Mr Carlson's Lab patreon

Another PCB Release! Build a Dirt Cheap Active Probe Or Buffer For Your Test Equipment Or Receiver.

🕑 Added 2019-01-16 14:10:03 +0000 UTC

Comments

LoSaYa

Thank you Mr. Carlson

Dan Barker

Why the through-hole transistors? Without the schematic to input, we have to enter the entire diagram to get it to use sot-23 parts.

Andrew Curlik

Is a parts list located anywhere for this?

Mr Carlson's Lab

Hi Garry. The 49.9 (50) Ohm resistor is to help minimize RF reflection. Without the resistor, the waveform distortion at some frequencies will appear to trick the frequency counter into thinking that it's seeing another frequency.

Garry Norbury

What is the purpose of the 49.9 ohm resistor

Emerald Pawn

enclosure: https://www.ebay.com/itm/5pcs-Extruded-PCB-Aluminum-Box-Black-Enclosure-Electronic-Project-DIY-50-25-25mm/372496860559?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

Emerald Pawn

I use these little aluminum enclosures and this pcb fits perfectly. The bnc mounts screw on each end.

joram kalfa

Hey Mr. Carlson, RE: PCB Files Release: The "Special" Capacitor Tester!" Is there a parts list for this project including the "size #'s" for the components. Shipping costs are an issue for me and I don't want to pay for shipping more than once. Thanks.

Mr Carlson's Lab

Hi Alan. If you used an op-amp that exceeds the frequency range needed, you should be fine. Use appropriate protection on the input.

Alan Jurisich

What's the advantage of this circuit over an opamp buffer? I'm assuming it's the diminished output you were saying is desirable. However, I'm not sure why diminishing the output to your scope is desirable. I'm creeping into RF circuits now that I have an old Magnavox console table to repair.

S.M.D.

Ok, I just finished making my PCB. Toner transfer method worked great for this. Could you Paul, please always include a part list pdf? Thank you!

Garry Norbury

I realise now that the 2n7000 is a moss fet

Garry Norbury

I noticed that the 2N5486 is obsolete in the UK,the alternative is the J106 I know you said most any jfet will work ,I tried the 2N700 and that will not work I have not got any alternatives to try ,so I will have to order some J106 ,it would be helpful if when you do a project you could make sure you can get the parts and they are not obsolete or put a couple of alternatives that you know will work Thanks

God 420

would this work on audio circuits

Roman Charak

Now I understand, Thanks you!

Mr Carlson's Lab

You're very welcome Gary!

Mr Carlson's Lab

Thanks for your input Steven.

Mr Carlson's Lab

Hi Roman. If you use 50 Ohm coax, you should have that resistor in series with the center conductor. If you use 75 Ohm coax, you can use a 75 Ohm resistor in place of the 49.9 Ohm resistor.

Roman Charak

Hello Mr Carlson. Is 49.9 ohms a critical value for the output of the Buffer Circuit? Also, would Vector Monitors or Vector scopes be suitable for a Curve Tracer project? I see a few for sale in a local Electronics Surplus/Salvage Store.

Steven Emert

Hi Mr. Carlson. Love your videos. I've been out of electronic circuits since the days before surface mount devices became commonplace. Could you consider a video explaining the different sizes and nomenclatures of the SMD numbering you were using throughout this video?

Gary Bevis

Wow, this is what I have been waiting for! Simple, effective and oh so useful, thanks Paul for all you do!

Mr Carlson's Lab

You're welcome Roman.

Roman Charak

Okay! I only had to re-watch your video 20 times to glean all the information I wanted. Wow, you create such comprehensive videos . Thank you.

Roman Charak

Hello Mr. Carlson - super neat circuit! Are all the capacitors ceramic capacitors?

Mr Carlson's Lab

You're welcome Scott!

Adam

I've been needing one of these devices! 🤗

Scott Boerner

Thank you, Paul. This is a great, useful device that you explain very well! I will be building mine soon.

Albert G.

Of course I loved your elegant board vs my thumbs only board. Actually, I am considering yours, not mine, for the SX-71 because the chassis and the above chassis are more crowded. The SX-71 is dual IF with the first IF driven by a separate 6C4 oscillator for the first 455 Khz IF. The cathode is direct connected to ground, so the only options are grid or plate. American Electronic Specialty Products uses a tube shield as a pickup and that may be what i have to do.

kmpres

Another nice one, and timely too! I'm almost ready to set up my TS-830s for actual use. This circuit should help me hook up an SDR to the old tube rig without destroying my equipment. Thank for the circuit files and video!

Mr Carlson's Lab

You're welcome Don!

Mr Carlson's Lab

You're welcome Yannick!

Mr Carlson's Lab

Glad to keep you busy Nick!

Mr Carlson's Lab

You're welcome Tom!

Mr Carlson's Lab

Glad you enjoyed Roy!

Mr Carlson's Lab

You're welcome Michael!

Mr Carlson's Lab

The transistors are not surface mount so you can add sockets to the board and use what transistors you have on hand.

Mr Carlson's Lab

Transistors to a few hundred MHz, and anywhere between will be fine. The board was designed to put in a communications receiver that operates to 30MHz.

Mr Carlson's Lab

Glad to share Ralf!

Mr Carlson's Lab

You're welcome Buddy!

Mr Carlson's Lab

Unless you are dealing with very high frequencies, squared off traces are just fine. You will notice that most surface mount components are square.

Tom Thornton

Great project Paul! Due to next to no room, I am planning to build an all SMD version to tap the first IF of my IC-756 Pro III to drive a SDR for a pan adapter. I was planning on looking into a buffer, but suddenly it shows up! Thanks!

Escabusa Roy

Thanks for another great designed circuit.

Michael, KE4EST

WOW Paul! You did it again! Fantastic circuit design. I will be making a few of these! Thanks so much for sharing!

Mitchell Smith

Outstanding! Just what I need to pick the IF off of my Yaesu FTDX-1200 for a panadapter. And sorry if this is a noob question but why are all the components surface mount except for the transistors?

Stanley Chytla

Hi Paul, I will definitely be building one of these. Thanks for doing the design and sharing. What would you expect the upper frequency limit be for the transistors used in this design?

Reb Elba

Very useful circuit which comes at the right time! I'll try an active probe version with a different JFET I have on hand. Many thanks Paul, for sharing all your goodies!

The Radio Shop

Oh yeas! Just in time for a few projects I am working on, This will come in very handy. As always thanks Paul for doing the leg work on this.

Robert St-Laurent

I see that you have 90 degrees angles on the traces. Our Australian friend EEVblog always comments that these should be avoided. What is your position on this?

Nick Vacalo

Yet another great project thank you Paul for Keeping me busy while looking for a job.

Yannick Turcotte

Thank you Paul, i think this device will be a great addon at the output to my 10 mhz gpsdo. Instead of finishing with an 7404 i'll buf the output with :) Yeah a nice little project to built. Thank you again!

Donald (Don) Stewart

I am excited to get at all the projects. As you know I,m on my first one but when its functional on to the next. Thank You.

Mr Carlson's Lab

Great! You're welcome.

Mr Carlson's Lab

You're welcome Jim!

Inventor Pardue

Will build 2 of these, this circuit provides a lot of buffering! Really elegant design, thank you.

Jim Edmondson

I see an SDR Panadapter on one of the old boat anchors! Thanks for sharing the design.

Mr Carlson's Lab

I'm sure you'll like it Michael. I have some Drake stuff in line for the bench, they should make some interesting future video's.

Mr Carlson's Lab

Great Mark! Glad to be that drive. I should add... Pretty much the same process, take a few resistors (from a batch), and see how they stand up. Some metal film resistors (1/2 Watt) are amazing.

Mark Bosse

Another great one. I feel like I'm at TEK in 1982, except with all the experience and material advances over the decades. Very same problems but much better solutions. I have one of those little rabbits running around in my head. Resistor breakdown potential. I am an experimentalist. I've been playing with my old Fluke 10K VDC PSU for a few weeks blowing up resistors. It would be fun to see you do a video about this topic. Especially in VT gear, I rairly find people that understand that a standard eBay resistor probably has a 200 VDC breakdown voltage. How do you select resistors that stay in one package at B+? You'd find a way to make something fun and that potentially will enabling people to get past that semester of lab sessions. Oh well, the once again man, your Pateron is dragging this old grumpy dog of the early digital days out of bed to live again. Many thanks.