Primary attraction of this rig is the "back to basics" analog design,
nothing hidden in IC's.
An LM386 for the audio amp is simple, works from 5-15 volts, but is not for the audiophile.
From wikipedia:? "The LM386 was invented by Ernie Leroy Long at Motorola in 1969. It was originally for part of a fuel injection system for a Ford Car."
If true, that makes it 7 years younger than the 2n2222.?
Here's an interesting look at a future proof replacement:??
Many similar analog audio IC's have become obsolete as the?industry moves on to class D switching amps.
But those new amps can create RF hash.
Fiddling with caps in a crystal ladder filter works to adjust bandwidth,
but I assume that the passband shape does not remain optimal.
Also, the extra cruft can add leakage around the filter, impacting the stopband.
Lots and lots of parts if you build something like the 2n22xx with all discrete devices.
If you are buying by the reel, they are very nearly free.
Jerry, KE7ER
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On Sun, Dec 15, 2019 at 06:46 AM, Michael Maiorana wrote:
They made some substitutions, like replacing the discrete?mixers with ADE-1 mixers. I am curious as to why Norcal kept the audio amp the way they did instead of going to a simpler integrated amp. Any ideas? They also did away with the variable bandwidth IF filter.?
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