Build a high impedance active RF/AF probe with amplifier. Ideal for radio and amp repairs.
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- Опубліковано 5 лют 2025
- Only $5 for 10 PCBs and every new member get $5 bonus. + Express 24 hour / 48 hour service on www.pcbway.com/
An RF demodulator probe is a valuable tool for repairing radios and other RF gear. Equally, an audio signal tracer is great for repairing audio gear.
What if we could have both functions in one tester?
What if it had a very high input impedance to avoid loading the device under test?
What if there was a PCB ready for the entire thing?
Well, here it is.
This project was inspired by Chris, at AllTheGearNoIdea, who kindly allowed me to do a PCB project for his design. This is the video in question:
• K7000 Velleman Signal ...
The Gerber files are available on the PCBWay website in the share section, so feel free to order your own boards and try out this handy gadget. Here is the link:
www.pcbway.com...
You can now support the channel:
/ mcaldeira
paypal.me/maca...
This video is dedicated to Zélia Camacho (31 Jan 1968 - 12 Apr 2022)
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Brilliant Video you have done an amazing job making the PCB and what you have built is far better than the probe I made. I am glad you worked with PCBway it’s great that they reach out and support the UA-cam community. Hopefully people will enjoy building the probe and look forward to comments and seeing how it could be improved. The gain of the probe is quite high so I would say it works better in the RF and IF sections but it’s difficult to achieve a real big dynamic range. Thanks so much for making the probe and I am really glad you like the end result. My very best regards Chris
Thanks Chris. I too would like others to try it out and give suggestions, then between us we could create the “probe of all probes” for the community 😊 I’ve had a few thoughts:
1) Some sort of AGC?
2) Auto detecting RF vs AF and switching between two separate sub-circuits before feeding to the amplifier?
3) Adding a “super-gain” section that can be switched in to sniff out noisy components?
I sometimes lose steam halfway through this sort of “dream project” and don’t carry it through, but if others want to participate, I can always do the boards 😊
Interesting project! Also looking at mr Carlsons super probe! It is a no contact probe so impedance not an issue. It is high gain probe amplifier with volume control and a squelch circuit which homes into noisy resistors (i.e. frying eggs, pops, noises) without any electrical contact! Far safer as well if you probe valve circuits and it’s powered by batteries as well! He demos it very well on his iTunes videos!😊
I’ve seen it and liked it too
Great video! Chris is a clever lad. I always enjoy his videos. Cheers to both of you!
thanks
This is great Manuel! I've been thinking about building something like this for a long time. Thanks very much for posting it. (Thanks to Chris too...)
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It would be very useful if we had the option to make 2 the same, i.e. not the smd option. I volunteer for a repair shed and lots of these would be useful
Congratulations on reaching 15K subscribers 👍😀 A handy little project Manuel, I have the K7000 Velleman Signal Tracer but I haven't bothered to make the probe, this will give me the incentive to finish it off. Thanks Manuel.
Thanks Dave. This is one I also put off for some time, until I saw Chris’s video 😊
OK, now you get me. I've wanted to build a probe like this for a long time, now it's going to be something for me too. So far I have always done this with the oscilloscope ;-)
Thanks also for mentioning Chris's channel.
pleasure
Beautiful build. I like the design. Thanks for sharing this with us.
I built a similar device utilizing a small portable guitar amp.
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The case needs googly eyes and a smile. Looks like a funky robot alien. I love it!! Well done! 👍🏻
thanks 😊
Brilliant job, Manuel revisited Chris's explanation of impedance too, SMD projects with 402 components is a burden on my eyes, Mr. Carlson makes it look too easy. The restoration UA-cam community is certainly great and your idea of a “probe of all probes” for the community is a good thought.
Hopefully some good ideas will present themselves for the “Probe of all Probes” ™ or POAP for short
😊
Mr. Carlson has also created a a high impedance active RF-AF probe with amplifier - I don't know which one is more sensitive, though. I suggest you build both.
Nice.
I can actually use the probe for my amature radio builds & it's within my skill set unlike high voltage projects, so definitely on my to do list.
I find old aluminum tube lawn furniture is a great source for metal tubing and have made several VHF antennas with it and apparently due to its fairly large diameter the interval of good impedance match was much broader than when I used 12 gauge wire.
👍 recycling at its best
The first lesson amateur radio enthusiasts should learn is how to spell the word amateur. 😉
@@SpeccyMan Well, google's auto spelling corrector does not always obey what you want the symbol or its spelling to map to when one insists it matches their selection for a symbol or composite symbol standing in for whatever they are having it stand in for. It always pays to go back and check what auto correct has done for sometimes it is cringe worthy with respect to what was intended. Most people don't. I normally do, likely because of by education being a mathematician thus keenly aware of the importance of grammar and definitions being well defined, but not always.
Nice probe and very sensitive, something I don't have on my bench and I'm sure it would become very useful. Even the amplifying board might have many other uses. I'm always short of an LM386 amplifier on my projects.
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I built probes for my eico units not too long ago. I found that my old cheap plastic with metal body solder suckers made perfect enclosures for them.
Good idea
Very interesting, have been looking to assemble such a device as an outgrow of an amplified loudspeaker.
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Nice project ..would be great to create it all to fit in probe enclosure, add alc (auto level control ic so manual adjustment is not necessary and you have at the end 3.5 mm jack fir headphones.
Actually 25 years ago I made one (fit in parker pen enclosure).
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Thanks for sharing! Nice placement of the pot. Nice speaker/dummy load. Maybe add a light bulb to be a visual flicker indication of what is going on when just using the Load? Designing/Adding an automatic volume adjustment would be interesting/useful... Hmm? An op amp control with a pot adjustment on the reference? I would add heat shrink over the metal probe tube, to prevent it from shorting anything out, while fishing around in the circuit. It would be slightly more comfortable to hold, as well.
More good ideas. Thanks.
Hello Manuel, a simple way to increase the input impedance and decrease the Miller effect would be to change the single input FET to a cascode input using two FETs remaining everything the same.
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I just made a big long comment suggesting the same thing. I, however, suggest a NPN BJT as the upper transistor of the cascode. The source of the upper JFET looks like a resistance with a value of 1/gm. With a BJT you get a lower number.
I love your videos. A great probe which must prove very useful. If it was mine I would put some heat shrink over the metal tube just in case ⚡️.
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Great work Manuel. Some brilliant ideas. I wonder if you could have made a hybrid board to use the FET and germaniums with smd components. I knew you wouldn’t be able to resist a go at smd. I used a switched potentiometer when I made my signal tracer but it’s all very dated now and my probe is nowhere near as good as yours. Cheers Graham
I planned to use a switched pot, but the the idea of blending it into my speaker/load came up 😊
A very well built gadget. Clever. Thanks for the presentation.
My pleasure
Great test probe. The LM386 is a good sensitive amplifier. I like the TDA7052 it has a volume control that is voltage operated at pin four and can be used as an automatic volume control. Maybe try for fun
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Manuel, you can get various *BATxx* devices from Mouser & Digikey. Also, the *LM386-4* puts out a full Watt!
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I use an oscilloscope probe in my signal tracer.
Best Regards.
that will work well
É um aparelho muito interessante antigamente eu usava Mini Jet 15 É também era muito bom .
Very nicely executed and explained! The device performs exceptionally well. One question... You tested it on the IF and AF stages with excellent results, is this capable of picking up the signal at say, the detector stage of a regenerative receiver?
Yes, it’ll pick up the signal all the way from the mixer stage.
For the probe you could use the aluminum tubes from wind chimes
Didn’t think of that
The Velmann kit works absolutly fine for most apps7
I am thinking of copper pipe ( diameter 22mm or 28mm) would make a excellent screened body for the probe with a thin plastic inner liner to prevent shorts! Copper off cuts are easily available from plumbers and copper braid would solder well for ground contact!
Yes, that would work very well.
I use an oscilloscope probe for my signal tracer, I install a BNC connector on it.
Interesting. I have few suggestions to improve your design: 1- for biasing purposes you need to connect the input of your op-amp to the middle of supply ( the positive input of opamp), not ground (actually that would become your AC ground which is different from DC ground) so you can get maximum swing out of your Audio amp, then connect the negative input with a feedback resistor to the output. 2. Use a voltage buffer stage before this stage with another op-amp. that is connect output of that op amp to negative input and use positive input as your input. 3. Use micro strip line for your RF probe so you do not get impedance mismatch and reflection at high frequencies. 4. Either use an AGC (Automatic Gain Control) or manual gain control for your RF probe preferably switchable. If you need help to design those circuits, let me know I will help you.
No problem. Thanks for the tips. The amp is however not an opamp at all. It’s the LM386 power amp chip which is spec’s to single supply rails.
@@electronicsoldandnew
Thanks for your info about LM386.
You are right about LM386, it is a strange type of opamp, since in a opamp a current source at the mirror point of opamp is used, they use resistor here, which in theory reduces PSRR (Power Supply Rejection Ratio)! Furthermore, two PNPs in LM386 connected in Darlington configuration at inputs would like the inputs signal be close to ground ( ie. Needs at least 2x-0.7= -1.4V from the emitter to turn on these transistors. ) Furthermore, differential to common mode convertor NPN load of the circuit needs at least 0.7V , I guess that is why there is 100 Ohm in series with the pot, in order to ensure PNP and NPN transistors are biased correctly. Here is the datasheet for LM386:
www.ti.com/lit/ds/symlink/lm386.pdf
For RF probing I would use near field magnetic or electric probe, instead of direct connection, since it causes much less interference with the signal, here are some videos about that:
ua-cam.com/video/6yR7JOkPrvU/v-deo.html
and
ua-cam.com/video/ctynv2klT6Q/v-deo.html
and
ua-cam.com/video/x1rn5YNLmVw/v-deo.html
and
ua-cam.com/video/2xy3Hm1_ZqI/v-deo.html
and
ua-cam.com/video/PSbsAl_lVro/v-deo.html
Thanks for posting a good video.
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It is very impressive. Very good!
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Perhaps you can use the enclosure of a solder pump. I build the one from Mr Carlson his channel and they used that enclosure. Good luck from Holland. Ron
Those solder pumps are perfect for this 👍
Thanks for your reply.
Hello, very cool project . I am going to restore tube ham radios . So very needed . The pcb site is saying 54.00 for 5 boards .
Download the Gerbers and see if you can get a good price elsewhere. The Gerbers are good for any manufacturer. The price is high because I added both boards in one and it uses cutouts. Didn’t know about that issue when I posted the projects
In the US you may want to try expresspcb. I don't think you will save much but it is worth checking their proto board service. They give you schematic capture and layout software to use.
I got the same estimate as well and they say you may have to pay customs as well, Strip board will do for me inside a piece of copper water pipe! It will a good screen with insulation on the outside surface!
Yes, I will look into that . That or just build Manhattan style .
Very interesting and helpful, great job.
thanks
36:21 Ah! A embalagem vem com as de descrições todas em Português ! Nice!
👍 também merecemos
Maybe you should insulate the outside of that metal tube. Put some contact paper or something around it. As it is grounded to the UUT if you hit that metal tube against some high voltage tube connection you will short it out and make a big bang like Electro Boom...
Absolutely right. Some heat-shrink is going to protect it a bit more. Thanks.
Electronics old and new me and my cousin are going to a Swap meet June 5th 2022 Sunday morning at 8 :00am 11:00am
I am not going to watch you build it because the schematic was what I was interested in seeing. I do have a few pointers for someone designing one of these.
2N5457 has 7pF of gate capacitance and 3pF drain to gate.
The 310 is about the same.
I would use parts in a SOT-32 package. They can be soldered and you get less effect from leads.
Parts with numbers like xxx4117, xxx4118, xxx4119 have a lower capacitance. They will work up to about 50MHz with careful layout.
If you change the input section to be a cascode followed by a "voltage follower", you can get more impedance transformation in the stage.
Alternatively, you can add a PNP common emitter gain stage to add a little gain.
A small resistance in series with the source capacitor for the input pushed the input impedance up a bit more.
You can get even higher impedance at the cost of gain by doing this with the 3 transistors with PNP version:
A slight feedback from the collector of the PNP back to the source can make the source want to go positive when the gate does. The Gate to Source capacitance will then have less AC voltage on it than the input and less current will flow in it. This makes the impedance a lot higher. You can get below 1pF of input capacitance with this method.
If you use an NPN BJT in the upper transistor of the cascode, you can make the base of that transistor AC coupled to the JFET's source.
(You can even apply a bit more feedback to it with great care)
This has the effect of making the drain of the JFET actually swing positive a little when the gate goes positive. This can take the drain to gate capacitance out of the picture.
The result can be a probe that you can just bring alongside a wire to sniff for a signal.
Awesome job and tutorial!! Almost as cool as your clever dimbulb tester which is why I originally subscribed!! Just wondering how this probe compares to Mr. Carlson's Super Probe? Thanks again.
Not sure. I was going to build his, but this one has served me well in all my needs so far.
That's a great little unit to have in your stack of testequipment.
Will the next version have a switch were you can select between AM and FM demodulation? 😋
You will not be able to check if the local oscillator is running with this would you?
If you had the option to connect a oscilloscope after the FET, then you might be able to do just that.
Good idea.
Got to get round to making one of these, also a subscriber to Chris’s channel.
Any chance of a video tour of your increasing shelf modules. I have seen the speaker dummy load one but interested in the others as building a workshop at the minute and will have something similar in the way of input/output panels. Cheers Tone
I’ll do that soon. Quite a few people have asked for the view of the workshop.
Or! You could use your 100w marshall into a full stack so your it can be heard for a couple miles away. In either case, your version is more portable :)
That’s an idea 😊 Won’t make me very popular with the neighbours
Hi, has someone made a SMD version?? Did anyone work out the JFET in SMD format and bias resistors that they wouldn't mind sharing, please. Cheers Darren.
This is great use for the 3D printer =)
I do find myself periodically making copies of your designs for my uses. The super probe might be the next one, so I might make a copy of your copy.
I'll go watch the original video as well. I do have a question though. How does a single FET amplify audio? Doesn't audio go into negative and positive voltage ranges? Yes I realize that there's an audio amp in the circuit but doesn't it get it's input from the single FET?
The Fet is configured as a normal gain stage. There are great explanations on the various Fet amp stage types on the web.
@@electronicsoldandnew I'll have to do some more reading for sure. I only have some basic information/understanding of amps as it is. I assume there is a bias voltage of some sort? Or am I thinking backwards.
The device can be biased in various ways, including the source resistor method, which provides the equivalent of a tube’s cathode bias.
maybe build it like a alien probe! with a battery. tda 2883 is a 3v chip, 1 lithium cr123. I can predict a blown j310 and those are expensive. just use 2 diodes or maybe just 1 diode - bias it with a 10 meg resistor.
Great job! Could you try if the probe works as a slope detector with 10,7 MHz if chain? We have a retro radio club, and we are making a club project of this probe, and somebody asked if one can use it with FM-radios.
I’ll give it a try next time I have FM to tackle.
I need help I just did a nice restoration of a Heathkit A-9c and came out great and is in great condition it sounds very good nice mids and deep bass with the pair of 6l6s
So I’m getting horrible alien digital sounds when I turn up the volume 1/4 way and louder to full volume
I tried everything it’s away from the speakers no wires are crossed over the inputs I did change the 12ax7 tube and the 12au7 it got about 15 percent better
Any suggestions on blocking this I know my HH Scott 222c has a shield for the preamp pots I hope I don’t have to do this and it’s not ac hum it’s dead quiet it will still make This alien noises with no input
Hi and thanks for your informative vid.
Q: why exactly does the LM386 to speaker require a capacitor to couple it? (Apologies, I am a novice 🥴 and your answer may well explain why my amp and speaker combo isn’t working in another circuit)
I’d you use a single supply, the output is at a DC level that is approximately half the supply, so you need to block the DC to separate the audio signal to the speaker.
@@electronicsoldandnewwhy simply cut the DC by using 1uf capa ?
The capacitor blocks DC and allows the audio through.
@@electronicsoldandnew it s what I Said. A question- for probe électronic music instrument liké sampler , is it RF or AF probing ?
i think my version has more gain on the front end as i can trace through the rf stage (on AM) even with no battery conected to the set undert test .sorry i can.t remember the type of JFET i used
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Thankyou for the video....can I ask you a question about your chair. What brand is it please I'm looking for the same with an high back cheers
This one is from IKEA. It’s great.
Hi Manuel. I'm just checking the cost of your PCB on PCBWay. It is not $5 for 10 PCBs as stated. It is $53.39 for a minimum order of 5 of your PCBs. But I do need only one (at most 2, as a reserve if something goes wrong on the assembly of it). It is that correct? It is a pity because this probe looks like it would be very helpful. Thanks.
I have no idea why that price is so high. May have something to do with the cuts on the board. You can download the gerber files and try and get it done by another supplier. Unfortunately I have no boards left as I have some to Chris.
@@electronicsoldandnew Thanks again Manuel.
Hi. I'm a student from Australia. This is a great idea. Is this project in a kit form? If not, are schematics and parts list for available for it please? I can buy the components but 5 PCB boards would be to many for me.
I’m afraid I don’t do kits at all. The schematic is visible from the video, and you can build it on perf-board.
Very useful video. Which leg of the transistors are you probing to get the audio? Cheers!
Base and emiter, I believe.
Cool! I wonder how this compares to the Auto RF/AF Probe by Restore Old Radios?
Hi: I really like the design but can you tell me the name of the PCB layout software used to do these boards? Thanking in advance.
I use EasyEDA
Oh I saw somebody already said that I didn't read the comments before writing one. Sorry :)
some use fet transistors as very low conduction diodes.
For aluminum tube. Look up Align T-Rex 500 (16mm dia) (or T-Rex 600 (21mm dia)) RC model helicopter aluminum tail boom.
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Excellent, Thx!
Pleasure
Unless you don't have the space...why not install the Probe-Amp in your Amp that's hanging from your bench!
Also, an *AGC* circuit would be a nice addition.
AGC is an idea. I like it 😊
Hi, Since it appears that you have used balanced audio cable for your RF probe's flex, I presume that the impedance of this cable is not important. Why is this? I have seen other active probe designs where the cable specified is either RG178 or RG174 (both 50 ohm coax cables). Is it just so the latter can be matched to the impedance of oscilloscopes, spectrum analysers, etc?
The length of the cable is minimal, and I don’t need to actually obtain any quantitative measurements from this, so matching impedances is not an issue here.
@@electronicsoldandnew Got it. Thanks.🙂
manuel cigar tube it´s ok , what about rc car models screwdriver ? is a nice suggestion
I don’t know that one 😊
Electronics old and new my other hobbys are lining to music records and CDs and fmstreo music
Did you see Paul Carlson's "super probe" circuit during your search? What did you think of that one (if you saw it).
I am kind of looking at making something similar myself at the moment.
I do admit I like the design you have featured quite a lot also. Too many choices lol :)
Of course 😊 I saw that when he first posted it on Patreon. I’m one of his supporters 😊
For me and my needs, his one is just a little too sensitive, so it probably is above my needs, That’s why I chose this one that Chris presented.
@@electronicsoldandnew That's kind of what I am deciding on too. Whether it, Paul's one, is a little too sensitive. :)
Hell, maybe I will just build both lol
Always the best option … do both 😊
What about testing tube radios with it? Will keep it working or blew out?
We’re going to find out soon enough 😊 The high voltage capacitor at the input is supposed to protect it, but only experience will tell.
manuel why not decoupling the j310 fet source with a 1nf capacitor ?or is it intentioned to not extend gain to rf frecuencies
The value of the cap used raises the gain of practically all frequencies. The smaller the capacitor, the higher the cutoff frequency of the frequency band amplified, so in fact it’s the opposite effect. No great thought was given to the value in this case.
Manuel, my comment it's about C2 10micro elco, from few hertz to hundreds khz its ok, decouples ok source fet, (455khz, 2Mhz.. IF frecuencies) at 10,7Mhz elco capacitor I think it's not tbe best decoupling method,... for rf voltage a ceramic capacitor, put the source at ground level and make fet's voltage gain, useful at V/UHF frecuencies.
Although someone, talked about using only schotky diodes, germanium diodes & fast silicon rectifiers(low cap) are also ok, in my humble opinion. It's a signal tracer probe, not a high (bucks) level ones, does its job👍👍👍.
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I think I'll build one. Just by chance I have a Grundig Satellit 700 on my bench now, the FM local oscillator appears dead, MF and HF bands are good, FM +5V bus good. Replacing CT505 (local osc transistor) accomplished nothing.
Keep at it. You’ll get there 👍
I'm curious why you add a large filter capacitor to your battery supply?
just to ensure smoothing. Large spikes can cause battery drop when the battery ESR rises as it flattens.
Another interesting project Manuel - keep up the good work please! Is there any way you can share the EasyEDA source files so we can modify your design to suit our needs? I believe that a PCB design can be exported as a json file or the design can be shared in EasyEDA by changing its status from private to public - assuming you would be willing to do this?
sure. email me and I send you the files.
@@electronicsoldandnew Hi Manuel, I sent an email a few days ago, have you had chance to see it yet? Thanks
I did. Just looking for the files 😊
@@electronicsoldandnew Thanks, no rush just wondered if lost in the SPAM folder.😀
Don't worry if you can't track them down Manuel, I'll have a go at recreating the board.
Just checked, also $53.39 for me. Any idea why the difference in pricing?
Don’t know why. Just download the Gerbers and get a quote directly. Else email me and I’ll send you the Gerbers.
Is this a kit or just the boards. If it is indeed a kit can you post a link to it. I could not locate a search window on the website. Appears to be an OEM service only.
No, just the boards.
is it possible to get the easyeda files so i can build it and make up a bom file for my self. any modidy and play whit it if needed thank you!
Greetings again. Excellent video, I have already assembled the "Power supply board for adding bluetooth module", with excellent results. In this case I wanted to make the request for the PCBs, but when making the request, an amount for 5 units of $53 (without shipping) comes out, I do not understand PCB design, so I do not know if there is something in the Gerber file that of a different configuration. If you can guide me, so that the cost is similar to your purchase (Only $5 for 10 PCBs and every new member get $5 bonus. + Express 24 hour / 48 hour) and be able to make this circuit. Thank you very much. a follower
Hi. I tried it myself and got the same result. Don't understand why. When I tried the quick order (where you upload the Gerber files), it quotes me the expected $5. I would recommend that you download the Gerbers from the Share page, and then order by uploading the Gerbers again to the order page, so that you get the low price. The actual page is this one:
www.pcbway.com/QuickOrderOnline.aspx
Hi, Just wondering if you could provide the order # of the required module to build the high impedance active RF/AF probe.
It’s pretty clear at 13:35 on the second version video. Not sure if the actual order number.
Again I have a construction question :^) what diameter tube fit the probe board best?
If I remember correctly, it’s about 22mm, but is just a matter of making it a couple of mm bigger than the PCB width.
@@electronicsoldandnew Thanks Manuel - that was indirectly the question, the width of the PCB.
The width of the PCB is 17.8mm.
@@electronicsoldandnew Thank you, sir. I asked because I have to lay this down on perfboard ('veroboard?") and very luckily found a 21-mm metal tubular mop handle that I've cut to length for the case.
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Muito top parabéns
obrigado
You can go contactless with this gain, back then when younger I build just the detector and no gain at all for RF service.
I’d like another gain stage for the contactless option. Maybe one you can switch in if needed and bypassed if not.
Nice !
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Electronics old and new Biuld a high impedance a ctive RF /AF probe with amplifier ideal for radio and amplifier repair HPC way H this cool my hobbys are painting pictures and lisining to shortwave and ssb iam thinking about getting my ham license I have 4 shortwave receivers
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Why is at PCBWay 5 x this pcb over 50 Euro while all other prints like the leakage tester or tube tester are all 5 EUR for 5 ?
I made the mistake of making this board with unusual cuts. I should have simply made a rectangular board and that issue would not have arisen.
How do we fix it so it will not cost $53??
Do you have schematic or parts list to get somehow. Thank you
You can get it quite easily from the schematics shown in the video.
Price
Hello M Caldeira. All my admiration for your content... I want to ask you if you can build an af/rf probe, complete, for me... I will pay the price you ask... Thank you...
I’m afraid not. This is a hobby for me and I have very little time as it is. Sorry.
@@electronicsoldandnew I was expecdet this answer... Sorry also for me, but, you have my respect...
Where can I purchase the PCB's
It is all described in the video description.
Germanium diodes are obsolete. Schottkey diodes are the way to go. They can work in a higher temperature range and
have no recovery time. Cigars come in tubes? I'm must be buying cheap ones. LOL This probe works great but might need
a replacement 9 volt battery sooner than you think. Like the repurposed computer speaker being used to hold all the works.
That probe you made at the end is fantastic Manuel. Steve
Some cigars come on those aluminium cylinders, which are great for this 😊
Can I use a BF 245 as Q21 ?
Look up the specs
mr carlson lab has something like this i guess i need to finish video in a bit lol
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Could it be used on a FM receiver? If my memory serves me I think on FM they call the detector a discriminator which I think is like a voltage controlled oscillator? Am I right? It sweeps a substantial part of the bandwidth?
I have used it in the FM sections quite successfully. These tube radios normally use ratio detectors.
JLC will give me the board for $2 (plus shipping)
How much
I don’t sell my projects
@23:20 a puff of smoke comes out of the fuses. ua-cam.com/video/TZKfO5F0IF4/v-deo.html
5 PCB's will cost me $AU103 wow expensive.
Hot glue - oh pahleez - gland it needz !
Pro- probes are impotant - for the depth for repair works.Possitive versus Negative - SIMPLE AS THAT
Could you sell some of your pcb:s? PCBWAY minimum is 5 boards for each project and around 50 bucks / order + shipping + tax. It eats if anything the idea of DIY =/
I’m afraid I don’t sell anything in my channel.
@@electronicsoldandnew Maybe personally?
ok, then.
I was certain that i had seen i probe like that somewhere and with a prober probe housing. I did on Mr Carlson Lab : ua-cam.com/video/uVkJqqZroN0/v-deo.html
I noticed that you build to be a stand alone unit for your desk.
Shouldn't it have been build as your "Udend the shelf" modules like your Dummy Load?
I considered that, but I found that for radio testing, I prefer the “mobility” of the speaker unit.
Great Video My needs are - looking at yours and Carlson. Needs - Sniff out noisy components for Vintage Receivers Like Pioneer SX- since they have a lot of Noisy transistors and RF I think? to sniff out High FHZ oscillation for Amplifiers like Phase Linear 400 II and 700II - Can this one do it? and Carlson probe do it? Were can I buy boards kit? ebay? (or do you have to create account and they make them)
Both mine and Me C’s probe will do that. The boards can only be ordered as I don’t sell anything.
@@electronicsoldandnew Thank, I think yours is easier to built w full size components, Don't know when I have to to build but could order part now Any Mouser or other BOM?
Afraid not. You can get that info from the schematics.