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.
- 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.
- 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.