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From: john larkin <JL@gct.com>
Newsgroups: sci.electronics.design
Subject: Re: RF Metrology
Date: Sun, 29 Sep 2024 14:06:23 -0700
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On Sun, 29 Sep 2024 20:47:39 +0100, Cursitor Doom <cd@notformail.com>
wrote:

>On Sun, 29 Sep 2024 19:57:34 +0100, John R Walliker
><jrwalliker@gmail.com> wrote:
>
>>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
>
>Not really. If you just think of it as a slight impedance mismatch in
>the cable between the SA and the signal generator. However, this model
>has the facility to be able to save files of the screen display
>(although I very much doubt it'll save a real-time video of the
>sweep).
>And John - it's the 'Ultra' version. I already had the base model and
>this is a worthwhile upgrade. 

Ultra what? Got a link?



>Jeroen - it's more a problem of available time!