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Thread: Transmission near the beach

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    Default Transmission near the beach

    This question isn't about ham radio per se, so let me know if it's not allowed here. But I thought this would be a good place to get some information from you radio experts.

    I'm using a 5GHz wireless video system from Tiltamax at the beach, and the reception is terrible. Normally this system works well up to 150ft in clear line of sight. But here at the beach it won't go 20ft without lots of interference. If I move the transmitter 50ft father from the water, it works much better. But for this work, I need the transmitter to be right at the shore. (It's mounted on a handheld camera.) I think the water is absorbing the signal. Is there any solution for this, like a different type of antenna?

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    Yes the water is affecting the 5 GHz transmitted signal as Microwaves don't perform well around Water even if you have a Gain Antenna, the Water will act like an attenuator to the Microwave Signal. I was taught to stay away from Microwave Point to Point Links that had to cross water because of the water attenuation problem.

    The interesting thing about your system is, Where is the receiver located while your at the beach?

    Dan
    WA9WVX

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    The receiver is also on the beach, about 50ft away, for a monitor.

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    How your reply doesn't make sense as you originally said, "If I move the transmitter 50ft father from the water, it works much better." which means that you would be almost on top of the receiver. Does the receiver have an external antenna port / connector? Otherwise between the Water and any bit of Moisture in the air is attenuating the 5 GHz Microwave Signal.

    Dan
    WA9WVX

  5. #5

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    Quote Originally Posted by WA9WVX View Post
    .... Microwaves don't perform well around Water...
    Interesting point. Presumably frequency dependent to a certain extent, then. Slightly OT: I've never explored microwaves for ham radio, but at 2.4GHz, my radio controlled boats have no problems operating over hundreds of metres at our local lake. The TX power is very low and the RX antennas are buried deep inside the bowels of the boats in my case! As for antenna polarisation, the TX normally gets held at about 45 degrees and the short RX antenna wires in the boats aren't even straight, but curved to fit the space. Add the bobbing around on the water..... With this recipe for signal attenuation it seems that it's amazing that they work at all.
    Last edited by AndyG0CCX; Sun 16th Oct 2016 at 08:57.
    Current radios: VHF/UHF: 2 x Baofeng 2/70 Handhelds. VHF: Kenwood TR9130 2m multimode. HF: Kenwood TS930S-AT
    Home antennas planned: G5RV / G7FEK / end fed wire. 1/2 wave vertical for 10m. 6 element beam for 2m. Vertical collinear for 2/70
    Website for the 'day job': www.andrew-gilbert.com

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    I will clarify: When I move the camera/transmitter away from the shore, I also move the monitor/receiver. So the distance between them is always roughly 50ft. They both have rp-sma antenna connectors, with 4" antennas. Two on the transmitter and five on the receiver. I'm wondering if there's a different type of antenna that's better suited for water.

    This is transmitting HD 4:2:2 uncompressed video, which surely requires tremendously more bandwidth than the an RC boat.

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    Spooky,

    What I need now is where you're located in reference to the beach, is it near Salt Water, i.e. the Ocean or is it near a Fresh Water Lake? This will indicate whether the 5 GHz RF Microwave signal is being limited to a smaller distance.

    Dan
    WA9WVX

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    It's the pacific ocean

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    If you're on the ocean, with waves and a swell running, aren't you going to have issues with attenuation due to cross polarisation as things bob about? And do you sometimes get waves that block line of sight?
    Current radios: VHF/UHF: 2 x Baofeng 2/70 Handhelds. VHF: Kenwood TR9130 2m multimode. HF: Kenwood TS930S-AT
    Home antennas planned: G5RV / G7FEK / end fed wire. 1/2 wave vertical for 10m. 6 element beam for 2m. Vertical collinear for 2/70
    Website for the 'day job': www.andrew-gilbert.com

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    Spooky,

    I'm wondering "if" you considered contacting Tiltamax here in the USA as they're in Burbank, California with this RF signal problem?

    Tel: +1 (626) 560-4031

    Add: 2801 W Magnolia Blvd. Burbank, California, 91505

    I still believe the Microwave 5 GHz problem is associated with the Ocean Water, perhaps the water's surface temperature, any percentage of humidity near the ocean, perhaps even RF Multi-path signals causing the unwanted attenuation between the transmit unit and the receiver unit (which I believe has built-in Diversity receivers because of the two individual antennas). I've done a lot of reading on Microwave Frequencies as far as Water Absorption versus Frequency and what each individual website seems to agree on as to the higher Frequencies near 71 through 76 GHz, the Water Moisture / Humidity, Clouds, Fog, Winds on the Ocean Water can destroy or make useless a Microwave Tx / Rx System but not as much at 5 GHz.

    Since this product is made in China perhaps the Tiltamax engineering staff might have overlooked field testing their system in and around any ocean body of water. This kind of application that you are doing or others can be easily overlooked by accident on their part and this why I'm suggesting to go to telephone, call Tiltamax and explain the problem you're experiencing. I even researched the possibilities of recommending a better antenna but most if not all were Parabolic Dishes and Flat Panels for Gain although they have such a narrow beam width 3 degrees for the half power points, you would need a second person constantly aiming the Dish antenna with your every move therefore it's not practical.

    Dan
    WA9WVX

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    Spooky,

    It's 6:30 AM here in the Midwest and I've been up for about 2 hours thinking about this problem you've encountered. I've been so engrossed with the water issue that I overlooked a basic issue being RF Path Losses. Since your 5 GHz Wireless unit would depend on Line Of Sight for Microwaves, I did a basic calculation for the Frequency versus 1 Wavelength which equals 1/2". Now the two antennas on the receiver unit are 4" tall indicating that they are Collinear Vertical Antennas perhaps +5 dB Gain (Just guessing) as that is a plus but at what level this receiver is sitting, maybe you have on the ground away from the water and most beaches slope upward 2 to 3' above the water level either at a lake or the ocean. The sand on beaches are not perfectly level with people or animals running across the sand create miniature Hills that can appear as 5 GHz RF signal Path Losses or RF Attenuation. In most Microwave installations the transmitter & receiver are mounted on tall towers for the necessary Line Of Sight Point to Point Communications.

    With your application, I'm guessing that your receiver is just laying on the Ground since you haven't provided where it is and the same holds true for the transmitter unit. Here's only a suggestion, raise the receiver unit up 2 to 3' above the Ground for a better Line Of Sight RF Path. You can use a table, a chair, a wooden post or whatever is handy and make sure those two antennas are Vertical. Height, Low Path Losses, RF Power Output & a Sensitive Receiver are the name of the game when operating at UHF or Microwave Frequencies. I'm guessing that the transmitting unit may only be radiating 50 milliwatts of RF Power as Tiltamax does not provide any technical data for their units.

    Try this idea before calling the USA Office to verify whether I'm right or wrong.

    Dan
    WA9WVX

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    I had both the receiver and transmitter mounted on portable stands about 6ft off the ground. I appreciate your thoughts. Unfortunately I can't test anymore, since this was a short term rental, and now the project is over.

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    My 1st post here!

    Water in the air (aka humidity or precipitation of any kind) is how water attenuates a pt-pt path.

    Over a highly conductive surface as salt water you are getting a reflection off the surface of the water or multipath. This is a common problem for commercial microwave paths and has been since the 1st path over water and even very large wheat fields in the Midwest US.

    Try raising one and even lowering the other to test.

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