Build this Spectrum Analyzer Protection Circuit
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- เผยแพร่เมื่อ 5 ก.ค. 2015
- The little white boxes reveal themselves. Schematic included. These are intended for lower frequency use, and are great protection while sweeping communication receiver IF sections. They are also designed to lightly couple you to your "DUT"
- วิทยาศาสตร์และเทคโนโลยี
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Outstanding stuff. Love the fact that you're an obvious expert, fastidious maker, precise technician and have an artist's eye for color, layout, aesthetics and efficient form. Add to that your vids are clear and you take the time to make sure the subject is well lit and focused and the audio is always right up front. AND you have great diction!! I'm an old retired two-way radio tech and now I just fool around with amateur radio for fun (for 50 years) but I'm always delighted to learn something new, or see something visually confirmed that I always knew. Thanks so much, Mr. C. and many 73 JEFF K4UIE
If you ever shot a analyser front end you know how important this little box is! Great video Paul!
TRXBench Thanks Peter!
Once again, thank you for your time and sharing your expert knowledge for the benefit of us viewers. Much appreciated.
Peter Byrd Thanks for the nice comment Peter! Glad to share.
Once again, another great instructional video. The limitation for many is crafting superior printed circuit boards that even approach the apparent quality of yours. Here again is a marketable product for those of us who may prefer to buy than build. Thanks again!
Fred
Are there any products like this on the market?
Genius is simplicity. Spot on.
I'm new to electronics. Thank you for sharing your vast knowledge with us all on TH-cam. 100 year's from now, people will be watching this for sure!
timothy svec Thanks for the nice comment Timothy!
UNLESS Paul expresses ANY hint at being a conservative, a patriot -- OR -- discussing anything politically incorrect.
(as deemed so by the green-hair SJW ugly college chicks or their pussy-whipped men running Silicon Valley and the tech giant ops) Steven Crowder was the latest in creators to be canceled and vaporized. They started with Alex Jones, did up the Prezzz and moved on to anyone questioning the CCP-Virus details or election fraud matter.
Thanks btw == I just built a pair of these for my o-scope and my spec-analyzer. GREAT CHANNEL!!
Thank you for such a great quality videos! : )
Another excellent video and thanks again for sharing your design. I work with spectrum analyzers at work, but don't own one. Hopefully one day I can add one to my collection and incorporate this circuit. Best, Don
RestoreOldRadios Glad you enjoyed Don!
More enjoyable learning, many thanks for sharing your lab tools, appreciated.
Steve Pocock Thanks Steve!
You're one of the best video blogger ever!!! Fantastic :)
Hi'gak Iya Thanks for the kind words!
Thanks as well for the nice video contents.
By the way,I have a humble request if you don't mind. Can you make a tutorial in making your own PCB design from start to finished? Since I've subscribed to your channel and watched all your videos,I've notice that you are making your own pcb design and they are very neat. Maybe you can give us some design considerations and tips in designing a pcb :).
Hi'gak Iya You bet! I will do a video on them soon. Thanks for the comment!
Great project Mr Carlson. I will be using 1n914's as I have tons of them. I thank you, and my 8566B thank you.
Todd Anonymous Glad you enjoyed Todd. Thanks for your comment!
Thanks for the lightning fast production in response to our queries! Well done! 73 - Dino KL0S
Dino Papas No Problem Dino! Glad you enjoyed.
Thank you for the great video. Very well explained.
All the best.
Bobby
***** Thanks Bobby :^)
I always enjoy your videos. Thanks.
Jessie Daniels Thanks Jessie!
Yes I believe another name for it is a "DC block". I used to use one on the input of the spectrum analyzer when I was probing around an RF circuit sniffing for frequencies I was looking to tune with voltage controlled oscillators. The DC block provided protection for the spectrum analyzer in case you inadvertently hit a voltage test point which could blow out the face plate of the spectrum analyzer.
Very nice, you have given me some ideas about how to protect some of my own equipment.
+John Cunningham
Great! Thanks John, glad your enjoying the video's!
I did enjoy the video, nice design .
Amen on the being careful what you put into your spectrum-analyzer. I have to REALLY have a compelling reason to hook mine up directly to any circuit. I have an HP-8557A which has a 30VDC but ONLY 2.2VACRMS input capability! I've had to repair this unit and it is not for the faint-of-heart (just look up a manual for one of these and you'll see!) as it is full of specialized and one-of-a-kind parts that are nearly impossible to find. In the past, I used a very small-value capacitor and a 120dB step attenuator, then "work my way up" to getting a usable/displayable signal.
So, anyway great video on both the value of "light" coupling and protection of the SA's front end. Also, nice construction project and showing the value of placing a "service-loop" on the BNC center-pin to prevent breakage/damage to the PCB.
Finally, another project idea might be to make a high-gain broadband RF amplifier with a detector that would allow your viewers (without spectrum analyzers/scopes) to be able to both very lightly-couple and display the amplitude on a analog multi-meter for alignment purposes...
+SpinStar1956
Thanks for your comments!
Very helpful, thank you.
Another great video Paul. Very useful flat, wide frequency ranged coupler.
I've never built a PCB using the etching method and laid out on the computer. It would be great if you showed us how you do it.
I know, I said to myself; "What, that's it?" LOL I am so use to your long drawn out sagas. I "LOVE" long drag out sagas!
I see approx 3,350 watches on your DeForest Crosley Empress video as of this moment. Congratulations are in order here!
Great work my friend,
Tom
***** Thanks Tom! I try to speak to all levels of experience at once, so I'm playing with a fine balance all the time. Some say "long winded" I prefer "Considerate to all." The Deforest Receiver was the labor of love. That dial sure is nice. The owner is going to send some pictures of it when it's all together. Maybe I will edit a quick shot of it in a future video. Thanks for stopping by!
I built one snd it works quite well. I used 10 1N4004 diodes insted of 12. Thats all I had. Thanks
I reproduced this circuit using Circuit Maker and etching it to a single-sided copper PCB - using 1206 caps. I only added a 50 ohm resistor to ground before the 10nf cap at the output. I made a pair of them and so far, so good. I’ll try them on the IF alignment of a SX-99.
Hi James. The input to your analyzer should be 1M Ohm for proper results. Adding the 50 Ohm resistor to the TG side is OK, and suggested.
@@MrCarlsonsLab Paul, my spec-an is Siglent SSA-3032X - it has 50 ohm input. So, understanding that the 50 ohm resistor basically sets up a voltage divider, should I turn up the TG signal ? What is your suggested mod to make the 50 ohm match to the input of the spec-an ?
@@MrCarlsonsLab Well, no response. I’m going to try a simple in-line 50 ohm terminator on the SA input and see how that goes.
@@jameshall5835 I have the same SA, how did this work for you?
Thanks for the great video. Very informative, as always. My HP 8590B only has a 50Ω input. This may seem like a dumb question, but…would an inductive coupling scheme be a better way to provide attenuation, isolation and impedance matching for 50Ω input S.A.s, or is it best to stick with capacitive coupling?
Very interesting video. Thank you. I would welcome your thoughts about building an isolator for the audio jack for smartphones that would allow various apps such as signal generators and spectrum analysers to be used in a safe manner whereby the smartphone is electrically isolated from the circuit under test. Ideally this should be both way (output and input).
This guy is the BEST in the U.S.
MrMac5150 Wow, I hope I can hold up to that :^) Thanks!
MrMac5150 He is the best in the US but he in Canada, so does that make him the best in North America?
Mark Fritz
Well after all the tech youtube videos I have watched, I would like to change that statement to: THE BEST IN THE WORLD.
Excellent video congratulations, as all your videos are! I would like to see a version to be able to make these measurements with my 50homs spectrum analyzer :(
Nice and clean projecto
Tnx for share another piece of art
73
Silvio Pinheiro Thanks!
HP used to sell a DC block to connect to the front end of your spectrum Analyzer, Also they had reverse power protection for some of their Signal Generators. The DC block was nothing more than a cap. Try changing your volts/div to a smaller value and see what your curve looks like? Great video keep them comming.
Gregory West Thanks for the comment Greg!
Nice little circuit :-)
smbrob Thanks!
Very nice video. I am adding my request for a impedance matching for 50 Ohm input on my spectrum analyzer. I am wondering if you really need to worry about impedance matching as long as you get your flat line when using the tracking generator.
Great video and advice, as always. Thanks a lot!
tikabass No problem, thanks for stopping by the channel!
Mr Carlson's Lab I am becoming quite a regular viewer. It is always nice to see a talented technician at work. We do spend so much time alone in our line of work, that we sometimes end up lacking in inspiration. Your videos do help a lot in that department. Awesome!
tikabass Glad to be that inspiration!..... And glad your enjoying the video's! More to come :^)
Hi Paul, I am a novice in electronics, can you make a video on how to use a spectrum analyzer? I know there are videos on this on TH-cam but you have the gift of teaching and your level of detail is perfect. Thanks
Will do in the future Denis, thanks for your input!
Thanks, enjoyed the video. Would something like this also work with a Scope input to reduce capacitance, so you don't detune an IF stage? Would it still be useful if built with non-SMD components? Thanks again,
I'm interested in learning how you're calculating how many pF of coupling you have there through the capacitors.
I was wondering if you can do any videos on VNAs or using one do do an alignment? I'd like to see that. Great video!
Beautiful. You are a crack Mr ..!
What if you built a cheap spectrum analyzer using one of those RTL Dongles, it wont be accurate to a t. but your just snooping?
Thanks Paul for your videos. I am restoring a Hammarlund HQ-129-X. I do not have a spectrum analyzer but I do have a late model Tektronix 2 channel oscilloscope and I just bought a Siglent SDG1025 function/sweep
generator. The scope has a 1 Meg input impedance and the function generator can be selected for a 50 ohm or Hi Z output. The back of the function generator has a trigger output that I will feed to the oscilloscope trigger input. Can you tell me what type of protection circuit should be on the output of the function generator and what should be on the input of the oscilloscope to align the IF? I think I need to build a demodulator box to rectify my signal coming into the oscilloscope. Thanks, 73 Mark
This is a great thing and video! Do you know where you can get something like this on the market already assembled? My days of working with tiny parts are in the past, unfortunately. Thanks again for a great video.
Thanks Paul, great video! Exactly what I was looking for! Do you think there will be any issue using perf board and through hole components?
Thanks again. 73 Chris
Oh I haven’t seen this video yet ! Yay.
Hy, i have recently got a spectrum analyser, i will use it for old tube radio, but it hase a 50ohm impul, +10dbm and 0zero volts dc imput. Can u make a vid about how to use it and how to adapt this little boxes to protect my spectrum analyser?
I'm currently building my own small spectrum analyser, quite a basic one, however I'll add something like this to the front end, really good video as always Paul.
Paul M0BSW
Paul Collins Thanks Paul, glad you enjoyed!
Paul I wish you would make a video same but using a Rigol 850 Spectrum if you have one. Mine is a bit complex due to the menu and not great manual.
Thanks Paul. Maybe you could build one with a switch to change between 1M, 75 & 50 Ohms.
Robert Calk Jr. Definitely possible. If I do, I will do a quick video on it. Thanks for your comment!
Mr Carlson's Lab
Ok, cool. I need to invest in more SMD components, and start making my own PCB's.
What mod is required for a 50 ohm input I am in the process of getting one of the RF explorer spectrum analyzers and I want to protect the front end of that they also recommend using a 30db attenuator on the inputs even when stored to protect the input the front end front from large RF voltages which I already ordered 2 of them to protect the unit. I would build one or of the units you have shown in the video.
Great video, as always! It's also very timely for me since I just picked up a HP 3588A analyzer. One quick question: Is there a design consideration for putting 8 capacitors in the circuit? I won't be using surface mount components, so could I just use a single 12 pf high voltage (6 KV) ceramic cap as an equivalent? Thanks again, and keep up the good work ... so much to learn.
Design Research That would be absolutely fine. Thanks for the comment!
Its valid your suggestion , BUT if that capacitor go short out for a given reason, you are in trouble... several caps increase the reliability from my humble point of view .....
were can i find a grid square plastic or glass for an old scope, which has a 6inch viewer round
Thank you!
I stumbled upon your channel a few days back and guess what i watched nearly every video even thought i have little to nothing to do with RF or HAM radio (got a little RTL SDR decoding Pocsag,FSM(german) and sometimes i tune in for voice)
It's just stunning how you can ban (mesmerize?) me and i absolutely love the 20+ min videos you just take your time to explain everything in detail! Great!
Maybe the Dave Jones of radio technology?! Keep up the good work
SUBSCRIBED
MrKillerpics Thanks for the sub, and nice comment! Glad your enjoying the video's too!
Such a great idea to build this thing.. thanks mr Paul. I really enjoyed this video.. maybe some episode you can tell us too where we can buy those parts in a legit store or site that selling cheapes.. you know our money value here is very big difference than yours.. $1 is equivalent of php52 now..
Great video as usual. Paul I need the 50 ohm impedance I think for my old HP 141T. Can I use a 10x Scope probe and a 2w dc block like you find on Amazon to keep my Analyser safe??
If you are looking at something for the input, IE: high impedance to 50 Ohms, You may want to look at my Sony CRF 320 video for ideas. The safety would be in front of that.
always great when something you slap together works even better than expected?
Marko Ahonen You bet.
Fantastic work as always. I don't have a spectrum analyzer but I know that I've killed 2 MP3 players and 2 channels of my PC sound card with "high voltage". Sound card took about 200V spike from a Vacuum Tube Vu Meter project, the first MP3 player took a few KV from an ignition coil (I was trying to make a singing arc with a 555 timer) and the Philips MP3 player took about 7.5V reversed polarity and wen't kaput in the sense that the audio stage is dead. So after so much grief with them, I've considered making myself a protection box with some diodes, resistors and capacitors. Cheers :)
+ciprianwiner
LOL, you've been busy experimenting. Good stuff!
Another Great video Paul! Very kind of you to act so quickly to all of us who wanted to know what was inside the magic white box. I like so many others have a Rigol with a 50 ohm input I might try to build up the combination of the two circuits and see what happens. It would be an awesome bit of kit if we had one with select-able output impedance. That last sentence was so Dave Jones! Do you not get a bit concerned with the alligator clips penetrating the wire you are lightly coupling too? I was thinking it might be better to use a different type of clip more like a scope probe clip.
Mark Fritz Hi Mark, Thanks for the nice comments. At the time, my intention was just for my use. Had I known there would be so much interest in these, I would have made one for 50 and 75 Ohm inputs as well. That little circuit that Michael mentioned below looks like a winner though. I didn't look at the current consumption, maybe a couple of small batteries at the probe? I will have to look into that.
This simple little video has generated a great number of comments. This is certainly an interesting device. Now for my question. . . . Would it be possible to show how you make your circuit boards? They look professionally done. I dabbled in this about 15 years ago making attenuators at work. My boards worked fine, but the sure didn't look as good as yours do. Thanks again. Nice video!
Stephen Moore You bet! I will do a video on them soon. Thanks for the comment!
Mr Carlson's Lab I agree with Stephen. I would love to see how you make those PC boards. Mine never turn out like that. I would also like to know what kind of etching solution you prefer.
Thanks for another great video!
xraytonyb I don't agree with Stephen, and never have. Mind you that is not relevant to this channel, and as usual I enjoyed the really professional presentation and I'm sure I'm repeating myself but I am so impressed with the quality here. BBC TH-cam. (PS first bit was just stupid joke)
This is a handy little device! I don't have a spectrum analyzer at this time, but I'm using an old RCA WR-50B analog RF signal generator which has an output range of 85 kc to 40 mHz. What I've been doing is putting a capacitor in series with the leads from the signal generator for blocking DC. I have various rating caps that I keep on hand for different receivers since alignment procedures vary somewhat with make & model receivers. The clamping circuit is valuable. This may be worth me building one! With the BNC connector on the end of the box, it can pose an issue of shorting against other components & terminals in a chassis. What could be done is, install a hard-wired pigtail coax out of the box with a BNC connector at the end of the lead far enough away from the chassis. What's your take on that? Frank Ferraro--Audio Craft Electronics.
Frank Ferraro That would work as well. It's totally possible to eliminate the BNC at the box if needed. Thanks for your comment!
Hi John, looking at that very small and neatly made PCB I wondered what you use to solder all the "surface mount" components. Is it a conventional solder iron or what?
Stuart Grant Hi Stuart, Just a normal iron with a hooked tip. I will do a video on those boards in the near future. Thanks for your comment!
Paul
Sweet! Thank you a bunch!
Michael Lloyd No problem!
Mr Carlson's Lab Uh oh. I just caught the 1MΩ impedance part. Both of my spectrum analyzers (Agilent E4411B and Rigol DSA815 TG) have 50Ω I/O. I don't use either on my tube radios for fear of messing up and blowing the front end out. I have a couple of HAM rigs (Drake twins and Yaesu FT101) that still use tubes. When I finally get around to restoring those I'd like to be able to do the alignment with a spectrum analyzer.
What do you think of this little FET probe circuit? Other than requiring power it seems like a good solution (circuit is hyperlinked where it says Figure 1.)
www.edn.com/design/analog/4322333/High-impedance-FET-probe-extends-RF-spectrum-analyzer-s-usable-range
Michael Lloyd Looks great! I see they are using the same diodes at the input of the op-amp. Looks like a good solution for impedance conversion.
hi.....i really enjoy your videos..they are very informative
can you please make a video on spectrum analyzer..
we or at least me would be very grateful....thanks again
much obliged
mountainhawk Good topic for a future video. Thanks for the comment!
Why is one lead shorter than the other? Also, wouldn't the input capacitance be 12.5 pF in series with 0.01 uF, not 12.5 pF?
Hi Paul !I was wondering how you would change this circuit to work with a Spectrum analyzer with a 50 ohm input.My analyzer has an input MAX RATING of + 20 DBM and +/- 25volt. ---- Very good videos many thanks, John
+John Bellas
Hi John. If you read through the comments, a poster left a great link to a schematic for 50 Ohm application. Thanks for your comment!
Do you have the circuit board pattern file for this ? I would like to iron it on some copper and make a couple of these. I’m a member of your Patreon channel as well, but did not find it there. Thank you. Jamie WB4YDL
just a question what software for your video did you use if you dont mind me asking?
Any chance you could share the artwork for the spectrum analyzer protection interface so that I could make a couple of them for my new Rigol SA?
Craig W9CLA
Looking for this too. Did you ever get a reply ? De Jamie WB4YDL
Blow out the front end,--- which circuit board is the front end,---- I have a Hp 3580A.?
I would love to build this, any chance on a board sketch already made up?
Hi and thanks for your infos. What about that B+ line. What means B+? Is there a B-? I saw it in a diagram of a VHS machine and I didn't understand the notation.
I would like to buy the unpopulated circuit boards you made for them.
+darylynn621 my email is kb5zxm@gmail.com or kb5zxm@yahoo.com
Very good
How much you charge for one you say you have extra parts I could never make one as nice as yours thanks Paul
+DENNIS N Hi Dennis. When I get to making more boards for these, I will let you know.
thank you
this video.... it went so fast! had me laughing there :)
paul have you ever pushed its limits to see what frequency it drops out on'''' like trying it up to 30mhz and see if its still flat'''Nice video paul''''
Berni Kendrick...................Great video Mr Carlson but like others I would appreciate a video on how you make your PCB boards they look really professional certainly better than mine.
berni ken Hi Bernie. I will definitely do a video on the boards soon. Thanks for the comment!
That's great news
Hello ! I have seen the datasheet of the BAV99, and you say that limiter circuit limits 10Vpp, how do you know, if the current is low enough, that the diodes won't be "on" at 4,2V and not 5 and limiting to maximum of 8,4V and not 10V ? Maybe you never even get close to this values but...
CT1ELP Hi, there is a reason for the "about" word on the white board. Thanks for your comment!
Mr Carlson's Lab OK !
Thanks for the "confirmation" and keep up the good work, you have an amazing lab a nice videos (a bit long some).
LOL! I tend to be thorough :^)
Hello Paul
I have a big supply of Attenuators I used for catv installs not sure but maybe 75 ohm being cable tv could these be used in 50 ohm lines ,would that be a mismatch,,wanting to use them for spectrum analyzer use
+DENNIS N
Ya, unfortunately it will cause impedance matching issues.
I thought it may thankyou
Your Welcome Dennis.
What model is the HP spectrum analyzer?
After some research, I found that this will be a real problem on a 50 ohm input SA, basically everyone you find today.
Where can I find some of that high voltage silicone test lead cable?
Digikey stocks it. Unfortunately, I don't have a part number for you.
The closest match I've found is Pamona Electronics Test Lead 18AWG 10KV BLACK 50' on Digikey, part number 501-1281-ND. I'll bet this is good for replacing some of the point-to-point wires in old tube gear as well?
I have an question: if I have tube radio from 1962 do I have to change anything? or repair?
TM80 NotGoodWithNames Yes, the electrolytic's are well past their due date. All paper caps need to go as well.
that sounds like work... it's an stereo radio by aga it has telefunken tubes.
15:00 "This is not intended for high frequency use."
Tho those leads are probably the least of your problems in the high frequency domain, the row of capacitors are going to be a nice hairpin filter, and considering the vast amount of turns in the design it's going to have a lot of inductance. So yes, I see what you mean with not intended for high frequency use. Tho that box looks a little to small for a better high frequency design. Tho still a rather nice piece of equipment.
+Unknownety
It is a purpose driven device, designed really for low frequency IF alignment, coupled to a vacuum tube grid or last IF transformer. Thanks for your comment!
Super video! Would you be willing to make the PCB drawings available so I can try my hand at making them (using your other excellent video as a guide, of course!)
Charles Robideaux I may post the layout. It's in Traxmaker, so you would need the program to open it. Thanks for your comment!
Mr Carlson's Lab Hello, I have downloaded and installed Traxmaker. Also have a laminator that I am modifying for this usage. Tnx again for your very informative videos!
Hello again!I have assembled all the parts to build a few of these marvelous protective devices. Would you be so kind as to share the Traxmaker layout for the PCBs? Tnx in advance and keep up the GREAT Videos!!
Do you have any of the Spectrum Analyzer Protection Circuit boxes? Mr Carlson's Lab
Great video Paul - what am I going to do for the rest of the evening! I am currently scouting EBay for a Spectrum Analyser for IF alignments on tube radios (450KHz - 10.7MHz typically). Can you tell me what to look for bandwidth and resolution wise?
g4rko Barry Hi Barry. I have used many analyzers, and I have to say, this one is one of my favorites. This 3585B goes down to 3Hz resolution bandwidth. If you look at the A model, they sometimes have an error attributed to some needed isolation on a circuit board. These units are very fragile, and HEAVY! I would want to personally pick one of these up with my own vehicle.
Mr Carlson's Lab Thanks Paul, very helpful.
g4rko Barry Glad you enjoyed Barry!
Hi Paul
any ideas
my instek S/A gsp-810 only displays from center to right not all across, if I connect it to computer it displays fine in monitor using the remote software
+DENNIS N Hi Dennis, are you talking about the LCD or the CRT?
the crt the lcd is fine
Horizontal deflection issue? Do simple things first, like look for loose wires inside, cold solder joints, so on. If you display a signal on the screen, does the portion of the screen that's dark just abruptly cut the trace? Is the center of the screen (on the analyzer) accurate to whats displayed on your external monitor ( do things line up?)
Yes reset all connector wires use mag glass to look at all solder joints and the trace on the crt stops going right to left so only displays right side on crt
all caps look ok checked voltages that were marked on board all ok I have no service manual may never get one
thankyou again
+DENNIS N The problem is "most likely" in the deflection circuit somewhere, or in the circuit that drives it. Whether it's digital or analog, I don't know, as I have no schematics or familiarity with the circuit. The fact that it's displaying on your external monitor tells us that the digital portion seems to be working..... So something in between is the issue.
Fine job OM 73s de Sv2bnr
I have a question, have you ever used that conglomeration of parts and tested to see if it worked. I have my doubts that it would save the front end of anything. I worked for a cell phone company manufacture of test equipment and how we eliminated the possibility of overload the front end of the receiver part of the communications moniator was to sample the input power before it was connected. We used a diode as a peak detector driving an IC Compactor which operated a relay. If the power was sensed to be to high, it would NOT connect and would light a LED as an indicator of the power being to high.
a ''cell what'''' never heard of a cellphone'''''''''megaphone''''yes
I just finished building two of these boxes! I created the pcb layout in Driptrace. I etched the two boards in a bath of muriatic acid and hydrogen peroxide. I used liquid tin to cover the copper traces. I soldered all the surface mount components on, which is my first time soldering surface mount. The test on my HP 3588A spectrum analyzer looks really good, so I'm looking forward to trying these out on my Hammarlund HQ-120X when it comes time to do an alignment. I posted a photo of the boxes: www.flickr.com/photos/87241965@N00/33516373892/in/dateposted-public/
OMG... TWO of your capacitors were crooked. Please re-do the assignmnent and re-post.
LOL
Good job btw !
Could you please mention the specs of this Protection circuit in text
The schematic is at the 1:50 mark. I'd imagine that this is built to extreme overkill to not damage a $20,000 spectrum analyzer. Quite a lot of variation of this circuit would obtain similar results. Trial and testing is the only way to check this circuit for accuracy. A Nano VNA (vector network analyzer) is available online and does a great job with this. W2AEW has great videos on VNAs. I'm not sure if Paul has any, but that would be cool is he could do one.
dear mr carlson
What's the chances to purchase some of the PCB's?
RICH MC CLUNG Hi Rich. When I get some time, I may make some. If so, I will let you know.
Thanks for the reply. I'll be waiting to hear from you. I really like your videos. Some swell information. I have several of the same pieces of gear in the cue for retirement projects.
@@richmcclung282 @mr carlson's lab -- Still Waiting... any news? This channel is my go-to for everything electronics. I purchased a Rigol dsa815tg spec-analyzer and would like to build a few of these to protect it.
Thanks !
@@PowderMill NADA>>>>>
Sometimes the most handy tools are the ones we make.
bobkins270 I agree. This one also stops bad nightmares :^)
There is little capacitance at each of diodes.
after the bnc is it a fuse ?
A small piece of flexible wire to allow for slight movement of the center pin of the receptacle inside the female bnc. They can loosen up as they are not a pressed fit and when you remove the cable and install it the clearance inside the dielectric plastic would allow that mechanical strain on the circuit board and loosen up the solder joint.
I built the 1M unit for my tracking generator .,but my S. A. is 50 ohm input .How about showing the 50 ohm design.
You sure know your stuff. Thanks PWS.
Add a 50 ohm resistor to ground at the box.
man you really like to do things the professional way lol.
scaleop4 Is there any other way? :^)
man i cant blame you hahah
With all those caps in series and the shunt caps across the diodes you have limited the lower frequency response of the SA. I have used a SA for over 40 years and have never blown the front end of and SA. This circuit is NOT fast enough to protect the input of the SA. The only way to protect the front end of the SA is to use a fuse In doing so the circuit is more complicated.
I use this at 455kHz all the time, (flat through the sweep span) And.... It sure is fast enough. Watch more of my video's and you will see it in action.
Another nice video. Thought you would have been tired from the DeForest Crosley rebuild. :-)
Keep an eye out for an email I just sent using the address I found from About.
Donald D'Egidio LOL, thanks for your comment!
Nice Circuit, here is how to improve it:
Instead of capacitors use resistors, they have flat frequency response, as you said this circuit has high pass frequency response.
The value of the resistors depends on the input voltage, so you might use a switch to select the voltage range.
Normally though, as you know, an attenuator is used to achieve what you are trying to do.
You can also use inductors to ground after each capacitor, to make it like transmission line. The value of inductor and capacitor depends on what impedance you want your transmission line to be (75 Ohm or 50 Ohm).
But the capacitors are there to block DC.
Most spectrum analyzers get damaged if they have even a tiny bit of DC at the input.
@@youdonotknowmyname9663 Most spectrum Analyzers have a manual that indicate what is maximum input power. For example, for tinySA is 1dBm; so you need to to measure the power with power meter first, then use correct attenuator value to measure your signal. Normally the input of spectrum Analyzers are AC coupled, any way. More over:
1dBm =1mW=V^2/Zo=> 1mW*Zo=V^2 => 0.050=V^2 => Maximum V = 0.223V => So it does not matter if 0.0223V is AC or DC, because it is very low any way and this is maximum RMS voltage at the input of this spectrum analyzer.
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