[time-nuts] Spectrum Analyzer Specifications

Bob Camp kb8tq at n1k.org
Thu Mar 24 16:29:22 EDT 2016


Hi

I’ve built maybe a dozen of these over the years. I have never used a board for any of them. 
They all go down on a piece of scrap copper clad and point to point / dead bug wire up. You
get a good ground and leaded parts are easier to work with anyway. 

Bob

> On Mar 24, 2016, at 9:04 AM, jimlux <jimlux at earthlink.net> wrote:
> 
> 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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