UnUsual Signals From Afar - FM Skipping
Sometime back Mike Siegel brought up this question of how distant FM radio transmissions came up on our frequencies.
Mike Siegel: Mystery of the unusually long distance FM radio receptions
The following are comments following his request:
Frank Dillon: Strange radio traffic from afar is known as a "skip" and really isn't strange. It is radio signals bouncing off the inosphere back to earth then bouncing back up. It's the reason the helicopters could get altitude with the HF ARC 102 and were able to talk to folks back in the world. Rare to see a helicopter with the HF installed -guess ya had to be a General to have one, but I recall seeing a couple.
Carl Betsill: Mike is correct in that FM signals don’t usually skip. Skip is simply radio waves bouncing off the ionosphere and coming back to earth at a far distance. FM frequencies greater than 30 MHz rarely skip. Our Centaur FM radios were 30-70 MHz. There are exceptions to this and they are referred to as e-skip and are more common in spring and summer. Another term for skip is skywave. Frank is correct that Mike was experiencing skip, but it is unusual in those frequencies.
The ARC 102 was a High Frequency AM radio that uses skip to transmit at long distances.
Click here to see more than ya wanna know about skips:
Don Borey: I was working forward operations at Tay Ninh one day when I started hearing some other U S unit using the FM frequency. I asked them to get off our frequency. At the time we were running a VR across border in Cambodia. After some heated exchanges about to whom the frequency was assigned, I asked where they were. The voice said he was in South Korea. After some further discussion, he agreed to switch to another frequency. That was my only experience with skip. I did not have any HF antenna as I was just sitting at a field desk.
John Kelly: I was on a night mission somewhere (maybe even with Siegel?) and I heard someone asking for a tool to be handed up to him on an oil rig or something of that nature. I called out to this voice which was in English and discovered that it was an American working in what I recall as Kuwait or Saudi? We chatted and I gave him clues as to who we were and where we were. He was very impressed that we could communicate but, eventually, we lost the signal.
Larry Patterson: I remember having voice contact with that oil rig. We exchanged letters with letters a time for two. Where they are now, who knows!!!
But the radio messages were as clear as if communicating with the Unit.
Skip radio is amazing!!!!