More like $40 in parts, without a board, etc.
The RPD-1 is $20.70
LT1678/LT1679 is a nice low noise opamp that does rail to rail and is
about $5
etc
On 3/24/16 4:42 AM, Bob Camp wrote:
Hi
Pretty simple:
Double balanced mixer, RPD-1 is one option, there are others.
Fairly simple L/C lowpass between the mixer and an op-amp.
20 db positive (non-inverting) op-amp amplifier string after the mixer
Output of the string goes to the sound card. Use a good (dual / quad) audio op
amp
Quadrature amp picks off the output of the first op amp stage, switch and
resistors to set gain, pot to set op point.
====
So what you have is an old style quadrature phase noise amp and “PLL”. More or
less a very junior version
of the 3048 test box. Like any setup of this sort, you check two similar
oscillators. They run in quadrature and
you do a few “measure this with switch in position A” sort of things to set
things up each time.
Nothing exotic.
Bob
Any documentation on this $40 phase noise test set?
Rick N6RK
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