Bertus you have one hell of an organised link system, thanks it looks just like I saw on websdr, I now know I think what sdr is, its the graphic look of all the signals

 

Hello,

Most of the links I gave you are the results of search queries.
I still use the advanced Yahoo search for searching the web.
http://search.yahoo.com/web/advanced?ei=UTF-8&fr=altavista&p=

Like it says in my signature:
You don't have to know everything, if you know where to find it.

Bertus

 

Good afternoon folks, I have a stereo system and somehow through moving house several times lost the aerial/antenna for the fm stations.
It was like a oblong shape, I have looked on ebay, Amazon etc but cant find anything similar.
Would it be possible to make one?
Hope you can help, thank you... John

 

http://www.ebay.com/itm/INDOOR-FM-R...407630?hash=item1a007e018e:g:9qIAAOSwMsVXjY7b

http://www.ebay.com/itm/AXIS-FM-Dip...246459?hash=item3f67baf97b:g:AiwAAOSw8aNXGUBJ

 

http://www.ebay.com/itm/INDOOR-FM-R...407630?hash=item1a007e018e:g:9qIAAOSwMsVXjY7b

http://www.ebay.com/itm/AXIS-FM-Dip...246459?hash=item3f67baf97b:g:AiwAAOSw8aNXGUBJ

Ok thanks for reply, I am in the UK so I will try searching on ebay again using different search terms.
Cheers... John

 

Going back to your thread-starting post, the tank circuit along with the NPN transistor (likely with a small pico-farad capacitor across the emitter and collector) is called a Colpitts Oscillator.
http://www.electronics-tutorials.ws/oscillator/colpitts.html
You may also want to look at the other types of oscillators such as the Hartley
http://www.electronics-tutorials.ws/oscillator/hartley.html
http://electronics.howstuffworks.com/oscillator.htm

I don't want to kill you with links, but the colpitts is the most common among basic RF transmitters. The problem with most of these types of oscillators is frequency drift, either when touched or if your hand comes near the tank circuit. they are great for learning how they work...especially with harmonics (spurious frequencies). If your unfiltered oscillator center frequency is 120MHz, you will have harmonics at 240MHz, 360MHz, 480MHz and so on. Without a spectrum analyzer, it is difficult to determine the center frequency. If the signal goes away after you back away from the circuit a few feet, you have a harmonic. If you want a more stable oscillator without much harmonics, consider using a crystal controlled circuit. A bit more design is required, but the payoff is worth it.
Go to the link below and click on APP NOTES
http://www.crystek.com/home/crystek/appnotes.aspx

 

Going back to your thread-starting post, the tank circuit along with the NPN transistor (likely with a small pico-farad capacitor across the emitter and collector) is called a Colpitts Oscillator.
http://www.electronics-tutorials.ws/oscillator/colpitts.html
You may also want to look at the other types of oscillators such as the Hartley
http://www.electronics-tutorials.ws/oscillator/hartley.html
http://electronics.howstuffworks.com/oscillator.htm

I don't want to kill you with links, but the colpitts is the most common among basic RF transmitters. The problem with most of these types of oscillators is frequency drift, either when touched or if your hand comes near the tank circuit. they are great for learning how they work...especially with harmonics (spurious frequencies). If your unfiltered oscillator center frequency is 120MHz, you will have harmonics at 240MHz, 360MHz, 480MHz and so on. Without a spectrum analyzer, it is difficult to determine the center frequency. If the signal goes away after you back away from the circuit a few feet, you have a harmonic. If you want a more stable oscillator without much harmonics, consider using a crystal controlled circuit. A bit more design is required, but the payoff is worth it.
Go to the link below and click on APP NOTES
http://www.crystek.com/home/crystek/appnotes.aspx

Ok thank you very much, this is far beyond my minimal knowledge but I will have a look and continue learning. Thanks again... John