A non BFO alternative to hear CW on an AM receiver

[@xamesm]

Slightly related, and you probably know this already, but you can resolve SSB and CW with two AM transistor radios, use one to listen and put the other next to it, then tune it around until they heteroydne and resolve the signal (i.e. the 2nd radio acts as a coupled BFO).

[@VK2QRZ]

Pete did a video on this awhile back in his garage. I’ve yet to replicate it but probably due to my inexperience.

[@VK2QRZ]

kzbin.info/www/bejne/ZneYdKuDep54j9k

[@radiotec76]

I did that with two shortwave receivers and listened to 20 Meter USB QSO's using nothing but a wire antenna from a 9th story condominium apartment in Freeport in the Bahamas back in 1977. Talk about cool!

[@thinkingjohn2099]

I seem to recall doing that with 2 SW receivers many years ago, I think by receiving the oscillator from one set, so long ago now

[@2ftg]

I recall reading about a soviet russian bug sweeping/RF sniffer device that used a diode detector AND a diode switch at the front of it to get a tone if there was a carrier of any type in there. So that could also be done. A diode shunt rf switch or a 74hc4053 switch before the diode detector.

[@jjoeygold]

Classic NE555 interrupter or a or RC transistor osc

[@MatFarringtonInfo]

Your NanoVNA could be a carrier source too.

[@vk3ye]

True but unnecessary if the job is done by leaving the transmitter crystal oscillator running.

[@MatFarringtonInfo]

@@vk3ye yeah goes against the minimalist approach taken this far.

[@F4EGX]

I would have liked some illustrations in the video to support the speech, to help non-English speakers to understand. Thank you for your video. :)

[@Neo_Chen]

It couldn't work on the audio stage if it is AC coupled.

[@PaulaBean]

At the end of the video the rain is really a thing! Luckily you weren't manipulating electrical wires, or bad things might have happend.

[@ERICtheLATE]

I think to keep it electro mechanical, 0 ic chip possible, clamp or weld the shaft of a small dc motor to a brace, and use abs or timing sensors from an auto, placed very close to magnet section of motor can, to get excited by pulses of the magnets swinging by, as the motor can is attatched to a propeller, impeller, or just a heavy ring of metal with momentum to rotate it, and occaisionally giving it a flick as you are recieving. Otherwise it can be rotated by wind, water, or a big light feathered prop above a few candles to rotate it from heat rising. The flywheel will be safest and easiest, and if the sensors eat up all the audio power, a flywheel with bumps to flick a switch as it rotates would be absolute primal simple for creating a carrier beat oscillation.

[@AlexBurtonMusic]

Like you, I want to build a purely mechanical CW receiver. I wonder if we can use an oscillator created by rotating a motor made of magnets at high speed for this purpose.

[@cris7472]

Maybe check out reed receivers ( see Wikipedia ) as used in the early for firefighter pager system.

[@MrKarlGP]

Electro mechanical... current through inductor creates magnetic field, attracting nearby ferromagnetic bridge making the circuit... which breaks the circuit!

[@MrKarlGP]

Rinse and repeat ;)

[@MrKarlGP]

If this is a light semiconductor junction, high frequency modulation possible

[@MidlifeRenaissanceMan]

@@MrKarlGPthere is a video of a bloke who made a spark gap transmitter and Cohera

[@MrKarlGP]

Chris Wilson that's really old school! I meant more like an actuated relay, a bit like the reed suggestion made by another commenter... basically a very sensitive switch, although a Schmidt trigger comparator with adjustable hysteresis is ideally needed to drive it otherwise any signal hovering near the trigger threshold would make it chatter on and off wildly. Hey, I guess the coherer would avoid that! Although would need tapping to reset it.

[@brianveitenheimer4492]

Easy. An automotive points type distributor driven by a variable speed battery powered electric motor.