70kms P2P link(netbo5 with mANT 30 antenna) drop signal strength at day time, during night time from 9pm rssi hit around -45/-46 but during day time rssi drops to -71/-72, Can anyone give me a reasonable reason regarding this issue

Isn't mast or holder moving due to temperature change?

I have heard that a such link have had been blocked/exacerbated by open-hearth furnace or sth. similar generating strong and "high" magnetic field from time to time during the production process. Maybe it is similar situation ?

I have heard that a such link have had been blocked/exacerbated by open-hearth furnace or sth. similar generating strong and "high" magnetic field from time to time during the production process. Maybe it is similar situation ?

Any solution to resolve the issue

None if you do not steer clear of it making additional transmission point.

Have you change frequency and transmit power...there may be some interfearence in a day time..or is there a cloud between the two point during day time..

Is the link passing over water?

Had the exact same issue with a pair of 30dbi ubnt rocket dishes and Netmetals, its about 90km

Signal would drop early in the morning and just before dark.

This would happen for 3 days in a row and then work perfectly fine for a month.

Changed the dishes to 34dbi ones the signal still drops now and then but it doesn't affect the throughput much, clients don't even notice