Why is it der Privatsender?

Privatsender ends in -er, and most nouns ending in -er are masculine: in a German dictionary, 86% of them take der.

All nouns ending in -er
Sense 1
der

Meaning

[1] Radio transmitter that is private hand

[1] Rundfunksender, der in privater Hand ist

Examples

[1] "The other day, when I couldn't sleep at night, I saw a documentary on one of the private venues"

[1] „Neulich, als ich nachts nicht schlafen konnte, sah ich eine Dokumentation auf einem der Privatsender.“

Declension

1 Singular Plural
Nominativ der Privatsender die Privatsender
Genitiv des Privatsenders der Privatsender
Dativ dem Privatsender den Privatsendern
Akkusativ den Privatsender die Privatsender

Pronunciation

Dictionary entries include material from Wiktionary. Wiktionary