What´s packet gain in ping test ?? no packet loss !! but packet gain !

I see no "packet gain" in the ping test utility..

I've seem packet gain in tests of links with particularly dirty RF. Last time I saw it was on a link with a polarization mismatch (90 degrees off).

You can see "packet gain" information only if there is really packet gain, otherwise you see the packet loss information.

I noticed very high packet gain on one of my AP's based on MT 2.9.6 and Ubiquiti SR2 card. SR2 is connected through 3m CFD-400 cable to 15dB gain omni antenna. When using default tx-power, packet gain can reach even over 1000%, meaning very bad performances. One ping sent, over 1000 of them received, very strange. When I put power to -25 to -23, everything works fine, no ping gain, no ping loss. My SR2 is working on 2452 MHz at the moment (channel 9), no associated clients at the moment. Here is frequency usage:

FREQ USE
2412MHz 0.3%
2417MHz 0.3%
2422MHz 4.5%
2427MHz 1.3%
2432MHz 0%
2437MHz 2.3%
2442MHz 15.2%
2447MHz 2.8%
2452MHz 0%
2457MHz 0.6%
2462MHz 1.5%

I am thinking of several reasons could cause this. First, there is no watter in connectors, I checked that. Then, this is hill area, I suspect on reflection either from the hill or from surrounding roofs. Even my omni antenna is not above the highest point of the roof where it is placed. Part of the antenna is higher in the opened area, bat part is not and this part of the roof is quite close to the antenna, maybe 2 meters away with angle of 45 degrees.

This is scan for other AP's in the area:

ADDRESS SSID BAND FREQ SIG RADIO-NAME
AB 00:90:4B:D4: 2.4ghz-b 2412 -84
AB 00:02:6F:37: 2.4ghz-b 2422 -68
AB 00:02:6F:38: 2.4ghz-b 2437 -81
AB 00:02:6F:3A: 2.4ghz-b 2437 -85
AB R 00:0B:6B:35: 2.4ghz-b 2442 -93
AB 00:02:6F:35: 2.4ghz-b 2442 -77
AB 00:90:4B:D2: 2.4ghz-b 2462 -90
AB 00:90:4B:D4: 2.4ghz-b 2462 -79
AB 00:06:25:54: 2.4ghz-b 2442 -85
AB 00:02:6F:03: 2.4ghz-b 2417 -93

I deleted parts of MAC addresses and SSID's for privacy reasons of these guys.

Quite busy environment. As a solution, I would try to get horizontally polarized omni antenna and put it little bit higher (maybe one meter), just to cross the roofs highest point. If this doesn't help, I plan to replace Ubiquiti SR2 with Wistron-Neweb CM9 because I don't want to waste extra power of SR2, I will just use it somewhere else and let CM9 cover this area.

Maybe this is also important to mention. I have just one client there, at the moment, and his device is D-Link DWL-900AP/E. I tested ping with some small Linksys router behind this bridge.

Any suggestions, please?