fpv antenna question

[Tomstoy2]

I'm running a Foxtech 5.8ghz 200mw vtx and cloverleaf and skewer on reciever. Getting good range for the system, but now I want more. My 500mw vtx is trashed and are currently out of stock.
So, I'm contemplating going to a 5 turn helical on the goggles to push me out farther.

I'm curious, if I do this, what I can expect for results? Also, should I put the Skewer on the vtx or keep the 3 turn cloverleaf?

 

[RTRyder]

I just upgraded some of my 5.8 gear and I'm getting results almost as good as what I can do with my high powered 1.2 gear. The key to the performance was two things, the RX and the antennas. I upgraded from the Immersion Uno to an Immersion diversity and I'm using am SPW on one side and a 10db crosshair on the other. If I plug a cable into the RX and get video to the goggles that way I get amazingly clear video with pretty much no loss of signal or static as far as I can fly at my usual field, I've found I can even get a lot lower than previously and not lose signal.

Using the goggles with built in RX is losing some power vs the diversity RX but the difference in that case is I'm using an 8db crosshair on the goggles and getting almost as good reception and range as I do hardwired to the diversity. Just for comparison I tried the goggles using a 3 turn helical and was disappointed in the result. The helical works very well as long as you stay withing the sweep of the antenna but that tends to be a lot narrower and more focused than the crosshair. With a crosshair I can fly way off to the sides and even behind myself and maintain video quality far further than with the helical. With the helical whether I use it on the goggles or the diversity going out to the edge of the field drops the video quality dramatically and flying behind doesn't work at all.

I've even found that the anemic 100mw Immersion vTX I have gets a lot better range just using the crosshair on the goggles and using the larger crosshair with SPW on the ground station. I can push it all the way out to the end of the field which is over a 1/4 mile and I've been at or over 400 feet with no degradation of the signal on the 100 mw, with the 600mw it will go farther than I have room to fly.

TrueRC in Canada is now building the 5.8 crosshairs for sale, but at $75 a copy I find them a bit on the pricey side so I make my own. If you have the tools and are good at soldering it costs less than $10 for the materials to make one, problem is they're fiddly little antennas to make and the dimensions have to be spot on for it to work right. That said the first one I made was off about 1.5mm in one dimension and it still worked OK, since then I've developed a way to get the tolerances right down to where they should be and they work fantastic.

As for the SPW, they work best on an RX. I've heard of perople using them on both ends so it does work but what I understand from the folks that know is that the 3 lobe on TX and 4 lobe on RX works best, and in my experience the crosshair antennas work best of all of them.

Ken

 

[kloner]

fpv labs has the crosshair tutorial and all the measurements you need for that he has. i did mine almost like it but i used the bottom of a cup to keep my fingers from moving the wires. Amazing little antenna

when ken switched up from a uno to duo, he went from 250mw of power on uno to 3 watts on duo.... it's a whole different ballgame

this is using what he has but an uno on a tracker

the junk is wifi/cell phone related, the shearing at the top is a problem with some of the older receivers and new v2 600mw tx's. if you buy everything today you shouldn't see that.

man, look at the rssi, dragonlink is a joke

I also really really like my cannon, it was a 12 turn heli but it was super directional and nad zero side and rear coverage. it was out front or nothin

 

[Tomstoy2]

Ok,so let me understand this right. With a crosshair I can get more range than my spw and not suffer directionality of a helical all without changing my reciever. Then, when the Foxtech 500mw vtx comes back in stock, changing it out wil give me all kinds of distance?l

 

[kloner]

kinda, the trick is any directional patch whether helical or crosshair, the higher the gain or the more turns in the helical case the more directional they get. a 3 turn heli has a 70 degree beam, 8.5 dbi and has a mile to the side, couple miles behind and four to five out front, keeping more line of sight than if you had a higher gain antenna. It is unbelievably easy to be your own tracker with low to mid gain directional patches of any kind. It's not like it shuts off cause you got to the side, it just gets "junkier" and you go over and move it till it gets better. Reminds me of my rv's antenna for tv, you twist the handle around till it comes in better..... like that. on a crosshair, the only thing that gets bigger to increase gain is the back late, on a hli the backplates are all the same size, but the boner gets longer........

500mw, yes, and possibly all kinds of more interferrence. Somewhere in here theres a line you can cross that it starts going from an improvement to a problem, happens with one little thing going to big, especialy power out of something emitting rf signal. 500 is a good power to choose,,,,,,, you just don't have alot of room for seperation then it can go either way. Alot of the people you see here having problems don't have the stuff seperated enough,,, kinda common problem with multis

 

[Tomstoy2]

Thanks Kloner. Makes sence. I actually have pretty good seperation now on my Hexa. I have the vtx mounted below the load rails on it's own cf plate, antenna pointed down. Video quality is excellent. I get the point about more power and more chance of inteference. That's why I'm exploring reciever antenna's.

 

[kloner]

any of the directionals will blow your mind. makes it penetrate below los alot more, always has a nice crisp signal.

 

[R_Lefebvre]

Cloner... you talk about seperation, you mean about between the Vtx and the control Rx? I have a problem with the addition of a telemetry link. So I'm running 900MHz telemetry, 2.4GHz control (with telemetry also!), and 5.8GHz video. So far I am not having any issues with all of this on a small quad. But the VTx is only 200mW, and I expect the other two are small as well.

However, I'm also building an antenna tracker. I plan to have a 900MHz patch, 2.4GHz patch, and a 7 turn helical 5.8GHz all on the same tripod. Hope it's not a problem.

I've also heard it stated, and it makes a lot of sense, that it is better to go directional than it is to just increase power. Because if you are using Omni antennas, and just add power, sure, you get a stronger signal, but you also get stronger noise from all the reflections. Directional antennas are much better in this regard, because they have stronger signal in the direction they are pointing, and actually *reject* noise from the signal bouncing off all the things around you!

 

[kloner]

You will want to keep the entennas seperated on the tri pod. usually we measure stuff in wavelengths and usually at least one wavelength of seperation is the norm for most antennas. the 5.8 wave is 3.33333" ..... and so on.

honestly, i've never seen this done, keeps us updated. Yes the stronger gain on an antenna is alot more powerful than a higher power transmitter. they say anything over 500mw is too much,,,, i use 1 watt, the legal limit here. i have one 500mw in the telink, same lawmate product,,,, looking back there wasn't a whole lot of difference between it and my 1 watt just using 3 turn helis.....

this is the two, the big pile of gravel that i dive down at the wash is a 5000-6000 feet away, the big open field i fly to next, looks like an abandoned development at the end of the houses is 1 mile from where i was standing and all this was through trees you see when i launch

everything else the same except no eagle tree osd

this is the 1 watt, stats on screen

same ground station, same 3 turn, 2 different planes with different power. the later has alot better seperation but i also found when i got home the left rear lobe on the cloverleaf was broken at the shield side,,,,,, i expect a cleaner signal next time

when is say seperation, it means the part on the craft, all of em

a zII has like this

see al the wire between each piece and how far apart they are. Thats an osd, logger, video trans, rc rx, gps ant, esc spread around a 56" wide wing

then you get a quad and it's like this

the red and black wires lead to the eagle tree logger, barometer laying up against the flight controller, other side has the osd laying up against the controller, then the video and rc antennas are about 12" apart. not much seperation

then this is a f450, all the same stuff

all tighter and closer together. with uhf, this one didn't work very well at all. too close, no seperation.

this is the plane in the top video, great seperation for the components, why it works so good

 

[Orracle]

fpv labs has the crosshair tutorial and all the measurements you need for that he has. i did mine almost like it but i used the bottom of a cup to keep my fingers from moving the wires. Amazing little antenna

Hey Kloner

Is this the thread you were referring too regarding the necessary dimensions? Here

I would buy an antenna but shipping one all the way to SA would just be silly money. I think given a few tries I could make my own though and with a decent tutorial. I am currently using a CP and skew planar, but I'm looking for more range

Cheershttp://fpvlab.com/forums/showthread...-Circularly-polarized-antenna-tutorial!/page2

 

[kloner]

yes, thats it. there is a excel spreadsheet to download somewhere in there that has all the numbers you need.

to go further with better reception, directional patch antennas like those is a good start..... Honestly, i think i flew twice spw to bluebaem, everything else was patch antennas, either helical or crosshair. Crosshair grows the reflector plate to add gain, helicals grow longer out the front. Helicals can have 10 db gain and not seem much bigger than one with 5db..... helicals are total opposite, to run a 4.5 turn or more anything lower than 5.8 is massive, takes special servos and tracker to hold em. There big and heavy, but man do they work good. Thats when you can fly behind stuff

 

[kloner]

i don't think youd have enough time to hit the chute if something went wrong. Everytime i've had an issue it happened faster than i imagine getting shot. Don;t know it's commin, next thing you know it's o the ground. I've only crashed 2 good times. all the others were controlled enough to not even count, nothing broke, just bounces really hard.

these f450 are amazingly strong. all exept them legs sticking off the arms, that kinda garuntees a broken arm, why i got away form em

 

[Tomstoy2]

Chutes are a good idea, in theory. If you have an expensive rig, expensive camera, flying high enough,,,, but Kloner is right, things go bad it happen real fast! Plus, chances are real good if they go that bad the acft is tumbling. I'd be afraid it would tangle the lines rendering it useless.
I often wondered if a folding landing gear that acts as an airfoil would actually be a better idea.

Been thinking of making a crosshair, myself. It's not so much tx power as the ability of the receiver to see it. Seems easy enough to do, just hard right now to find the time. Damn work just gets in the way,,,
Hmmm, maybe I should just make it at work,,, :highly_amused:

 

[kloner]

hahahah the biggest thing on those is the bailen,,,,,, you want one, has an option not to and you want it ful of air, not glue. other than that all the measurments are there. if you read the last post ibcrazy talks about how hard they are, it's kinda true, i have had 2 good ones and 5 bad. on heicals, they all just work,,,, on those i use the crazy trap, he has options there too. super simple, both need that small copper tubing like for a ice maker, my hardware store sells it by the foot


EDIT,,,, on a 5.8 crosshair the single most important thing is the thickness of the wire it uses as the antenna,,,, i used a single strand out of stranded wire, like 12 gauge strand wire you get at a hardware or auto store, the stiffer stuff, not like whats on out batteries, that's too thin. I tried one with .035 welding wire and that's fine for 1.3, but as the frequency gets higher, the wire has to shrink, alot

 

[kloner]

on a cloverleaf, the single most important step not mentioned very loud is when you peel the shielding off the rg316 it has a length from the outter wire to the end of the inner wire and inbetween there is a short stub unshielded,,,, the hot side of the clover, the one the middle wire connects to has to be shortened however long that piece of unshielded coax is there, it's usually a mil or 2 but some people like more room for error and that's fine, you just gotta trim it out

http://rchelicollective.com/zen/kloner/antennas/

 

[FerdinandK]

just learned that there are also helix-arrays possible, so I hope to get a 4x10Turn array (+18db,24° opening angle) within the next time to be able to test it on my tracker. Currently I am using a 8Turn helix which really works great, so keen to see if the helix array can top that.

best regards

Ferdinand

 

[kloner]

please share


Alex swears the crosshair can't be topped....... I've been out there flying and fealt both ways. They sure are compact,,, this is a 10db 1.3 patch

the same thing in a helical is 16" long, has a dong 3" across and the reflector is huge 12"x12". That tracker would blow up trying to raise it

 

[FerdinandK]

I am using 5,8Ghz, Things are a lot smaller here

Starting with that:

and here my current antennas:

And this is the picture of the Helix array:

http://fpv-treff.de/download/file.php?id=510&mode=view

best regards

Ferdinand

 

[kloner]

hang on, lemme rub one out to that real quick,,,,,,, ok. yea, that's bitchen, huhum

lol

 

[Tomstoy2]

Kloner, you sick puppy!!!

I did it twice,,,,,