOSFET, we use fast SiC MOSFET(s) from Wolfspeed / SUPSiC. 3D render: Actual picture: ...