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Crash9

Range Video 900mhz audio problems

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Hello, I'm new to this site and have been using Range Videos 900mhz setup with a patch anntenna and I really like it but, I'm having trouble with the audio :( and can't seem to get rid of the noise and I was reading a thread on here about the cheapy eBay wireless cameras having the same issue. The mic I'm using is a inline 1volt type recommended but I only hear static unless I tap on the mic then i can sorta hear it. When I remove the mic and just plug it in to my recorder it's perfect audio, so I'm left to believe the problem is with the TX or RX. any help would be great. Thanks

Here's a link to the TX and I have the matching RX

http://www.rangevideo.com/900mhz_500mw.html

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Removing the Tx's mic and terminating its input with 10K ohms should result in low audio noise from the Rx. If not, and you are sure the Tx is installed correctly, and has clean/adequate DC power, then something evil is going on. Also, ditto on the Rx -- verify clean legal voltage there too.

The big black slug trimmer near the wire harness appears to be for the sound sub carrier. The little white trimmer cap appears to be for fine tuning the RF freq (don't play with that one).

BTW, you might want to contact Range before tweaking anything. A replacement Tx or Rx, while still under warranty, would be dandy. Messing with the Tx may jeopardize that.

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Here's the pic of the board inside the 900 RX. If anyone can help with which pots might help tune in the audio better that would be great.

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Thanks for the reply Mr.rc-cam, I sent off a email to RV a couple of day's ago and still waiting for a reply. Yeah I'm not touching a thing until I'm sure on what to do.

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Regarding the Rx, the black slug at the top is probably related to the sound sub carrier adj. The little trimmer pot below it is most likely video amplitude adj.

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I have notice during troubleshooting that I have perfectly clear audio when the CCD camera is not powered :huh: up so it seems the I'm getting all my innerferance noise from rf radiating from it and also notice that the wires are not shielded :o (the only ones are the wires/connectors I added) and the power wires run along with the video signal :( . I'm going to see if a seprate battery might help along with separating the wires and replacing them with shielded.

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Edited by Crash9

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Are you sure it is RF interference that is disturbing the audio? That seems odd. Maybe it is dirty power. Exactly how are you powering the Tx and camera? That is to say, what is the battery source, and what sort of Vregs are you using?

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Yeah I honestly didn' think that would do much but I had to give it a try and it did nothing. My batterys are lipo 3 cell @ 12.3 volts 900mAh during these test and using 2 separate batterys also did nothing. Camera and TX are rated for 12volts 120mAh each. No Vreg, and everything wire direct and not sharing any power with the planes gear at this time.

I did notice that I can leave the CCD camera powered and when I unplug the video the noise stops and audio becomes clear again with the camera still powered- plug in the video signal and the noise comes back.

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Edited by Crash9

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From your description, I believe the sound sub-carrier adj is goofed up, rather than RFI from from the camera's cables. But anything is possible.

If you have another video source (camera, VCR, etc.), it would be good to try it to see if the problem still appears. If it does, then either the video Tx or Rx needs attention.

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Thanks Mr.RC-Cam, you have been very helpful. I did try another CCD camera from a different maker with the same results (buzzing static :unsure: ). So I'm with you on this, that something needs a little adjustment.

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Well adjusting the audio pots only change the static from white to pink noise so I put them back to the way it came. I'm woundering if I can add a bigger preamp for the microphone to override the noise :huh: .

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Well adjusting the audio pots only change the static from white to pink noise so I put them back to the way it came.

Which side did you tweak? Tx or Rx or both? Frankly, without a working Tx/Rx set to use for reference, it will all be guesswork on what to tweak.

I'm woundering if I can add a bigger preamp for the microphone to override the noise

If you are totally sure your mic has a line level (one-volt) rated output, then more audio gain will probably cause distortion. What mic are you using?

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I just recieved a email from Vova at Range Video :) . At this time there isn't a microphone set up that works :( , that they know about. He is running some test of his own to see if he can recommend something and has forward my ?s to the engineers at the company that makes the 900 gear.

I'm using a tie-clip- omnidirectional electret, which comes with "357" button battery from Radio Shack rated at 1.55volts. I've also tried a Shure sm57 dynamic , PZM pizo type and a couple others. They all have about the same audio level, but it's hard to till with the buzzing going on. The tie clip one seems to be the best for the set-up (I'm guessing). Anymore suggestions on mic set-up. I'm willing to try just about anything and it might help RV. Thanks again :) .

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Food for thought. I do have to have my volume almost max to hear the audio that is coming through and some noise would be expected at max.

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Do you have a part number to the tie clip mic? It might not have line level output. The supercircuits PA3 mic might be worth a try (it is definitely line level output).

If you are at max volume, then I do agree you will hear some noise.

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I have the PA3 microphone from Supercircuits that seems to be working fine right now with the 900MHz system.. This was the mic recommended by Vova, and it sounds like it is what he uses on his AVS setups. I haven't flown the setup but I have no issues so far with the mic. The mic is very sensitive, I'm wondering how noisy it will be when I'm flying the plane. I may need to add a POT to the audio line on the plane if it is too loud.

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Crash,

What type of camera is that? My KX131 had an inline voltage regulator to take 12V down to 5. I don't see that on yours, but I can't tell if it is a KX131.

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Mr. Pibb, My camera is the KX151 CCD from RV. The back of the camera has a input voltage of 12v120mAh. wires I removed that came with it had no Vreg. It's good to know that yours works with the PA3, I'm keeping my finger X. Vova made no mention of the PA3 in his email to me :huh: . I ordered a PA3 from Supercircuits and it will be here tomorrow so I will post my results. Thanks

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Do you have a part number to the tie clip mic? It might not have line level output. The supercircuits PA3 mic might be worth a try (it is definitely line level output).

If you are at max volume, then I do agree you will hear some noise.

I could't find a part # on my RS mic. I plugged it in and the other mics I have to my sony camcorder and it had the highest audio where the others where to low. that's the only test I've done.

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Well the PA3 mic took it to the other extreme, now it's louder and distorted even inside the plane :( , it's just as Mr.Pibb posted to sensitive, but I can work with it :) . I did notice when I was adjusting the audio pots inside the TX and RX I could bring down the audio but it still was distorted from to much input gain so I also think that a POT inline before the TX is a good idea and I will try that next. I did get to fly the set up over the weekend :D and I'm happy with the results of my video :) . Thanks again. Love this stuff....

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Sounds like you are close. Reducing audio levels is easier than increasing them. I suggest trying the attenuator shown below:

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