Active Probe, Schematic Included
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- เผยแพร่เมื่อ 24 มิ.ย. 2024
- This is a 1:1 RF active probe that I designed for a specific use. If your working on any RF related circuits that require very light coupling, this may benefit you.
- วิทยาศาสตร์และเทคโนโลยี
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In 91 yrs of my life; I have never seen another like Paul. He is truly a "Cut-Above". Thanks Kind Sir for sharing your talents with us.
Thanks for your kind comment Pat!
Great man
I hope this guy works for a respectable testgear company and he is paid a lot for his work, cause he has a huge bag of knowledge!
He's worth whatever he's paid.
Amazing Paul, your explanations are crystal clear, your English accent and the talking speed are so comfortable. Again Paul, thank you very much for your videos, I hope to support you in the near future.
Many thanks!
I just love your lab, Mr. Carlson. :)
Thanks for sharing.
Always professional and a joy to watch.
Thanks for sharing Paul, your lab makes me happy! This probe is awesome.
+saturn5tony
Thanks Tony! Glad you enjoyed the video.
Wow, such a simple design for such a great tool. Thanks for all the insight.
+Justin L.
Your welcome Justin!
Great design, Mr Carlson! It takes a lot of knowledge and experience to do this.
Thanks for all of your efforts. I think a lot of us out here are very grateful.
+Thema inproblem
Your welcome!
Another excellent and interesting video! Thank you Mr. Carlson
Another excellent video, always impressed by your extremely tidy printed circuits.
+g0fvt
Thanks! That toner transfer method works well.
Great video. I really liked the impromptu tour of the working lab.
+Michael Lloyd
Thanks Michael!
I very much enjoy your videos and you are a wealth of information! Thank you.
thats so neat how gifted you are with electronics.
great video....i learn a lot of stuff every time i see your videos
Dear Paul, you seem to lead a charmed life full of horse shoes. " I just happened to have an input probe with an adjustable cap floating around in my stuff." The packrat in me is envious of your awesome collection of gear. Well done my good man, well done. My grandfather, who lived thru the depression, impressed upon me the value of repair and to never, never, throw away something you might someday use.
Thanks for your kind comment Gary!
Nicely done Paul. You are a superb teacher and I've leaned a lot from you. Greetings from Arizona.
+Thema inproblem
Thanks for the kind words!
Hi Pat. I realize you have a very significant subscriber base so no reply is just fine. I just have to say that your incredible knowledge is such a pleasure to see. Above and beyond that, your kind demeanor is a tribute to you and your life choices. Just found your channel and now I’m going to have to visit everyday for as long as it takes to make it through all your presentations. Take care and thank you for being such a fine gentleman!! Oh and Patreon is a no brainer for your channel! I’ll support your channel through that app . Andy
This is exactly what I need right now, and Mr Carlson delivers!
(Yes, I realize it's years later, TH-cam algorithm works in mysterious ways...)
Nice little probe. But your lab, Mr. Carlson... that is a slice of heaven. I could see myself getting lost there for days and admiring those beautiful test equipment. Magnificent! :) Thanks for your time!
I'm glad you're enjoying the video's! Thanks for your kind comment.
I just found your videos and I LOVE them....please keep building
Thanks! I will as time permits.
Just curious, did you major in EE and are you an EE yourself or is this just a hobby for you. Im a HS student rn but I really want to get into either electronics or coding
+MrCarlson, thank you so much for this video and for your channel. The content is excellent, presentation is impeccable, and pace/depth/completeness is unlike anything on TH-cam. Kudos and thank you!
Thanks for your kind words Cody!
Excellent video. "behind the scenes" looks so familiar :) Thank you for sharing knowledge. This is priceless.
+Robert Gogol
Your welcome Robert!
great video of the skilled work you do But me being very knew to all this rf radio related stuff its still blowing my brain cells to bits ....keep up your brilliant channel ...
+retro80s
Thanks!
As usual, very interesting , congratulations good video!
Great video. Love the behind the scenes. Thanks.
+PelDaddy
Glad you enjoyed the video!
Enjoyed the extra video at the end, I think most of our shops get messy when working on a project. Glad to know your human. 😀
+Chuck Legg
LOL, thanks Chuck!
I too have a 3585B, my favorite pies of test equipment, and it is Heaven for working on HF rigs and designs, as well as audio and high frequency vibration analysis.
Thank you very much Paul for sharing this nice video with us.
+esmaeil nam
Glad to share Esmaeil :^)
Interesting project.. Big thumbs up... Can wait for next videos..
+Jurva-Markus Vehasmaa
Thanks Jurva-Markus!
I feel MUCH better about how cluttered my shop gets when building a project. Although, your "messy" lab looks better than my lab when organized LOL. Thank you!
Glad you enjoyed!
Very interesting presentation. Thanks for sharing.
Thanks Paul. It must be nice to have such a great lab!
+Robert Calk Jr.
Thanks Robert!
That's wonderful design....... Keep going.... :)
Wonderful, thanks for the clear explanation!
You're very welcome!
i refrain from skipping ads on your channel - although i do kill the annoying audio.
my way of expressing respect and gratitude to you.
Thanks!
A lot to take from this great video. Would be nice if you could start a series like fundamental Wednesday or some day on RF stuff, loads to learn from. Specially for those who are more into embedded, power or controls world.
Great work!
+Syed Mazahir Rizvi
Thanks for your input Syed!
Really good info. Thanks, Paul!
+Mike Lentsch
Your welcome Mike!
This looks like a fun project and I'd be interested in building one of these. I believe Paul mentioned in one of his recent Patreon videos he may have an updated version of this project in mind. I'll be very interested to see what he might have come up with.
Great vid. Thanks for showing round the lab.....looks like a scene from an old Vincent Price movie.
+notionSunday
LOL, Thanks!
I loved trying to follow along to this one!
+Shaunak De
Glad you enjoyed!
One thing to note here is that the output impedance of this circuit is not 50 Ohms. It is in fact very small, even smaller than the re of the bipolar because of the shunt feedback from the Opamp. You need a series resistor at the emitter of the bipolar to the output. It would reduce the dynamic range, but provide improved frequency response.
There are actually quite a few reasons I built the probe in this manor. Normally, I would add that 49.9 Ohm resistor between the emitter and the cable center conductor. I could write a book at this point, right down to the differences in the op-amps (same part #, different results) One of the major reasons was that dynamic range reduction. This probe originally had a specific intention that can be viewed in the CRF-320 video. The probe was to be flat, and unity gain (or close too) within a small spectrum, adding that resistor complicated matters, found through experimentation. Thanks for stopping by, you have an interesting channel as well!
Thanks! I assumed that you were already aware of the output impedance. The comment was meant for someone who may be skipping through the video and would mistakenly think that the resistors at the emitter would provide 50-Ohm termination. Great work, your patience in your restoration videos is admirable!
Mr Carlson's Lab first of all: great video! I undestand both of your explanations regarding the output impedance. If you make a sweep with a 50 Ohm generator into the output of the circuit with the input shorted (50 Ohm would also work ;-) ) you may get surprised. Its all about the flatness of the whole system. Best regards and thanks for your great work!
Oh, okay, now I see what is going on. Had to rush out for a while and missed the last part. Caught up now. Thanks.
Great one! Thanks!
Paul, Wow! that was pretty amazing. I love the way you explain every step along the way. And the circuit you built is very clever. Also like the way you utilize every piece of test gear. I am also looking for another spectrum analyzer. Really in the need for a more modern one with tracking generator. The old IFR 1200 just does not cut it since there is not tracking gen. he option is about a grand but still no onscreen display. I want to be able to do some V/UHF duplexer tuning. Plus want to homebrew a 4 cavity VHF duplexer :)Great job as always my friend.
+The Radio Shop
Thanks Buddy! That IFR 1200 is still a real neat piece of equipment. Take care!
Excellent job Paul! really all thumps up as I exactly know what it means to do a build like this. wish I had a bit more time....
Take care and talk to you soon 73
+TRXBench
Thanks Peter!
Excellent video, as usual, thank you Mr. Carlson.
You're Welcome Gort!
I have got the impression that you love measurement equipment, and dont need to think about room temperature in wintertime....
I would enjoy knowing how you distribute power to all your test gear... especially the grounding system... as well as protection for over voltage between and during work sessions. Consider a video on that subject! Thank you!
I love all your videos, Paul! You've taught me a lot! This week I plan to build a couple of your spectrum analyser protection devices to use with my HP3585A to align my SP-600 IFs. By the way, has anyone ever told you that you look like Vinzenz Kiefer?!
THANKS Paul, another excellent video!
+old64goat
Your welcome!
Very good work thank you for sharing
+DENNIS N
Your welcome Dennis!
Im sure you had pleanty of offers,your a smart person wish i had your brains.
Fantastic project and again an excellent talk! Thanks for sharing! Just one question: why not have the runner of the 1k connected to the minus input of the opamp and the high end towards the output?
My wife collects closets full of clothes but this gear is really worth it!
Great video - THX!
Another think to note is about the 1K potentiometer. It do not chage the gain, it just modifie the current in the output transistor. IF instead of that you replace it by, for instance two 1K resistors with the - pin in between, or better you put directly the minus pin at the juction of two output 100 ohms resistors, your gain will be x2. In such a way you could add a 47 ohms resistor at the output. Then loaded by 50 ohms, the gain will be equal to 1 and maybe the small variable capacitor you put add the end will deseapper because the emmiter of the output transistor will be really loaded by 50 ohms and not byt the capacitance of the cable.
Paul, fantastic project as always. Would love to get a SA one day (or repair one).
+rupert handford
Thanks Rupert!
I like the sound of the probe you are talking about at 9:00. This was a great video a learned a lot as always. Thank you so much for all the hard work and effort you put into these videos. You make learning a pleasure.
Nice lab!
+Daniel Rogers
Thanks Daniel!
I can't believe you have only 20k subscribers. Information on your channel is priceless. Dave from eevblog could learn from you and still his channel is larger. It is not fare.
Paul is much more hands on, analog and RF oriented than Dave. Dave has teardowns and explains newer tech from a very armchair and consumer perspective but Paul is more oriented to people who actually do build, are hams, are advanced experimenters etc.
+Martynas Mirauskas Yeah, and Paul doesn't attack the personal beliefs of people. Which wouldn't be so bad if someone did, as long as they provide some basis or facts for their accusations. But as far as I'm concerned, to call someone stupid for their beliefs and not provide any facts to back it up, is the hallmark of lunacy.
+Martynas Mirauskas big difference in output. Mr Carlson is far more detailed, he's like +TheSignalPathBlog Dave is just entertainment.
+cny02253 I don't consider myself as an 'advanced tinkerer', but I just love the amount of detail in Paul's in-depth videos. Alan (w2aew) also provides great explanations, I learned heck of a lot from his vids; at the end - Dave is like a pop music, has a larger audience, but not as pleasant as other genres; but great for entertainment sake.
+dr. Chernobyl Dave is knowledgable, but he is spoiled by all the freebies and money he gets for reviewing products.
Great video! What electronic design and layout tools do you use?
Isn't it amazing how everyone knows where everything is in their labs but search the kitchen for a mug to make coffee.. hihi P.S I am learning so much from you videos, thank you. vk2wgw
+Glenn Wilson
Glad your enjoying Glenn!
Paul, fantastic, and just what I was working on RF Probe, But wasn't keeping those Tol., Sorta Got a Chuckle, at the ending sweep of camera wondering if the little Young lady came in the Door and seen it , What her words would be? lol lol Yea just a little project what it can do to your Bench area lol Yes enjoyed it and saved this one for future Special RF Probe I may need . Yes keep them coming , man the hits on you unbelievable. 73's .
+Ranger Dale
Thanks for the kind comment! Glad you enjoyed Dale.
The active probe would be a nice and useful item to have in my collection of test gear. I checked eBay to get an idea on the price of an HP 3585B. I found one but the seller wanted more than the price of a new Rigol DSA815-TG. :P One of these days I would like to buy a spectrum analyzer. Spectrum analyzers are rather expensive beasts so I'm more likely to have a go at making a basic one from scratch. I don't need one that covers more than about 0 to 500MHz.
Great job, congratulations. I would like to see an active probe for a wider band.
Amazing stuff! Love your lab.
+Justin L.
Thanks Justin!
Actually, for headphone users the camera's microphone seems far better because is not picking up all of the breath-in noises :) anyway greath channel, you're a fantastic teacher.
+franzgol
Thanks for your input!
Very good video..
+Daniel Stimpson
Thanks Daniel!
Take a drink every time he says "flat". ;)
I did
I'm curious to know how the 1M resistor on the input of the op amp is determined. Thanks.
Very well presented Paul. I liked the comparisons you used in the circuit design explanation for us tube guys. Every little bit helps thank you.
+hankus253
Thanks Hank!
Your video series should be a show on the Discovery channel. Seriously - many people learn from you (myself included). Many more can too :)
+Ron C
Thanks for the kind comment Ron!
Is there any way of getting a copy of the drawn PCB design, as it is so critical for a successful (first time) outcome?
regards Bob_R
great video thanks
Your welcome!
What would you recommend as a replacement for the fet? What charasteristics should I be looking at when picking a replacement for this spesific fet? Thanks you, awesome clip!
Hi, great video. I am wondering, why the need for the source-follower FET on the input stage? Couldn't you AC couple the probe tip directly to the LT1812 input? Seems like this would avoid some potential bandwidth loss and gain uncertainty in going through the FET. Why is the FET stage needed?
Dear Paul, I am sorry to say whether for good or bad, we took a poll and have decided to clone you. Keep up the great work for the followers.
Bill
+Bill A
LOL! Hey, id get twice as much done.... That would be great! Thanks Bill! :^)
Thank you for the excellent video Mr Carlson. I see that your probe will have very light loading on the circuit under test. Did you ever quantify the input impedance of your probe? X megohms and Y picofarads? Thank you
Thank you!....., You (yet again), just saved me a pile of trouble having to do this myself from scratch!....... I just haft to figure out where to etch your name?, on the board of my build of your probe lol.
+ytrewq6789
Your welcome! LOL, my name is to big for the board size :^)
The 3SK74 are done now, like so many parts.
Thank you!
+Rob H
Your welcome Rob!
Good info.
+wade hicks
Thanks Wade!
That flat response for the If's is super. What kind of microscope do you use ? Looks ideal for work on small circuitry.Very well kitted out lab an when ya see a mess ya know there's good R&D goin on.
+Tom OConnor
Thanks Tom! The trinocular microscope came from a university, unfortunately the name is no where to be seen.
Hi what software program do you use for your boards?. Thanks.
Great video and a very good looking soldering!
+senohpi
Thanks!
Nice vid, thanks .
Question tho , what is that huge grey enclosure in the corner ? looks like a 10kw am tx ;)
+Chipz0r
Its an old GATES transmitter :^)
Awesome.
+Raymond Earle
Thanks Raymond!
awesome!!!
+Damian Molina
Thanks Damian!
what software do you use to design your projects
Wow! I'd give you Thumbs Up, as usual, just for showing all the Equipment you have! To the rf probe: Did you experiment with the number of connections you placed stitching the two sides pf the PCB together? Common practice for normal, non-rf, circuitry would place many stitching vias along those edges. Thoughts on the possible effects of more side-side connections?
Hi. If this probe was to go higher than it's intention (UHF+) Then the "stitching" would be needed. This is only intended for the HF region.
Cant beat Mr Carlson's explanations. Thanks!
+Ignacio Simón
Thanks Ignacio!
hi Mr Carlson!
is it possible to have a copy 1:1 of the printed circuit board?
THANKS!
and...Happy New Year!
i2NDT Claudio
Hi Mr Carlson, good video. You forgot to mention I think that the inductor blocks RF from leaking out your DC path. I am not familiar with the two gate FET. I understand that you can hook it up; to build some advanced gain circuit, but why did you pull the gate to the drain instead of the gates together?
+Daniel Johnson
Richard is correct, the second gate is commonly used for gain control or mixing. Since I'm using this as a source follower, I just tie the 2nd gate to the drain.
Great project Paul. Looks like it turned out very nicely. Hmmm, a project in the 40MHz range. You have my curiosity peaked. :)
Would love to get the PCB layout file. Any chance you could forward it?
Mike
+MikesRadioRepair
Hi Mike, When I find some spare time, I will set up a file sharing (something or other) :^) The video will be coming soon regarding the restoration. Thanks for your comment!
I did enjoy it, though I suspect not as much as you did! :)
+Pablo Padilla
Thanks Pablo!
Hi there Your probe is amazing . I do alot of audio work for a hobby . Do you have a kit of this probe mainly for the circuit board as this would be great to build . Thanks John
John Weegenaar, Paul has been asked if he has kits or boards of any of his projects and his answer is usually a 'no' with some sort of suggestion that the maker should make boards themself... in other words, "NO."
Very good Paul! Wondering if you have ever thought about getting a file sharing account of some sort to post PDF's (like Alan W2AEW does) or drawings, schematics, PCB art, etc.?
Anyway, instead of using a SG, one could hook this up to a sweep generator and look at the output in X-Y mode on an oscilloscope, sorta like we can with filters? (Keeping our impedance ducks in a row of course.)
+cny02253
Thanks! I'm thinking of setting something up (file sharing) But it's all about time. Using a sweep generator and a scope would be just fine, as long as you know your 3DB down point, and your test set up is flat.
The LT1812 is a 100MHz unity gain stable low output impedance opamp. Only works because the gain is so low.
It already has high input impedance so I do not understand what the FET adds to the design. All it does is the same as a capacitor would.
More more more!
+Donald Holben
Glad you enjoyed Donald!
I am all ways inpressed by your printed circuits board!! Question on the schematic on the op amp on the + side is that side going to erath !! thank you terry
+terry uren
Hi Terry. The plus symbol you see on the op-amp is the non inverting input. The supply connections are not shown.