Steve Evans ) writes:
Hi everyone,

Below you will find my attempt to show in text-form, a circuit
fragment from a 145Mhz amplifier:


--------------capacitor-------------------------------transistor base
|
|
I
|
coil
|
|
|
|
------------------------------------------------------------GND

The cap's value is 1nF; the inductor's is 0.4uH.
The cap (I assume) is to couple one amplifier stage into the next
(50ohm source/load) with minimal attenuation of the desired VHF
signal. But like what's the purpose of this inductor to ground??


It's there to bias the transistor.

In this case, the base of the transistor (I'm assuming bipolar so I
say base) is at DC ground. But if you just shorted the base to ground,
the signal could not get into the transistor. So you put that RF choke there,
so the base sees ground at DC, but the signal sees a relatively high
impedance.

MIchael VE2BVW