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philthyy

Easystar Antenna position

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I finally am ready to start assembling my Easystar and am wondering how to position my video TX antenna. I seem to recall reading somewhere that the best postition is straight down, but I also seem to remember seeing Vrflyers Easystar has the video TX antenna straight up, right behind the camera in the cockpit of the plane. So which is best? And why? (I always gotta know why...its one of those things)

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Over the planes. Most of antenna have a swivel point, but a coaxial cable pass inside tthe swivel point, each time you swing the antenna, this coaxial cable bent and crush, slowly you will have degradation on the video power transmission, you will not notice it before long time. The best is to always kept this antenna straight.

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Yes up saves damage to your aerial but down is a little better for long distance flights. As usual a compromise.

Terry

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Each to his own Rob, the reason down is normally a little better is because there is less blocking by the wing and fus. With a lot of our planes this effect is minimal as the plane are made of material that can pass microwaves.

I too prefer the 14db patch for long range flights but I find a helper or some other type of pointing system is required due to the narrower capture angle. I recomend the 8db patch for general use as its practical to use it on a fixed tripod and is a big improvment over the standard whip. At the end of the day only you can make the disission as to the best setup for you, I just try and help that disission :)

Terry

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Thanks for the replies guys! I've been flying this setup for long distance(over half a mile anyway) for two years now, with my antenna pointing down. I just would rather have it straight up in the Easystar...no landing gear to protect it. So what is this 14db antenna you are talking about? Where can I get one? Or get plans to make one? BTW, I use a 1.2 system. Not a cheap Hong Kong unit though.

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The 14db patch is normally 4 patches together and sometimes called a quad patch. I dont know of any for 1.2ghz but that dose not mean you wont get one. Unfortunatly its not easy to make one because of the problems matching the 4 patches properly.

Terry

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I got my 14db patch from

HYPERLINK

It's advertised as having a 30 degree beamwidth, but my experience has shown it's pretty effective past that. I don't have anyone aim my antenna while flying, either.

pattern_hg2414p.gif

They also sell a 8db patch for 1.2ghz.

HERE

pattern_hg908p.gif

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Rob000

I know that is not the post theme, but look this patch antenna ( I have it)

Is the PA-L01 of www.antenna-tw.com

http://www.antenna-tw.com/pdf/PA-L01.pdf

It has 80º horizontal & 80º vertical, but in the practice is 100º

100º with 18 dBi gain!!!!!!!!!!!!! I never seen so wide coveragein a 18Dbi patch

I like it so much and use it for long range flight only.

t_antena_dettallado_182.jpg

post-2-1163843159_thumb.jpg

Edited by sergio00

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Sergio, I don't know how they get 18dbi gain at 80deg, that just dose not add up :huh:

My 18dbi patch is only 18deg beam. Have you done any propper testing to verify this ?

If you are using that with your 3W transmitter you then I guess you could fly at 50 miles range with no problem :o

Terry

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Hey, don't forget about how the antenna specs work...

18dB is the peak gain that will only be obtained with perfect alignment (0° H and V).

Then, the specified beamwidth is defined by the points where the gain has gone down to 0dB.

Everything inbetween should be read from the gain diagram you posted.

The outer circle represents the maximum gain (i.e 18dBi), then each circle means a 10dB loss (if I guess the numbers correctly on Sergio's post, a bit small...).

If you read that correctly, you'll see that you'll have those ~18dBi over a couple of degrees, then the gain falls to 8dBi at about 15°on each side (30° beamwidth), and to 0dBi at around 30° (60° beamwidth).

So, if you're flying more than 30° off the antenna's centerline you could as well use a stupid whip and have the same gain.

Worse, if you're 90° off, which easily happens when flying close to you, you'll get about -10dBi. That's a great attenuation.

The higher the peak gain the steeper the slope will be, and the greater the attenuation at "odd" angles will be.

That's why I don't use an antenna with too much gain. Ideally you'd choose your antenna according to the flight you plan on doing, that is a whip if you want to fly all around you at short distance, a high gain one pointed in the correct direction if you want to do a distance flight, and everything that goes inbetween.

I don't want to bother and often do both types in the same flight so I always go with the 8dBi, which is a good compromise. I point it in a way before the flight, take off, fly around a bit closely, and if I feel like going far I know I'll go where I pointed the antenna.

The gain diagram reflects the envelope you should fly in. Up to you to determine the scale, i.e what distances correspond the peak and "holes".

Edited by Kilrah

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I don't want to bother and often do both types in the same flight so I always go with the 8dBi, which is a good compromise. I point it in a way before the flight, take off, fly around a bit closely, and if I feel like going far I know I'll go where I pointed the antenna.

Hi

I thought that even a low gain patch antenna doesn´t let you fly backwards to you, but now after reading (again :rolleyes: ) your reply I´m not so sure :unsure:

Do you mean that with the 8dBi patch you can fly all around the antenna? I supose that if that´s possible obviously you can´t go so far at the back of the antenna like with a standard whip, but if would be possible to move away around 50-100m of the back of the antenne then I have to replace my whip.

BTW, I found this post searching for information about transmitter positions because I read somewhere that is better to fix it vertical, but I´m not sure if it´s true and why, so if anyone might explain it would be appreciated :)

Andres

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Sure you can fly at the back of the 8dbi pach antenna, 300 feet with no problem, and up to one kilometer in front. The angle of the antenna depend if you want to stay close or fly far away. Antenna should be 90 deg (perpendiculare) to the planes

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I have to buy a patch, many thanks :)

What I meant about the position, is the tx position, I know the antenna, for flying around must be vertical, but the tx position has any influence?

I remind what I said before of someone saying it´s better to have both, the tx and the antenna vertical, and realiced that I initially fix the tx vertical, but after the 3-4 flight I changed it because I had to bend the antenna to remove the batteries. I then rotated the tx and fixed it horizontal with the antenna bend to be vertical.

And lately I´m having a little worse video signal, so I wonder if this may have any influence <_<

Thanks

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I think you may get the signal blocked a tiny bit by the horizontal TX if the aerial is pointing up and not down.

Terry

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I completed my second flight with my Easystar FPV fixed cam with my wife as the spotter. I am happy to report that I managed to recover the plane on both flights without damage, lol.

On the first flight, I used a 3 dbi whip ant on the rx and the signal had fewer cut-outs than the second flight, where I used a 14 dbi patch att, pointed straight towards the sky on a cardboard box a foot off the ground. I was flying in a radius of about 1500 feet around the ant.

Question: Should a patch ant. be pointed straight at the plane? It seems I am almost better using the whip ant. unless I have somebody available to point the patch att at the plane as it moves? Thx.

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14dBi is a lot, so yes, you'll need to point it pretty accurately. The more gain the more precise you have to be.

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Also bare in mind that if your flying overhead or round your patch it may by polarized wrong at times unless its circularly polarized. Your patch needs to follow the polarization of your TX aerial.

Terry

Edited by Terry

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Terry, I´d ask you what do you mean but obviously I need to learn a lot of things about aerials :huh:

Does anyone of you have any link wich explain what is necesary to know for our application about aerials?

Even if there´s some "easy" way to do it yourself and there´s some guide would be great.

Thanks all :D

Edited by Andres

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Yes me too. I am not sure what is meant by polarization and such. My whip ant on the plane points straight up and same with the whip on the gound but it appears that the patch must be pointed at the plane - that seems to work even though I don't yet know the physics of it all.

Had my spotter point the patch at the plane like you guys suggested and it worked great - no interference at all and I went out about a half km or so. Flight lasted 3 mins since the wind was blowing plus 20km per hour and I had to go full throttle just to get it back to the field - it scared me really well. :D

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