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best way to improve video range?

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What's the noise figure for your LNA? 25dB seems way overrated. From what it looks, amps above ~15dB are way too noisy to be useful, at least with the common video RXs. I have a very low noise 15dB one, that does improve at least 25%. Never tested more.

Edited by Kilrah

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The specs on the LNA look pretty good, they are

High IP3 2100-2500MHz LNA <0.8dBNF, >25dBG

It was expensive enough to be good !

JetPilot

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Yep, 0.8 is pretty good.

I don't think you could make use of the 25dB unless you have a long co-ax to loss over come, that's what they are made for.

We do get a secondary benefit though if the NF is better than the receiver it is used with but with 25dB you may just swamp your receiver front end.

Try adding an attenuator or some more co-ax between the LNA and the receiver to bring the signal level back closer to the designed level for the receiver. If the LNA NF is better than the receivers then it you will still see an improvement.

Terry

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Thanks for the suggestion Terry, creating line attenuation is easy to do :D I have one of these LNA's for both 2.4 GHZ and 900 MHZ. I still have a lot of testing to do, but the initial results dont show any great improvement. I suspect that there may be a lot of noise where I have been flying, so I will go out to the middle of nowhere this weekend and try it where I know there is no noise. I will post my results.

JetPilot

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yes the teoretical improvement of 4dB I have measured and tested in lab,

is best case senarios, that is with worst case receivers !

Here is the LNA type I have tested,

http://www.webx.dk/rc/video-wireless/Lna2425/lna.htm

This item I got clearly perform extreamly well, see the NF value !

The Gain of 15 is a bit high, I would say an LNA mounted directly on antenna and receiver directly on the LNA, then you only need 6-10dB gain max, and as LOW NF as you can get !!

if your NF is over 1.5 it is useless ! and waste of money to add that LNA,

modern RX systems MUST have NF under 1.5

the older types had 2 or even worse.

But I still see a few dB in the compleete signal chain to ba gained with LNA,

on all my receivers.

2-4dB is the same as with a transmitter to explain the power gained.

500mW +2dB = 800mW

500mW +4dB = 1.2W

or

1W +2dB = 1.6W

1W +4dB = 2.5W

to explain the RANGE gain in free air visible sight:

10dB gain will give you 3x range distance with same signal quality.

20dB gain will give you 6x range distance with same signal quality.

so is there is cheaper or smarter way to get gain ?

YES !! antennas is the real way to go !!

LNA will help a tiny bit, and should only be used with care for the advanced user that have tried all other things and uptimized all other things, then this is the last way to get the last few dB.

In our FPV world the problem is plane is moving and changing position and angle all the time,

but if it is possible to make both antennas point to each other and be directional,

we can gain 20dB link easyly ! and 30dB or the hardcore dudes with the really big and complicated antenna setups

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I have concidered this but feel it may cause more problems than it solves. If you only have 1 dipole mounted on the aircraft then you must have 2 dead areas of transmission either front and back or to the sides. You could use a turnstyle type aerial as some have used in the past or 2 transmitters on different frequencies.

I am interested to hear more from guys that have tried horizontal polarization.

Terry

Hi Terry you may had resolved your problem by now. I found mounting horizontal polarization. TX & RX. Gave better results. This plane I have FPV over 2 miles.

Here is a video using RX (not diversity) With the 2.4GHZ 14DBI patch antenna and 1 watt TX on plane. No one is aiming antenna! Somewhat long vid best part is about halfway through it. If you prefer. :)

Go here:

Edited by lvsupertech

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This plane I have FPV over 2 miles.

Here is a video using RX (not diversity) With the 2.4GHZ 14DBI patch antenna and 1 watt TX on plane

With 1W I would expect 2 miles anyway, I have flown to 1.5 miles on 100mW.

I would think the only way to be sure of what is best would be to fit a plane with 2 TX's, one with the aerial H and the other V. Then record them on the ground and compare.

Terry

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I loved the video LVSuperTech ! The desert is an awesome place to fly, wish I was there. You were REALLY high at one point :D It looked above 12,000 foot mount charlston ??

As far as the video range, you can get a lot more than that. With a 1000 mW TX, 3 dbi vertical antenna on the plane, and 14 dBI patch I get flyable video to 8 miles. I have done 6 without the LNA. Of course your RC range becomes a problem at around 2 miles.

Thanks for all the good info on LNA's terry. Given the information, I should have gotten the PHEMT LNA with a noise figure of .7 or lower. The one I got is a Hi IP 3 with noise figure of better than .8, but 25 dB gain.

JetPilot

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