Antenna Question for the FPV guys

[CoppellDarryl]

Ok, this isn't really a problem that I'm looking for a solution to. It's really more of me just trying to optimize my system.

The picture below shows my FPV TX antenna placement. My antenna is basically straight out the back, pointed downward. I did a range test the other day and got good FPV image to about 1500 meters before I chickened out and turned it around to come back. (I'll go for more distance after I've scouted the flight path out a little better beyond 1500 meters). Anyway, naturally when I turned it around, the quad, gimble, and Hero 3 were in between the TX antenna and the RX antenna. So on the way back my image was fading into and out of snow some while at the great distance. (1250-1500meters).

My question is, if I had a longer antenna wire it would place the antenna even further behind the quad. Depending on the height and distance I'm wondering if that would improve my reception slightly when I had the Phantom and it's gear in between the TX antenna and my RX antenna?. If I had a longer antenna, I could also get the coil of the TX antenna a little lower toward the ground, which I think would make even more sense.

Any thoughts or should I just leave well enough alone?

 

[ianwood]

1,500m. Well done! Anyway, it's a common issue. LOS gets interrupted by the gimbal. Some have reported that a slightly longer antenna helps especially one with a 90 degree elbow. Going backwards can keep you from losing signal all together. Or switch to home lock and you can yaw to see around you and work on improving reception.

 

[Jdacal]

Mine's on the side and I've only been able to get 1020 Meters so far at about 120 Meter altitude. 600mW transmitter, what's the output on yours?

Edit: corrected mW from 620 to 600

 

[FlyingHigh]

Is having that pointed down a noticeable increase in range?

 

[CoppellDarryl]

Is having that pointed down a noticeable increase in range?

I've always had it pointed down. Everything I've ever read said to point it down. I did have it going off of the side originally, but still pointed down. I didn't have the greatest of luck with it there BUT I only had a few flights with it that way and I really didn't try to take into account any nearby trees or other objects that might have blocked the signal. I just kind of thought that having it face the rear I would get better signal so I tried that. Please note that for my test I found an area where I could fly and the signal from TX to RX would be unobstructed. There were a few trees eventually that I flew over but I think they were below the signal and didn't obstruct any. (I flew at 50 meters high).

 

[CoppellDarryl]

Mine's on the side and I've only been able to get 1020 Meters so far at about 120 Meter altitude. 600mW transmitter, what's the output on yours?

Edit: corrected mW from 620 to 600

I have the standard DJI 5.8 transmitter. (I ordered it here, http://www.heli-world.com/detail.aspx?ID=10932) I'm not sure what the transmitter power is. The only specs I have found on it say it's tranmitter power is "28 dBm ± 1 dBm"

I'd love to know what it is if someone knows maybe they can reply here.

 

[Jdacal]

Mine says 27.5 dBm output power so you are probably 600mw too.

 

[Damienlovegrove]

I bought one of these: http://www.ebay.co.uk/itm/191009295666? ... 1439.l2649

It means my coax can be straight and not bent (see antenna pdf for reason it should be straight) Now my antenna points straight down and is below gimbal and stuff. Perfect!

I hope this helps.

 

[CoppellDarryl]

I bought one of these: http://www.ebay.co.uk/itm/191009295666? ... 1439.l2649

It means my coax can be straight and not bent (see antenna pdf for reason it should be straight) Now my antenna points straight down and is below gimbal and stuff. Perfect!

I hope this helps.

I was unaware of that! Thank you for this information!

-

 

[goldfishrock]

I bought one of these: http://www.ebay.co.uk/itm/191009295666? ... 1439.l2649

I use the same with a Fatshark Antenna, works really nicely and only weighs a couple of grams ;-)

 

[CoppellDarryl]

I bought one of these: http://www.ebay.co.uk/itm/191009295666? ... 1439.l2649

It means my coax can be straight and not bent (see antenna pdf for reason it should be straight) Now my antenna points straight down and is below gimbal and stuff. Perfect!

I hope this helps.

My DJI AVL TX is reverse polarity so I had to find a RP SMA adapter. But I found it here if anyone needs one.

http://www.data-alliance.net/servlet/-s ... ale/Detail

 

[CoppellDarryl]

This is a new question but FPV related so I'll keep this thread going.

If you can't tell, I'm really enjoying FPV. My next upgrade I'm thinking of is a dual antenna system on my ground station end. I'll probably get a helical antenna to go with the omni directional one that came with the AVL Kit. I know I will need a diversity controller, and another reciever to attach to the helical antenna to. My question is since the AVL transmitter on my Phantom is a DJI product and has 6 channels (I think it is 6 anyway), won't I have to specifically get another one of the DJI AVL Receivers so I can set it on the same channel?

If so, does anyone know where I can purchase just the receiver? I can't seem to find them by themselves anywhere.

 

[Damienlovegrove]

Yes RP is the type you need - Sorry for the confusion.