Re: RF Metrology

On Sun, 6 Oct 2024 17:46:02 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 29-09-2024 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?
 

Measurement of good vs bad cables:
>
https://www.youtube.com/watch?v=AqFDxQjJAdA&t=50s
>

Very precient of you, Klaus. I was just about to ask about others'
experiences of cheap Chinese RF connectors. I'm reluctant to hook them
up to my expensive Western analyzers in case they get damaged by poor
fit or some such issue. I have to say, though, that the only issues
I've heard about in this regard are damage to the Chinese connectors'
center pins (being pushed in) during insertion. I could live with
that, so long as my expensive test equipment remains unharmed.