How can I send audio through a mini coaxial jack?

I have an outdated (but retro & cool-looking) Sony Watchman FD-500. It has a powerful radio & speaker as well as a 5" black and white tube television. Although digital broadcasts have pretty much ruined any chances of getting TV signals on the screen anymore, there is a 1/8" headphone jack-sized input on the rear for "EXT ANT". i found a coax-to-jack converter that allows me to plug in video inputs like a Nintendo once i tune it to Channel 3.

I was wondering if this same jack can also be used to feed in audio from an iPod or phone. Since it looks like a normal headphone jack I tried the obvious, a direct input, but something isn't going through. Here's a link to a page with photos:

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akellyirl4 years ago
Your problem is the EXT ANT signal is an RF (Radio Frequency) signal so you need to modulate your Audio up to RF to plug in there. You can buy units that do that. They're often used in cars/automobiles. You tune your radio to the frequency it's modulated to and listen as though it's a radio station.
The 1st one I found with a Google search was:

There might be cheaper ones.
noapparentfunction (author)  akellyirl4 years ago
my suspicion was that the raw audio was being pumped in a format that the radio wasn't listening for, since it's expecting RF frequencies to decode.

the Super Nintendo i was testing with uses RF output so i guess that's why it worked on the TV with only a simple adaptor. thanks!
This instructable might be suitable if you hook up the aerial/antenna to your Sony :
Ext Ant = External Antenna. You might be able to add an extra connector that would let you drive the internal speakers, but you aren't going to be able to do that from the external antenna input
+1, that plug is not connected to the speakers, unless you open the box and rewire it.