Thursday 17 August 2017

Design Goals

Thanks for all the feedback. In an effort to keep the cost down where we can, here is a list of the features we'll look to design into the radio:

  • 80m, 40m and 20m pre-selector BPFs
  • 2N3904 based RF receive amp with manual attenuation
  • 2N3904 based IF amps (not bilateral at this stage)
  • Diode low power signal switching (no relays)
  • Junkbox Yaesu XF-92A 9000kHz SSB crystal filter
  • J310 or some other discrete component based mixers. Otherwise homebrew DBMs
  • Teensy (any version should work, I'll use a 3.1 as I have one in the junkbox)
    • FFT spectrum display
    • Software LPFs: CW-N (200Hz), CW-W (700Hz) and perhaps a notch
    • 2.8kHz LPF for the mic audio
    • Compression on the mic audio if we can 
    • 700Hz sinewave for CW modulation
    • Software based audio AGC
    • Drive external analogue S meter
    • Memory channels
    • VFO and Memory scan
  • Si5351 for VFO and BFO. Teensy controlled
  • 0.96" OLED
  • 2N3906 PA pre-driver
  • IRF520 or IRF510 PA (will start with cheaper 520 first)
  • 80m, 40m and 20m LPFs (probably wafer switch selected)

Again, I am not an expert in homebrew, so I'll just do what has worked for me in the past. Hopefully, we can make it an interactive process where we all learn.

I'll be away for a couple of weeks. Once I'm back, we'll start with a basic Teensy setup to drive the screen, rotary encoder and Si5351. It'll have basis audio pass through for initial test. That will then form the basis for the rest of the radio.

Until then.

Charlie, ZL2CTM  

Saturday 12 August 2017

New Radio Project.

Hi. This is a new blog, and am just testing it. Below is a picture of the Teensy driving the OLED screen and the Si5351. On the screen is a FFT spectrum showing 0-22kHz. More to come!