hi everyone well ive always been fasinated with transmiiters especially am transmitters. Just recently whilst looking on ebay i purchased a ready built from Greece. This was a 10 watt transmitter. The support from them was practically nil however i managed to get this working . Following a few examples i built a coil using copper wire and gave this 50 turns on a tube . i had now made taps at every 10 turns ; b went to ground ie a copper earth connector and 'a ' would goto the antenna.
idid notice that wen a+b was coonected the sound quality became very good . however something had gone wrong and after an hour all transmissions became very weak
im not sure what ive done wrong or if the a and b should be connected this way. im completely new to this so please be patient with me.
ive now returned the tx for repair so hope to get it right next time. lol
really appreciate some advice on the above the + and - to same coil is this ok as iver now destroyed another transmitter and not sure were im going wrong now sending again for repair. This is the 4th am tranmiitter terrible
There are quite a few ways to tune up a shortened medium wave antenna. What you show kind of looks like the standard method shown here.. (never mind the math, just randomly found picture)
Usually you set the bottom tap to achieve proper impedance matching and then the top tap to match the antenna wire.
Are you sure you burnt out the final? Did you test it on a dummy load to make sure it is putting out its normal power level? The tapped coil matching like you are using works well but you have to be careful with the impedance matching not being to low or else it starts looking like a short circuit to the final output transistor.
If you are running enough power you could use the simple light bulb test where you insert a light bulb in series with the antenna and coil and tune up for maximum brightness, then you know you have a close match.
many thanks for your reply. It helps to know im correct in my diagram. Sorry im completely new to all this so enjoying the journey but much to learn. Dummy load how would i maKE THIS and the light bulb test dont really understand this and how it works. Is there any simple diagrams i could follow. i mean simple please
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