Doofer 0 Report post Posted May 25, 2007 Hi there. This has probably been covered before, but I can't find it. Recently, I went FPV-ing but forgot my tripod (for mounting my 8dB patch antenna on). My flying site is some farmland with a cellular 'phone mast near one corner. I usually find (with my antenna sensibly mounted a couple of feet off the ground, facing away from the mast) that as range gets extreme, I get interference flecks. Anyway, I just laid my patch antenna on my rucksack, pointing up and slightly away from the mast, perhaps 6-8 inches (max) off the ground. To my suprise, range was fine (10mW 2.4GHz Tx), even when Dierdre (my war-torn Easystar) unexpectedly snorted sod some 200+m away. And no interference flecks... I expect some of you have experimented with receiver aerials close to the ground - and I'm confident someone can make sense of this (apparent) improvement in performance? Quote Share this post Link to post Share on other sites
Mark Harris 0 Report post Posted May 25, 2007 Hmm interesting. Could it be the evil mobile tower signal is getting eaten by the grass/bounced away before it gets to you? Quote Share this post Link to post Share on other sites
Terry 5 Report post Posted May 25, 2007 Yep, very odd. Guesses include, patch was outside the the strong beam of the phone mast. The ground was reflecting more of your signal into your patch, luck or something as yet unknown Terry Quote Share this post Link to post Share on other sites
rob10000 0 Report post Posted May 25, 2007 I've never flown with my patch antennaes more than 2 feet off the ground, and would prefer to keep them as low as possible. I think that the chance of multipath interference would be much less with them on the ground. Quote Share this post Link to post Share on other sites
wilson 0 Report post Posted May 25, 2007 I've never flown with my patch antennaes more than 2 feet off the ground, and would prefer to keep them as low as possible. I think that the chance of multipath interference would be much less with them on the ground. Indeed, the closer you have your receiver's antenna to the ground the better. Quote Share this post Link to post Share on other sites
Kilrah 2 Report post Posted May 25, 2007 I've heard that too, it's better to have the antenna on the ground than above on a tripod. Personally I always have it at ground level, on one of those little 20cm tripods just to hold it in place. Quote Share this post Link to post Share on other sites
Terry 5 Report post Posted May 26, 2007 WOW, looks like I just learned something ! I must be the only guy that did'nt know ? Dose anyone know the reason for this ??? I would guess that close objects like trees would soon get in the way as you fly out. Terry Quote Share this post Link to post Share on other sites
Doofer 0 Report post Posted May 26, 2007 I knowotchermean, Terry - I find it really hard to fly low at distance with the aerial like this - no problem with the picture, it just seems 'wrong' somehow(!). Quote Share this post Link to post Share on other sites
lvsupertech 0 Report post Posted May 27, 2007 I've never flown with my patch antennaes more than 2 feet off the ground, and would prefer to keep them as low as possible. I think that the chance of multipath interference would be much less with them on the ground. Yes I tend to agree with Rob. I have flown VR FPV with diversity and standard RX's with 14 DBI patch antennas Horizontally polarized. Only 18 inches off the ground facing about 70 degrees up. The reason not straight up is that your signals will be received while taking off and landing. Here is a video I have. This one though could have been better on the ground If I had ground checked the plane taxi first, and finding the right spot for the RX box of diversity. This video is not using the diversity, because the camera and TX not compatable with. Headset is from future hobbies.com. email; wade[AT]futurehobbies.com. Other planes I have has future equipment is great!! If you like check out video. Quote Share this post Link to post Share on other sites
Terry 5 Report post Posted May 28, 2007 Maybe someone with the Oracle could do a test if they have 2 identical receivers and patches. One mounted at ground level and the other at head height, any takers ? Terry Quote Share this post Link to post Share on other sites
Vrflyer 0 Report post Posted May 31, 2007 Yes I already read that, but did not beleive it... I will try it too Quote Share this post Link to post Share on other sites
Terry 5 Report post Posted May 31, 2007 I have been thinking about this while I was walking the dog, I can only think that by putting the aerial at ground level it misses most of the background noise that would otherwise reach it. Your plane however is at a higher angle and so its signal still reaches the aerial with no problems, result is less interference and longer range. If this is correct then the more sensitive receivers will be effected most, anyone with a poor receiver may not even notice the difference ! Also if you intend to fly at less than 500ft and over a mile away then putting your aerial on the ground is probably not an option. Terry Quote Share this post Link to post Share on other sites
Hartwig 0 Report post Posted June 5, 2007 (edited) Another thought comes to my mind, regarding the fresnel zone. In the Online Range Calculator (http://www.compex.com.sg/home/WDC.asp) you can see in the last two fields the minimum height clearance and the Fresnel Zone clearance. So maybe the point of better reception is related to the angle at which you put the receiving antenna regarding to the ground. Maybe that clears the Fresnel Zone, better than the positioning on a high tripod with a more flat angle. Just a guess... Edited June 5, 2007 by Hartwig Quote Share this post Link to post Share on other sites
