[time-nuts] Spectrum Analyzer Specifications --> phase noise test set

Bob Camp kb8tq at n1k.org
Fri Mar 25 15:29:29 EDT 2016


Hi

> On Mar 25, 2016, at 1:55 PM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 3/25/16 5:07 AM, Bob Camp wrote:
>> Hi
>> 
>> The reverse isolation issue is indeed one of the weaknesses of this setup. For testing
>> OCXO’s isolation is not a big deal. A normal OCOX has very good output buffering
>> to give it the stability you are after. If you are running (maybe) a VCO with no buffering, that
>> assumption falls apart. The VCO will  / can injection lock through the mixer. In that
>> case you *do* need an amp to provide enough isolation to prevent the injection lock.
>> 
> 
> 
> But if someone were building a little module for a cheap and cheerful noise analyzer, then the buffer amp would be a separate module.

That’s how I have always done it in the past. The need for the bufferer is rare enough that including it in the 
basic analyzer module is not cost effective. The HP 3048 has the same basic issue (isolation) and they made
the same decision there. 

Bob


> 
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