I did not see a thread for this, so I thought I would create one!

Overview
The AM Radio trick is a method of playing sounds on your monochrome calculator. I am uncertain as to what models support this method, but it is in my current understanding that all monochrome calcs (at least the TI83 line) support. All of the tests I have done were with my TI83+ and Omnicalc.

Instead of using the link port, this trick involves using an old radio. You place the antenna near the back of the calculator and using compatible programs, you can play sounds using your calculator.

This trick takes advantage of a chip inside of the calculator. You are able to "hear" the chip as the electromagnetic waves that are produced by it can be picked up by a scanner of radio.

My findings
I have a Uniden BC75XLT scanner that is capable of picking up radio frequencies anywhere from 25 Mhz to 500 Mhz. I did some testing on what frequencies came in the clearest and this is what I found.

You can use this with a normal radio, in my experiance the clearest signal was found on 89 Mhz on the FM band. Strangely enough, the trick is names AM, yet I get music on the FM band.

For non-traditional bands, I found the clearest to be found on the Amateur Band and TV Low VHF Band. This encompasses frequencies from 50 Mhz to 54 Mhz for the Amateur Band and 54 Mhz to 88 Mhz for TV Low VHF Band. This correlates with the 89 Mhz reading on a normal FM radio.

As for hotspots as I call them, specific frequencies where sound can be picked up the easiest, I found a few, mostly around 50 Mhz. I made a nice little chart below with my findings:

Frequency:
50.015 Mhz This is the first frequency that sound was discernible
50.030 Mhz
50.115 Mhz
50.200 Mhz
50.265 Mhz - No sound, just backgound of chip
50.285 Mhz
50.370 Mhz
50.625 Mhz - Very Clear
50.715 Mhz - Very Clear

Thats about it. There are a few more scattered around, but these will (should) deliver a good result. It is important to note that the chip was never designed to transmit on FM frequencies so it is possible that it is on a per calc basis. I imcluded the TV Low VHF band as a result.

It is also important to note that interference is detected as far up as 122.8 (possibly higher) in the Aircraft Band. This is interesting, and leads one to believe that interference like this is why phones are prohibited during take off and landing.

I just found this interesting and wanted to share.
which calculator are you using? I'd guess that 50Mhz is a harmonic (maybe 9th?) of the clock frequency.

iirc, notipa used a shortwave radio to directly measure the clock frequency of several ~6Mhz calcs.
Hm, I almost want to try this myself; my HackRF will theoretically work down to 100 kHz, which should reliably capture AM so we can see a bunch of harmonics.

Can you share what program(s) you tested with on the calculator and maybe some photos of your test setup?
Certainly!

I placed my calculator just under my antenna. I do have a slightly modified BC75XLT, I have attached a old set of rabbit ear style antennas. I had a very similar setup to the below image


The program was a BASIC program run with Omnicalc installed. The BASIC program was:

Code:
While 1
real(31,"MLT180O6G"
real(31,"MLT180O4G"
End


Oh one more thing, I had to adjust my squelch to its second to lowest level to hear the sounds. A similar thing may need to be done, but I have little to no experiance with SDR's.
Any of the sound programs for the 83/+ etc line of calcs (anything with a linkport) work with an AM radio close by iirc.

QuadPlayer by Ben Ryves and of course mobileTunes by Kerm are examples:

https://www.ticalc.org/archives/files/fileinfo/368/36889.html
https://www.ticalc.org/archives/files/fileinfo/432/43293.html
I remember picking up signals at 95 mhz from my TI-89 through my android phone radio. There would be a beep whenever it processed a calculation.
I want to try to pick up signals from my 82, 84CE, 85, and 86 with my Tivdio v-115 AM and SW radio. But first, I need to locate the charger for my AAA batteries.
Also, the SW band is extremely tedious to scan as well.
I should test my 84+CE, but I have to manually move, as my scanning function has no way of determining if the signal from the CE is a signal or interference. I have to put my squelch on the lowest setting to hear the signal anyways.
I pulled out an 84PSE but the batteries in it are long dead, so I won't be able to test this myself until at least tomorrow. Until then here's my local wiffies.

Pi Time wrote:
I want to try to pick up signals from my 82, 84CE, 85, and 86 with my Tivdio v-115 AM and SW radio.

Actually, nevermind. I tried the TI-82 with and without the program, the radio was too weak to pick up anything on the AM band.
However, I am aware that newer TI-83 Plus units don't come with an internal foil sjield so they possibly emit more signals.
To be more clear, the hardware in my radio is not sensitive enough for this task.
Nothing interesting with an 84PSE. The below spectra include starting and stopping the program LAX18 supplied, with no interesting results.


It's possible I need more gain, or the 84PSE doesn't exhibit the same noisiness.
  
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