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AXI Motor Models

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  1. Is it true that every time you have a standard 75Ohm video termination (75Ohm resistor to ground + 75Ohm resistor in line) that the video level is divided by 2? Is that why some of the MAXIM video switches have a fixed gain of 2V/V? For the 470uF capacitor, I might try a Tantalum with an ESR of 100mOhm. This should work well shouldn't it?
  2. That is good that the switching between receivers should be seamless. Now the last obstacle for me is the bias circuit between the Airwave module and the Maxim video switch. I have no idea whether the circuit below is correct. Will the video termination circuit below work if I select the correct value of pullup resistor? (Rbias) Or have I done it wrong? Matt
  3. Hi, thankyou for the help. Video terminations can be confusing! I am just experimenting with building a diversity receiver. Airwave modules are the only ones that I can find (apart from Comtech) which have RSSI out. I have revised the output drawing and was wondering if the capacitor should go before or after the output resistor? And also is the polarity of the capacitor the correct way around? (with positive towards the chip) I changed the chip to one with a fixed gain of +2V/V because to my knowledge the 75Ohm terminations halve the amplitude of the video signal. I wonder if switching the video at random times (not in-between sync pulses) would cause any noticable interference on the video? Thanks
  4. I am working out how to connect the video output from an Airwave receiver module (AWM625) to a Maxim video switching IC. (below) I am also wondering what termination method I would use to connect two MAXIM video switches in a daisy chain. Between pin 8 and pin 4 below, do I not need the resistors? Do I need a 0.1uF capacitor for AC-coupling? Do I need a voltage divider to shift the video signal upwards so that it does not go below the rails? (below right) Also, is that how I would connect the final video output to an RCA connector? (Just a 75Ohm resistor to the pin) Here is the circuit diagram for the Airwave module: I don't know if the 75Ohm termination resistor should go before or after the 470uF cap that Airwave reccomends. Do I need a 0.1uF cap just before the input pin 4 of the MAXIM? Do I not need the 75Ohm termination resistor to ground? Do I need a voltage divider to shift the Module's video up to levels within the Maxim's rails? Thanks, Matt
  5. I just discovered this fantastic OSD product! This is the best R/C product I've ever seen with every feature I would ever want! Would my Hitec QPCM HPD-07RH reciever work with the RSSI signal strength indicator? Where abouts in Australia are the boards produced and shipped from? I'm looking forward to getting one! Matt
  6. Yes, you are right. When I first tested and connected up the reciever to power, the capacitors all exploded! I replaced them and installed them the right way around. The Range Video TX arrived but I can't test it because its raining. There are photos of my downlink setup here: http://www.rcgroups.com/forums/showthread....=10#post6332767
  7. Yes, your right. If I decided to get one, I'll use channel 3. Do you think that would work? Matt.
  8. Thanks for the replies, I haven't had much free time lately to work on the problem. The problem is the transmitter. The reciever is fine and I've used other recievers also. I've worked out that the circuit is fine. Also in my last post you can see how close the SMA is to the module pin: ~2mm so that shouldn't be a problem. The only possibility left is: The module could be faulty??? My other option is to buy a new transmitter. I need around 500m of clear video. If I do buy a new transmitter what power would you recommend for this kind of range? I'm very tempted to buy this 500mW transmitter: http://www.rangevideo.com/500mw.html But do I really need all of that power?
  9. Mr.RC-Cam and Vrflyer, Thanks for the help. I went to an electronics shop and tested my transmitter on one of the recievers that they sell. The performance was identical to the reciever I made which meant that the reciever I made is fine but the problem is in the transmitter. I've concluded that the problem must be a fault in the transmitter's Airwave module. I can't get the transmitter's range to improve so I will use the reciever but I'll buy a 500mW transmitter from: http://www.rangevideo.com/500mw.html I also moved the connector but there was no performance increase:
  10. Thanks for the help. On the receiver, I found that the centre SMA pin wasn't soldered to the antenna pin. The reciever antenna wasn't connected at all! So I re-soldered it but the signal quality didn't improve. I'll try what you suggested and see if I can get it working.
  11. Do you mean solder the SMA connector to the case of the module and the middle SMA pin directly to the antenna pin? If you look at the 9th photo on this site you can see where I found out how to mount the SMA connector. It looks pretty similar to mine:http://www.delemarre.ciscon.nl/id118.htm
  12. Hi, thanks for the help. The place I've been testing is inside my house and outside along my street where there are many houses, but it was line of sight. Here's a picture of the SMA connector and the copper traces: It was really hard to solder the connector to the 3 module pins (To the middle/right of the photo)because they were 1.27mm apart. The two outside pins coming through the cut in the circuit board are Ground and the middle pin is the antenna pin.
  13. I have bought the Airwave 612 RF Transmitter (500mW) and Airwave 623 RF Receiver and completed the circuits. I have tested the circuits and the video link works but I get dropouts when I move the transmitter around in certain places. The worst thing is if I move the transmitter about 30 metres away or more, from the reciever, the video becomes completely fuzzy. From what I've heard, I should get over 2 Kilometers of transmittion range from this transmitter. Are these two modules compatible or did I get the wrong reciever? Could it simply be an antenna problem? Could it be a problem with my circuit? Thanks for any help, Matt Here are the parts for the transmitter: Here's the camera: Here's the completed transmitter and reciever Here's my downlink setup: (Eventually it will be in a case)
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