Why four antennas inside Phantom 4

[Roger Pettersen]

Am posting this because I'm not able to find an conclusive answer to my question on the net, and to the fact that I`m looking for a way to amplify the video stream FROM the phantom 4 (regular Phantom 4not he pro version). The question is academic, and Im NOT planning to do any modification that is not according to any regulation. My question is as follows:
1) why is it four antennas on the Phantom 4?, some seams to indicate that all four is for both video and control, others that two is for video , and two is for control.

2)Why is it two antenna on the Radio control ?(Transmitter) some seems to indicate that both is for video and control. and some even indicate the left side is master and right side is slave (on a diversity system) Some indicate that one is for video and the other is for control

3) when looking inside the Phantom 4 , all four antennas seems to go inside the light bridge with different colors on the coax (wite, black dark gray light gray) what is (if any) the difference in regards to signal ?(video, control)

4) As I mentioned I`m looking for a way to boost the video signal FROM the plane. Will the regulars amplifiers sold for boosting the RC signals be compatible for amplifying the video signals FROM the Phantom 4 ?

 

[IIIDaemon]

[QUOTE="Roger Pettersen, post: 1125447,[/QUOTE]
.
...Roger, I've been experimenting with doing just that, by way of Tuning the Antenna on the Craft.. re: Boosting Signal from Craft, ..to each 'is own, but I'd suggest looking into the antenna(s), what I mean by that is with a better understanding of antenna's in general and these antenna in particular you'll find that a lot of the avail signal energy is wasted, due to poor antenna performance i.e. Tuning, Impedance Matching etc..., holding the Ctrl in your hands, the Left Conn/Antenna is the Transmitter, the RIGHT, Receiver.. from my tests so far, admittedly lacking to date, on the craft, both FWD legs are the Video Antenna (incl Compass), Rear Legs Ctrl Signal Antenna...
.

.

.
IIIDaemon
www.GasRecovery.net

 

[Roger Pettersen]

Thank you for the reply, i think we who are interesting on the matter should stay on this tread and exchange experiences. What is the video antenna on the picture? The black or the white ? another thing if the left antenna on the controller is the transmitter and left is the receiver, why is all the boosters log range kit come with booster/amplifiers to both left and right antennas ?

 

[Roger Pettersen]

By the way, I think the not so optimal performance on the antennas is to the fact of the broadband characteristic on the Light bridge frequency usage. So if you optimal the antenna you might consider to lock the link on one frequency.

 

[IIIDaemon]

.
...Roger, if you're interested theres more on this subject on my website, Equip-Page, Phantom-Tab...
.

.

.
IIIDaemon
www.GasRecovery.net

 

[John Locke]

on the craft, both FWD legs are the Video Transmitter Antenna (incl Compass), Rear Legs Ctrl Signal Antenna...

FYI, based on RF measurements I made with an RF meter, the video transmit antennas on my P4 come from the left legs. The right legs had no substantial signal, so I deemed those are control receive antenna legs.

I haven't taken my P4 apart, but I'm curious why your findings don't match for antenna location and function. I'm wondering if they changed this later in production, since my P4 is from the initial production run. Anything is possible with DJI.

P3P differs from the P4 for antenna location. The P3 locations make more sense to me. The video antennas on the P3P craft are kitty-corner from each other.

 

[IIIDaemon]

FYI, based on RF measurements I made with an RF meter, the video transmit antennas on my P4 come from the left legs. The right legs had no substantial signal, so I deemed those are control receive antenna legs.

I haven't taken my P4 apart, but I'm curious why your findings don't match for antenna location and function. I'm wondering if they changed this later in production, since my P4 is from the initial production run. Anything is possible with DJI.

P3P differs from the P4 for antenna location. The P3 locations make more sense to me. The video antennas on the P3P craft are kitty-corner from each other.

.
...Thats correct, my mistake, I should have said '.. both FWD Antenna are the VIDEO Antenna, AFT are the CTRL Antenna, and Yes, Left is Transmit, Right Receive, my apologies... the word 'Transmitter' in that line has been removed...
.
IIIDaemon
www.GasRecovery.net

 

[Roger Pettersen]

FYI, based on RF measurements I made with an RF meter, the video transmit antennas on my P4 come from the left legs. The right legs had no substantial signal, so I deemed those are control receive antenna legs.

I haven't taken my P4 apart, but I'm curious why your findings don't match for antenna location and function. I'm wondering if they changed this later in production, since my P4 is from the initial production run. Anything is possible with DJI.

P3P differs from the P4 for antenna location. The P3 locations make more sense to me. The video antennas on the P3P craft are kitty-corner from each other.

What color is on the coax on the video signal (your phantoms left legs)

 

[IIIDaemon]

What color is on the coax on the video signal (your phantoms left legs)

.
...Roger, '..FWD legs are the Video Antenna (incl Compass)..' Light-Grey...
.
IIIDaemon
www.GasRecovery.net

 

[John Locke]

.
...Roger, '..FWD legs are the Video Antenna (incl Compass)..' Light-Grey..

Based on my understanding of DJI's Lightbridge video downlink, it's a one way communication path, much like digital TV broadcasting from a hill. The video link does not use bidirectional communications like other brands using WiFi, which uses a two way handshake protocol, usually TCP/IP. The evidence I gathered indicate there are two transmit antennas from the craft for video and telemetry, based on the RF measurements I took, these are the two left legs. I presume the purpose of two antennas is to determine the location of the craft, and the craft azimuth, using the Go radar screen (that's only a guess). The RC has one receive antenna (right side antenna) for video/telemetry and one transmit antenna (left side, based on my RF measurements) for control signal. As for the craft receiver antenna, since I've never had my P4 apart, I would assume that's in one of the right side legs, and the compass is in the other leg (likely front/right as you state).

 

[N017RW]

Dual antennas provide physical diversity. This is commonly seen on cell towers where ther are two receive and one transmit per cell face. One of the two antennas will always have a better signal that the other. The system is constantly switching between the two based on SNR.

 

[billy_LB2]

Hi All - so has anyone been able to determine which LHS Leg is for what? One is for Video Down and the Other is Telemetry Down, is what I get from this forum.

So what is clear is that:

On the RC (looking at the RC as you hold it in any hand)
LHS Antenna is the UpLink Transmit Antenna?
RHC Antenna is the DownLink Receive Antenna?

The P3A like all others (but correct me if wrong), have 4 Antenna's, 2 X at front, 2 X at rear.
I dont buy that there are 2 downlinks, a Video and Telemetry. If there was, how come none of the screen captures show an additional carrier in the RF captures? All I see is a FH signal and a Video Downlink, where's the Telemetry link?

So the 2 Front Legs on a P3 or P4 are the Video Tx right?
Rear Legs are the receive for the Uplink Transmit??

Any confirmation would be great

 

[John Locke]

Hi All - so has anyone been able to determine which LHS Leg is for what? One is for Video Down and the Other is Telemetry Down, is what I get from this forum.

So what is clear is that:

On the RC (looking at the RC as you hold it in any hand)
LHS Antenna is the UpLink Transmit Antenna?
RHC Antenna is the DownLink Receive Antenna?

The P3A like all others (but correct me if wrong), have 4 Antenna's, 2 X at front, 2 X at rear.
I dont buy that there are 2 downlinks, a Video and Telemetry. If there was, how come none of the screen captures show an additional carrier in the RF captures? All I see is a FH signal and a Video Downlink, where's the Telemetry link?

So the 2 Front Legs on a P3 or P4 are the Video Tx right?
Rear Legs are the receive for the Uplink Transmit??

Any confirmation would be great

You can read this thread which shows the RC antenna orientation, and shows how the P3 are different than P4 craft for where the transmit and receive antennas are located in the craft landing legs.

 

[billy_LB2]

John,
Got it and thanks for the response.

P4 (assume all versions) have Antenna's configured as follows:

LHS Front, LHS Rear = Video Tx
RHS Front, RHS Rear = RC Rx.

For P3 (Assume all versions) have Antenna's configured as follows:
RHS Front, LHS Rear = Video Tx
RHS Rear, LHS Front = RC Rx

The config on the RC doesnt change?

Cheers