Path Loss over distance...

It seems from your calculation that you are already including a portion of the effective area term in the Friis Transmission formula of wavelength^2/(4*Pi). You also need to include the gain of the transmitting antenna and the gain of the receiving antenna into your calculation. Assuming half-wave dipoles for each side (transmitting and receiving), which have a gain of about 2.15 dB, this would put you in the range that you are seeking.

Regards, JHazen

Hi Thank you very much for your reply.

I did assume that the emitted power from a WLAN station could not exceed

20dB totally, hence the calculation did not consider how this emission was divided between the different parts, but I might have misunderstud something about that. Since you are talking about a gain in both ends it will increase the range that I have calculated, right? The range that I calculated was vay to long, so I need to find some attenuation in the path between the sender and the receiver, or some thing that I have not considered in the transmission technique...

Btw, the caltulation of the range was done in the followring way:

Transmit power 20dB; Receive sensitivity -94dB; PathLoss = 10*log((lambda/(4*pi*Dist))^2)

Dist = lambda/(sqr(10^(PathLoss/10))*4*pi)

With a PathLoss of -114dB it gives a maximum distance of 4985m, which I think is way to much even in a theoretical calculation...

Regards... Thorbjørn

Hi again

I have found severeal sources that mentions a "Fade Margin" on the receiver side, which will make the range calculation closer to reality. The sources I have found mentions Fade Margins from 6-20dB which is quite a big span, and reduces the maximum range to 500-2500m. Is there any rules that makes it possible to determine the fade margin? Links or sources are very welcome...

Regards Thorbjørn

Hi,

You're correct that the gain would increase the distance. It occurred to me last night after I wrote my comment what your problem really is. Your transmit power, 20 dB, is an error. If you transmit 20 dB (100 Watts) at 2.45 GHz, the local regulating bodies will probably shut you down. It should be read 20 dBm instead, which is 20 dB with respect to

1 mW, or 100 mW. This would be 30 dB below what you were calculating for your link margin. I think this will account for your correct distance.

You're correct that the fade margin is included in the Friis Transmission formula, but usually this has to do with loss due to vegetation, rain, buildings, and the height of your antenna--which affects how far it can transmit over the horizon. Only the last one would apply to you, because you said you wanted to calculate in an open field. There are several books out there that help you calculate this margin, but mine (_Radiowave Propagation for PCS_) is at work right now.

I hope my previous comment about dBm will help you.

Jeff Hazen, Wireless Engineer