# New PTP650 connectorized Long Range Installations (Connecting Main Oil Fields)

PTP650 - Long Range (Back-to-Back) Installations | SYSTEL Telecom | Egypt | Broadband Team  ..

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Hi Mohamed,

Thanks for sharing this with us. It looks as though everything is working well! You certainly seem to have some serious towers there.

How close is the measured link loss compared with the LINKPlanner project?

Mark

Hi Mark,

Hi Mohamed,

Thanks for that. Let's do some mathematics, just for fun.

The Free Space Path Loss (L) is found from a standard formula:

...where d is the link range in meters, f is the frequency in Hz, and c is the speed of light.

The speed of light is about 299,790,000 m/s. That's close enough for now.

For the first link, and 5.8 GHz, we get L = 141.5 dB, matching the prediction from LINKPlanner.

Now, when we look at the status screen for the link we see Transmit Power = 23 dBm and Receive Power = -59.9 dBm. The PTP 650 link has computed Link Loss = 128.9 dB assuming 23 dBi antenna gain like this:

L = 23 -(-59.9) + 23 + 23 = 128.9 dB

This result is less than the basic free space path loss over 48.8 km, which is very unlikely. I guess the reason is that you have higher gain antennas (29.5 dBi) but haven't adjusted Antenna Gain in the Wireless Configuration page of the web-based interface. Could this be the case?

Thanks, Mark

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Hi Mohamed, what antenna did you use for this link?