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From: Cursitor Doom <cd999666@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: "Sampler??"
Date: Tue, 30 Jul 2024 15:11:35 -0000 (UTC)
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On Tue, 30 Jul 2024 14:51:10 GMT, Jan Panteltje wrote:

> On a sunny day (Tue, 30 Jul 2024 11:20:47 -0000 (UTC)) it happened
> Cursitor Doom <cd999666@notformail.com> wrote in
> <v8aiaf$10lqo$1@dont-email.me>:
> 
>>On Tue, 30 Jul 2024 10:36:51 GMT, Jan Panteltje wrote:
>>
>>> On a sunny day (Tue, 30 Jul 2024 08:58:35 -0000 (UTC)) it happened
>>> Cursitor Doom <cd999666@notformail.com> wrote in
>>> <v8a9vr$v9r2$1@dont-email.me>:
>>> 
>>>>On Tue, 30 Jul 2024 05:16:24 GMT, Jan Panteltje wrote:
>>>>
>>>>> On a sunny day (Mon, 29 Jul 2024 09:29:04 -0700) it happened john
>>>>> larkin <jlarkin_highland_tech> wrote in
>>>>> <72gfajl8ke966lsu54bpajpang9dvgmt63@4ax.com>:
>>>>> 
>>>>>>On Mon, 29 Jul 2024 05:19:06 GMT, Jan Panteltje
>>>>>><alien@comet.invalid> wrote:
>>>>>>
>>>>>>>On a sunny day (Sun, 28 Jul 2024 21:40:41 -0000 (UTC)) it happened
>>>>>>>Cursitor Doom <cd999666@notformail.com> wrote in
>>>>>>><v86dsp$3n74$1@dont-email.me>:
>>>>>>>
>>>>>>>
>>>>>>>>I still can't see where the 'sampling' bit comes into it.
>>>>>>>>AFAICT, there's are two signals into this thing and one signal
>>>>>>>>out. The signal from the LHS is passed through a very fast diode
>>>>>>>>which generates harmonics from that fundamental. The signal from
>>>>>>>>the RHS is unmodified and mixed with the desired harmonic to give
>>>>>>>>the necessary output signal which is then filtered to get rid of
>>>>>>>>the unwanted mixing products. If that's all correct, as I believe
>>>>>>>>it is,
>>>>>>>>where does any *sampling* come into it?
>>>>>>>
>>>>>>>A 'sampler' is fact a non-linear mixer.
>>>>>>
>>>>>>In the audio world, a "mixer" is a linear summer.
>>>>>>
>>>>>>In RF, a mixer is usually a multiplier, typically a 4-quadrant diode
>>>>>>thing or a Gilbert cell type circuit. Or a 2-quadrant thing like a
>>>>>>pentode. Or even a single diode. All do some flavor of multiplying.
>>>>>>
>>>>>>Some mixers inherently multiply a signal by a square wave, which
>>>>>>resembles other multiplier-type things once you lowpass filter the
>>>>>>output. That's a "synchronous detector", which we usually do in an
>>>>>>FPGA.
>>>>>>
>>>>>>A sampler is a signal multiplier too.
>>>>>>
>>>>>>These are all variations on the basic idea of multiplying two
>>>>>>signals.
>>>>> 
>>>>> A the word 'mixer' in RF is not the same as a multiplier,,
>>>>> Multipliers are like harmonic generating stages say you have a 1 MHz
>>>>> distorted sine wave and then a second stage tuned at 3 MHz,.. turned
>>>>> to third harmonic.
>>>>> 
>>>>> mamamatical speaking RF mixing is indeed multiplication.
>>>>> 
>>>>> Like Shakepierce once said:
>>>>>  "What's in a name..." CocaCola wihout coke
>>>>
>>>>I think in this context, HP is using the term "sampler" to mean
>>>>something which 'sniffs' a small amount of a signal for testing
>>>>purposes. Like a few turns of wire around a transmission line will
>>>>'sniff' a small sample of what's going on in the line.
>>>>Where I went wrong was rigidly thinking HP meant 'sampling' in the
>>>>manner a sampling oscilloscope works. That's what threw me. I tend to
>>>>interpret things very literally. :(
>>> 
>>> Would be nice to see a real circuit diagram of that thing.
>>> What is the model / type number?
>>> I am curious.
>>> So far I have been able to find circuits for most stuff I came across
>>> with google.
>>
>>It's the HP8566B - a very well known lab-grade analyser of the day which
>>many RF designers still use. There is a *ton* of service info on this
>>model online. However, I have not been able to see a *proper* schematic
>>for the "sampler" in the A11A5 board which is where the issue is.
> 
> OK, thank you, I will google a bit..
> I got the user manual now:
>  https://elektrotanya.com/
hp-8566b_spectrum_analyzer_100hz-2.5ghz_2-22ghz_usr-
programming_1984_sm.pdf/download.html#dl
> Then trouble shooting manual part 1
>  https://xdevs.com/doc/HP_Agilent_Keysight/
HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf
> Seems to have at least some circuits (just a quick look)
> and part 2
>  https://xdevs.com/doc/HP_Agilent_Keysight/HP%208566B,
%208568B%20Troubleshooting%20&%20Repair%20Vol.%202.pdf
> also has some circuits I will have a look at the hundreds of pages, will
> take some time.
> I presume you have these?
> Took 10 seconds to find with google

Yes, I have all of those and more. I think altogether there are 7 very 
large manuals for this analyser. However, I've not been able to find a 
single actual schematic which gives component level detail of what they 
call the "sampler" - and that's unusual, as they've given a great deal of 
attention to providing very full service details in all other respects.

> 
> OTOH my 1.4 GHz RTL_SDR sticks cost 30 dollies($$) or so,
>  https://www.ebay.com/p/22032165355?iid=335019807057
> I can use a 5 dollies($$) satellite LNB as down mixer to go from 10 to
> 12 GHz to say 1 GHz (modified a LNB for xtal locked to Rubidium
> reference)
> Also build a small downmixer so it can see 2.4 GHz too Plenty free
> spectral display programs online for it,
> I wrote my own:
>  https://panteltje.nl/panteltje/xpsa/index.html
> it also has an 'harmonic' button to look for the next harmonic when you
> select a carrier...
> The latest version has some more stuff and runs on Raspberry Pi..
> The RTL_SDR sticks can even receive GPS signals...
>  https://panteltje.nl/pub/run_50_outside_2728000.gif uses this guys
>  software<;
>   http://michelebavaro.blogspot.nl/2012/04/spring-news-in-gnss-and-sdr-
domain.html

I wouldn't trust myself to build something like that. I'd get spurious 
signals and wouldn't know if they're truly spurious or not. Plus I like 
boat anchors and their imposing presence. I also like lots of knobs, 
because lots of knobs = no menu system and no menu means it's a lot easier 
to find what you want.

> For 100 Hz to 20 kHz a PC soundcard or maybe USB audio stick (as I use
> for my Raspberry)

I have bespoke audio generators. Boat anchors again.

> and there are several audio programs with spectrum display

I have an HP audio spectrum analyser - another monster - which I could 
power up if necessary for that purpose. It would probably go bang, though. 
Hasn't been switched on for years, you see.
> 
> There are so many possibilities...