#175: Filter functions in an HF Upconverter used with RTL-SDR Dongle Receiver

(see links below) This video describes and demonstrates the functions of an RF preselection filter, IF bandpass filter and LO filter in an HF upconverter application. I'm using a "Ham It Up" HF upconverter from NooElec.com to demonstrate the filter operation. This upconverter was designed by NooElec and Opendous, and performs very well, with about 10dB conversion loss. It is an open source design. A 125MHz LO (local oscillator) is used to upconvert the HF band. It uses a Mini Circuit ADE-1+ diode ring double balanced mixer, a Elliptic (Cauer) low-pass preselection filter and a Butterworth IF bandpass filter. A walk-through of the schematic is presented, and the operation of the filters is demonstrated using a signal generator and spectrum analyzer. The probe being used is a Tek P6150. Here are some relevant link for this video: My previous video on the basics of upconversion:    • #174: Using a mixer to listen to HF, short...   The Ham-It-Up Upconverter from NooElec: http://www.nooelec.com/store/sdr/ham-... Detailed circuit description and open-source files are found at the following two links: http://code.google.com/p/opendous/wik... http://code.google.com/p/opendous/wik...