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Old Dec 07, 2011, 07:14 AM
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Switzerland, LU, Buchrain
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Originally Posted by madman962 View Post
Can anyone tell me what type of range I should be getting out of a 2.4 ghz spektrum DX6i using an orange RX including satellite antenna?
500m safe if you have video tx on board (FPV flying). Beond this it get's dangereous. Speckturm are nice RC-systems, but among the 2.4 radios on the market, their DSM2 (I know their latest versions have something else, but the DX6i falls into the DSM2 cathegory) way of transmitting is not really so good compared to almost all other systems on the market these days. DSM2 transmits on two frequencies which are selected at boot time, and since they do not hop they have to transmit with less power too to remain complying with ISM rules. The on board video transmitter will further reduce the RC-reciver sensitivity, and the result is a turly not so good range. That's usually no problem for regular RC-flying, but with FPV, where you tend to fly out and where you have the video transmitter on board too it becomes questionable.

Markus
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Old Dec 07, 2011, 10:51 AM
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Amherst, VA
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Originally Posted by TheNiceGuy View Post
I got 2 flights in on the setup today. I took it out as far as I could see, and actualy lost sight of it twice, and was able to use FPV to get it back in LOS. Overall, the video was better than stock antenna and patch. However, I was still getting quite a bit of drop outs, 'snow' (interference/range), and 'slide projector' (multi-pathing?). I wanted to record, but couldn't use the laptop today. This was all within visual range, not sure how far that is, but I assume within 1km? I wanted to try this out with the matching VRX, but ReadyMadeRC accidentally shipped me the wrong VRX, so itll be a while till I can do that. I'm hoping that clears everything up. If it doesn't, any ideas? I know this LawMate 2.4 500mw is capable of much better range than that.
Below are some pictures. The VRX is a good 10" from the other stuff. I set the CL with 1 'petal' forward, and tried to use the lipos as RMI shields. Separate 1000 3s for cam/VTX power.
The whole experience was good though. Figured out a good way to space things out. Everything else made such a small platform unflyable.
If this is not good, I can mount the CL under neath in that ball, although it will affect handling.
As a side, the tops of two 500ml water bottles make a great 2.4 CL antenna shield. Like a monocoque egg - almost unbreakable. You can even mount it with the cap to fuselage.
Sounds like external interference. WiFi maybe?

-Alex
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Old Dec 07, 2011, 07:10 PM
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There are several wifi points underneath the flight path. Theres a couple of spots maybe 100m away off to the left of my groundstation also. More info here. Its pretty hard to get away from wifi here. When my Lawmate VRX comes I can try channel 8, 2.5ghz.
The only things I can think of are to match VRX/VTX brands, and set the VRX up and away from me as far as possible. I could also try building another antenna set to the 31mmX62mm standard.
There is something wrong though if someone like Markus is getting 2+KM crystal video on a much weaker 200mw 5.8, and I can't get clear LOS on a 500mw 2.4.
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Old Dec 07, 2011, 10:32 PM
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Originally Posted by IBCrazy View Post
I just did a mile on two cloverleaf antennas. This blows a Vee/patch out of the water. I also did a test with a 4 turn helix and a cloverleaf and turned around after 1.5 miles as I was running to the end of my radio range. No loss of signal in a bank, no multipath problems. Just solid video. I'm not used to video this clean.

Needless to say, I am VERY proud of this antenna!

-Alex
What transmitter were you using?
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Old Dec 08, 2011, 05:11 AM
Firepower
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North Brisbane, Australia
Joined Mar 2010
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Originally Posted by TheNiceGuy View Post
I guess building these correctly is a slice for everyone else, but I'm finding some 'unsure' areas. Perhaps with an engineering background, or extensive experience in RC, this is all obvious, but the terminology, materials, etc. are mostly new to me. A simpler guide would help.
Alex was very kind to provide me with some build materials
and a sample lobe. Initially (this is how my CL was made) I bent some wire along the template lobe, and later made a photocopy of the lobe, but this proved to be difficult. For example, the mig wire comes coiled with a slight bend. So I used read backwards on this thread, then later used the search function to get exact sizes for 2.4ghz, and couldn't find them. So I started reading from the beginning of this thread. As of yesterday I have made it to page 19. Its going to take me a while to get up to page 122+. I deducted the approximate measured sizes from this post. I haven't confirmed this, but I think "1/4 wavelength" is each side of the lobe, and 1/2 wavelength is the arc (as a straight wire). So:
Quarter wavelength in mm = 76755/f in MHz

So for:

910MHz = 3.32"/84mm
1280MHz = 2.36"/60mm
2.4GHz = 1.23"/31mm
5.8GHz = .52"/13mm

So for me, 31mm sides and 62mm arc. Total wire length is 124mm, 1 wavelength.
Again IIUC, this is the MIG wire measurement from solder point to solder point: where it leaves the coaxial cable sheath at 90degrees, to where it meets the coaxial wire center in the middle. Thus you need teh actual MIG wire to be a bit longer on each end, say 3mm and 10mm, to accommodate solder.
For you on 5.8mhz, 13mm sides, and 26mm arc. 52mm total length, etc., etc.,...
I was concerned with distortion or length loss/gain due to bends, but Alex mentioned that the length is not important.
For the SPW antenna, I cut 4 lengths of wire to 137mm, lay them as flat as possible on a ruler, and marked them off all together with a marker at the bend sites mentioned above. Then pliers, and then by hand bend the arcs to approximates lobes. Then the unbalanced business of soldering.
I have broken the solder points 3 times trying to bend to different geometries. I'll only get away with that a few more times I think, then I'll have to order more wire and cables to make new antennas.
My antenna are still giving very poor video, so I'll have to try more bending of lobes.
As a side, I have seen a new type of video distortion. doubled images, and when I twist the VRX antenna, color saturation changes. Is this "multi-pathing"?
Also, what happened to the jig videos?

If I can get these antenna working, and if there is any interest, I can make a "Super Simple antenna making guide" for new people.

EDIT: My bench tests are surrounded by houses and wifi networks. Is this a special problem for 2.4 CL/SPW combos over my traditional 2.4 whip/patch?
Thanks for your information. I made the CL in the photos and have cut and bent up six more thanks to Alex's information but just thought the other way of making them with the wire running down the braid would be easier for me. ( I was on holidays in a motor home and bent the six more up with nothing else to do at nights)

The sizes were provided but guess I was just looking for an easy way out of a pattern but really it is not necessary if you sit down and spend time and work it out.

I guess it would be really difficult to comment on antennas, as everyone takes them at different camera angles. I just tried the CL in the park next door with a patch on the receiver and the picture was good for as far as I went. I'll try again tomorrow in the daylight and measure the distance.

A simple guide for new people would be good. The more information when you are new at it makes it a lot easier.

I might tonight have a go at another CL with the wire down the braid or a SPW.
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Old Dec 08, 2011, 05:47 AM
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Originally Posted by IBCrazy View Post
Sounds like external interference. WiFi maybe?

-Alex
wifi routers put out 70mW with 5db duck antennas... is that really enough to disturb his 500mW broadcast that is probably different than the wifi frequency?
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Old Dec 08, 2011, 07:03 AM
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Originally Posted by daronj View Post
What transmitter were you using?
Fox-700. And that was last year. I have since pushed that setup 5.1 miles!

-Alex
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Old Dec 08, 2011, 07:07 AM
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Originally Posted by chatch15117 View Post
wifi routers put out 70mW with 5db duck antennas... is that really enough to disturb his 500mW broadcast that is probably different than the wifi frequency?
They actually do more than that. My spectrum analyzer shows min jumping as high as -8db signal strength. Pretty high considering my 1 Watt transmitter at the same distance shows -6. They are also spread over the whole 2.4GHz spectrum. Any WiFi hotspot is spanning 2414 to 2486MHz. They use FHSS technology.

-Alex
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Old Dec 08, 2011, 08:42 AM
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Digital transmissions are 2.4ghz are allowed to be up to 1watt without any user licensing.

Although, I live in Chicago, and fly 2.4. You would expect ALOT of noise, but it really isn't to bad. I think his problem might be something other than noise floor.
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Old Dec 08, 2011, 09:28 AM
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Originally Posted by IBCrazy View Post
They actually do more than that. My spectrum analyzer shows min jumping as high as -8db signal strength. Pretty high considering my 1 Watt transmitter at the same distance shows -6. They are also spread over the whole 2.4GHz spectrum. Any WiFi hotspot is spanning 2414 to 2486MHz. They use FHSS technology.

-Alex
that's pretty high. Normally I get -30dB even when standing next to my router on 100mW(default is 71mW)

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Old Dec 08, 2011, 11:10 AM
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I'm certain there is a very big difference between your analyzer and mine I measured mine with a wideband sweep antenna with no input attenuation.

Set your analyzer to frequency sweep and take snapshots. You will notice significantly higher readings.

There is one great thing abut interference from WiFi: it will never completely block you out. The other nice thing is that houses and buidings are great Faraday cages. Not much signal leaves the house.

-Alex
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Old Dec 08, 2011, 07:42 PM
I think it'll work this time!!
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Alex,

Could a CL antenna for 900mhz be built on the base of the "junk" antenna? I have one, and I'm getting itchy waiting for my RG316 wire to come over on the "slow boat!"

Bob
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Old Dec 08, 2011, 09:35 PM
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I measured the leads with a caliper to be as exactly to the length for each let as I could get it. After I'd gotten the mig wire soldered to the three portions of the shield, they were a little loose. So, I wove a single strand of a stranded wire (around 30ga?) around the coax, going over leg 1, under leg 2, over leg 3, under leg 1, over leg 2... and then soldered it to help reinforce things a little.

I thought if anything, the extra reinforcement was forming a bit of a ground plane around the end of the shield to each of the legs. Planes have far lower impedance than wires, so I thought if anything, I was effectively shortening the loop which should have raised the frequency above the target, if anything.

Maybe I just got the gap between the shield and the top of the 3 arms too much shorter than "typical". There a gap of about 1mm there.

I only bring these things up because I'm trying to understand what little changes might affect the resonance of these things as some of the other circularly polarized antennas are supposed to be more sensitive to build than the Cloverleaf.

Is there anything I can do to tweak this thing as it is now? I know it isn't terrible, but 6% low in frequency isn't all that good. (I was aiming for 2.44GHz.)
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Old Dec 08, 2011, 11:19 PM
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how thick should the copper wire be for 1280mhz? millimeters please

I have 24 feet of #16 copper wire, i assume it is 16 gauge. I will stretch it to shrink the diameter. it looks like it is exactly 1mm wide so a 20% stretch will get it to around .8mm.
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Old Dec 09, 2011, 12:22 AM
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templates are coming once i get around to installing primoPDF
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