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Posts posted by jonpet55

  1. Polarisation-diversity would be the only advantage. If you are flying distant gentle missions then I say don't bother but if you fly 3D or over head i say go for it.


    Ok, thanks for the reply.

    I will fly non-acrobatic and distant.

    Another problem just popped into my head:

    The rotor will be refreshed a little less than once a second, so when landing near the rotor, it can get problems following the fast motion. This could be solved by a low gain antenna not being controlled by the rotor, fed into the diversity-controller along with the other high gain antenna.

    Again, I am wondering if this is neccesary... When the plane is so close to the high gain antenna, I'll guess it will get a good signal strenght no matter where the antenna points.

  2. I am currently working on the ground station for my FPV-project, and need help to decide whether I need a diversity receiver system or not.

    About the project:

    The transmitter will transmit video from a KX131-camera with overlay from a custom made BOB-4 based OSD on the video channel, and APRS-packets from a TinyTrak3 on the audio channel.

    The APRS-packets will be used to calculate azimuth and elevation for the receiver antenna(s). I have built Bob Ball's PIC-based TNC, and is allmost finished with the rotor controller and az/el-calculator. The software is made using basic for PIC microcontrollers (a PIC18-series microcontroller will be used due to advanced trigonometric calculations and lots of float-type variables), and show the calculated angles on a 16x2 LCD-display. The rotor itself uses a 180/180-degree az/el setup with standard RC-servos, which means the antenna will be upside down when accessing azimuth-angles from 180-360 degrees (I will build a more rigid rotor with small geared DC-motors later).

    Diversity or not?

    Because of the precise antenna rotor, I will use high gain antennas with 30 degree beamwidth or lower. This means I will receive a minimum of reflections from the ground, nearby buildings eg. So, is it really necessary with a diversity system when the antennas have such low beamwidth?

    I was also thinking about polarisation-diversity; either LHCP/RCHP, or vertical/horisontal. What do you think about this?

  3. Thank you for your great answer and the positive feedback on my project!

    I think that answered about everything I thought was unclear.

    The 4011 is aviable in both TQFP44 and DIL40, so you could actually breadboard the 4011 too, but then size is the problem... The 4012 is aviable in DIL28 and SOIC28. SOIC28 is not that hard to solder (while TQFP is close to impossible to solder by hand), so I think i will go for the 4012. By the way I use an Olimex programmer too; the PIC-PG1 (I'ts on time buying a new one). ;) I bought a FMA Co-Pilot yesterday, so i'll combine it with the DragonOSD. I have an EM-411 GPS laying around too, but i want a smooth compass and a good autopilot, so now i have to buy an EB-85A too... Is it easy to change the GPS-baud rate to 4800 baud in case i want to test it with the EM-411? About the PCB; I think I'll wait designing a PCB until you release the new schematic, so i'll just use a weroboard for now.

    Again; really impressive stuff! Can't wait to get my Microchip samples...

  4. Daniel Wee, i am really amazed by your project. The 5Hz GPS combined with pixel-resolution scrolling on the compass, and with UAV-capabilities too, makes it the best OSD-solution aviable in my opinion. I would like to build my own right away. What programmer do i need for the dsPIC30F-series? I use a lot of PIC16-series microcontrollers, but i guess my simple JDM-programmer is not enough for the dsPIC30F-series. I can see you are planning on using a 4011 instead of the 4012? I sampled both from Microchip, the 4011 in standard PDIP packaging, and the 4012 in SOIC packaging (maybe i'll make the first SMD DragonOSD? ;) ), just to be sure. I plan to make my own PCB-layout, so i am also wondering if the schematic on page 7 still is up to date? By the way, how does the DragonOSD autopilot perform in low altitude? When i first saw your project, i was very sceptical of only using a GPS for UAV-capabilities (no pressure sensor, piezo-gyro, thermopile-sensors or anything like that), but after seeing your videos it sure seems to work very nice. Have your ever had any troubles with the autopilot?

    By the way, check out my project, EOS1. I have created

    a thread here on RC-Cam and a video is aviable here.

  5. Thank you for your response!

    Hartwig: The dew will appear on the inside of the plexiglass, and i thought about using a demoisturizer. The problem is that some of the components generate a lot of heat, and without moisture there is nothing to carry the heat away. That would of course cause the components to overheat, but other components with low power consumption would also be too cold; i use standard rated components which is unable to operate under 0 degrees celsius.

  6. Thank you for your reply. The camera has a 4 mpix resolution, and the pictures are shrinked very much. The main problem isn't resolution, but pictures of the horizon at this altitude is heavily blurred by the atmosphere, especially because the weather was hot and moist when the payload was launched. I also had problems with dew on the plexiglass which the camera took pictures through, mainly because of the huge difference in temperature inside and outside the payload (-70 degrees celsius outside and 20 degrees celsius inside). If the camera had a more sensitive CCD, it would certainly help too, because the motion blur on multiple pictures is caused by long shutter time.

  7. I just found out that my high altitude balloon project could give much inspiration in this forum, so i have decided to share it here. I was thinking whether it was relevant or not, but i soon found out it certainly is. It is radio controlled, its goal was to take aerial photographies, it transmits telemetry, it transmits live video in FPV, and it flies. :) I hope it is ok to post it here.

    Ok, to the project:

    The primary goal with this project was to send a payload carrying a camera to an altitude where the horizon fades from blue to black, i was hoping to archieve up to 100 000 feet. The secondary goal was to find the payload in good condition and recover the pictures on the memory card.

    The project was finished in the beginning of April this year, and the payload was sent up to the Edge Of Space (EOS) 15/4/2007 (since most readers in this thread is american; 4/15/2007).

    Here is a few pictures of the finished payload

    Here is a list of the components used:

    - Opentracker OT1x; APRS-encoder

    - Stripped Haicom HI-204III SiRFStarIII GPS

    - BlackWidow 600mW video transmitter

    - Olympus ยต[mju:] 400; the primary camera

    - Siemens S55 cell-phone

    - 3700mAh 7.4V lithium polymer battery-pack

    - Pioneer ND-BC1; the secondary camera (wide angle lens)

    - 1200g Totex balloon and a parachute

    - Waypoint W-084; this R/C-servo will release the parachute after 2 hours

    - A controllerboard mainly consisting of a PIC16F628A microcontroller which:

    - Trigger the camera-shutter

    - Toggles between the secondary and primary camera

    - Power off the video-transmitter when it has reached ground to save power

    - Power on a 120dB siren when it starts to fall

    - Regulate 5V for all the 5V components

    - Controls the servo for the parachute

    The project was a very big success. I archieved a range of over 80 kilometers with the 600mW transmitter, and the payload was found in perfect condition after being at over 90000 feet. Check out pictures and video here:


    Pictures from the launch-site

    Some of the components

    The pictures taken with the primary camera

    Comparison of the pictures from EOS1 and Google Earth

    See my information page about EOS1 - in norwegian

    Hope you like it!

    A new project, EOS2, is already started. It is far more advanced, and every component can be controlled from the ground. The camera can be tilted and it will transmit a lot more telemetry (temperature inside and outside, voltage, humidity, altitude, position, and so on). I will make much more of the electronics from scratch, and it will countain a cross-band repeater for the 2m/70cm ham-radio band.

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