Looking at an escort jamming example where a Prowler is trying to prevent a Bear from localizing some Tomcats:
105616 Search.c:1307 - Unit EA-6B Prowler ICAP II, lngECMRange = 1000
105616 Search.c:1590 - ECM Escort ECM=0, ECMTmp=0, ECMTmpE=0, RadRng=230, JamRng=100, JamRadRng=266, TarRadRng=221, JamTarRng=46
105616 Search.c:1637 - ECM ECMRadRng=266, ECMTarRng=46, ECMTarRngTmp=0, RadTarRng=221, ECMRng=100, RadRng=230, Rng50=48, ECM=0, ECMTmp=0, ECMTmpE=0
105616 Search.c:1650 - ECM Emitter=Tu-95RT Bear D, Target=F-14B Tomcat, ECM=EA-6B Prowler ICAP II
Bear's radar max range is 266nm, Prowler ECM max range is 100nm, Bear is 221nm from Tomcats, Prowler is 46nm from Tomcats, Prowler is 266nm from Bear
The ECM isn't providing any benefit to the Tomcats in this case indicated by ECM=0
Here is a case where a Flanker radar's range is reduced 6% vs some missiles thanks to a Prowler:
105641 Search.c:1307 - Unit EA-6B Prowler ICAP II, lngECMRange = 1000
105641 Search.c:1565 - ECM Direct ECM=0, ECMTmp=6, ECMTmpE=0
105641 Search.c:1590 - ECM Escort ECM=0, ECMTmp=6, ECMTmpE=0, RadRng=65, JamRng=100, JamRadRng=78, TarRadRng=32, JamTarRng=68
105641 Search.c:1637 - ECM ECMRadRng=78, ECMTarRng=68, ECMTarRngTmp=0, RadTarRng=32, ECMRng=100, RadRng=65, Rng50=49, ECM=6, ECMTmp=6, ECMTmpE=0
105641 Search.c:1650 - ECM Emitter=Su-27S Flanker B, Target=missile, ECM=EA-6B Prowler ICAP II