Any document for RF amplifier designing!!!

[Shahriar]

Hi

Does anybody have a tutorial for designing RF amplifiers? for example how to calculate L2 or L3 in "4 Watt FM Transmitter " in project section.
or where th Base-Emitter voltage of T2 or T3 comes from to turn on the Transitor?

ThanX in advance
Shahriar

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[SM2GXN]

Hi Shahriar!

L2 and L3 are used as collector load for T2 and T3, have forgotten how to calculate those but got it somewhere in a big pile of books but there is probably someone here on the forum that can tell you right away, if you go by the book it's not that simple though.
T2 and T3 is working in class C so no voltage at the base is needed, since this is FM there is no need to run the driver and power amplifier as linear amplifiers.
There is lots of books on how to calculate rf amplifiers, for example
THE RADIO AMATEUR'S HANDBOOK by ARRL, have to look in my bookshelf tomorrow on more titles  ;D

Bjorn

 

[SM2GXN]

Now I have gone through my library  ;D
There is two books I have that could be of interest:

1: Lenk's RF Hanbook
Lenk says: This is a "something for everyone" RF book. No matter where you are in electronics, this book provides basic, practical considerations, test and troubleshooting information that can be put to immediate use.
Sounds good, doesn't it?

2. RF Circuit Design by Chris Bowick
RF Circuit Design is written for those who desire a practical approach to the design of RF amplifiers, impedance matching networks and filters.

I can recommend these two books, they are good.

Now to the RF chokes (L2 & L3), as a trial value use an inductance that produces a reactance between 1000-3000 Ohms at the operating frequency.
Let's say that your transmitter are going to be used at 100Mhz then the formula would be:

Using the formula with reactance 2000 Ohms and frequency 100Mhz : L=2000/2pi*(100*10^6)=3,18uH.
Remember that these values are not exact, to calculate the exact value I will have to put more braincells in work and I don't have them right now  ;D
There is lot more to say about RF chokes but this is a good start.

Bjorn

 

[Shahriar]

Dear 4-1000A

Thank you very much for your replies. I took a book from my university. Its name is "Modern communication circuits". In one of its chapters all of the RF Power amplifiers is described.

ThanX again
Shahriar

 

[ante1]

Hi Guys,

This book might be of some help.


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[SM2GXN]

Hi Ante!

Still to hot here! 
Thanks for the book, excellent even though some of the formulas will put me under big stress  ;D

Bjorn

 

[ante1]

Hi Bjorn,

You are welcome; it was not my intention to make you stressed! ;D  You could wait until winter when it’s cooler to read it! ;D  It’s hot enough here too!