|I have read about many people receiving signs/ADC's via electronics, although I personally haven't. I think that our loved ones use very creative ways to get our attention. It's always connected with what either THEY and/or YOU can relate to.
The closest I can compare is with numbers...My "Gang" (I've lost several people over the years) will make me notice specific numbers or will leave dimes in odd places. They have also brought attention to license plates.
They know I'm more of a "right brain" thinker, plus none of them were into electronics, so my signs tend to be with nature, songs/sounds, and smells.....even physical touch and very occasionally visual.
As for timing? The really intense "wowzers" occurred shortly (within days, weeks, or months) after the loss. But the ones I listed above have continued over the years.