Receiver Extras and Plans

 
 

I designed an accurate S meter for this receiver, and it works great. It’s based on an AD8307 demodulating log amp, operating on the audio signal. It was published in QST, February 2008, p. 33-36. Due to copyright rules, I can’t supply a copy of that article. But I’m more than happy to answer questions.


Here is a graph of the S meter’s response error. For a ±1 dB error band, it achieves a 96 dB dynamic range.

An Accurate S Meter

This thing will never be done; I had no intention of getting it perfect the first time. This is a learning experience. So here are a few things I have in mind.

What’s Next for the Receiver?

Speakers?

Thus far, I haven’t added power amps to drive speakers. I might use some of those powered computer speakers, or something else. For now, my trusty Sennheiser HD424 headphones work great. They have 10K ohm coils, so opamps can drive them easily.

AGC

For really high-fidelity listening, operation without AGC is the way to go because there is no chance of transient distortion. But for the average rag chew, and especially to prevent speaker blasting, some kind of AGC is desirable.