Wifi over water
Wifi over water
(OP)
Hello, I want to try a point-multipoint link in 900MHz over water. I known about the problem of multipath and the implementation of circular polarization is not an option because the small angle. The good thing is that I can put one antenna over a Buildin at 100mts hi and the vessel is also hi (20mts) How long do you think I can rich with this cain of system? I want to use a omni over the vessel but then I can use another type of antenna over the buildin because the vessel´s way is alway the same and is straight.I hope someone can advise me before I through my money.
Regards
Regards





RE: Wifi over water
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Wifi over water
RE: Wifi over water
With full details about what you intend to use I can provide more detailed numbers.
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Wifi over water
RE: Wifi over water
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Wifi over water
RE: Wifi over water
Good luck.
RE: Wifi over water
Hyperlink Technologies
HG918G-NF-2
http://www.l-com.com/item.aspx?id=22180
RE: Wifi over water
www.MaguffinMicrowave.com
Maguffin Microwave wireless design consulting
RE: Wifi over water
Wouldn't ducting be seasonal/unreliable (as well as being more land-based/shoreline in nature rather than beyond the coastline)?
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Wifi over water
RE: Wifi over water
I'd look for alot more info on it before venturing that way.
I think that 18 dBi antenna will help you. 900 Mhz is probably better than the higher frequencies. The loss between your two antennas in your link will be typically lower at 900 mhz by the ratio of the physical sizes of your antennas on the building plus add 20*log(fhi/900mhz) ratio(assumes omni antenna on the ocean and formula relates to effective area of omni antennas).
RE: Wifi over water
"The circular polarization thing works worst mathematically at around 6 degrees incidence angle since all of the vertical polarization energy is absorbed at that angle by a flat ocean. Hence if you send circular you receive horizontal polarization over the water at that incidence angle.One thing I've often thought about but haven't seen, is to have a receive antenna aboard ship for a program such as this using two antennas atop each other. Combined them into a magic tee (zero/180 degree outputs) to have sum and difference outputs. If you can point the null of the 180 degree output properly (between the tranmitter and the ocean), then the energy bounce off the ocean will always help one channel and always hurt another channel of the magic tee output, hence dual receiver front ends to detect the highest signal would stop multipath fading. I believe the antenna separation must be large if the transmit antennas in this system are close to the water. It works best for picking up low flying transmitters approaching ships that pop into and out of dead spots due to multipath on a calm ocean day. Antenna diversity would help too, but not as reliably at the magic tee, or so I think. Proof is always in the measurements, and sometimes in the paperwork. I've seen alot of trees killed for nothing by useless ink.kch"
I´m gonna star with an omni 8dBi over a small vessel and a parabolic of 15 dBi over a small buildin. I guess with this I´ll have an idea...Talking about multipath do you think that is a better option to use 900MHz not only because of the losspath but also the absorve coefficient from the water at this frequency?
regards....
RE: Wifi over water
www.MaguffinMicrowave.com
Maguffin Microwave wireless design consulting
RE: Wifi over water
RE: Wifi over water
For example, distant FM broadcast stations can often be heard in the Spring mornings on your car radio, and their broadcast antennas are often installed on top of very tall buildings, or very very tall towers.
What sort of signal is being carried by this radio link?
Are we talking about the unlicensed (YMMV) 902 to 928 MHz band? Is the base station in a large city (a building was mentioned)? If you aim a high gain 900 MHz antenna into a coastal city from offshore, then you're going to pick-up every wireless speaker, wireless headphone, older cordless telephone, wireless intercom, etc. And this environment may change from moment to moment.
If this radio link is for data, might it be simpler to use a mobile data USB stick (or smart phone), one with a socket for an external moderate gain antenna, and access the commercial data network. A bare device can reach several kilometers, add an external antenna and the range could be out to the horizon (maybe).