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IA-Flyer

remotely located 2.4GHz radio TX antenna

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First things first.

I'm delighted you're still around Mr. RC-Cam!

It's been quite a while since I was flying around using a RadioShack (X10 based ) video sender using high gain RX antenna. :)

I have a new small project I could use some advice with.

Due to the extreme cold and some health issues, I would like to remote mount my control transmitter antenna on the roof of my car.

It's a HiTec Aurora 9, 2.4GHZ using a module with a IPX connector on the modules board.

I'm not looking for a range increase, or decrease.

I renewed my HAM license a couple of months ago.

I've ordered in these parts so far and its not a huge deal if I need something different, or it just wont work. Technically or legally.

6" RG178 mini PCX U.FL to SMA Female cable.

http://www.ebay.com/itm/131064460489

2 Watt Amplifier.

I would have ordered a 1 watt amp, but this shipped from the states.

http://www.ebay.com/itm/290900017532

3 Meter RG174 cable

http://www.ebay.com/itm/320919834832

Plan on using a 2db dipole from one of my 2.4GHz video transmitters.

At this point I should stop talking and listen, but if you remember me.......

I used this line-loss calculator trying to run some numbers.

Not figuring the line to the amp just the line to the antenna.

2W in, 3 meters RG174 = 500mW at the antenna. (guessing somewhat lower with connectors and antenna efficiency)

15db attenuator = 123mW ??

Yes, No, thoughts, corrections, go away kid your bothering me. lol.

TIA

Jim

<edit> DJI Phantom 2

Edited by IA-Flyer

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I did a quick calc. After the 15dB attenuator you'd have about 16mW. My math:

33dBm (2W) - 6dB (3 meter RG174 coax) - 15dB (attenuator) = 12dBm.

12dBm = 15.8mW (http://www.rapidtables.com/convert/power/dBm_to_Watt.htm)

Couple of comments:

The specs to the 2W RF amp states that 9 to 13 dBm is required on its input to achieve the 2W output. So you will need to determine the RF output level of your R/C Tx and then attenuate it to this range.

The long coax will be in the receive path for the R/C Tx. I don't know anything about the Aurora, but if it has telemetry then the received signal will also experience a -6dB cable loss. Multirotors don't fly far, so any decrease in telemetry range would probably not be noticed, but keep it in mind.

There's other ways to do this. Here's two alternate solutions to consider.

1. Remove the existing RF module from the R/C Tx and remotely mount it (with antenna) on top of your car's roof.

2. Connect a R/C Tx (that is placed on your car's roof) to the trainer output of the pilot's Tx. The roof mounted Tx is set as the "master" and it emits the RF.

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"1. Remove the existing RF module from the R/C Tx and remotely mount it (with antenna) on top of your car's roof."

Thanks! Thats exactly the option I was looking for.

I should have thought about in the beginning but didn't.

I even have a TX-Ready module that connects to the pins. Brain lock.......

I'm thinking of using a 10 foot USB2 cable to the module and connecting the woven outer shield to the TX ground only, leaving the other end open. I'll use one of the inner wires for ground on both ends and share it with a regulated battery ground to power just the module.

Thoughts?

Thanks again!

Jim

PS: I'll play with the amp later if I need more range with a plane.

Have you guys discussed this RF Meter yet?

I know it would be a joke for a long time radio enthusiast, but for a hobbyist would it give me the power out of my TX?

Edited by IA-Flyer

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I'm thinking of using a 10 foot USB2 cable to the module and connecting the woven outer shield to the TX ground only, leaving the other end open.

There's some debate about only grounding the cable screen's source end. But in your situation I doubt it matters if you ground both screen ends or only the source end.

I plan to evaluate the ImmersionRC power meter in a couple months, but for now I can't offer any feedback. No doubt there's already some user comments, so check around the various FPV forums.

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I'll be looking forward to the review.

I tested ImmersionRC's new RF power meter and it is a nice tool. I can post a short mini-review if there's any interest in hearing about my experience using it. Otherwise, just buy one and enjoy it. :)

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Looks like a good bit of kit for testing aerials, quite tempting...

Terry

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Affordable / useful test equipment for 5.8GHz FPV is hard to find, so this new power meter is one of the few options available.

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My ImmersionRC RF power meter came in back in february.

I would have posted about it sooner but I haven't came out of my work shop since. :)

I can't believe everyone doesn't have one of these. It's a real eye opener.

I've found a bad antenna instantly, before blowing the vid tx. Found the 4 or 5 highest power (ham legal) frequencies out of 32 without testing them one at a time in the air.

Found the best antenna combo and the difference between removing the plastic covers on 5.8gHz clovers and leaving them on.

Tested the power output and found the most powerful channels in a ebay 200mW mini TX (with a permanent Antenna) by comparing it to known transmitters using the same RX antenna connected to the power meter.

I'm starting to sound like a shill for immersinRC but as you can probably tell, I'm just excited.. There isn't much out there I've found that is this usefull for someone that flys FPV. It's like a borescope for a competition target shooter.

Heck, I flew my phantom with a TS832 that puts out 340mW after it warms up to 2000 meters a while back with clear video all the way. 2.5km in another flight but I wasn't recording the video feed for that flight.

I'm setting up several other birds right now so this thing is going to get a workout!

Here's a flight to 2km with my phantom 2 using a pair of skyzone goggles $12.00 Chinese clovers.

Alot easier than the old days when I had someone pointing a high-gain yagi at the plane.

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It is indeed satisfying to be able to confirm the RF power and compare antenna performance.

I recommend that you download the VAT-30W2+ 30dB attenuator data sheet from the mini-circuits web site. This data sheet has a useful attenuation performance graph that I use to make corrections to the meter's attenuation offset value. Although the graph represents statistical average values, I found that it was a close match to the actual performance of the 30dB attenuator provided with my meter.

So I use the graph to adjust the attenuation values that I enter in the meter's menu. This allows my ImmersionRC RF tool to achieve measurement performance that is nearly identical to my HP and Tek spectrum analyzers. Those things cost 300X more than the meter, so it's cool to duplicate the measurement performance at such a low cost.

Give it a try. After adjusting the meter's attenuation value you're going to see that your 5.8GHz RF power measurements will be much lower than before. But closer to the truth. :)

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