|Mar 10, 2012, 02:31 PM|
Yet Another Newbie 5.8GHz Setup - A Catalog of Statics
About this thread
Last update of this post: April 27, 2012
There are two types of thread which I find especially useful when looking for information: those which focus on a particular element of the setup (Video TX, OSD, Telemetry, RC link, antennas, ...) and those which discuss a complete setup, how the elements were selected and how it is put together. This thread is meant to be of the second kind.
I am very new to FPV so I'll ask questions and report on progress here. I'll try to keep an index of important findings and discussion in this first post in order to try and make it useful for others.
Note: Do not hesitate to post anything you like in the thread (remarks, questions, suggestions, comparison with your setup, ...), it is not meant to be a monologue!
Current Status: Trying to make a light FPV POD
My setup seems to work great in a 500m radius (I have not really tested beyond that). Still a lot of testing and tweaking to do but it starts to work. I am currently trying to see how light I can get the pod to be able to put it on small planes. Not really looking at long range for the moment.
Video of my very first FPV Flight: http://www.rcgroups.com/forums/showt...5#post21227784
Have a look at the latest posts to see what we are discussing (I try to keep this first post up to date but there is a delay :-)
Thread index and useful links
Do not hesitate to suggest things I should put up here.
FPV Flights Videos
Original First Post: My newbie 5.8Mhz FPV setup needs help
I have been planning to attempt flying FPV for a while, I have read quite a lot about different options, antennas, etc...
Today I have put together my first setup which is composed of a cheap 5.8MHz 200mW transmitter, an small SD video recording system and the cheapest goggle I could find.
Here is a picture:
I flew the plane around and recorded the video, just to see how it would perform. The result is not a complete failure but I have a range problem. I thing I am not getting more that 100 to maybe 200 meters where at least 500m should be fairly easy to reach.
Here is the video:
In the next few posts I will provide details about plane, antenna, receiver, recorder and goggles. The information might be helpful to someone and some of you experts might spot some mistakes I have made.
|Mar 10, 2012, 03:37 PM|
Video TX/RX (5.8GHz 200mW) and Antennas
For the video transmission I have chosen this kit from HK:
My RC link is at 2.4GHz so I needed to choose between 900MHz and 5.8GHz. For the first attempt I chose 5.8GHz because I am not looking for long range, my flying area might have some obstacles and smaller antennas are required.
I went for 200mW because it is supposed to give a range of 500m+ which is sufficient for me (and can be extended with the right antennas, for extreme range see http://www.rcgroups.com/forums/showthread.php?t=1441664).
The camera I am using is this one:
When I got the TX and RX I made some experiments indoors and was really disappointed by the range and quality of the video link. After some hours browsing RCGroups I found that probably the stock wipe antenna are not the best option.
After reading a bit more mainly from rcexplorer.se tutorial and IBCrazy wonderful tutorials, I built a Skew-Planar Wheel antenna (http://www.rcgroups.com/forums/showthread.php?t=1352583) for the receiver and a Cloverleaf antenna (http://www.rcgroups.com/forums/showthread.php?t=1388264) for the transmitter.
Here are some pictures:
I am not sure how good my antennas are but using them has improved a lot the range and quality of the video link indoors (so I assume this would also mean that it is improved outdoor but this is not sure). I cannot really test anymore because I have destroyed the wipe antennas to build the new ones.
As shown by the video in the previous post using this setup I got only about 100m (maybe even less) of reliable range so there is probably something wrong. Maybe my antenna are not good enough, maybe they were not properly located, maybe there are interference in the area... What do you think ?
On the plane the antenna was upright in front of the plane and the RC RX was about 10 cm away (as far as I could get it).
On the ground the antenna was not very high and also in the upright position.
Here is a picture, if that can help:
Should I have placed the antennas differently? Maybe the receiver antenna should higher? Could that make such a huge difference in range?
Opinions, advises and suggestions for experiments I should make are welcome!
Next I will post a few findings on the RC305 receiver (I might have made some mistakes there as well :-).
|Mar 10, 2012, 05:25 PM|
Setup of the RC305 5.8GHz Receiver
I got the RC305 receiver out of the RX/TX kit I bought but the receiver can also be purchased alone for $24 (I am thinking of buying a second one to set up diversity but that is another story):
For my setup I needed to power it up and get the A/V out and get the signal strength.
For the power supply, it works from something like 7V to 12V but by opening it up it looks like everything runs from 5V (or less) and the rest of the power is dissipated by a linear regulator which basically just heats up the whole thing. To avoid wasting power and heat I am bypassing the linear regulator and powering it up from 5V directly. It seems to work ok.
Another problem is that since the antenna is on the receiver, to be able to put the receiver+antenna somewhere up in the air I did not want to have too many wires going from the receiver to the rest of the ground station. So I have used single 4 connectors properly shielded cable. Here is a picture:
Green: Audio (the audio quality I get is crappy, so maybe I should have chosen the other channel)
Here is how it look ready for action:
BTW, on the ground station I get the 5V using a cheap switching mode EBEC which I power from a 2S lipo. This is much more efficient than the linear regulator integrated in the receiver and I also power the goggles from it :-) (The one I use cost only $4: http://www.hobbyking.com/hobbyking/s...dProduct=15212)
I think that is it for the receiver. Just shout if you see something I might have overlooked or damaged by doing these mods!
|Mar 10, 2012, 08:13 PM|
Couple of things.
1. your TX/camera pod looks really dense. With the 5.8ghz antenna basically beside it, you are going to be cuasing some reflections, and if that pod gets between the TX antenna and the RX antenna, you will basically be blocking the signal.
2. although you antenna's look good, 5.8ghz can be tricky. It could be possible that they aren't as good as they look. Might try buying a set for some peice of mind.
3. Check for background noise on the channel you are using. Power the RX up alone, and look in the goggles. If you see lines/flashing in the snow, you've got external RF. However, seeing as you live in norway, and that looked like a fairly remote area, you are prolly free of RF.
4. The RX mod worries me. FPV is best when you use K.I.S.S. Granted, providing 5V to the module isn't a big deal, but If others are having sucess with unmoded RX's, and yours is modded and not working so well, that is what i would change first. I think a new RC305 is somewhere around $30? so not a big investment.
5. If for some reason you feel your current rig is fine. you might try building a helical. That said, i think you've got problems that aren't going to be solved by more gain.
|Mar 11, 2012, 05:21 PM|
1) I will try to clear the transmitter antenna from obstacles. The problem I have is that the antenna connectors are a bit exotic to me and I have ordered twice some connectors thinking that they would fit but they did not. I need to find the right connectors and a piece of coax to make another antenna with more clearance.
2) For my antennas, I think you are right, there is a good chance that I have not been accurate enough with the dimensions and/or shape. I need to try other antennas.
3) To check the background noise, the problem I have is that my goggles seem to switch to a black screen when there is no signal so I do not really see the snow so I I not sure I would see any interference. Today I tried switching between different channels and observed indoors that the RSSI was a bit better on channel 7 or 8. I went flying an got about twice the range as yesterday (I was on channel 4 yesterday). I'll post a video as soon as I will have time to edit it.
The only other difference with yesterday's flight was the position of the receiver antenna. Today I had it on a pole about 2m high instead of about 1m yesterday.
I guess there are 3 reasons to explain the doubled range today:
1. Better RX position
2. There was interference on channel 4 so channel 7 works better.
3. My antennas are better tuned to the channel 7 frequency.
What do you think is the most likely reason? (Or could it be something else?)
4) Of course I should get another one. I wanted to get another one for experimenting with diversity anyway and at this price... I am ordering it right now.
5) I think you are right, at this point there must be something beyond gain. I'll still build a helical for the future diversity experiments!! :-)
Thanks again for taking the time to give me this feedback it is really helpful!!
|Mar 11, 2012, 06:00 PM|
Goggles: Turnigy 320 x 240
I got them from HK but they do not seem to have them anymore. They only have the widescreen one now (http://hobbyking.com/hobbyking/store...dProduct=16072) but I guess it is pretty much the same hardware.
Here is a picture:
My main motivation for choosing this model is that they are among the cheapest goggle available and people still seemed able to fly with them :-)
I was really not convinced by the glasses and because I actually have glasses I could not really use them as such so I went directly for the ski goggle mod.
The glasses were easy to take apart and the build quality of the video unit seems quite good to me. To use the goggle you have to plug them to the gray box which contains the battery and the connections for the A/V signals. I did not really like the idea of having a separate battery for the goggles and the wires and connections were quite stiff so I decided to remove all of that and use a smaller shielded cable to both power the goggles and provide the video input (I did not bother with audio). This was very easy to do, I just opened the video unit and soldered 3 wires to Ground, VCC and Video IN.
Normally VCC is directly provided as the voltage of the 1S lipo battery which is in the gray box so it varies between 4.2 and 3.3 volts or something like that. I tried with 5V but the backlight was heating up a bit so I now power it with about 4.4 or 4.5 volts. That makes the picture quite bright and nothing seems to be heating up. (To lower the voltage from the 5V provided by the EBEC of the "ground station" I just added a diode in series on the positive side of the goggle power supply).
Anyway, with this setup I have a single wire from the "ground station" to the goggle which is quite convenient.
NOTE: It is very important for the wire carrying the video signal to be properly shielded. I made some experiment with random wires and the loose on the video quality is very noticeable even with fairly short wires.
For the casing, I went with the typical ski mask approach. On the first attempt I put the video unit too high so it was not really usable. It is now fixed but you can probably tell from the pictures that it was a initial attempt :-)
Here are a couple of pictures:
I had to paint it black to avoid too much light coming in.
I have not yet flown with these goggle but I am really happy with them. I can use them with my glasses, they are quite comfortable and the picture quality seems quite good to me. They obviously do not have the best resolution but I have no problem navigating the menus of the video recorder or reading all the information from the OSD.
|Mar 12, 2012, 01:48 AM|
Buy SMA-RP pigtails with semi rigid cable. Solder antennas at the end of those and you are home. Pigtails are usually 15cm long and the cable is rigid enough to keep it upright even in an airflow. If it bends, just cut it down to 10cm but not less then that. Keep those antennas away from other hardware.
|Mar 12, 2012, 03:06 PM|
|Mar 12, 2012, 06:39 PM|
Video of the Second Test
As I said in some of my previous post, the second test was made on a different RF channel (7 instead of 4) and with the RX antenna a bit higher.
Here is the edited video:
It was much better than the first test but range is still too short at only about 200m (This time I have the GPS OSD to actually estimate the actual distances).
|Mar 12, 2012, 11:44 PM|
Joined Dec 2006
for DIY antenna, I buy this one on ebay:
(choosing SMA or RP-SMA cable depends on your Video Tx/Rx RF output connector)
RP-SMA male to RP-SMA male jack center straight RG316 cable jumper pigtail 50cm
SMA male to SMA male pigtail cable RG316 30cm
It is free shipping, one piece cans DIY two antennas, extremely cheap.
|Mar 13, 2012, 01:52 AM|
Be careful with RG316 cable. Keep it short. It is not good at 5.8GHz.
That is why I have pointed to a pigtail with RG402. RG405 is even better.
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