Antique Wireless Association Signal Sniffer build

[duckduck]

I built the AWA Signal Sniffer:

https://www.antiquewireless.org/homepage/pcb-item-3/

This definitely isn't the most cost-effective way to get a small audio amplifier. I built it to support the AWA and  because it's a simple project. I can always use some more experience soldering. I'm still an electronics noob. I paid USD18 for the PCB (delivered) and USD35.74 (delivered) for the parts from Mouser. I made a few (expensive) upgrades and got the faster shipping, so you could definitely do it cheaper. The PCB comes with a schematic, layout, and a BOM with Mouser part numbers. A couple of components were not in stock and had long lead times (the pot and the red banana jacks) so I had to make substitutions. It went together easily in one evening after the duckling was in bed.

I tested it out using my AWG / signal generator and I was able to easily hear a 2.5mV RMS sine wave. I'll call that a success. I've got a lot of troubled hollow-state audio amplifiers that need a good fixin-uppin, so this sniffer is going to be nice to have in the lab.

EDIT: I used this pot. N.B. that it is unswitched. You'll have to unplug the PP3 battery when not in use or add a switch. Also, you'll have to fuss with the mounting legs to get it to fit, but the leads fit perfectly, it's 20k, and it's audio taper so it's better than a sharp stick in the eye.

https://www.mouser.com/ProductDetail/652-PTV09A-2020FA203

EDIT EDIT: I found that six M3x5mm screws work perfectly to fasten the PCB to the case. If you're a fastener snob like me you will use stainless Torx screws and feel smug about your vast superiority over the sad little people that use inferior rust-prone Phillips hardware.

[Ford_Prefect]

I found those M3 x 5mm torx stainless screws at Monster Bolts here for anyone else who is interested.  Agree completely with your assessment of 'sad little people' who use non-amazing fasteners. 

https://monsterbolts.com/collections/all-metric-fasteners/products/socket-star-button-a2-m3

[eloso]

Nice job 

And you took me back a long time for some self-indulgent reminiscing    of a time when I was 14 and my only test equipment was something like this amplifier, a basic multimeter (20kohm/volt none the less!) and a signal injector (a 1khz square wave generator, built into a fat pen shaped enclosure and that was so rich in harmonics it was a kind of signal generator working on all frequencies at the same time  ).

Armed with that extensive collection and not much knowledge I used to repair neighbours audio/radio equipment and black and white televisions. Couldn't do colour - way too hard. Good for learning though and we had some great neighbours who were very willing to give a 14 year old a chance.

There is probably a serious point in here somewhere that you can do a lot with a little but we won't mention that.       

Thanks for sharing your build. Makes a nice change from talking about $30K 'scopes !

Cheers


Eloso