Faster diode, like HSMS-2850 [1], and different leg lengths (tune for 5Ghz).

[1] https://datasheet4u.com/pdf-down/H/S/M/HSMS-2862_AgilentTech...

Thanks. Appreciate the reply. From a brief look that might detect 2.4ghz too?

Really wish I was clever enough to do electronics!

Depends on the length of the antenna. I'd bet you can get a length close enough to be a quarter-wave 5Ghz and 1/2-wave 2.4ghz antenna. Just buy a 2.4/5Ghz combo antenna and slap the diodes across it.

I love simple solution like this. It'd be cool just wandering around being able to detect mobile and stuff with a tiny led.

This sort of thing is definitely why I come the HN.

Just curious, what does your username stand for? :D

Nothing. obviously the last bit stands for hacker news. Just randomly pressed letters.

Okay, I was just curious because you were saying nice things about HN and there's a popular abbreviation IFL for I Fucking Love, so I had to wonder!

Oh, I didn't know that and searching for ifh abbreviation on urban dictionary brings back what I think your curious about. Unfortunate coincidence. All my usernames are random strings. Good to know though.

For 2.4 GHz each leg of the antenna should be 30 mm. For 5 GHz just under 15 mm.

See Dipole Calculator: https://www.omnicalculator.com/physics/dipole

And you need a faster diode.

Shorter antenna and faster diode. A Schmitt trigger would allow for much more sensitivity, but it would not be a passive device (requires a power source)