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Old Mar 06, 2011, 09:42 PM
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First 900mhz range test

So I finally had time to test my new 900mhz 500mw video system from Readymade today.

I setup the RX connected to a tripod and a PoS portable dvd player. I started with the stock whip antennas for the RX and TX.

I put the pod with the camera and TX into my boat and sent my wife out across the lake. The signal completely died at less than 1/4 mile (boat GPS).
I quickly swapped the RX to the 8db patch and it came back. We were able to go .9 mile out (total) before the video dropped completely again.

The video was marginal (at best) beyond 1/4mile. LOTS of drops, static, lines, etc. Multipathing I presume. But the camera TX was only about 6 feet above the surface of the water. No WAY one could have piloted a plane like that.

I have since learned that my patch antenna should have been mounted a few inches off of the ground, not 3-4 feet (which was the case earlier today).

In all, I think my first test was successful - if not educational at least.

Now - It's obvious that the stock TX whip antenna is junk. I was going to order one of IBCrazy's Vee antennas to replace it. Anyone care to wager what sort of range I will get with it?

--Ray
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Old Mar 06, 2011, 09:46 PM
I AP'd myself again......
aviatordave's Avatar
Yawn....Iowa
Joined Mar 2005
2,500 Posts
There is a calculator in this forum for that, I think it went 5 miles or so?

http://www.rcgroups.com/forums/showthread.php?t=1394218
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Old Mar 07, 2011, 12:38 AM
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Canada, AB, Lac La Biche
Joined Aug 2010
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I can't remember exactly what or why it was, but when I got my wireless internet ISP connected at my home and the tech was looking for the tower he could get the strongest signal from and was aiming at a tower across the lake from me, he mentioned that water can really have an effect on how the wireless transmission behaves, same goes with grain fields waving in the wind etc. Tech told me he'd seen homes have a perfect strong signal all winter and have it go to crap when vegetation or ice/water conditions changed.

I know my ISP dish has a clear shot at the top 20' of their closest tower, just over the tree tops, and I was hooked up with 5.8 GHz system, but when the tree's hit leaf-on stage my internet became very erratic so I had them come out, even though they were getting strong signals I could not get a reliable connection, so they put a 900Mhz yagi on and I was fine. However my data speeds were limited to 3 megabits and I was paying for 5 Mb, so they came back out, tried different aerial/dish combos and eventually got it ok with a 2.4Ghz and I got my speeds back. No way they could get 5.8 working again when trees were leaf-on though, even though the LOS was clear.

Now I don't know is this would pertain to analog fpv video signals or not, but I would be curious to see if you get the same results over dry land. I have the same system on order from RMRC, hopefully get it this coming week. I will likely be doing a test over the lake as well, but we'll be heading out in our jeep instead of a boat
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Old Mar 14, 2011, 08:03 PM
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SO I finally had some time this weekend to do more testing. First I simply lowered my L-com 8bd patch antenna about 8 inches off of the ground (velcro'ed to a tripod). Then sent the boat back out with the xmitter. I was able to get 1.4 miles before the video got too unstable. Most of the multipathing issues that I was seeing were also gone - but still had some issues.

The other side of my house is a massive corn field that happens to be bare right now. So I did the same test over land. I was able to get almost 1.6 miles LOS.
No multipathing that I could detect at all. The video was much cleaner over land vs. water. However these test were done at ground level. I have no OSD so I can't say how far out it will go in the air (I still stay well within LOS).

I have access to a very nice spectrum analyzer, so hopefully after CTIA I will have a chance to sniff my flying area.

Just wanted to throw the results from my ground tests out there.

Cheers and 73's --Ray
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