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FredericG

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Everything posted by FredericG

  1. As Mr.RC-Cam mentions it depends on the BW of your setup. Perhaps you could check the BW before you buy something. My modems come from Eladio and I think they are on sale here: http://alai.h3m.com/~s0350672/catalogo/ Frederic
  2. Sorry, I missed your question. I reassembled the receivers again so that I can fly. I think I will wait until winter before looking into the issue again, the problem is not important enough for the time being. In Belgium you need to fly when the weather is good Frederic
  3. Well no, I did not kwow this I did a quick search on farnell for example but did not find anything. Even with your link, I have trouble finding my way to the right component I suppose that replacing the component is the most obvious route. However, Thomas mentions that these components do not like to be handled manually. Buying another receiver might not be a good solution as a friend mentioned that "it is a well-known issue that some lawmates have a low audio-bandwidth" Do you guys think that the trailing "N" and "d" could indicate a different bandwidth? Did they change this to h
  4. Yes, these are the receivers that where used for the Oracle issue. I did not have a look at the video signal again but I have some info on the audio. I transmitted a block wave that looked like a triangle on the bad RX. When I turn the variable cap in on or the other direction the amplitude of the audio-signal reduces but the shape does not change. So, I suppose it correctly "tuned". I opened the other side of the RF-box. No adjustable stuff there. I changed channels, but with the same result. I had a look at the ceramic filters. One of them is identical on both boards, it says
  5. On the other side of the mother board there is a small pot. What would that be for? It is also on the mother board that the switches are to select one of the 8 channels. How does that work? Would it be a good idea to test with another channel? I know a lot of questions Thanks, Frederic
  6. Well the receivers are not identical. The good one is a "portable" version with a build-in battery, I bought this one 1,5 years ago. The bad one is a "standard" receiver and I bought this one half a year ago. The transmitter was bought at the same time as the the bad receiver, so they should be compatible. What is interesting is that, while the video looks good, the image from the old good receiver looks "better". It looks brighter while the video levels are the same. My USB video capture device shows the image of the new receiver is "darker", my goggles do not show a difference. Could it be
  7. Thomas, what do you mean with "audio carrier must be adjusted correctly on the transmitter so it is centrered"? Does this relate to the audio signal that is provided to the TX or is this related to the TX-RX link (the carrier on which the audio is modulated perhaps)? To be sure there is no misunderstanding. I use one TX and the signal is received by the two receivers simultaneously.... On the -scope graphs you see the audio signals of both receivers. Does the fact that the audio signal is reversed tell us something? Thanks, Frederic
  8. It looks you are absolutely right. I measured the bandwith with a sinawave and the cutoff-freq (-3dB) of the new receiver is only 2KHz, while the older one goes upto 20KHz. I was assuming that he limited BW was due to a design-change, but I suppose 2KHz is not acceptable for audio and should be seen as a defect. Right? Is there something I could check/fix or do I just send it back? Thanks a lot, Frederic
  9. Here I have dramatically lowered the signal amplitude: (1V/div) And here I have increased the signal: (2V/div) Frederic
  10. I integrated a DZL modem in my Oracle diversity receiver: The problem is now that the DZL modem does not seem to work in combination with my new 2nd lawmate receiver. I experimented with adjusting the level of the audio signal to the TX, but I never get a signal that is good enough for the modem to decode... It looks to me as if the signal heavily filtered. These are the signals that the receivers are generating, both signals 1V/div, the bottom signal is from the old receiver.
  11. Afterwards I did the same test with the system installed in my plane. Here the plane is outside and I am inside. This is with the OSD that generates some "blacker than black" The overshoots are gone but the black is a bit below black. I can however not see false sync-pulses. To be honest, I start wondering if this is really our problem. However, what else could it be? AFAIK, the sync pulses is the only thing the device uses as input. When I now enable both receivers, there is some switching, but not a lot. The sync pulses are hardly affected by the filter, so I suppose I can increa
  12. This is interesting. I started measuring inside the Oracle. I looked at the video-signal after the filter and the sync pulses from the LM1881 (pin 1). The filter is doing a good job filtering the overshoots generated by the A/V system. As far as I an see (I should have a better scope) I cannot detect false sync pulses. This is with the "better" osd board printing much more "I" characters than before. What is very confusing is that the signal looks good to me, but when I enable both receivers, Oracle starts switching rapidly. This is indoors, I know, but the pulses look good to me...
  13. I still have another TX, exactly the same lawmate .5W. For reason it has become VERY sensible to vibrations, but OK for this test. I tested with both transmitters and both receivers. Unfortunately the signal at the RX looks the same. I include a more detailed picture. The bottom black line is the level of the sync tip, the dashed line should be around 100mv. In the datasheet of the LM1881 I have read that the threshold for the sync pulses is a fixed (typical) 70 mV. Some spikes must reach this value. I think this "better" OSD will also cause trouble and it would be a lot of work to swap
  14. Regarding the color-burst. I have also seen this, sometimes it is visible, sometimes it is not. I think this is because the scope is in digital mode and does not take enough samples. Is this reasonable? I think this is also the source of the "ragged" aspect of some of the signals that are taken at higher timebases, you do not see the real peaks. Another remark is that the last 3 images are taken with another spare board. It looks to me that this board puts black exactly at the black level while the board installed in my plane puts black slightly below the black level. In both cases, at the
  15. Now, when I look at the signal at the RX side, there is over and undershoot. 0.2V/div: The problem is that I do not know how I could solve this. I thought that I could influence the "color" of the borders, but I did not succeed yet, I think this only works in "full mode" Could I filter the video signal before it is fed to the LM1881? Thanks, Frederic
  16. I think we are getting close (but I am not sure this is good news :-) ) I took a picture of a white surface so that my photo camera could generate a perfect PAL image and used that as input for the OSD. Than I modified the OSD code to display only "IIII". First I used my PC capture box to terminate the signal, it looks good. Level is almost 1V and black (the borders of the "I"'s) is at black level. .2V/div: So, when I let the TX terminate, the signal is much bigger, but still looks good: .5V/div
  17. Now, the same line (I think/hope) at the RX side: It is the first time that I look at video-signals. A difference I see is that at the RX side, the levels go well below black while it is less the case at the TX side. I suppose I could also measure at the sync-pulses on the PIC and show them together with the video signal to see when sync-chip miss-triggers. Thanks, Frederic
  18. Then I looked at the signal when the OSD is active. TX side, 0.2V/div, 5 us/div:
  19. I did some more measurements. The levels on the TX side are too high: 1.5V. 0n the RX side around 1V. Is this 1.5V dramatic? Could this be the impedance problem with the new lawmate transmitters? I attachment a picture of the RX side (above) and the TX side when I shine into the camera with a light. 0.5V/div Then I did some tests with the camera looking at a gray surface. The 2nd picture shows how it looks when OSD is not active, 0.2V/div 5us/div, TX side
  20. Thank you for your help. The waveforms I posted are measured at the RX side. Both receivers generate the same signals and have 900mV p-p. As you suggest, I will also look at the signals on the TX side. This is a standard BlackBoxCamera board, I do not have any schematics. May I assume there are no errors there? It is however my own software, the way I configured the OSD-chip might be different from other applications. My comments on the switching come from in-flight observations. I assume that the system is working properly with OSD disabled. I will investigate further. Thanks,
  21. Not sure if this is important, I also attach a picture of a line where there is no OSD content. Frederic
  22. I am experimenting with my new Oracle Diversity Receiver and it is obvious that there is also a problem with my STV5730A based OSD I do not know how the Oracle should behave, in general I have the impression there is a lot of switching back and forth but when I enable the OSD, the Oracle switches much more often or sometimes goes mad. I could use a little help. I attach a few pictures of the video signal when the camera is looking at a gray surface and there is some OSD content on the screen. Does this look OK? The timebase is 2 and 1us/dev. I also checked the Vpp when shining with a
  23. Yes, the other thread clearly indicates that there is no frequency-table in the eeprom, that it works differently than I assumed and that RF module has less responsibilities than we thought. Yes, I think this leaves us with the options you mention Thanks for you help, it's very much appreciated ! Frederic
  24. It is indeed a strange approach. Each time they invent a new module, they need to update the TX software. They also have 2.4 GHz modules. Does the TX also generates that? It is strange. I would think that the module communicates to the TX what frequencies it can generate and that the TX just selects one. Interesting, I thought that it would be possible to extrapolate from a few know values, but obviously not So, we think at least the carrier comes from the TX, would the module do the modulation? Suppose the TX provides the carrier and the PPM (or PCM), Would it perhaps be doabl
  25. From the other HeliFreak thread I know there is an EEPROM (with an SPI interface if I remember well) that contains a serial number, an area code and a band code. This would allow the TX to identify the module. By changing the band, other subsets of for example 35Mhz become available. So this must be the way the TX recognizes the module. I do not know anything about PLL's. Is it common for a PLL to have an SPI interface? If this is an PLL with SPI, I would expect it to be connected in parallel with the eeprom and have its own SS. What do you mean with "sounds very tricky"? Thanks, Fre
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