Video downlink TX power: What is legal ?

Discussion in 'Electronics' started by Johannes Thor, Oct 2, 2013.

  1. Johannes Thor

    Johannes Thor Distributor

    Joined:
    Jul 26, 2012
    Messages:
    31
    Likes Received:
    6
    Hi everyone,

    as many US customers are asking us for copter systems with long range video downlinks, the question about what is the legal maximum TX power always comes up. I know that for most EU countries 25mW TX power is maximum, but I heard from the FCC that in the US it is 1mW. Is that true ? How do you work with a restriction like this ?

    Regards
    Johannes
     
  2. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    Johannes the rules are likely very complicated and may also depend on frequency of the transmission. Example 5.8gHz for SD video we use has TX available that are 1500mw. Other frequencies might require an amateur radio license.
     
  3. Johannes Thor

    Johannes Thor Distributor

    Joined:
    Jul 26, 2012
    Messages:
    31
    Likes Received:
    6
    Well, I heard that for 5.8 GHz the maximum TX output power allowed is 1mW..
     
  4. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    Mine is an Iftron Mondo Extreme. ReadyMadeRC has there line of TX also into the 1.5w range.
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
    Staff Member

    Joined:
    Jul 31, 2012
    Messages:
    10,372
    Likes Received:
    1,162
  6. Maxis Gamez

    Maxis Gamez Member

    Joined:
    Jul 1, 2013
    Messages:
    60
    Likes Received:
    2
    Based on that link looks like 5.8ghz at 500mW is prohibited? Or am I reading that incorrectly?

    Thanks!
     
  7. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    Maxis note that it says 'unlicensed' and the the max is 30dBm which is 1 watt before you need to be licensed. And then lists exceptions. And I believe an amateur radio license is sufficient. But with the Iftron and the standard whip antenna, which is only a 3dbi gain, you wouldn't be getting close to the limits. TX about 31.5 dBm + 3 dBi antenna = 34.5 EIRP dBm's and the max is 53 EIRP dBm.

    Aren't you glad that you asked :cool:
     
  8. Gary Hilgemann

    Gary Hilgemann New Member

    Joined:
    Apr 20, 2013
    Messages:
    11
    Likes Received:
    3
    Hi,

    thanks Johannes to open this thread.

    I can explain the FCC rules in europe where Gary Haynes is absolute right, that this is very complicated. I try to explain as good as i can the situation for Europe and i´m very interest to understand the rules the in US / Canada and ASIA.

    EUROPE:
    In the licensed 5GHZ band band is allowed to send up to 1Watt when your device supports DFS (Dynamic Frequency Selection) and when it uses the right suband = channels.

    This is cause some radar devices are also sending in some channels of the 5GHZ band and the radar has a higher priority where your device has to switch the channel and to reduce the output transmission so that the radar service is not interrupted. Makes a lot of sense to me.

    Now, the biggest missunderstanding that i often read that it is allowed to send with 1 WATT on UAV / Flying vehicles, even the transmitter receiver supports DFS as well reducing the DB.

    When your application is a "BASE /GROUND" application, where you setup the transmitter on your camera and you send the signal over the 5ghz band to your receiver and both devices are on the bottom/ground (and not in the AIR), then it is allowed to send with 1000MW/1WATT. If you use suband 1 , you even have 200MW, which is nice to get a range of >100meters stable wireless transmission.

    On Brushless Gimbal / Handheld you are saved.

    UAV and EUROPE:
    When your application / transmitter is in the AIR, then the output transmission power must not higher then 25MW (0,025WATTS) . Maybe you ask, ok, i send with 5dbi antennas with a 25MW transmitter on the UAV and on the receiver i install, lets say 23DBI anteanns. In this scenario you are sending in unicast with 200MW from the receiver to the UAV transmitter, which means that you use more then the allowed 25MW to your UAV in the AIR.

    The reason for this limitation is the 5GHZ freq. beam that you fire up in the AIR can interrupt the electronic in AIR-Planes, helicopter or other services that uses the 5ghz band. With 1000MW you can interrupt the 5hgz band a lot, believe me. The 2.4GHZ is more limited, but most of the control data for the UAV goes thru this band, dont use it for video transmission on UAV.

    I have seen so many solutions on UAV, even analog or digital that are sending with 500mw or more. As long as it works and you have no accident, everything is fine, but when you will have a crash or accident with people, you can be for sure (as always :) ) that your UAV insurance company (hope you have one) will not pay the damage and you have to pay the whole damage by yourself.

    US / CANADA / UAV:
    I´m very intereset to know the situation on UAV in the US and Canada, cause we have a lot of request on this. As far i have heard and research by myself, it is allowed to in the US to have only 1MW on UAV. Can anyone confirm this please?

    The fcc-rules:
    http://www.afar.net/tutorials/fcc-rules/

    Describe only the basic rules of FCC Rules for Unlicensed Wireless Equipment, where i think that these are for BASE / Ground Applications, but it doesnt describe the rules on UAV / Planes etc.

    If anyone has more information, please post.

    ASIA / UAV
    Would be nice if someone knows the FCC rules in ASIA as well.

    Thanks
    Gary
     
  9. Gary Haynes

    Gary Haynes Administrator
    Staff Member

    Joined:
    Jul 6, 2012
    Messages:
    5,211
    Likes Received:
    460
    Gary (from the other Gary) you made me laugh this morning. If the EU folks think our radios interfere with airplanes that's like the rules here in the U.S. about turning off electronic devices on the airline during takeoff and landing. Don't use your iPad. Of course the pilots are sitting up in the front with the Jeppesen Flightdeck charts/maps all running on the iPad full time all the time.

    So in this area sounds like the U.S. is actually a bit ahead of the folks on the other side of the pond. I am in total shock that this is possible.:D

    Andy had the correct section and with a bit of math you will see there is wide latitude. As you mention it is really about radiated power. Shoot if you could fly a 1000watt TX but had a dummy load on the antenna your would be legal since you weren't radiating any energy.
     
  10. Gary Hilgemann

    Gary Hilgemann New Member

    Joined:
    Apr 20, 2013
    Messages:
    11
    Likes Received:
    3
    Believe me that we sometimes "shake our heads" for so much bureaucracy here in EU. But we do not make the law or rules.

    If there is no different between a ground and UAV wireless video application in the U.S., it would make sense to pack the suitcase so that we use high power video transmiiter o_O

    If someone has more other infos about this I would appreciate to read it, specially the FCC rules in ASIA would interest me.

    Gary
     

Share This Page