Re: wireless range vs. power

Thanks to all of you, I replied to this particular post because it had
the most questions for me to answer.
I do hope that Im not appearing to be lazy here, I've never had to
work in wireless systems as I am an aerodynamisist recently turned
image processing geek. I was expecting my question to have an easy
answer but as usual here wasn't so sorry and thank you for taking your
own time to help me.

On Apr 2, 11:54 pm, Jeff Liebermann <je...@xxxxxxxxxx> wrote:
On Wed, 2 Apr 2008 08:00:06 -0700 (PDT), Adam Chapman

<adam.chap...@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
I've ordered a wireless webcam that will be out onboard an autonomous
aircraft for a university project.

I've done that. You're about to have a battery problem.

The camera has a "2dBi Diversity Antenna" and transmits video over an
IP protocol in the 2.4-2.4835 GHz range.

Duz this camera have a manufacturer and a model number? A URL with
the specifications would be nice.


The camera is a Trendnet IP-TV301W model, specification at
http://trendnet.com/products/proddetail.asp?prod=110_TV-IP301W&cat=48.
I don't physically have the camera yet because the university is still
processing the account, which in my experience can take a very long
time. If it is possible to estimate transmission ranges with certain
equipment, I would have an easier job justifying the expense to my
department.

2dBi is a simple monopole antenna. It has a radiation pattern that
looks like a donut. There's a big null when in line with the antenna,
such as when the aircraft is flying directly overhead.


The 2dBi antenna can be replaced, if there is a better type then I am
happy to use it. I would prefer an antenna that emits as spherical a
pattern as possible, otherwise we will have to limit aircraft
maneuevres.



Now the aircraft needs to operate in a 500x500m area, although I
expect that my ground station computer will be placed some distance
away from the operating area.

I have this thing about numbers. How far is "some distance"? How
high does the air thing have to fly? What's the MAXIMUM distance you
expect to see an image?


I have just recieved more information from the competition organisers,
who tell me that all flying will be within 500m of the launch site and
flying is not permitted above 400ft (121.92 m) This gives the max.
Euclidean distance as 514.65m, although i expect we will be measuring
that distance on the aircraft with GPS, and with the civilian accuracy
limitations on GPS (~ +- 12m), I would suggest a target transmission
distance of 550m.

Due to safety rules we will never lose sight of the aircraft so we can
expect no obstacles between transmitter and reciever.

I've been slowly writing this reply all day, and thinking a lot as i
do so. A helical antenna looks the best as it is the most isotropic,
although it is also pretty big for our aircraft. However even that has
+-45 degree 3dB lobe, so i might have to have the aircraft bank more
when closer to the centre of its circular mission area.

The link calculator link from LR told me that if i put an antenna with
a 7dBi gain (like the one at _) on the UAV and at the ground station,
i will have a range of over 7km with a 100mW transmitter, which I
assume can be achieved using an in-line amplifier. Does this
calculator use the range in the direction of the strongest energy
emisiion from the antenna?

I guess that more than on antenna on the same aircraft with different
orientations would interfere with each others signals?

Adam
.

Relevant Pages

  • webcam for autonomous aircraft project
    ... If it is possible to estimate transmission ranges with certain ... such as when the aircraft is flying directly overhead. ... The 2dBi antenna can be replaced, if there is a better type then I am ... How far is "some distance"? ...
    (alt.internet.wireless)
  • Re: wireless range vs. power
    ... If it is possible to estimate transmission ranges with certain ... such as when the aircraft is flying directly overhead. ... The 2dBi antenna can be replaced, if there is a better type then I am ... How far is "some distance"? ...
    (alt.internet.wireless)
  • Re: wireless range vs. power
    ... Now the aircraft needs to operate in a 500x500m area, ... transmission range from power and frequency. ... Communication is a 2 way operation and you would need to know the Rx sensitivity, Tx o/p, Antenna gain... ... of both the devices to get even a vague idea of the Link distance that would be achieved by 2 staic devices. ...
    (alt.internet.wireless)
  • Re: Pitot tube for the antennae
    ... from where the coax would be grounded to the fuselage. ... spot for loading into the frame than with a simple tower but I believe ... VHF-AM in the aircraft comm band: ... All of this stuff would be a compromise, not a good antenna but one ...
    (rec.aviation.homebuilt)
  • Re: Horizontal Dipole - zero degrees elevation
    ... Have you tried doing this calculation with a horizontally polarized VHF antenna? ... Richard and Dave have answered your question -- the reason for the zero field at zero elevation angle EZNEC result is that the model ground is perfectly flat and infinite in extent, and the observation point is essentially at an infinite distance. ... Programs which calculate reflection coefficients for various ground shapes aren't very useful at VHF and above, because local features, especially in an urban environment, cause reflections that are often much more significant than the ones calculated by the program. ...
    (rec.radio.amateur.antenna)