in your circuit, what will C3 be for 100Mhz

For 100MHz:
C3 - between 1pF and 15pF.
C2 - about 40pF.
L1 - 2 turns magnet wire dia 0.5...0.7mm, wrapped on forming rod dia 5mm.

and that arrow is pointing to capacitor? is capacitor not 2 metal plates seperated by insulator?
looks like inductor but okay : inductor wires have capacitance maybe

Same in DIY capacitor - one metal plate is piece of insulated wire,
second metal plate is bare wire, wrapped on insulated wire.
Read:
Link 1
Link 2

 

Ouch, forgot to tell. At 100 MHz already is meaning of pcb material. If U use the old dark brown paper-vbasis bakelyte-textolyte, then dont surprize. It loss any sense over 20-30 MHz. If U use the yellow colored glass-fiber textolyte it loss sense about 100 MHz. Only whitish sorts are applicable for higher.
Other point - what are the caps U use, especially uin the tank and in the loop, both. COG=OK, X7R = dont wonder, instead paint it green and throw into grass. Next generation will groom-up better, probably.
Third point - diameter of wire for tank coil and it insulation method. The Focault will allow for electricity transport to use so thin layer as 6,5 microns. Probably there stays oxides or scratches, or sth else?

 

Thanks : for this your circuit what is the inductance? want to test analytic skills

Also is there any way to know what base voltage is going to be before hand? no right?

and for transistors, seems 2n5179 will do a great job

I don't know. I made it because I wanted a small battery operated transmitter, so I started with a capacitor value that I've seen used in similar circuits at this frequency and a small coil. I may have had to trim the inductance to get into the part of the band that I wanted and certainly had to spread/compress the turns to tune it into a blank spot.

If one was interested in that, one could calculate a range of voltage based on the expected beta of the transistor at various currents.

Agreed: The 2N5179 would probably do quite well.

Sometimes you just want to make something so you can use it and neither need nor want to work out the details. For a production design, you do work out all of the details and make best estimates possible if the details are not knowable. As I told my engineers, you don't want to be the one they are looking for when at a distant factory $500,000/shift production lines come to a halt because of yield or design problem.