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From: Jan Panteltje <alien@comet.invalid>
Newsgroups: sci.electronics.design
Subject: Re: RF Metrology
Date: Mon, 30 Sep 2024 06:00:14 GMT
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On a sunny day (Sun, 29 Sep 2024 22:52:24 +0100) it happened Cursitor Doom
<cd@notformail.com> wrote in <1vijfjd186gmgjn6dbf93v4ehv3v1ts7pt@4ax.com>:

>On Sun, 29 Sep 2024 14:06:23 -0700, john larkin <JL@gct.com> wrote:
>
>>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?

Mr doom, just cut theURL after the item number, like this:
https://www.ebay.com/itm/175723143799


It is a nice box, but I stay with my RTL_SDR sticks, low freqwuency converter I have.
For that 160 dollies I have 160 / 31 = 5 of these: 
 https://www.ebay.com/itm/201773887159?

I have 2 of these, but older models, running 24/7 on raspberries:
  https://www.ebay.com/itm/284834935943
   mine are 1 ppm, this seller claims .5 ppm

And wrote my own spectrum analyzer for it:
latest, now lso runs on raspberry:
 https://panteltje.nl/pub/xpsa-0.7.gif

Older version can be downloaded:
 https://panteltje.nl/panteltje/xpsa/index.html

website needs updating..