# Weird result during ttn mapping **URL:** \ **Category:** LMIC\ **Created:** [April 26, 2019, 6:55am UTC](https://www.thethingsnetwork.org/forum/t/weird-result-during-ttn-mapping/25415 "2019-04-26T06:55:46Z")\ **Posts on this page:** 1\ **Showing post:** 14
**Author:** ![cultsdotelecomatgmai](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/cultsdotelecomatgmai/32/35697_2.png) [@cultsdotelecomatgmai](https://www.thethingsnetwork.org/forum/u/cultsdotelecomatgmai)\ **Post date:** [April 27, 2019, 6:48pm UTC](https://www.thethingsnetwork.org/forum/t/weird-result-during-ttn-mapping/25415/14 "2019-04-27T18:48:54Z")
Hi @kjetilsn, if all the gateways are configured correctly then you may have encountered transient tropospheric ducting. > **[Tropospheric propagation | Tropospheric ducting](https://en.wikipedia.org/wiki/Tropospheric_propagation#Tropospheric_ducting)** > > Tropospheric ducting is a type of radio propagation that tends to happen during periods of stable, anticyclonic weather. In this propagation method, when the signal encounters a rise in temperature in the atmosphere instead of the normal decrease (known as a temperature inversion), the higher refractive index of the atmosphere there will cause the signal to be bent. Tropospheric ducting affects all frequencies, and signals enhanced this way tend to travel up to 800 miles (1,300 km) (though some p... I have encountered this many times in my past work as an engineer on 3G and 4G mobile networks. Distant (hundreds of km away) UHF terrestrial TV broadcast transmissions appear temporarily and disrupt the 700MHz band. This happens much more than we realise, it’s just not recorded very often. There are even tropospheric ducting forecasts, such as… [https://tropo.f5len.org/forecasts-for-europe/](https://tropo.f5len.org/forecasts-for-europe/) --- _[View the full topic](https://www.thethingsnetwork.org/forum/t/weird-result-during-ttn-mapping/25415)._