Spy Nerd - Laser Communicator

RE: Spy Nerd - Laser Communicator

scottiebabe — Sat, 06 Nov 2021 03:36:29 GMT

Success! I managed to find cheap pocket radio,

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The circuitry is almost identical to the solder kit I showed above. Taking shabaz's recommendation I wound a few turns on the ferrite antenna:

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With the addition of a photodiode I had a working prototype for the receiver side. Too cool! I am feeling like a spy[View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-e3d77943-58c1-4a91-830f-6798c53a3a6f/6521.contentimage_5F00_403.png:16:16]

[View:https://www.youtube.com/watch?v=eFZkmyyG1SU:740:466]

RE: Spy Nerd - Laser Communicator

scottiebabe — Thu, 04 Nov 2021 00:12:17 GMT

Dollar store pocket radios may be a relic of yesterdays. Though you can now buy a water-resistant Bluetooth speaker for ~$3 USD, just amazing.

You can find the FCC application for this Bluetooth speaker at https://fccid.io/2ASKA-LM2682BS

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I will check the local Hobby store next for a basic AM pocket radio, before making a purchase on Amazon.

RE: Spy Nerd - Laser Communicator

dougw — Wed, 03 Nov 2021 13:23:52 GMT

Cool - a laser phone

RE: Spy Nerd - Laser Communicator

shabaz — Wed, 03 Nov 2021 10:39:59 GMT

Hi Scott,

Nice project. If you don't find a suitable receiver, then one suggestion is 'Tecsun R-909' which is a low-cost basic radio, although there may be cheaper models since this one covers shortwave too.

I bought it specifically because it had a superhet design and ferrite rod for AM. My aim was to somehow mount its PCB so I could probe the signals on a 'scope or spectrum analyzer. Basically to use it like a more traditional sibling to an SDR experimenter board I'm working on. Anyway, photos are attached below, not great quality since they were just taken with mobile phone.

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The cord mechanism for the tuning, I cut this off, although it does make the tuning more awkward:

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The long slide switch in the photo below is shown in the highest shortwave band position, but if you move it furthest left, then the ferrite rod is being used for AM broadcast band.

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The IC is CD1691CB, a datasheet exists for it, although in Chinese (but translatable using say Google Lens).

The black wire with ring terminal is for the FM and shortwave antenna. The other two white and black wires on the right are for the 4 ohm speaker.

The battery terminals in the photo below were desoldered and replaced with a norrmal 2 x AA battery holder.

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