Scanner TODO

Currently I use my UV5R as a scanner. I’ve got the local repeaters programmed in, and let it do its thing. It mostly works but has a few problems:

• I can’t easily modify the scan list. Especially with the rinky-dink antenna, there are times I can barely pick up a repeater, or am picking up just enough noise to open the squelch (70cm simplex, I’m looking at you). Or there’s someone that seems to be someone nearby that occasionally runs a bunch of DMR on GMRS.
• The scanning rate really isn’t very good.
• Various other UI nits with the radio, e.g. displaying name OR frequency, but not both

Honestly, being able to easily manage the scan list from the radio itself would probably solve most of my immediate complaints, but why let that stop me from having a dedicated scanner?

I’ve been watching ebay & craiglist and there are a few options, but they’re expensive enough that I’m annoyed at how they don’t quite fit what I think I want, so I’m planning to build my own. It looks like an rpi (even the ~$5 pi zero) + sdr dongle should be sufficient for this, so I can cobble together something relatively compact.

Thinking through my requirements:

• Program in a bunch of frequencies + friendly names.
  • I may want per-preset squelch settings?
  • Listening for CTCSS tones and not just squelch could be nice, but might be too much for the limited hardware?
  • Would be nice to bootstrap together stuff to keep this all in sync between radios. For the moment, at least, I just have the UV5R programmed with Chirp, so that shouldn’t be too bad.
• Toggle button for scanning or not
• Ability to manuall step up and down through presets when not scanning
• Stretch goal: ability to free-dial a frequency?
• Ability to toggle a channel on/off
  • It’s there when stepping through outside scan mode, toggle on/off from there
• Display with this info
  • I think generally I only care about the pretty name, but being able to see that and the frequency/acive state would be good. Maybe just flip or scroll between the two while actively receiving/not scanning?

A nice wood-grained box on my desk with big metal knobs would be nice, but so would a portable little unit to carry around the house. I’ll probably try building something large and hanging a decnet antenna off it first, and then see about a smaller unit that’s more like an HT.

Thinking through the hardware:

• RPi + SDR dongle + the random bits for power + antenna
• A speaker + volume control
  • And/or line out into some other audio system
• Some sort of display. Probably just one of my little OLEDs and paint text, but for character, many-segment VFDs would probably be neat. Function over form for now, though…
• A rotary encoder + knob for stepping through presets
  • Probably will initially be boring up/down buttons, though, since they’re easier
• A momentary SPST to enable/disable a preset
• A latching SPST to turn scanning on/off
  • This could also be momentary & handled in software, but a real toggle would be more satisfying
• An overall power switch? Turning volume all the way down might be good enough?
• Visual indication of RX. Could do it on the OLED, but could also do a blinky light

Neither the hardware nor software seem particularly daunting, so it should mostly just be a matter of sourcing the pieces and finding the time to get up to speed on working with rtl-sdr.

Stay tuned.