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Hartwig

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Posts posted by Hartwig

  1. -AT-Terry: I didn't modify anything on the modules snce I don't know what exactly is adjusted by these pots. Could you send me a small screenshot to see where exactly this video adjustment pot is located? And what exactly does it adjust?

    -AT-anthonyrc: Hi Anthony, great to hear from you :-) It's good news that you have such results an I'm very interested to find out how to get my gear working in the same way. Can you give me more details on how you did it? If you want you can also PM me about schematics or whatever. Did you apply certain filtering? Do you use an OSD on the TX side, or just camera?

    Cheers,

    Hartwig

  2. -AT-qnzkrew:

    I recommend "TrackOn" from www.hinztec.de as a software for your laptop. It enables you to do realtime tracking with the APRS data sent by TinyTrak. Works perfectly well. You also need a decoder on the receiver side to convert the FSK signal coming from the audio output of the video receiver into RS232 serial data. A good self-assembly kit is the "AS232" from AATIS. It's on a german site. But other TNCs also work.

    You can feed any Graphic into TrackOn to be used as a map. Just take a screen shot from GoogleEarth and load into your TrackOn maps directory, initialize the coordinate parameters when importing it, and you're done. It works very very nice and reliable, plus it's extremely easy to use :-)

    Cheers,

    Hartwig

  3. These days I tested DZL's Modem on different TX/RX setups. I think it's quite interesting what I found:

    TX: Airwave 612

    RX1: Airwave 623

    RX2: Comtech FM2400RTIM8B

    VideoSource: KX131PALCASED

    AltiOSD

    AudioSource1: EM-411 GPS with DZL Modem (Modulation: BPSK)

    AudioSource2: EM-411 GPS with TinyTrakSMT (Modulation: FSK)

    In all setups every way of Audioen-/decoding works fine as long as there no video fed into the TX. As soon as I activate the AltiOSD, or even just the Camera (with one or more bright objects in the picture) the audio signal on the receiver side freaks out, using the Airwave 623. When the video level has high peaks in its signal, the 623 shows up with crossover artefacts in the audio which look like spikes at the times where the video has its peaks. If the picture is merely dark or medium bright, and no AltiOSD active, the audio is clean.

    Much better results on the TX612 with Comtech receiver combination. The Comtech inverts the audio phase, and the DZL Modem works much better. The spikes are still there, but much less than with Airwave modules. Also the DZL seems to be more immune to the spikes when the Audio input is inverted?!

    However, the audio output level of the Comtech's is much lower than on the Airwave's. So either the DZL feed into the TX needs at least 2.5Vpp or the Comtech's audio output needs a little amplifier stage to be usable by the DZL.

    Quite impressive was the FSK encoding of TinyTrak, because it works very nice on both setups, even with all the spikes. On the receiver side I used a homemade Decoder Modem named "AS232" (see AATIS projects) based on the FX614. The only thing to look for in this setup is the audio level matching between receiver and modem input. The modem hast a wide range, ~100mVpp - 2Vpp.

    However, the TinyTrak delivers APRS data format, which can't be used in Navigation systems that require straight NMEA from the GPS. For the TT visualization I used an an application called "TrackOn" which works perfectly well, and accepts selfmade maps, PC screenshots from GoogleEarth, GoogleMaps or whatever. Very nice.

    Summary:

    Transmitting RS232 from GPS down to Laptop or PDA for use with standard navigation software via DZL's Modem performed best when using the Comtech Receiver.

    Transmitting GPS data in APRS format works in either TX/RX combination and seems very robust even in noisy RF-environments, but needs an APRS capable Visualization program.

    So far my test results :-) BTW, it's real fun to fly FPV in the dark with goggles, and to see the plane's position displayed in realtime on your laptop's map :-)

    Needs sufficient light for the KX-131, of course.

  4. -AT-Terry: I recommend a LM2940-5.0 or LM4940v5. Even an ordinary 7805 will do. The only thing you MUST ensure that the input voltage for the regulator stays above the regulators minimum input value, lets say 6.0V for the low-drop will work for sure.

    They tend to get hot, so you might consider a switching regulator in series to provide the required 6Volts to keep it just warm. Have a look at www.dimensionengineering.com. I'm using the "AnyVoltMini" in series with a LM4940v5. Works perfect in all situations with all kinds of batteries and voltages.

    Cheers,

    Hartwig

  5. Just a question, please forgive me if it's too stupid, though I know it's complicated, and maybe not too realistic, but I'd just like to ask:

    Does somebody have already tried transferring data within the vertical blanking interval of the video signal? Just like videotext / teletext / intercast?

    What do you think of this idea? I don't have the programming skills for this (yet), but I would just like to to hear your opinions on this idea, since the video signal seems to be much more reliable and more immune to noise than the audio channel, at least on the airwave modules and comtech.

    Cheers,

    Hartwig

  6. I heard that the RF carrier's level of the audio is (in most extreme cases) about 30dB lower on comtech transmitters to reduce harmonics in the RF spectrum.

    With the Airwave modules it should be about 20dB difference between video and audio carrier level. I heard the optimum must be around 17-18dB to achieve about the same range in distance of video and audio.

    From previous tests I had audio dropout much earlier than video. But I still didn't have a chance to test Thomas' modem. I will do it on the field this weekend.

    BTW, -AT-Thomas: Inthe schematic diagram of the modem the resistor of the filter of the modem on the TX side is 10k. Maybe it should be 1k instead, along with the 10n cap. When I used 10k along with 10n Capacitor the output was just triangles. When I changed it to 1K I got nice square waves with round edges, as you told.

    Also on your screenshot you marked the 1k values quite obviously :)

    Thanks again for this modem! It's really great!

    Cheers,

    Hartwig

  7. Regarding Video PowerSupply from the Main battery I did a couple of tests with various regulators. Here are my results:

    As long as the voltage of the main battery stays above 6V, the LM2940 5.0 along with its two caps works very well, no additional reg required.

    If the voltage drops below that, you get horizontal lines from the motor in the video picture.

    So if you want a clear video picture with just one battery on board, make sure the voltage at the input pin of the linear reg 2940 5.0 stays well above 6V, so it has sufficient headroom to do its work. Also it shouldn't be much higher than 7.4V because of heat issues with the linear reg.

    A switching reg without this linear reg won't eliminate the distortion (horizontal lines in the video) coming from the motor.

    It "only" helps to maintain a resonable input voltage for the linear reg. This one does the "cleaning" work.

    (BTW, the switching regs from Dimension Engineering are a great choice regarding performance, weight, size, price, shipping. If you consider a replacement of your current BEC, or even adding another, their webpage is a great place to look for it.)

  8. Have a look at this:

    http://webpages.csus.edu/~heinega/Two_Came...cuit_Design.htm

    Also another project on this page:

    http://www.petesprojects.com/stereo-video/index.htm

    Generally you need two cameras which sync-locked to eachother. It's easier to do with CMOS cams but they have several drawbacks. Picture quality isn't as good as with CCD's, and the sync doesn't always work perfect, the slave cam might reset white balance and shutter as well on every sync pulse it gets from the master.

    Best way to go is to buy two identical CCD boardcams capable of accepting external sync (preferably gen lock), run one with internal sync and slave the second cam to it.

    Everything else can be easily done with the circuits described on those pages above.

    For cam have a look at:

    http://www.pacific-board-cameras.co.uk

    I haven't tried those, yet. However, in theory they should work. BTW there's another thread:

    "3D Stereo imaging idea on the cheap"

    Cheers,

    Hartwig

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