I found everything beside the FD700, an ultrafast diode. I think it is there to set a 50% duty cycle to bias the last transistor, but no matter how I cant find it. It is an 30V, 700ps switching time, 1pF capacitance. any suggestion on substitute. what about the 1N4148?
can you improvise in your kitchen if you don't have kitchen utensils and food to cook? how are you going to build your linear amplifier if you don't have the needed?
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hey that's a good point duh. yes i'll maybe use my debit card but, us in third world countries are kinda poor. but i tried futurlec just now, they still dont have that FD700 diode.
oh, it is finally working. I only bulit one with the first 2 transistor though. it worked well, the range i havnt really tried but it is more than 100m, with the meter you guys discussed in pg 19 or so, it shows an reading of 100mV. however there is a strange noise broadcast in the background, something that sound like 200Hz squarewave. Then all of a sudden it stopped working. I looked at everything and there are all fine, I had to remove Q2 to make it work again. Why is that. I though the tuned circuit with Q2 centered at 98Mhz gives good power over the entire band?
Now I am thinking about building a mini amplifier for a commercial FM transmitter i brought, what about this circuit for amplification? they said the output of the transmitter is about 100uW on the manual.
I have some questions here for the mod4 FM transmitter:
What is the type of configuration for the oscillator? Earlier post if not mistaken stated Colpitts? But how come it is different from the configuration I found on the net?
With all the 2N3904 BJT transistor, is it possible to change all the existing one to FET type? as FETs are more energy efficient. If possible, any good suggestion which FET is suitable for that fm transmitter?
I planned to inject RDS signal into this fm transmitter, any idea how can I make it work?
I have some questions here for the mod4 FM transmitter:
What is the type of configuration for the oscillator? Earlier post if not mistaken stated Colpitts? But how come it is different from the configuration I found on the net?
There are a few ways to make a Colpitts oscillator. This way is used in most FM transmitter circuits.
With all the 2N3904 BJT transistor, is it possible to change all the existing one to FET type? as FETs are more energy efficient. If possible, any good suggestion which FET is suitable for that fm transmitter?
Thanks for the reply audioguru, I thought the RDS carrier frequency should be 57kHz (3 x 19kHz) instead of 20 kHz as you stated. Or am I missing something?
In my Mod4 FM transmitter, C2 stops the audio preamp transistor from amplifying the carrier frequency and C5 makes the base of the Colpitts oscillator at ground because it is a common-base amplifier for the RF frequency.