Testing I/F Frequencies

Feb 12, 2006 1 Replies
J

I am building a 2m/6M radio receiver and studying it's design at the same time. I am "lost" when it comes to visualizing how the I/F stuff is working. I have "CircuitMaker" and wanted to create a circuit which I could simulate and see how it's working but can't find a schematic of how to do it?



I am interested in seeing how by combining two frequencies the output is "the sum and difference" etc, and the basic working of Intermediate Frequency. BTW the radio is a "dual conversion" type where it takes the input freq and converts it to 10.7Mhz then converts again to



455Khz, etc. If it matters the kit is the Elenco AR-2N6 receiver.

Thanks!



Jim Douglas


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B

There is a long history of confusion about this, due to the RF world and the rest of the world using "mixing" differently. The secret is that in RF, "mixing" really means "multiplication". If you multiply 2 sinusoids together, the product has components only at sum and difference frequencies of the original inputs. This is that same old trig relationship you probably already forgot from high school for the product of sines or cosines.

sin(A) * sin(B) = 1/2 * cos(A-B) - 1/2 * cos(A+B)

As an aside, this is the same relationship behind Fourier analysis. You migth want to check out "Gut-Level Fourier Transforms - Everything You Need, You Got In High School" at

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Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

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Home of DaqGen, the FREEWARE signal generator

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