Replies to This Discussion

ModeratorPermalink Reply by Taylor Cox on June 1, 2010 at 9:38pm

Are you talking about an antenna for the xbee communication modules?

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Permalink Reply by Lew Payne on June 1, 2010 at 11:13pm

UAV wireless links can take place on several different bands; which band are you referring to, in particular? Also, as you already know, the UAV as well as the ground station requires an antenna; which are you referring to, in particular? To obtain 17 dBm gain at 900MHz would require an antenna a bit larger than most FunJets can carry. One final thing... what testing methodology did you use in order to determine that your particular design provides 17dBm gain? Do you have a diagram showing the major and minor gain lobes, from both the vertical and horizontal planes? If not, how are you able to make this claim?

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Permalink Reply by Fahad Naseer on June 2, 2010 at 12:08am

yes i have diagrams for major and minor lobes. Yes size is also larger but it is for ground station will work as a reciever.

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Permalink Reply by Lew Payne on June 2, 2010 at 11:56am

Helical antennas were invented in the 1940's by John Kraus (W8JK). Is there anything substantially different in your design that makes it stand out when compared to the standard helical antennas that have been developed over the years (see this link)? If not, perhaps you should consider publishing a construction article rather than a research paper. Since you don't really seem to be very forthcoming in your responses, I'll assume you have not yet discovered something that violates the laws of physics.

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Permalink Reply by Lew Payne on June 2, 2010 at 6:16pm

One note of curiosity... since you're using a helical antenna at the ground station end, and since helical antennas come in either LHCP (left-hand circular polarization) or RHCP (right-hand circular polarization) depending on which direction their helix is wound... and since you're not using a helical antenna on the UAV... how are you mitigating the losses from receiving and transmitting with different (or no) polarizations (since both ends of the link must use the same polarization)?

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Permalink Reply by Fahad Naseer on June 5, 2010 at 10:22pm

there are losses but the cost for antenna is very less, efficient results , so there is a trade off between losses and cost.

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Permalink Reply by RoboCopter on June 6, 2010 at 12:31am

What frequency does it work on?

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Permalink Reply by Morli on June 6, 2010 at 7:34am

I guess it is 400 mhz UHF <10mW module if my memory serves right( unless he has moved from it to better module since then)

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Permalink Reply by Fahad Naseer on June 6, 2010 at 9:27am

900 MHz.

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Permalink Reply by Morli on June 6, 2010 at 7:38am

Fahad,
can you pls post the link to your antenna and tx module? I am curious about "antenna is 17 dB" as to how/where you got that number. Thanks

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Permalink Reply by Lew Payne on June 6, 2010 at 8:09am

I notice that you really like to remain vague, and not give any information which would "lock down" your answers (and thus subject them to public scrutiny). This will be the last post I'm making in this thread, for obvious reasons. Antenna losses of the type we're talking about can be quantified using the Polarization Loss Factor (PLF). Since you did not state what type of antenna (wavelength and design) you are using on the UAV, I'm unable to complete the formula. Suffice it to say that you are experiencing at least 3 dB loss from polarization issues alone, which is the equivalent of cutting your transmit power in half.

What you term "efficient results" is what I call "lack of understanding of antenna theory."

Attachments:

• Polarization Loss Formula.jpg, 13 KB

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Permalink Reply by Fahad Naseer on June 6, 2010 at 9:27am

Dear
i am using vertically polarized monopole antenna on UAV of 900 MHz (.33 wavelength). but now i have replaced it with helical antenna of 5 turns at 900 MHz that of circular polarization, and at the ground station i am using helical antenna gain 17.3 dBi (kraus relation) frequency is 900 MHz, antenna length is 1.49m. HPBW is 24.5 degree. This information is clear, no confusion here. i am sharing my design with u people to learn about antenna i am not master of antenna but i have designed & constructed several antennas, but this time i found a new result so that's why i shared with u all. i have calculated really the gain was 17.3 dBi.

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