For those of us still using QA400, some measures to facilitate building some proper x10 and x100 measurements probes…out of old scope probes.
This is part 1 , in this video , I show how to measure and make sure you get the proper results.
In part two I’ll show, how to build them and the results on screen with 103,5 db THD+N with the probe and no signal versus the 105,1 THD+N with no probe attached…and verus first try adding a simple resistor to the end of a probe results in part 2 
Here is the second video
The loop back mode test showed better results of 104,8 db closer to the analyser actual direct loop back results…
Why not just draw a schematic with values and take some close-up high quality photographs of the steps involved? Post an instruction series of pictures and text here. You’ve managed to stretch out how to modify a 'scope probe to two youtube videos and 37 minutes of people’s lives.
I’d agree,
In general a video is good for story telling, not so good for a recipe or instructions, where direct access to the content is desired, not linear at a fixed pace.
So when I want to find out how to do something I avoid videos if possible as I can generally get the information I want from a text/image webpage in seconds.
Imagine if datasheets were videos… 
Hello John,
Thank you for your critics , which will help refine my next videos 
.
As you know the QA400 spectrum analyser doesn’t have a 50 ohms input impedance.
My first issue was figuring it’s real input impedance at the frequency of interest.
I made the video to detail, how I went to determine it’s input impedance.
(Which turned out to be around 9 K ohm at 1khz , so that someone else could judge if my methodology was ok for him .)
They are detailed articles on internet on the same voltage divider principle , I used , I just did the math in the exact same way, using those values just like in a 50 ohm case.
The interesting part for me was that I found, by « measure », that for a x10 (-20db) probe I needed to add about 82 k ohm always at 1 KHz, x100 and for (-40db) to be 901k, in order to make passive probes for the QA400…
Lastly the interesting part was in the noise reduction afforded by proper custom probe building, this is why I linked to my video which details not only the above but let someone else form is own judgment based on my lab (real life) measured results .
As you know in restoring old equipment, « real world » means very often, much more « time » to get to reproductible results…
I will next time, give a quick schematic of where I go, directly at the beginning of the next such video.. that’s a great point thank you !
Eric
Hello Mark,
Some of what I replied to John applies here, specifically :
« The most interesting part was in the noise reduction afforded by proper custom probe building, this is why I linked to the video which details not only the above but let someone else form is own judgment based on my lab measured results . »
What is not (always) in a spec sheet are what your decisions will afford you for results, this is more like an application note…in video. Some like it , some don’t.
I film, so someone else can judge by himself…
I am preparing a video on capacitors and they are tons of videos on the subject, but when it’s well made you can judge by yourself, redo the math and check…
Sometimes with errors, even when the methodology is sound….(just evidently a double check which was forgotten by the author! ….)
something I will introduce in my video, is too always try cross check your results by two methods when possible, just sound engineering…
Eric