I really enjoyed reading W0RW's aircraft carrier QSO. -- "My Flashing Light QSO with the USS Bennington" -- https://www.eham.net/article/46413
In about 1965 I was the sponsor of a high school radio club. There were about 10 teenagers in the club, and most were hams who wanted to participate in field day. We set up in the hills above Los Angeles. They all wanted to operate the 2 stations and did not want to take rest breaks even in the middle of the night.
So, groups of us hiked up on low hills probably about 100 yards apart. Fortunately, we had some extra wire, flashlights, and a few keys. The flashlight bulbs (PR_2 ?) worked OK up to ABOUT 12 WPM which is about the limit of the human eye to decode. Most of the kids had no trouble at all reading this perhaps 10 to 12 WPM flashing light. Very few of us ever had tried this before. I sat up on a hill nearly all night making QSO’s via light (and nearly froze!)
Some of the kids even hooked up a slowed down bug and tried, but do not think this worked too well. We did not try and put these QSO's in the FD log and I believe the best DX was only a very few hundred yards. Everyone was happy, hungry, and tired. I was really surprised that nearly all of us could read the signals easily.
Later I worked in telephone communications for many years when many of our circuits in Alaska still used dial pulse dialing. Typically, each telco channel had an LED(?) light which pulsed in sync with the dial pulses from rotary phones. The non-hams needed to hook up test gear to troubleshoot problems, since they could not decode the LED flashes. Many of the hams could easily read the flashes at least accurately enough to see that calls from say Fairbanks to Valdez were not completing. It was not 100 percent copy, but good enough so often we did not need to drag out the test equipment.
So, try this next field day, it should be fun. LED lights should respond quickly to just about any speed, but the human eyeball brain computer cannot see discrete flashes above possibly 12 or 14 WPM (not sure exactly what the limit is).
Rick, KL7CW -- Palmer Alaska
| KL7CW | 2022-01-24 | |
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| Re: Flashing Light QSO's | ||
| I have read several articles in the last 2 decades about ham experiments with LED light communications. These may have been in QST, or perhaps one of the British magazines. I believe some involved a LED at the focal point of a refractor, or reflector telescope. At least one of these used the same LED as the detector for RX when not transmitting if my memory is correct. I believe, but am not sure, that they had success for a few dozen miles. They may have just used on off keying, or possibly they modulated the LED. I am not sure which color LED they used, or possibly they used an IR LED. With the detector keying an oscillator, the 12 WPM limit would not apply, and even voice or data communications should be possible. KL7CW Reply to a comment by : W0WCA on 2022-01-10 I have had this thought for years but never tried it: Two stations with switched LED’s, photo detectors hooked up to CPO’s. Telescopes might be involved. Laser pointers would be good also but probably a safety issue. Comms in the terahz range! Simple idea – probably already been done but would be a fun science project. | ||
| WB4M | 2022-01-20 | |
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| Flashing Light QSO's | ||
| When I was in the Boy Scouts around 1961, we had a merit badge called "Signaling". We send/rcvd code with flashlights all the time. We also learned how to use flags to send code.. talk about slow. | ||
| W0WCA | 2022-01-10 | |
|---|---|---|
| Flashing Light QSO's | ||
| I have had this thought for years but never tried it: Two stations with switched LED’s, photo detectors hooked up to CPO’s. Telescopes might be involved. Laser pointers would be good also but probably a safety issue. Comms in the terahz range! Simple idea – probably already been done but would be a fun science project. | ||