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JetPilot

MobiComm Receiver Problems... Is this a good recei

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I have been looking for a better receiver to improve the range of my 2.4 GHZ video systems and bought a MobiComm receiver and the digital tuner to go with it. I mounted everything in a nice, grounded, shielded case and put it on the back of an 18 dBI patch antenna.

The performance of this receiver is horrible :angry: The sensitivity is not anywhere near what my lawmate reciever is, and putting a 25 dbi gain LNA on it did not help much... I tested it both ways. Where I get a clear picture with my cheap lawmate receiver, I get a very weak signal and a bunch of snow with the MobiComm reciever. Even when the signal is strong, the picture from the MobiComm just plain sucks. The contrast is so high the picture is not nice to look at and takes the fun out of FPV. I have adjusted the video level with no success, the best it does still looks far worse in contrast and color than my cheap lawmate receiver.

This is not a tuning issue, or IF shift issue, I have gone down that road and everything is on frequency... Has anyone else used the Mobicomm receivers ? What were your results ? Is this a bad receiver, or do all of these perform this poorly ?

JetPilot

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I know of some radio hams that use that receiver and are very happy with it, I have not used it myself though. I have used the 18dbi patch that you have in the picture and had no luck at all with it, I found it impossable to keep the plane in the beam. Even in side by side tests on a ground target I was pushed to get a stronger signal reading than a 14dbi patch, it's in the loft collecting dust if anyone wants it !

Terry

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The beam of the antenna is very narrow, which is to be expected from a High Gain antenna, it would be very difficult in close. I tested it with the plane a couple miles out, so it was not to hard to keep aimed. I will test it against a 14 dBI patch next, if its not a lot better, I will go back to the 14 dbi patch. The super narrow beam is only worth the extra trouble to aim if the signal is a lot stronger.

I fixed the low signal level issue with this system, I had an antenna connector the wrong polarity... But the video picture still looks horrible with this reciever :angry: Even with a very good signal, I am getting a very high contrast, slightly blurry picture when compared on the same system as my cheap lawmate receiver.

JetPilot

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The ham guys I know that have used this receiver also use the matching transmitter so this may make a difference. Is there any adjustment on the board ?

Terry

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It's true, some sets use some emphasis-like signal tricks. If you don't use the matching unit it causes trouble. I've seen that on a couple of occasions with video transmitters too.

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The board has a pot on it to adjust the video, and it makes a big difference in the video, going from an unstable signal through a good range then to black and white. I have adjusted this to the optimum video, but its still contrasty and kind of blurry. I have the video from the receiver going to a video amp so that I can use multiple outputs, the same video amp works very well with my lawmate receivers...

What do you mean by a matching unit ? I am using a lawmate video transmitter on my plane, the mobicomm TX is not someting I would ever put on a plane, its big and does not have enough power.

JettPilot

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yep that's the problem, the matching transmitter is too big for our planes, well most of them anyway.

Just out of interest how dose the video look before it goes through your amp?

It is also possable that your transmitter mod level is too high, with your normal receivers adjusted to it you won't notice it and will assume it is your new receiver that is at fault. This happend to me a while back when I met up with a friend to do some FPV flying. We had both adjusted our receivers to give a perfect 1v peak signal using our transmitters but my transmitters were modulating at a lower level than his. When I tried to monitor his flight with my receiver is was washed out and breaking up !

Terry

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