High gain video receivers

[elossam]

Most of the video receivers I know has a sensibility between -82dbm and -85dbm but there are at least three that claims for values over -90 dbm

http://www.allthings.com.au/Wireless/video%20receiver%20mini.htm (-92dbm)

http://www.nghobbies.com/cart/index.php?main_page=product_info&cPath=94&products_id=348 (-91/-95dbm)

The 3th one is from airwave model AWM650G-RX (-90dbm)but it´s not updated on AW´s web and AW support doen´t answer my info request.

I´m skeptical about those specs because if they are true, the differences are big enough to make them look like little jewels in the RC/FPV community but I never saw any feedback about them. Has anyone experience on any of those models (or anyother over -85dbm not listed above)?

[Mr.RC-Cam]

Keep in mind that the sensitivity data that is published is dependent on the test setup. For example, you might measure -90dBm with a non-video test signal and then see the same module shrink down to -84dBm when full video bandwidth is present.

Also, from my experience, the sensitivity of the mass produced video tuner modules varies by several dB, even when they come from the same lot. Long story short, you probably won't know if you have a golden egg until after you try out the one YOU bought.

I can say that those bargain priced China made receivers are usually equipped with low performance tuner modules. So if you need longest range then you have the right idea about sticking with the brands that others have used with success in their long range application.

[elossam]

Thanks mate, I understand what you say. Initially I though the common level was arround -83dbm due to the nature of the tunners (based on sat TV) where thanks to the type of antennas used and the fixed Rx position doesn´t require higher values. This i.e. the origin of COMTECH tunners and may be other ones. Is there is a physical law that makes impossible to get better gains without falling into a noise factor beyond acceptable or is a matter of money?

[Mr.RC-Cam]

Is there is a physical law that makes impossible to get better gains without falling into a noise factor beyond acceptable or is a matter of money?

The answers are: yes and yes.

My gut feeling is that we would see nearly -90dBm video receiver sensitivity, with good selectivity, without much effort by the manufacturers. However, from what I can tell, they don't really care about improving receiver performance. Basically, most users are not aware that the receiver performance is as important (if not more) as the transmitter. So everyone involved tends to focus on the Tx's RF power instead.

There's a lot of things about the typical wireless video system I don't like. Overall technical performance is often not as good as we think. But despite all that, the image we see usually looks better than it deserves to be. However, there is so much room for improvement -- I'd love to start fresh on a design that was built for performance first, cost second. But, there is no real market for that, so we get what we can get.

[elossam]

If I could only get real -90dbm ..... what a dream, those -6dbm difference implies a lot of weigh and system simplification in the RX station and/or lot of weigh and energy consumption onboard. Will keep my eyes and ears open as allways to see if anything new arrives to the market in that direction.

[Sebastian]

Hi,

we have a receiver in stock with around -90 up to -93 dBm.

http://www.globe-flight.com/-NEW-GF-24GHz-4-Channel-HighEnd-A-V-Receiver

we get with 8dBi antenna and only 10mW up to 1,5km range without a big noise.

Thats not using airwave chips but special high quality ones.

regards

Sebastian

Edited February 10, 2010 by Sebastian

[elossam]

Hi Sebastian

Thanks for the link. I see you have also the first unit I posted here (the one from Intelligentflight http://www.globe-flight.com/24-GHz-4-channel-A-V-receiver ) and it´s rated in your web at -85db while in the first link it shows a channel vs sensibility from -91 to -95 dbm (see http://www.nghobbies.com/cart/index.php?main_page=product_info&cPath=94&products_id=348) I wonder why there are such differences and where did they get such detailed info. In your case and being more according to what is in the market, the -85 dbm is something you have meassured?

About the unit you linked, the range test could be a way for testing but again, where does this specs come from? the manufacturer or your self meassuring?

It could we worth to test one unit, must check my current TX channels first but along the last years I´ve collected to many "miracle" stuffs and I don´t want to increase the "maybe-in-the-future-could-be-usefull" box.

Let me know and meanwhile I will check the channels we are using.

Another think if you don´t mind, does this Rx have a RSSI output (operative or at least accesible in the inside board)?

Edited February 10, 2010 by elossam

[Doofer]

Hi,

we have a receiver in stock with around -90 up to -93 dBm.

http://www.globe-flight.com/-NEW-GF-24GHz-4-Channel-HighEnd-A-V-Receiver

we get with 8dBi antenna and only 10mW up to 1,5km range without a big noise.

Thats not using airwave chips but special high quality ones.

regards

Sebastian

Your website suggests this receiver is "only fully compatible with our new transmitter" - in what way?

What range would you expect with this receiver using a typical 8dB patch antenna and the usual 10mW transmitters we are using from RC-Tech, Rangevideo etc.?

[elossam]

I suspect he referes to a channels correlation. If your tx uses in different channels you will not be able to get the same range results.

About the max range with a 10 mw tx, he doesn´t explain if it was a flight test or a static test when he talks about 1.5 km range. According to the results of a range calculator at such distance the remaining gain will be close to 3dbm, too low IMO for a safety flight. Setting half this distance as range target will result in 9 dbm margin which sounds more consistent for a flight. In any way note there are lot of thinks that can affect the range and it´s quite difficult to get an accuracy meassure of all those variables. That´s the reason of keeping some db margin instead of relying in the max theoretical range.