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From: John R Walliker <jrwalliker@gmail.com>
Newsgroups: sci.electronics.design
Subject: Re: RF Metrology
Date: Sun, 29 Sep 2024 19:57:34 +0100
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On 29/09/2024 19:02, Jeroen Belleman wrote:
> On 9/29/24 19:14, Cursitor Doom wrote:
>> Greetings, gentlemen,
>>
>> I bought one of those TinySA Ultras recently and have spent some time
>> testing it today. I have to say it's amazing what they've done for the
>> price. I mean, truly amazing. I do have two other 'proper' lab-grade
>> RF spectrum analyzers, but I think I'm going to be mostly using the
>> TinySA in future as it's just *so* convenient and doesn't weigh a ton.
>> Anyway, to get back to the point of this post, having checked out the
>> TSA and establishing I didn't buy one of the fake versions that are
>> out there, I turned my attention to my mid-level RF SA, an HP who's
>> model number escapes me (not the 8566B I've posted here about before
>> which is now fully working, but a newer model that's about 1/3 as
>> heavy. I say I can't recall the model number but it's not relevant to
>> this question anyway. "So what is the fucking question, CD??" I hear
>> you not unreasonably cry. Well, it's this:
>> When I'm feeding an RF signal into the SA, I'm seeing differing
>> amplitudes at different frequencies. So I've programmed in a sweep
>> from 10Mhz to 5.4Ghz at -49dBm using my Aeroflex RF signal generator
>> and I'm seeing the displayed amplitude vary as it sweeps through the
>> range. But this only happens when I'm using a cheap, Chinese N-type to
>> SMA adaptor at the signal generator output. Would I be right to
>> suspect some imperfection in the manufacturing of the adaptor could
>> cause such an effect? I do have a VNA I could characterize the adaptor
>> with but it's a bit of an effort to do. It would seem like the SA is
>> showing the adaptor's shortcomings in the frequency domain. But is
>> that a feasible hypothesis?
>>
>> Your pal,
>>
>> CD.
> 
> Aren't we getting a teensy bit lazy?
> 
> Jeroen Belleman

I have seen transmission (S21) losses of around 1dB at about 1.2GHz
just from failing to tighten an N connector sufficiently.
We do need to know the magnitude and frequency of the problem in
order to give helpful comments!
John