UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - 87.9 MHz FM Car Radio receives phone calls. Explanation?

Graham G3ZVT · 16th Aug 2021, 10:36 pm

Yes people had these phones that worked handset to base on around 49MHz and base to handset just above MW, about 1700kHz both NBFM and many an unmodified MW radio would tune in with no problem, and recover sufficient audio by slope detection.

You effectively tapped your own line and broadcasted it to your neighbours.

I even heard a BT spokesman interviewed on the radio claim he had no idea that these phones were so insecure, BT sold them in their showrooms (remember them).

16th Aug 2021, 10:36 pm	#13
Graham G3ZVT Dekatron Join Date: May 2010 Location: Greater Manchester, UK. Posts: 18,713	Re: 87.9 MHz FM Car Radio receives phone calls. Explanation? Yes people had these phones that worked handset to base on around 49MHz and base to handset just above MW, about 1700kHz both NBFM and many an unmodified MW radio would tune in with no problem, and recover sufficient audio by slope detection. You effectively tapped your own line and broadcasted it to your neighbours. I even heard a BT spokesman interviewed on the radio claim he had no idea that these phones were so insecure, BT sold them in their showrooms (remember them). __________________ -- Graham. G3ZVT