WORK IN PROGRESS
The hardware is made up of
- a QRP Labs SDR receiver module, covering 1-30MHz. Synthesiser input @ x4 frequency, output Audio IQ to
- a Teensy and Audio Adapter, and connected display, encoder, PTT switch, band & sideband buttons, SWR bridge inputs
- a home grown RF & AF IQ mixer, a set of BPFs, a QRP Labs 10W PA and a set of LPF, covering 5 bands 80-40-30-20-15. This will be the most difficult part of the project, why doesn't someone make a module for this?
Controlling the SDR are
- a PTT DPDT switch or relay (5V for RX & PA, 3.3V for Teensy PTT)
- a Band select button
- a USB/LSB sideband button
- a rotary encoder for Tuning
- a frequency tuning step button (on encoder)
with an 2.8" or 3.5" TFT colour display (ILI9341 or ILI9488)
One thing that has not, yet, been thought about is CAT control of the transceiver. If I do it I will chose the more simple Kenwood ASCII command approach.
Dream layout KISS
Starting to gather the parts
In both chains there are two Hilbert audio BPF with +45 and -45 deg phase shifts, and two Biquad filters of 300-2.3kHz to sharpen up the overall filtering. Choice of sideband is made by software swapping Hilbert +45 and -45 in the chains. I hope to use 96kHz audio BW, may have to modify the RX. How do I get the audio adapter SGTL5000 to run at 96kHz rather than 44.1kHz???
PTT will switch the audio configurations above, and also chose the input/output configuration. On TX MIC & LINEOUT, on RX LINEIN & HP OUT. Sideband switch will swap the Taps +/-45 of the FIR filters. The frequency is handled by an interrupt routine from the rotary encoder, and the frequency step is a button input, as is the band/start frequency.
These audio components and pathways are defined using the new Open Audio F32 library (a 32 bit floating point audio library for the Teensy). An S meter will show the rms signals and if am clever the peak also, and an FFT will display a spectrum and water fall over a range +/-48kHz of the centre frequency.
This is my first proposal, fairly simple with the functions currently being written to handle each part shown. I plan to use a low cost ILI9341 2.8" or 3.5" screen.