replaceing mic input with line in on fm transmitter

[picbits]

wh

where is the pdf

This thread was 9 years old before you replied to it - the forum has undergone a number of moves and changes since then.

 

[JimB]

where is the pdf

Probably lost in a major server crash which happened a few years ago.

JimB

 

[audioguru]

Your FM transmitter has the electret mic and transistor not biased properly. It is missing pre-emphasis that all FM radio stations have so it will sound low level and muffled when heard on a normal FM radio since all FM radios have matching de-emphasis.
Is your line level signal stereo or mono?
The transmitter circuit must have the 4.7k input resistor changed to 47k and have an input coupling capacitor added.