EMRFD Message Archive 529

Message Date From Subject
529 2007-03-16 12:28:57 Steve White Testing receiver front end filters

I am building up a little SA602 receiver for 20M and plan on using the front end from the 2N220 receiver. This is just the filter not including the rf amplifier. Since I still have lots to learn I thought this would be a good place to ask some questions and learn.


  1. Once I get the front end built how do I verify that it has the proper input and output impedances?  I need a 50 Input impedance and a 1.5K output impedance and want to be able to measure these. I think that the SA602 has a 1.5k input impedance if configured for an unbalanced input.  I have a good Tek scope and a swept signal generator.  You can view the schematic of the front end at Jim’s web site  http://www.k8iqy.com/qrprigs/2n220/2N220Schematics.htm...  I think I know how to sweep the frontend with the signal generator and view the pass band on the scope but not sure how to measure the input/output impedances.
  2. I think the 2N220 front end has a 50ohm input impedance but the output impedance is an unknown to me.  How do I determine what that is and more importantly how do I change it to meet my needs??

My little receiver is working but needs a better front end than what I have already which is way to broadband in order for it to perform like it should.


Any comments or hints to any web pages or books would be most helpful.


Steve NU0P