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Low level AM Transmitter Circuit and little description.

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hi,
i think i saw such simple circuits in older ham magasins and recently on the internet,
By the way , i found a circuit on my laptop (downloaded in the past... ) , i wonder what is it for ? (and why did i save it )
bast533.jpg
can it be a little grid-dip meter ?
 

i think i saw such simple circuits in older ham magasins and recently on the internet,
Click to expand...
Yes it is an old way . many of the peoples that haven't access to the PWR meter or ... using these circuits !
By the way , i found a circuit on my laptop (downloaded in the past... ) , i wonder what is it for ? (and why did i save it )

can it be a little grid-dip meter ?
Click to expand...

Ha ha ! you are alike me ! i have gang of circuits in my computer but i don't know why i have saved many of them !!! too :grin:
Yes it seems a grid dip meter ! because it is like an oscillator and then a micro ammeter to indicate it's ratio . ( you knew it's name !!! :smile: )
 

The emitter-coupled oscillator is belonging to the class of negative impedance oscillators. The negative impedance can be adjusted by the emitter resistor respectively a current source over a wide range.
 
Hi Zsolt1
What are the wave forms that i can see in your post #143 ? gate of what ? drain of what ?
Best Wishes
Goldsmith
 

hi,
you asked for measurements in post #108 from the oscilator. It's built with jfet (BF244) not bjt.
:grin:
 

you asked for measurements in post #108 from the oscilator. It's built with jfet (BF244) not bjt.
Click to expand...
Are you referring to the circuit originally shown in post #28? There should be a MHz carrier signal rather than 2.5 kHz?
 

yes it's the same circuit as i sed in post 83 i belive, anyway it's the transmitter i built and i posted a picture about it to .... My transmiter has multiple coil pairs, so i can cover a large range, i did the measurements on a random position of the switch, so a diferent wawe length was selected. Actually it was on 7 MHz before i conected the scope (it has a frequency meter with a lcd on the front panel) , the frequency changed when i conected the scope . I suspect that it oscillates because magnetic linkage of coils. (frequency changes a little when i re-asamble the metalic box, now i remember that's why i had some trouble with coil dimensioning... :grin: )
Any way Eshal's new circuit will work better with the new oscillator, so i belive we progressed a little... :grin:
 

hi,
you asked for measurements in post #108 from the oscilator. It's built with jfet (BF244) not bjt.
Click to expand...
Hi My friend
Oh yes , now i can remember ! that's brilliant , however with a little change in quiescent point you can increase it's amplitude more .
remember that's why i had some trouble with coil dimensioning.
Click to expand...
Why trouble ? did you try sandwich winding ? ( at first it seems delicious ! and at second it will consequence lesser leakage ! :grin: )
And a law : when you want make a high precision transmitter , there are some ways to create a fixed frequency carrier signal , first is a crystal oscillator ( like miller's oscillator ) . or a low frequency oscillator and then a or some frequency multipliers ! ( there are many other ways , available too )
Best Regards
Goldsmith
 

Eshal said:
Hello experts!

Hello I hope I can help you.
I read somewhere that you can make a AM transmitter just by using a stabilizer like the LM317.

Maybe you can find that article. Building it should be a peace of cake !

<good luck !> Regards.

I do not know exactly where I found it a few years back, I'm sorry but hope you do find it ! Albert.

How is everyone.

I am newbie here.

I am in the 4th semester of Electronics Engineering. Yet I have studied Basic electronics, LIC, and only analog electronics not yet digital. Also I don't have any knowledge about Power electronics because still we have not studied it yet as well.

So my Analog Communication teacher give us an assignment and told us to make the Low Level AM Transmitter.

Teacher said that we students can pickup any circuit diagram from internet and make a transmitter on the breadboard. And then we can submit only in 3 weeks. Our teacher knows that we student don't have much knowledge that we could design with our own knowledge so he recommend to pickup the diagram from internet.

But my thinking is not as my teacher. I want to learn something. If I pick it up from internet then I can't be able to learn anything. Therefore, I turned to this forum.

Please tell me about low level AM transmitter:
And please anyone of you provide me a low level AM transmitter circuit diagram with a little description of stages.

Please remember, it must with the consideration of analog electronics, not so hifi transmitter. It just transmit to a certain range. Please help me.

If you need any information you expert can ask.

Thank you.
Click to expand...

Hello I hope I can help you.
I read somewhere that you can make a AM transmitter just by using a stabilizer like the LM317.

Maybe you can find that article. Building it should be a peace of cake !

<good luck !> Regards.

I read somewhere that building a AM transmitter can easily be done with a Stabilizer like the LM317.
I do not know exactly where I found it a few years back, I'm sorry but hope you do find it ! Albert.
 

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