Friday, September 22, 2017

drawing the data together.

First let's take a look at a commercial kit. This is a converter to use with a car radio.
Now much to look at with the IC containing the oscillator and DBM. If you read the post ahead of this one you should have seen when using a level 7 DBM we will expect a 7db conversion loss. So this begs the question Are they loosing 7db  or is it more than meets the eye? Let's look at the circuit for the answer.

The signal goes in pin 1 and out pin 4. Where is the diode ring and transformers? They are using a Gilbert Cell.Interesting side story that I will not go into at this time but Gilbert did not design the cell? Anyhoo, the diode ring mixer produces a loss. The GC (Gilbert Cell) doesn't. In the transition from diode ring to the NE-602 there was a GC chip. I did a discrete build of one here.
Gilbert Cell from discretes
So the food for thought here is shall we build a GC from discretes, inset an RF amp to overcome the losses, or use an AF amp with some extra boost?

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