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Order / Gain Structure of RX Front End?

Jan 6th, 10:50

VE2EOT

Joined: Jan 5th, 15:22
Total Topics: 0
Total Posts: 0
Hey folks,

I'm working on a homebrew design for an HF transceiver and there seem to be just as many approaches to receiver design as there are radios out there.

Are there any best-practice rules on the order of blocks / gain settings for receiver front ends? What is the normal thought process that goes into deciding how much gain to put right after the antenna, after filters and attenuators, after the IF mixer, etc.?

I'm working on a basic block diagram for my project and feel funny just trying to arbitrarily stick things together.

73 VE2EOT
Jan 6th, 16:24

W1VT

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Typically a designer comes up with a compromise between sensitivity, dynamic range, complexity, and cost. Everyone has a different idea what is best.

One approach is to build "building blocks" connected with 50 ohm cables. You can then experiment to see what works best for you.

Zak W1VT
ARRL Senior Lab Engineer
Jan 6th, 23:53

VE2EOT

Joined: Jan 5th, 15:22
Total Topics: 0
Total Posts: 0
Thanks for the reply. I realize that every design has trade-offs. (very experienced non-RF designer here) But I'm looking for some starting points and rules of thumb at least to get me started.

A few things seem obvious, like not having too much gain up front where the amp could be overloaded before any ability to attenuate. Or having gain before any IF stage / filtering would help to filter out strong unwanted signals. I assume the first amp(s) bring the signal up to the level required by the first mixer, and then most of the gain can go after that?

I will do some experiments but just want to get a sense of the right way to approach things.

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