Upper Limit of Amateur Communications - Page 1
Forum section: electronics / rf-microwave

author: jonovid
author_rank: Super Contributor
timestamp: December 10, 2024, 07:01:00 am
content: Is laser communications or infrared light communications considered part of the Amateur spectrumdo you need a licence to play with long distance light or high power laser communications?

author: Andy Chee
author_rank: Super Contributor
timestamp: December 10, 2024, 07:39:19 am
content: Light communications is not defined by the amateur band allocations coordinated by the International Telecommunications Union.However, lasers are regulated by other legislative instruments (e.g. high powered laser pointers and blinding aircraft or road vehicles)As such, you’d best refer to local laws regarding laser and light shows, not amateur radio legislation.

author: Andy Chee
author_rank: Super Contributor
timestamp: December 12, 2024, 03:18:49 am
content: Also in case it hasn't cropped up in your internet searches;https://www.modulatedlight.org/Dollars_vesus_Decibels_colour.pdf(skip ahead to ~15 minutes)

author: ftg
author_rank: Frequent Contributor
timestamp: December 12, 2024, 11:26:27 am
content: At least in Finland the local communications regulatory authority only really considers the 100 Hz - 400 GHz range.I guess above that it's either free game or the job of STUK, the local radiation safety authority.Highest non-optical, non ionizing radiation amateur contact I'm aware of is the 725 GHz contact between DB6NT and DB2NP.

author: coppercone2
author_rank: Super Contributor
timestamp: December 12, 2024, 07:17:31 pm
content: i mean its like rare, where do you get two LOS locations?Its not like you can hop on at night or something, you would have to go somewhere on a schedule. its all LOSyou can make a optical telephone with your neighborthe whole fun thing of radio is distance

author: TimFox
author_rank: Super Contributor
timestamp: December 12, 2024, 10:18:40 pm
content: Some history of early earth-moon-earth (moonbounce) experiments with lasers:https://adsabs.harvard.edu/full/2004ESASP.561....3F

author: janoc
author_rank: Super Contributor
timestamp: December 12, 2024, 10:49:38 pm
content: Quote from: jonovid on December 10, 2024, 07:01:00 amYou don't need an amateur radio license for this, but as mentioned by others, high power light sources and lasers are regulated by other means that you will want to research, including regulations concerning interference with aviation or marine navigation. Lasers pointed at planes is the obvious issue but even bright lights may require permits and/or declaring them with the authorities. E.g. for various laser and light shows the organizers have to do this so that the aviation authorities can issue NOTAMs letting pilots know that in the area XY is something going on and they should be aware of the extra lights in order to not confuse them e.g. with nearby airport lighting or some warning lights on some mast. Accidents did happen for such reasons in the past.OTOH, unless you want play with moonbounce or blasting lasers into the sky for whatever reason, you don't need very high power to transmit data at all. A small laser diode is usually completely sufficient. For a short distance you can also use a regular LED. Even classic incadescent lightbulbs were used for this. As a kid I have built a simplex set like this for transmitting audio over a few tens of meters - the bulb was barely glowing. There you don't need to worry about breaking any regulations, just make sure you don't accidentally blind drivers (including ships and railways!) or plane pilots with the beam.Achievable distance is going to be limited by the dispersion in the atmosphere - and your ability to accurately aim the transmitter at the receiver. The latter is a pretty difficult and fiddly job, so practical upper limits of such optical links tend to be on the order of a kilometer or two.

author: Robert763
author_rank: Super Contributor
timestamp: December 25, 2024, 12:57:10 pm
content: Quite a bit of interest in infrared (IR) communications in the UK in recent years. Often termed 30THz. Range is LOS up to hundreds of meters. Many use narrowband (low rate) digital data modes designed for LF work.

author: madires
author_rank: Super Contributor
timestamp: December 25, 2024, 01:33:09 pm
content: Class 1M laser based FSO systems are usually unproblematic and can be used by anyone. Higher class lasers are a different story (check local regulations). The commercial systems we used (all class 1M) worked fine for distances up to around 2 km.

author: radiolistener
author_rank: Super Contributor
timestamp: December 26, 2024, 02:52:51 pm
content: Quote from: jonovid on December 10, 2024, 07:01:00 amAs far as I heard, some amateurs tried to use X-rays to conduct QSO with aliens

author: mark03
author_rank: Frequent Contributor
timestamp: December 26, 2024, 11:49:41 pm
content: Somewhere I thought I read that high-power LEDs were preferred over coherent laser light because of less scintillation (self-interference) in the atmosphere. I've always meant to play around with this but high-brightness LEDs have an inconveniently high (~ 140 deg) beamwidth for collimation. It's also a challenge to source the fresnel optics---cheap stuff usually has no data on focal length, for example.

author: drspastic
author_rank: Contributor
timestamp: December 30, 2024, 11:45:25 pm
content: the more powerfull laser pointers have been viewed from the ISS so with good still atmospherics i dont see why they shouldnt be able to bounce from a retroreflective surface on a satellite.a motorised tracker would be needed but all in all its a cheap experimental payload to slap a retroreflector sticker on the next few cubesats