Building a 16Mhz radio for Senior design project. have Q's - RF Cafe Forums

 Post subject: Building a 16Mhz radio for Senior design project. have Q's

Posted: Wed Sep 19, 2007 7:16 pm 

Hello This is my first post on this forum. I am building a 16Mhz radio for my senior design project and Have a few questions. I have been working in PSPICE and am ready to start building and testing.


1)What kind of capacitors should I use in my tuned amplifiers, oscillators, and filters? I have been looking online and there are so many to choose from. I think I should be using something with a small temp coefficient but what material should I use etc..

2)Does anyone know of a place online with low shipping costs and a good selection of components? I have been looking at mouser it seems to be pretty good any other suggestions?

3)In my transmit oscillator I am using an NFET to switch in and out a cap. I am having a difficult time trying to Find one in a TO-92 package with a good enough Ft. Does anyone know where I could go to get this? or perhaps suggest a better device for me to use than an NFET.

thank you for taking the time to read and answer my questions.

 Post subject:

Posted: Fri Oct 05, 2007 7:15 am 

Hi
I don't have a lot to contribute as to sources, since this depends where you live. In the UK (my home) it would be RS Components, Ambit, or Maplin.
The choice should be polystyrene or ceramic, and at 16MHz wire-ended axial leads would be OK. For an oscillator tuned circuit you want the high Q of the polystyrene, but at 16MHz maybe you need to choose ceramics with both NTC and PTC characteristics, then balance the temperature drift using an air-spaced differential cap, tweaked until the thermal drift is a minimum.
For the FET, an N-channel JFET like the 2N3819 would be OK for 16MHz.
For the power stage a MOS-FET would be good.