back to meters and sniffers

KA7OEI log sniffer:


I haven't built this yet but it looks pretty promising. It's wide-band, so you might get better selectivity
with a bandpass filter in the band you're hunting in. (such as 2-meter) It has both a meter and a speaker
output which is a great combination, and the reading is log-based so it should work well even when closing
in on foot. Including a switchable attenuator to throw in 20 or 40 dB of attenuation would be a good idea
to improve the range even more.

This is an old build (2005) but doesn't have any unusual parts. No FETs, the AD8307 is available for cheap
on a breakout board with support parts and SMA connetor. Meters are easy to come by, so all you're really
left with is the VCO for the variable tone output and a RAIL-TO-RAIL op-amp, whcih are common but you may
have to buy some if you don't have any onhand. Runs off a single 9v battery too, so no neg voltage hassle.

I suspect this will need a volume adjustment added to the speaker.


A Wide Dynamic Range Field Strength Meter.webarchive (1754 KB)

assembly and use instructions


schematic:



highest resolution images
last updated 11/12/2023 at 21:00:55