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Jan 06, 2016, 01:25 PM
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Car Radio vs Air Radio for Vehicle FPV


Hello Guys, I am setting up a Turnigy Trooper 4x4 for FPV and I am running into RC range issues.

I got the Trooper ARR from Hobbyking and the GT2B 2.4ghz Radio.
5.8ghz 200mw video and 700tvl camera.
910mhz 800mw vtx.

The camera is mounted on the roof of the truck and the vtx is on the back between the body mounts. The rc rx is right above the center shaft next to the battery bay.

Without the vtx on, I can go far enough with the GT2B that It is hard to tell if I am moving forward or backward with the truck and have perfect control. With the 5.8ghz OR the 910mhz vtx on, I loose control somewhere between 150ft and 200ft. I lose the rc signal at around the same distance with 5.8ghz or 910mhz.

I tried a 75mhz Hitec Lynx FM radio and was able get about 300-350ft with the 910mhz vtx. The range was the same with the vtx off. The 75mhz didn't seem to go as far as the 2.4ghz.

Would using an airplane rc system, (Turnigy 9X with FRSky 2.4ghz OR JR 72mhz FM) give better range than the car rc systems?

Is there something I might be overlooking with the car radio setup?

Thanks
pc_pilot
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Jan 06, 2016, 02:30 PM
A man with too many toys
I built a FPV Jeep a year ago and went through the same problems. The only solution that I found was using my airplane transmitter with Dragon Link long-range radio. I was going to try to figure out how to make Dragon Link work with my car transmitter but never got back to that project. I wonder if anyone has made that work?


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Jan 06, 2016, 03:19 PM
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Maybe if the car transmitter has a trainer connector you might be able to get it to work with the Dragonlink.
Jan 06, 2016, 03:43 PM
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Daemon's Avatar
910Mhz video steps on a lot of 2.4ghz RC receivers, including FrSky (which normally
would provide plenty of range, even on the ground).

Agree that a UHF system would be better for this specific application. I recommend Rlink
as one of the things it does very well is work low and behind obstructions.
Jan 06, 2016, 04:17 PM
A man with too many toys
Quote:
Originally Posted by pc_pilot
Maybe if the car transmitter has a trainer connector you might be able to get it to work with the Dragonlink.

None of my car transmitters have trainer ports. I donít think that is a feature on any car transmitter because itís not needed.



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Jan 06, 2016, 04:22 PM
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What about a 72mhz airplane radio? Do they work well with 910mhz video?
Jan 06, 2016, 04:29 PM
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Quote:
Originally Posted by RC Man
None of my car transmitters have trainer ports. I donít think that is a feature on any car transmitter because itís not needed.



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there are some with them, but they are usually called dsc ports. my gt3b has one. there have to be others.
Jan 06, 2016, 04:47 PM
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Derelicte, Are you driving FPV with the GT3B?
Jan 06, 2016, 05:12 PM
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no. I could set up a test though.
Jan 06, 2016, 06:41 PM
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branflakes's Avatar
I for one can confirm that 72 MHz and 900 vid is rather rock n roll. at one point my LOS is broken by 20 brick houses

EMaxx FPV Long Range Neighborhood run (9 min 33 sec)


rc transmission point was inside my bedroom simply punching out through the house and through all the others

its so sick to do ground based work no LOS restriction at all, but ruffians can steal it that's for sure. I can outrun any 15 yr old with this thing, tested. 79 inch rx antenna, heh.
Last edited by branflakes; Jan 06, 2016 at 09:52 PM.
Jan 06, 2016, 10:39 PM
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Branflakes, Which rc system are you using, did you add wire to the regular rx antenna?
Jan 07, 2016, 09:14 AM
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branflakes's Avatar
That mod took me about a year to arrive at but five mins to install

I had tried different types of control systems galore initially only getting to the end of the block before loss of control

Then I hooked by my Jr Quattro and one of the Jr receivers that you can bind to any tx and ran for a while with the rx mounted on the roof, high up, with an antenna guide to keep it vert

That mod was letting me barely loop my own block behind my house, from inside, so I knew it had punch potential. Then after reading here about wave fractions of antennas all I did was buy a replacement antenna for the rx, and solder them tip to tip for a half wave or full wave I can't remember if 79 inches is half or full wave approx 72 MHz but it doesn't matter, that was the kicker. Massive distance but one long antenna to figure out how to stand up.

So a few more weeks of testing and I found the mast that can take a roll wreck, and always self right, without bending or occlusion. It's old school servo guide tubes. Three are assembled end to end and taped with the long wire running up the middle. Then several are positioned around the base like tower support *with coat hanger wire* placed in the center as support. Home Depot metal guides are drilled into the bottom pan of the car and zip ties affix the mast to these bases.

Then it's all gorilla taped up as I use more tube guides around the center where the bend is harshest on a wreck. The combo of tape, wire, and multi tubes cannot be beaten. For five years it will self right, stay flexible, and hold my giant long antenna straight up for neighborhood or wilderness carving thanks for checking out!
Jan 07, 2016, 10:07 AM
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Thread OP
Thanks Branflakes, I will try the antenna mod on the 75mhz system I have.
Jan 07, 2016, 10:56 AM
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parajared's Avatar
Also airplane radios are geared to have more channels.

Although the Trooper isn't geared for this you may one day want a ground vehicle where the rear tires steer too and you need more than just your regular 3 channel ground tx for that.
Jan 07, 2016, 12:13 PM
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branflakes's Avatar
I think the current distance record for ground fpv, using analog gear is about a mile now. But this one above ranks top1-3 in terms of non line of sight work, what I find to be strangest is that the blockages don't reduce or increase my range. im only getting about a quarter mile NLOS -and- fully unobstructed dx, the houses don't matter nor the lack of them. weird dynamic there


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