I have tested the maximum range of the Phantom 4 RC/aircraft control and HD video downlink (DJI Lightbridge) several times in the past week and achieved 4+ miles!  Frankly, I was not able to find true max. signal range because I would reach what I felt was minimum safe battery level to return all the home and still had 4 bars RC signal and HD video link.

As shown in the flight log screen grabs below, I was able to reach 23,650 feet (4.5 miles) on first test flight and 20,900 feet (4.0 miles) on second test flight before deciding to turn the P4 around and bring it home. Battery levels were 62% and 68%, respectively, at the max. distance turnaround point. Please note these tests were conducted flying over mostly unpopulated farmland with no trees, buildings or landscape obstructions for at least several thousand feet. I flew in P mode with obstacle detection turned off, which I call P-Fast mode (38 mph max speed). I could fly further, I suppose, if I only flew one way, but I like to bring my P4 all the way back to home point with 10-20% battery capacity remaining.

Here's the setup I use for reliable RC and HD Link connections out to 4+ miles:
1) On HD page Select Custom channel and watch interference plot for several minutes; choose channel with lowest signal levels and no intermittent signal spikes (I choose Channel 20 90+ % of the time).
2) On HD page, set Transmission rate at minimum (4 Mbps); this will maximize your HD Link range (this is critical)
3) RC set to P-mode so you have full GPS functionality
4) On Sensor page, turn OFF obstacle avoidance. This will increase max. horizontal speed from 20 mph to to 38 mph. This will facilitate max. distance possible on a battery charge.
5) Two Antenna should be nearly vertical at whatever angle you normally hold the RC in your hands.  The two antenna should be parallel to one another with wide flat sides facing the P4 at all times.
6) I use one simple, inexpensive ($30) third-party add-on to improve signal strength and range - it is a well-made aluminum parabolic reflector sold by a NJ (edited) eBay vendor that easily slips over the two upright antenna.  The perfectly shaped curved aluminum reflectors, which are behind the antenna, reflect and focus incoming HD video and telemetry signals coming from the P4 aircraft on the two antenna.
7) Continuously readjust (or hold body position steady) as needed throughout the flight to keep antenna aimed directly at P4.
8) ALWAYS start with a fully-charged battery.

One of my first flights I ended up losing video signal about a block from my house. One of the best things about #RANGEGATE has been all the helpful tips. I realized I was positioning the antenna all wrong. Thank you for the additional tips above. I want to try a range test, but after the way my low battery RTH test went tonight I'm going to put it off for a while.

Nice to see that as long as done correctly everything works fine

Thanks David. Your checklist is really helpful.

Any chance you could put a link on here for the range extender your got from EBay?

Thanks for the checklist! When the weather clears up again I will have to do a flight with my antennas positioned correctly. We get a lot of rain here in Washington state so it's hard to fly all the time!

Homestead72 Posted at 2016-3-27 03:49
Thanks David. Your checklist is really helpful.

Any chance you could put a link on here for the ra ...

This is the same Aluminum Parabolic Reflector and the vendor from whom I purchased in OCT 2015. Even comes in a nice zippered case.

http://www.ebay.com/itm/Aluminum ... :g:fbYAAOSwd0BV6Vof

David it would be very interesting to do the test again without the antenna reflectors.  This would be useful for the rangegate discussion.

Took my P3 and P4 out yesterday and flew them both straight out and back from me in the same direction. P3 lost signal at 8,200 feet. P4 finally lost signal at 9,880 feet. Both unmodded.

Here is a AirShou screen capture of a 5000m flight. It has been edited for time. Note that when the Phantom reaches over 5000m the RTH point is well behind the the battery's remain capacity. This required returning in Sport mode. The craft did make it back but did not catch up to the RTH point until about 500m from the HP.

Jkeller84 Posted at 2016-3-27 18:52
Took my P3 and P4 out yesterday and flew them both straight out and back from me in the same directi ...

i saw your video  of the p3 with the dbs , did you try it with the p4 ?  i can't imagine what range you can get with the p4 and the dbs mod

GTDrone Posted at 2016-3-27 19:24
i saw your video  of the p3 with the dbs , did you try it with the p4 ?  i can't imagine what rang ...

Not yet

Jkeller84 Posted at 2016-3-27 20:28
Not yet

please let us know if you do the test,

I'm thinking about getting a p3 adv and the DBS or
the p4 and the dbs ,  i don't do  4k  or video production may be in the future , now what i do is just have fun with the fpv ;)

i don't know if its a good idea to upgrade to the p4 or get the p3 adv ,   because i don't have all the money for the p4  should i wait and save some money  for the p4 ?

GTDrone Posted at 2016-3-27 22:35
please let us know if you do the test,

I'm thinking about getting a p3 adv and the DBS or

If you want my opinion, I would go for the P3A. The P4 is a great machine but it isn't something that I would consider a "necessary" upgrade. If you have the money and are interested in great 4K footage, then definitely go for the P4. If you are a little tight on money and you are not interested in 4K footage and obstacle avoidance, then I think the P3A is a perfect fit.

Jkeller84 Posted at 2016-3-27 20:40
If you want my opinion, I would go for the P3A. The P4 is a great machine but it isn't something t ...

yea that what i think , but  the only reason I'm thinking about the p4  is because of the dual IMU and compass
and also the speed ,  thats the only thing that is making e think about wait and get the p4

Can this be related to that the P4 has a higher default bitrate in auto mode in combination with people not realizing how important antenna polarization is (sport mode/tilting radio wrong)? I just see that people that are doing things right get good range and those that complain never give much info really other than that they think they are doing everything correctly. Just a little observation ^^

david.p.mann@ea Posted at 2016-3-27 18:17
This is the same Aluminum Parabolic Reflector and the vendor from whom I purchased in OCT 2015. Eve ...

Cheers David.  I have found the exact same product on ebay UK.  Ordered!

DJI-Ken Posted at 2016-3-28 02:47
Here is a AirShou screen capture of a 5000m flight. It has been edited for time. Note that when the  ...

Phew.   Thank Ken.

I guess it is down to experience to know when to 'push through' the low video signals.  When that happens to me at the moment (beginner) I sweat and then hit RTH!!!

Really interesting video though.

Homestead72 Posted at 2016-3-30 17:02
Phew.   Thank Ken.

I guess it is down to experience to know when to 'push through' the low video  ...

That's really good that you hit the RTH and not panic and fly erratically and crash the aircraft.
Also, if you lose video, you can also look at the map view and just fly the green line home.
Whenever you lose video, look at your RC signal and you probably still have full signal so don't panic and just face home and head back and the video will come back.

DJI-Ken Posted at 2016-3-30 14:53
That's really good that you hit the RTH and not panic and fly erratically and crash the aircraft.
...

Yep.  It really is about not panicking isn't it..  Good tip about following the green line.  I'll have a try of that next time (in non panic mode!).

Cheers Ken.

david.p.mann@ea Posted at 2016-3-27 10:17
This is the same Aluminum Parabolic Reflector and the vendor from whom I purchased in OCT 2015. Eve ...

I think I might pick some up thanks for the info.