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canram
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horizontal or vertical polarisation for p2p-links ?

Mon Aug 01, 2005 11:40 am

Hello,

I´m just wondering wether horizontal or vertical polarisation is more suitable for p2p-links.

Thanks so far.
Stefan.
 
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tneumann
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Mon Aug 01, 2005 1:49 pm

Can't say that one is better than the other. It all depends on if there are other RF signals around
that will cause interferences. If there are, you need to find out if they are vertically or horizontally
polarized and then use the other polarization for your link. That will usually reduce the intereference
from the other signal by about 20dB.

--Tom
 
canram
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Mon Aug 01, 2005 1:51 pm

Thank you for your answer.

Is there an easy way to check out those interferences?
 
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stephenpatrick
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Mon Aug 01, 2005 2:39 pm

I agree with Tom.
On another thread we noted the lack of "SNR readout" or "noise floor readout", which MT say is an Atheros chipset limitation.
If that's the case, the only way is try the link at both polarisations with a bandwidth test and use the best.

I remember that one polarisation is less sensitive to rain, (can't remember), depends on what distance you are going to try.

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canram
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Mon Aug 01, 2005 2:55 pm

Oh, thats a pretty project for next saturday which will take the whole day :(
I cannot believe, that lack of "SNR readout" or "noise floor readout" is a chipset limitation. Lancom uses Atheros chipset too, but they have a "SNR" and "noise floor readout". Even the cheapest Homeoffice-Router Linksys WRT54G with broadcom-chipset have a SNR" and "noise floor readout".
 
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stephenpatrick
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Mon Aug 01, 2005 3:24 pm

Yes canram I thought it was surprising,

Perhaps we can have some comment from Mikrotik:

- Why is there no SNR or noise floor readout?
- Is it the Atheros chipset, or the driver?
- Any timescale to add this feature?

I think it's a pretty major problem when using unlicensed spectrum -

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