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Hello, 

What kind of polarization do you recommend for long-distance flying so without obstacles with a plane that always flies in a straight line and flat.

Another question, are there any receivers making more than -85 or -90dbm of sensitivity?

Thank you

Edited by swake

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Typical recommendations will depend on the FPV video link frequency. 900MHz, 1.3GHz, 2.4GHz, or 5.8GHz?

 

 

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5.8GHz FPV will be more reliable with CP antennas due to an increase in RF multipathing. You can use RHCP or LHCP; Both the vTx and vRx will need to be the same polarization (don't mix RHCP with LHCP).

Most modern 5.8GHz vRx's use the Richwave Rx chip, so -90dBm sensitivity is common. But variations in build quality can affect the actual sensitivity. Advertised sensitivity that is better than -90dBm is probably wishful thinking.

 

 

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I fly with an airplane MTD (My Twin Dream) which is made to fly far and high. The circular polarization is made for people who fly very low among the trees, etc ... When flying high there are no multiple reflections as we are in free field. You do not agree with her?

So for me I thought linear polarization was good for high flying.

I just found this on this forum: Terry say:

The only other thing worth a word is that pointing the aerial out the bottom of your plane is IMO the only way. The short wavelength of 5.8Ghz seems to be blocked very easy by servos or leads or almost anything. You will get interference simular to multipath but it is not.

So the frequencies 1.2 or 2.4 for the video are less sensitive to the multiple path? I understand better your question from the beginning.

Do you have brands and receiver references using the Richwave Rx chip?

I found on google that the UNO5800 use the module NWM662JPX, is it a specific module developed by ImmersionRC or some things like a RX5808 for example

because I can not find information about this module.

 

Edited by swake

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Quote

The circular polarization is made for people who fly very low among the trees, etc ... When flying high there are no multiple reflections as we are in free field.

The earth below your feet is a hard RF reflector. So 5.8GHz multipathing will still occur even when you fly high. But every flying location is different; So perhaps start with linear antennas and then upgrade to CP if you experience too much multipathing interference at your field.

Quote

I found on google that the UNO5800 use the module NWM662JPX

A few years ago ImmersionRC redesigned the UNO5800 and started using their NWM662JRX NexWavRF module. It has the Richwave Rx chip. Their original UNO and DUO designs had the Airwave chip based Rx module, which only has -85dBm sensitivity.

Quote

is it a specific module developed by ImmersionRC or some things like a RX5808

ImmersionRC was a late user of the Richwave Rx chip. Long after the success of the RX5808 (which uses Richwave chip) they took notice and started using it too.

There are many suppliers that clone RX5808 modules and other variants. Quality can vary. Two identical vRx's may have different performance. So like many Chinese made FPV products, you have to buy and try.

 

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I should point out that I was using very directional aerials on the receiver which also cuts down the multipathing. Also the same setup did suffer problems one time when I put the tracker on the roof of my car as I was too lazy to set the tripod up so it easy to upset.

CP seems to be the thing to go for if your building a new system as linear does not seem to give any appreciable extra range. Linear is simple though and does work for long range high flight with the right aerials. No matter which system is used I would always point the aerial out the bottom though if its practical to do so.

Terry

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