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More FPV Questions!

#1
I’m just looking for some input on an FPV setup. So far, I’m flying an AXN Floater with Turnigy 9X 2.4 Ghz RX/TX and a 900Mhz 200mW FPV setup from hobbyking. My video is pretty sketchy using the stock linear polarized antennas. I want to initially be able to fly out to around ½ miles or roughly 1KM, but I’m sure after I do that a few times I’m going to want to go a little further to about 1 mile or 1.5ish KM. My first question is will my current setup be able to go out to this range with minimal tweaking? The first and probably most important addition I plan on doing is antenna modifications. Would a cloverleaf antenna on the TX and a helical on the RX be good for my uses? I also had a few other questions that I’m still confused about. Will 900Mhz vtx/rx interfere with my 2.4Ghz rc tx/rx? And I’ve also read that you should separate your video and rc systems as far as possible, how far is sufficient? I don’t have a lot of room on my plane and I currently have the ESC and RC rx under the canopy in the usual position and the vtx on top of the plane right behind the canopy. The only reason I ask about this is because the last few times I flew I lost radio control of the plane frequently (and at relatively close distances 100-200 yds) and don’t know if it’s the FPV gear or the different rc RX I’m using. Instead of using the stock turnigy rx I got a hobbyking rx (only because it is a little smaller but I think I'm going back to the Turnigy RX). How far will a stock 2.4Ghz rc system go under normal conditions and will a 900mhz system with above antennas be a good match? Any information or suggestions you guys have is appreciated.
 

lobstermash

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#2
Hi Brett. You can get some interference on the control signal from the 900Mhz system. I was troubleshooting mine for a while, moving it around the plane, but switched to 5.8 (for portability reasons) before I ironed out the kinks. A simple solution to remove interference is to add a low pass filter.

A cloverleaf on the vtx and a skewplanar wheel on the vrx should be good for a few km. I made some up from the stock antennas. CP antennas are much easier to make and solder for 900Mhz (relatively high tolerance), so don't be afraid of giving it a go.

On your control system, 100-200 yards is pretty bad range for the Turnigy or Hobbyking antennas. I get about 600m with it on the inside of the plane. Mounting the antenna on the outside of the plane in a spot where it retains line of sight, and is away from the ESC and vtx should help a little with the range, but if you like FPV it's well worth going with FrSky. The rx has 2 antennas, so you can mount them perpendicular, the module beeps at you when RSSI decreases, meaning you have warning when you're pushing the range too far, you can attach a 7db patch on the tx which increases your range considerably, and the system has failsafe (allows you to add rth, or at the very least the motor is off on landing and (possibly) the plane will glide in for a landing).
 
#3
Well I moved some things around and put the stock turnigy receiver back on and it didn't make a difference. Lost radio control and had a pretty bad crash at a fairly close distance so I guess a low pass filter is the next step for solving the problem? Are there any specifications I need to be aware of or any will do? Thanks for the help.
 

lobstermash

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#4
I'd be wondering about your receiver... I've never had range that bad except when the coaxial cable on the antenna is broken. I've flown up to 500-600m without any interference with that 900Mhz system and stock 9x receiver.

On the low pass filter, I don't have one (yet, due to going to 5.8), but I'm told by a number of sources not to skimp on the cheap crap, but get a good quality one from ReadymadeRC (or similar). The cheap ones simply aren't up for the task and can severely reduce your video range. They're only about $30, so it doesn't hurt the hip pocket too much. Just to reiterate though, I'd strongly recommend FrSky for the reasons listed above.
 
#5
My original thought was that there was a problem with the receiver when I was using the hobby king one. But I switched back to the stock Turnigy and still have the same problems. Hopefully it's not my TX. FrySky is definitely on the future purchase list with a low pass filter.