hi the FR4 tand at 3Ghz is 0.02 and Er is 4.3 at 3GHz (note that Er is 4.7 at low frequencies only) some thing else FR4 is note built for high frequencies.
as told many times, FR4 don't identify totally the compound. many FR4's may be different between them.
As rule of thumb i've measured a tand=0.02 +/- 0.003 at 0.5...2 GHz
What is important, is not the exact value, but the fact that is ten times the tand of a Roger 's laminate.