Interface between my AnyTone AT-868UV (or any Kenwood speaker-mic standard radio), a PC gaming headset, and my iPhone (most phone headsets are the same):

• The Headphones get both radio and iPhone audio.
• The iPhone In gets both radio and microphone audio.
• External PTT available to mount where convenient (handle of an Arrow antenna?)

Components:

• All SMT components are 1206 SMT.
• The IC is any 4x OpAmp, but choose one that can drive some current since it’s directly driving the headphones; we don’t need high fidelity here, but the more the better.
• All 3.5mm connectors are PJ-320, 4-pin TRRS connectors. I got a bag of 100 super cheap on eBay years ago.
• The 2.5mm connector is PJ-208, 3-pin TRS. Similarly, a bag of 100 super cheap on eBay years ago.
• Board is sized to fit in my favorite cheap 100mm x 60mm x 25mm plastic project box: https://www.ebay.com/itm/272590733575
• Power voltage isn’t critical, anything the op-amp can handle and within spec on your power filtering caps is fine. With the right op-amp, you could probably go as low as 5v, or as high as.. well, a lot. Check your opamp.

Homage paid to my friend, Cliff K7RR SK, after whom Fox-1Cliff is named.

73 de KR6ZY See ya on the birds, SmittyHalibut.