31 replies to this topic

[Old Man Mike]

Hi Guys,

I just posted this in my RCgroups thread but thought some the more technical folks here would find it interesting.

Here a test showing the line of sight range for the omni CPOD antenna system when using only a 10 mw 1280 Mhz Video Transmitter:



In this test both the Single CPOD and Dual CPOD antennas have matching preamps at the base station. A single CPOD is also used on the quad copter. A few notes:

1) At maximum range I tried to find any weak areas by rotating the quad. You see a brief fade but certainly there is no problem using the video to fly FPV at this range.

2) The Signal Bar display is accurately calibrated in dB. The left signal bar is the Single CPOD and the right signal bar is the Dual CPOD. Here is the detail comparison which includes some time before and after the above clip:



3) Note that the Dual CPOD never hit the bottom signal level and only had a couple of very brief spikes below the 5 dB level. For close in flying with more high angle flights, the Dual CPOD averages approximately 4 dB higher than the Single CPOD. However when near the maximum range the Dual CPOD often shows 10 dB higher signal. Overall I think the two antenns compliment one another well for a diversity setup although it is tempting to make both base station antennas Dual CPODs.

4) This test was done in a diversity mode. You can tell which receiver is the active one by listening to the audio. The left audio channel is the Single CPOD (Left bar graph) and the right channel audio is the Dual CPOD (Right bar graph). The diversity system in this test clip starts off with the Single CPOD and does not switch to the Dual CPOD until past the mid point.

5) Based on this test, the full power of 1 Watt should have 10 times the range (20 dB) of the 10 mw system. That would be approximately 12 km. Again note that this is a totally omni directional antenna system so no rotation is required to cover the full 360 degress of azimuth.

OMM

[Mr.RC-Cam]

Good stuff.

[Terry]

what aerials ?
any pics ?

Terry

[Old Man Mike]

what aerials ?
any pics ?

Terry

Well since you asked:

Here's the current FPV omni antenna rooftop installation showing a signal and double CPOD 1280 Mhz antenna plus the FASST 2.4 Ghz Collinear:




Close ups of the single CPOD:





Close ups of the double stacked CPOD with preamp and combiner:





Pattern of the Single CPOD:

Left Hand Circular Polarization pattern



Right Hand Circular Polarization pattern



The key parameter is the high ratio between LHCP and RHCP. This ratio provides the important multipath rejection which is the primary objective of the design.

OMM

[Mr.RC-Cam]

Nifty stuff. What kind of circular aerial is on the Tx end?

[Terry]

Great stuff, thanks for the pics

Terry

[Old Man Mike]

Nifty stuff. What kind of circular aerial is on the Tx end?

Thanks,

The same antenna is used on the quad copter:



OMM

[Mr.RC-Cam]

Fantastic looking setup. Thanks for the photos.

[liteglow]

Hi guys

My first post... and the first question I want to ask: Did you find anyway to extend the range of the Loc8tor tags ?
I notice you got some of them on your quadcopter.

I love the Loc8tor, but the range is so darn poor, I use them on my cats sadly I cant find them if they go to far away.
Glad if you got some tip.


Back to topic, I love your antenna and the pictures, that is great !!
If you got so long range with only 10mW, what will 800mW give you ?


Maybe you can assist me some help, I got the Futaba 9C that give me long range (i hope)
But my 800mW video system is only giving me 200-300 meters of range

I`m very disappointed as I want to do some long range FPV videos (1-2km to start with)
I got the 800mW system from Sunsky.. dont know if that can be trusted, the soldering inside seems pretty bad.

Anyway, cheers and thanx for all help

[Old Man Mike]

Hi guys

My first post... and the first question I want to ask: Did you find anyway to extend the range of the Loc8tor tags ?
I notice you got some of them on your quadcopter.

I love the Loc8tor, but the range is so darn poor, I use them on my cats sadly I cant find them if they go to far away.
Glad if you got some tip.

The Loc8tor tags are good to around 500 feet in the field but certainly goes down drastically inside a building. Some have experimented with a foil reflector with the handheld unit placed the proper distance to provide a more directional and higher gain system. I've seen some examples/discussion about that on the internet but you will have to search for it.

Back to topic, I love your antenna and the pictures, that is great !!
If you got so long range with only 10mW, what will 800mW give you ?


Maybe you can assist me some help, I got the Futaba 9C that give me long range (i hope)
But my 800mW video system is only giving me 200-300 meters of range

I`m very disappointed as I want to do some long range FPV videos (1-2km to start with)
I got the 800mW system from Sunsky.. dont know if that can be trusted, the soldering inside seems pretty bad.

Anyway, cheers and thanx for all help

Thanks, the current system has been improved quite a bit:





Just for fun, here is a video of my quad HD/FPV system flying at 300 to 400 feet to a water tower 1.5 miles from my home. The trip took about 5 minutes however the video has been compressed to under 90 seconds so you should not get bored. I slowed it back down for normal speed when it arrived at the water tower.



The FPV video in the upper right shows how well the Video RF link is now working with the new tower installation of the dual 1.28 Ghz CPOD antennas for video and 2.4 Ghz Collinear for FASST control. When the quad reached the water tower flying at 400 feet there was no line of sight to the home tower and lots of trees/buildings in the path. I've tested it all the way down to ground level at 2 miles where there is still video and FASST R/C control.

For higher altitude flights the range should be at least 10 Km for the video system. Note that this is a totally omni directional system. The max range for the FASST system with the 15 dBi collinear and 5 watt amp is around 50 Km. While that might seem like overkill compared to the video, the loss at ground level for 2.4 Ghz compared to 1.28 Ghz is about 4 times worse so the R/C control matches the video link pretty well.

OMM

[liteglow]

Old man mike (btw how old are you)

Thanx for the reply, I love the QUAD video, do you think quad is better compared to a plane ?
how is the quad for wind, and is it harder\easy on long distance...

I have a EZ that I think would be nice for my first test in the FPV world :-)
But if the antennas you have is what I need for good FPV, I think I can quit right now haha..
I dont have room for 6 meters high antennas haha

Yes since my Sunsky did fail I will try to buy the Lawmate 1000mW, it seems to be more solid and better quality (maybe) !
What sort of antenna would you recommend me to use on the Lawmate unit RX and TX..

In my project I want 2 set-up:

1. FPV on the EasyStar with headtracking etc... the range should be 1-3km (for beginner Fun only that is OK for a start right?)

2. I also want to use the FPV system on my car, but then I`m driving around many houses and trees blocking the signal.
but the range I need to have must be 300-500 meters..

When driving the car, I can try to put the antenna on my house roof.



Thank you for all help and advice.

Cheers from Norway

[Old Man Mike]

Old man mike (btw how old are you)

58

Thanx for the reply, I love the QUAD video, do you think quad is better compared to a plane ?
how is the quad for wind, and is it harder\easy on long distance...

A wing plane can go much futher than a quad because the quad must receive constant power to stay above ground. At just under 2 Kg AUW for the quad with HD camera, FPV system and other extras, 2 miles is about the maximum distance that it can go and still return safely back home. Of course the big advantage with a quad copter is that I can hover in a near stationary position like this:

I have a EZ that I think would be nice for my first test in the FPV world :-)
But if the antennas you have is what I need for good FPV, I think I can quit right now haha..
I dont have room for 6 meters high antennas haha

You will likely be flying the EZ much higher than I fly the quad so the very high base antennas are not that important.

Yes since my Sunsky did fail I will try to buy the Lawmate 1000mW, it seems to be more solid and better quality (maybe) !
What sort of antenna would you recommend me to use on the Lawmate unit RX and TX..

The Lawmate TX/RX comes with a small whip that is considerably better (in terms of low SWR) than the typical whips received with the Chinese stuff. The challenge will be finding a good 1280 Mhz collinear antenna for the base which provide the 360 degree coverage with enough gain for good range.

In my project I want 2 set-up:

1. FPV on the EasyStar with headtracking etc... the range should be 1-3km (for beginner Fun only that is OK for a start right?)

2. I also want to use the FPV system on my car, but then I`m driving around many houses and trees blocking the signal.
but the range I need to have must be 300-500 meters..

When driving the car, I can try to put the antenna on my house roof.

Thank you for all help and advice.

Cheers from Norway

The best way to get good FPV range when there are many trees and houses is a high antenna for the base. Certainly a roof mounted antenna would be far better than anything on the ground if you want 360 degree coverage.

OMM

[liteglow]

Thank you for your help

I will share my videos when I got some..
atm I only have flight videos, no fpv videos.

This is a fun and great hobby.

Cheers

[Doofer]

Well, I'm convinced - CPOD definitely looks worth trying.

Where can I find a design for 2.4GHz?

[Old Man Mike]

Well, I'm convinced - CPOD definitely looks worth trying.

Where can I find a design for 2.4GHz?

I would like to offer a 2.4 Ghz design but the big problem is being able to constuct it. At 2.4 Ghz, the solder points become so significant that it upsets the pattern and axial ratio. Even at 1.28 Ghz it took several iterations from the model to finally get a working unit. Perhaps a better modeling program would be able to do a design where the real construction factors could be included but certainly the one I use (4nec2X) is just not able.

OMM

Edited by Old Man Mike, 20 August 2010 - 10:03 PM.

[liteglow]

OMM : Do you build and sell a 1200mHz RX antenna ? :-)

[Old Man Mike]

OMM : Do you build and sell a 1200mHz RX antenna ? :-)

I do not. I give my designs to Rusty for fabrication and selling. I'm not sure if he is ready to start selling them yet but here is his website:

http://aglhobbiesllc.com/shop/

OMM

[Helix1]

RC-Cam'er

You haven't by chance opened up your HD Hero? Any idea who makes the image sensor?

Thanks

Patrick

Edited by Helix1, 17 September 2010 - 01:05 PM.

[Kilrah]

It uses the standard Ambarella chipset that's found in every one of these small HD consumer cameras. There are several manufacturers for the sensors, but the markings are on the back of the BGA chip, so you probably won't find many wanting to desolder their gopro sensor to find out which one it uses

[Helix1]

It uses the standard Ambarella chipset that's found in every one of these small HD consumer cameras. There are several manufacturers for the sensors, but the markings are on the back of the BGA chip, so you probably won't find many wanting to desolder their gopro sensor to find out which one it uses

...... I was wondering about that as well - so, thanx, thats helpful info. If you ever do find out Kilrah drop me a note please. I've looked high and low on the net, but can't find any reference to it anywhere. I asked GoPro and got a "sorry, can't say" reply from them!