Hi guys
I have sorted the fact that i need a 5.8 gig set up and i think for my type of flying i will be using a pan and tilt antenna array, but i,m completely confused by, reading about the various types of antenna,s i am puzzled there seem to be so many choices of patch type to choose from.
i understand a patch antenna as a higher gain and therefore better range provided its pointing at the aircraft however i am more than a little confused about the various polerization variant,s available.
I will hopefully be using a patch on one channel as yet not known which type and a vertical on the second channel.
Since i am going to be building up a system i would really like to get it right first time.
I am intending to purchase a duo5800 diversity rx and start with a low power tx first, to practice with, until i find my paperwork regarding my long lost radio ham license, then upgrade the power of my airborne tx.
So if any of you guys out there can point the way it will be really appreciated ----------
i presently fly a Chriss Foss centi-phase, and a middle phase full house variant of my own design and my brace of 450 heli,s and in the middle of a long term scale build of the Cornwall air ambulance.
My 35meg sets are very old now and i now fly with a full range spectrum 2.4
But after having a good read on this forum will be using an Eazystar for my first steps into fpv
regards Dizzy
Have a good look through this video, its long winded but great at explaining a lot
Antennas 101 - Polarization, Diversity & Gain Patterns (http://vimeo.com/8826952)
With polarisation theres only 2, linear and circular
Linear is in the shape of whips and linear patches, circular is in the form of cloverleaf and skew-planar antennas and CP patches
You normally have a rubber duck or whip on th eplane, this is linear, so using a linear patch on the ground works with no losses while flying perfectly level. But being a plane its not actually flown perfectly level that much. Then you start to experiance high losses.
Circular to Circular has no losses in any orientation so better suits flying. This is what most are now converting too. Add to this your on 5.8ghz video and you have multipath issues associated with it, with circular this is greatly reduced
:) Thanks coyote for the advice.
Its all clicked into place now just goes to show how much i have forgotten since my college days. ;)
I first saw this on simon's site and has to be by far the best video i came across that was easy to take onboard and understand without it been too much :D
I can never understand why you always have some idiot who wants to pull the guy down for trying to help when 99% of us get what he's trying to put over ??????????
Hi dps-dave
Being very blunt about that video its probably the best way this subject can be put over.
Brill vid :)
Very well presented too. :)
It really would have been nice if this type of media was used in my day at college.
Instead for me it was the black board and word of mouth. And it was slow to sink in, if i remember correctly
regards Dizzy
Andy`s presentations about the best example i`ve seen yet, others get lost in terminology, over explain things and end up with more confusion than anything.
It is a basic break down however, exactly what he intended but skips a few things, but i dont think it would be as easy to follow if he`d done it any other way tbh.
agreed it was excellently explained. the one thing i wonder is, would an 11dbi liner patch have the same range as a 11dbi circular patch? in the video he compared an 8dbi circ patch agenst a 11dbi liner. makes me want to spend more money lol yagi's yumm :D
That depends, in his presentation he shows a linear antenna ( Rubber duck ) on the plane. In which case the 8dbi Circular patch would have a 3dbi loss between the linear rubber duck and circular patch. But would work well in banking.
The rubber duck ( linear ) to 11dbi Linear Patch in his example would have no losses while the plane was level, but up to 26dbi losses in maneuvers.
The same when comparing an 11dbi circular patch to a 11dbi linear patch. It depends on the antenna on the plane, with a linear antenna the circular patch would loose 3dbi, if you used a circular antenna on the plane the linear patch would loose 3dbi and the circular patch wouldn`t loose any.
So in general, circular is best, circular on plane, circular on rx. That way you minimise dropouts in maneuvers and reduce multipathing too, but circular rx antennas genrally are lower gain to linear.
Two more questions please: what circular polarised tx antennas are available?
and if one is going to have two diversities, that means four possible antennas- so why not add an omni for going behind, say for landing as some trackers are not ideal for close manoeuvres.
Theres about 5 practical antennas you could use on a plane. But two that really stick out as good and fairly durable given there delicate design. The Cloverleaf and Skew-Planar.
So far most my circular has been done on a cloverleaf, but a Skew works just as well, a Skew is better at multipath rejection too.
4 antennas on diversity is overkill if your using a tracker really. 2 is enough, in which case a CP patch on the tracker a Skew-Planar as second antenna of the diversity and a Cloverleaf on the plane is my suggestion.
The high gain patch for range,the Skew for close in work. When i say close in though the clover to skew can cover km, so its not that close lol
Hi, without hi-jacking the thread but keeping on topic i have a couple of questions about antennas too. As im soon to buy my equipment and dont want to buy wrong.
Ill be using 5.8ghz system, and would like to you a circular RX, where am to find these for sale?
Also, i hear about having more than one channel, does that mean i could have one in one direction and one in another and have them switch automatically?
thanks
Andy
CP Antennas for 5.8ghz :
7dbi circular polarised panel antenna for 5.8ghz (http://www.firstpersonview.co.uk/antennas/5.8ghz/7dbi-circular-polarised-panel-antenna-for-5.8ghz)
13dbi circular polarised panel antenna for 5.8ghz (http://www.firstpersonview.co.uk/antennas/5.8ghz/13dbi-circular-polarised-panel-antenna-for-5.8ghz)
You have several channels, but only broadcast on one at a time, if one channels bad you swap to another, or if two ar flying together one uses channel 1 the other 4 or 7 etc
Ahh ,thanks for that. Just the job.
Thanks
Andy
Thanks for the video, explains really clearly :)
Cheers good video, learnt summit new!!! ;D
Jim.