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gjestico

900mhz gear quality

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Hello,

I have recently purchased a 900mhz TX/RX set from a supplier that had a good online reputation.

I am currently running a 2.4g 200mw system (older Blackwidow setup + GP patch !). This has worked well for me but I still get a few dropouts at distance, and I am considering going to 2.4g control for the main aircraft that hauls this stuff around.

I have hooked up the new 900mhz gear for a bench test and was immediatly stunned by the crappy range. less than 20 feet. I tried 2 different video sources (camcorder, digital camera). The vendor sent me another TX and it was slightly better, like 25 feet range LOL. Even within range the video quality was very bad, with any white areas showing bad washout and noise/striping

Is this par for the course ? needless to say I wont be swapping the existing 2.4 gear anytime soon. It works flawlessy in comparison.

I would be willing to try another TX/RX set from a different vendor, But honestly , by the pics anyways, they all look like they are selling the exact same stuff.

I should note that this is a fairly high-end application and I am more than willing to pay extra for quality, within reason.

Thanks

Greg

Edited by gjestico

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Even within range the video quality was very bad, with any white areas showing bad washout and noise/striping

A washout symptom usually indicates that the video level on the Rx is not matched to the Tx (video levels are not calibrated correctly).

The vendor sent me another TX and it was slightly better, like 25 feet range LOL.

Lack of range could be a problem on the Tx's side, but I find that it is more often on the Rx's side. So suspect everything! The first thing I would check is the little wiener pin inside the antenna's SMA. Often these get pushed in, which results in a lost connection to the antenna. Easy to fix.

A 900MHz/500mW setup should give you a more range than a 2.4GHz/200mW setup, assuming similar antennas are used. In case your issue is caused by external interference, I would suggest you try the test at a different location in a wide open field. Range tests in and around the house are really pointless.

I would be willing to try another TX/RX set from a different vendor, But honestly , by the pics anyways, they all look like they are selling the exact same stuff.

You can't tell by looking at these RF products if they are all the same. Sometimes they are copies with inferior electronics on the inside.

My guess? Since you already swapped the Tx, the problem (if caused by your hardware) would be in the Rx. Make sure the Rx you use is specifically designed to mate with the Tx. Do not mix and match brands.

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Based on your advice I wrapped up my bench test gear and went out and did a test in a wide open parking lot this eve. Placed the TX on a plastic box on the ground well away from anything. The results were the equally horrid (possibly worse , indoor distance estimates were generous). I checked the pin on all the sma connectors and they were in correct position.

I have been reading some of the tech articles on the RC-Cam site, very informative. I appreciate the knowledge.

My test setup is as basic as I can make it, each TX/RX is powered independently by its own 3-cell lipo, no other ancillary gear is connected. I think this particular set is just bad. The TX/RX set came from the same supplier

So I have spent the better part of sunday tinkering with this stuff. I would like to find something that just works. I value my time. I never had this trouble with the 2.4g gear.

Looking over the DPCAV site, the 'Pro' 500mw 900mhz TX caught my eye. Plus the testing before shipout is a valuable bonus. I see upon further isnpection that the TX unit is not identical to the ones I have, specifally the channel switches are moved, and who knows what else inside.

Will I have better luck with the DPCAV gear ?

Also, I have need to use a simple dipole on the RX, the patch type is too directional ; the ground station is often in the middle of the flight radius and must work from all angles.

Thanks again.

Edited by gjestico

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Will I have better luck with the DPCAV gear ?

It's good stuff because of the additional testing and the provided filters. But my opinion is slanted because I work there.

If you replace the Tx then plan on replacing the Rx at the same time. My hunch is that your existing issue is due to the Rx.

Also, I have need to use a simple dipole on the RX, the patch type is too directional ; the ground station is often in the middle of the flight radius and must work from all angles.

Personally I find that Omni's on the Rx side don't do as well as something that is more directional. One important advantage with using a Patch is that the beamwidth helps reduce multipathing.

Since you had good results with the GP Patch on your 2.4Ghz system, it would be worth your time to create one scaled for 910MHz. If necessary, have someone point it at the R/C model if you intend to fly circles around the base station. At some point you might want to consider adding an antenna tracking system like the one that EagleTree will release in a few weeks; It will point it for you!

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The stock antennas that comes with the 900 MHz gear are known to be no good.

Check out the thread below for some ideas.

http://www.rcgroups.com/forums/showthread.php?t=927590

I did this mod on my 900MHz Tx antenna and the difference was day and night.

Had similar experience to what you are having currently. After the mod the signal have been rock solid.

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Well, despite trying several things suggested my the vendor, this thing just don't work. Vendor has told me to return the setup. I also note this particular vendor (who has handled this very well) has removed almost all the 900mhz gear from his site. I suspect I am not the only one having probs....

Edited by gjestico

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