Help me setup an RF amplifier

Hi guys,

I started a while age to venture into the world of RF electronics and i must say that its really fun albeit somewhat hard to understand from time to time. I am also reading up to the my amateur radio license here in Sweden.

Anyway... A couple of days ago i started to try out some small 433MHz RX/TX modules and they where a lot of fun to play with. So i figured i could maybe use them to open one of the entry doors at my Uni. The lab that i work at is on the 7th floor and sometimes we have visitors that don't have access so someone has to go down with the elevator and open the door. Its a real hassle when we have a lot of visitors so we figured we could maybe use these RF modules to open the the door remote from the lab.

However the transmitter is way to weak to get trough seven floors of concrete.

So we need a small RF amplifier and i thought it would be fun to build one.

A class-c amplifier would do fine i guess but I am kind of lost at this stage.

But to begin to do some calculations I need the input impedance for my transistors at 433 Mhz and the datasheets don't usually give any S-parameter data. For eg the 2n3688 transistor, that i have here, has no data about the s-parameters in its datasheets. So how do i do any impedance matching if i don't know the input impedance of the transistor? Unfortunately we don't have a network analyzer in this lab. :-(

Also it would be great if you guys could give me some tips on what books i could read to learn some more.

Cheers

transistores 2n3688

2N3688? Don't you mean 2N3866?

rf amp fun.

check , the books of less besser , Artech House - Practical Rf Circuit Design for Modern Wireless Systems Vol I & VOL II

also , about the input imedance of the transitr , u need to get the nonlinear model , specially the class C is a nonlinear class ,

also take care , Class C is good for FSK modulations , not envelop modulation , so check ur transmitter

khouly

2n3688 amplifier

RF PA 400MHz 2N3866

2n3866 fsk

this add-on amplifier is forbidden in many countries ...

only for some administrations and amateur radio authorized ( UHF 430 to 440 Mhz )

6 * F

Re: RF amplifier

VSWR: Oh sorry. Your right. Its the 2n3866

vfone: thanks for the post. i have actually come across this datasheet to. however i tried to simulate it and i got a very low gain so i assumed that either my spice simulator sucks or the values are off.

So my seconds question is: what about the input levels to the amplifier. what should they be for for that amplifier?

khouly: thanks for the tip! the modulation is just two level ASK modulation so it should work fine i think with a class c (?)

FFFFFF: yep. i know. we will check out what the legal limits are. and even if the signal is a bit to strong we will only be transmitting a couple of milliseconds say no more than 1-5 times a day. i don't think we will be bothering anyone with a small chirp like that.

again, thanks for the reply guys!

cheers

RF amplifier

it can work ASK with Class C amp

khouly