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Very interesting video. Personally, I'd enjoy seeing more in-depth videos such as this two part series on your probe experiments.

I really enjoyed this video, more on a engineering level. Plenty of tutorial and newbie help video's already., BTW, from years ago, An engineer is someone who knows everything about everything BORING; my wife concurs.

How do you learn to do all this? Books? Formal training? I am ignorant of it all, but admire highly. Would love to learn.

The Pin diode attenuator or Switchable attenuator matrix may actually have degraded Intermod performance at HF and some are specified at 100 MHz and above. The use of switched resistive attenuators are a good option.

Can someone explain why is the base of Q2 not biased in any way 5:08

Great learning for thanks for your kindness in sharing 73s wb7qxu

Mi heath kit wh 100 no se oye bien esta chirriando el altavoz.

Hi, Darren. Great channel, production and content = Kudos! Did you redraw the three schematics in KiCad, by chance? And, your board layouts, of course. If so, could you put the files somewhere where we could download them, please? Thanks for all you do for us!

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Hi! Can you sand me PCB progept? Thanks, Luciano 🙏

Hello, could this be used as an audio generator at 1500 kc output?

your talking my language ! thanks for great video 👍

Great video presentation and nice idea using the 1/2" brass for the shell. The 3D printed end caps are very clever. Also, your side by side comparison was very helpful in understanding the parameters of the probes. Since you utilized Ebay to source the BF998's for Jewsbury's FET probe, would you be able to share what price and quantity you ordered? I suspect that you would rather not provide vendor information but there seems to be lots of vendors from China that are offering the BF998's for around 50 cents apiece. Is that about what you paid? Since you have already acted as a 'guinea pig' for these components, I would feel more confident about buying a 10 pack or 20 pack if I knew a bit more about your purchase experience. I hope you create a follow up video regarding the grounding tip spring for the probes along with it being used for actual troubleshooting. Thank you for the wonderful videos you create and the knowledge you're willing to share.

On eBay and components: In the case of the BF998 MOSFETs, these were made in large numbers for the cable and satellite industry, so you are pretty safe buying these. The way to look at it for counterfeit/culls, is first how difficult is the device to make/fake. In the case of the BF998, they are a challenging manufacture just given what they are. Also, the culls would have been long ago destroyed, however anything is possible but unlikely. The next consideration, is there a comparable component that can be relabeled as a substitute; again the BF998 is pretty safe. Lastly, is this a component that is both scarce, does not have a good sub, and so is a make or break for a repair, and is expensive when found; this is the worst situation for dealing with counterfeits but usually not culls, due to age/missed-opportunity. My suspicion is that you have a mismatch coupling to the BF998 because that is such a horrendous amount of dB variance. I would try to set up a fixture to investigate the BF998 and see if you could learn anything from that. I've used these before but never in an instrumentation setting. Anyway, hats-off for the work and video--very enjoyable! 73...

I have a couple of HP 1 GHz amplitude & phase measuring instruments I bought from an auction. Of course the active (converter) probe tips were broken. I went through all kinds of troubles with getting or making the luckily replaceable tips. The threads were quite odd, I never could determine if they were # 000, # 00, or some metric size. I did not even try plain copper, nor brass. I wanted something reasonably strong and chose tellurium copper. It worked, but was a bit of a challenge on my tiny lathe and its standard tooling. I made the sharp end and the flange O.K. But to make the threads, I bought several different dies, only finding that the smallest sizes are not usually cutting type, they are forming type, intended just for the soft brass in time pieces. No matter, somehow I got a few actually fitting spare tips made. I would like to find carbide tooling, but have not seen anywhere for the small size used in my tiny lathe.

Your channel is gold. Thanks for sharing your passion to us

i played with the Hageman design a long time ago when the amazing OPA656 amp was still a thing. What I realized in kind of a dope slap moment is that Steve's real goal was to make 50 ohm SA input look like an oscilloscope input. It has that front end stuff so you could put a 10:1 standard scope probe on it and compensate it! I'd love to see you try that with your Siglent passive probe. I went in a different direction- I modified the design and used a 10 meg input R and no Cin and got the native FET input of the 656. It wasn't Agilent but it was pretty good, about a 1 pF IIRC. I never really cleaned up my design- I like your 1/2" brass and 3d printed ends. HP made some little adapter boxes for some of their gear as an accessory that did this- I have a 15709 that was an accessory for a QAM analyzer. Scope probe in, 50 ohm out. Discrete FET design similar to Pease circuit. Service manual/schematics can be found on line. I may tackle this again, I still have some old OPA656's and some newer grandchildren from Maxim and ADI. Nice job and good presentation- not too basic and not too detailed, kind of told me what I was curious about. Good luck.

Hello Darren, thanks so much for your efforts on this channel. Really appreciate it! When is the next episode of this project?

have you thought of using Old Gramophone needles for the probe? I find them amazing.

Nice work as usual...BTW, if you ever need a replacement indicator roller for the HG-10 apparently the "new" Heathkit store has replacements. 73 - Dino KLØS

After watching each episode, I can say WOW! And then again... Backwards...WOW! Outstanding job saving this 101 and power supply. I hope that when I find one that it will be a restored & working unit. Learned a lot from this series, thanks for posting.

Again, thanks for posting this video. It will help me determine if buying one is worth the effort. 73s

The Hot Water 101 was the radio that I wanted. Now after watching your video it is not without consequences following up after the purchase of such a challenging project. As much as I would enjoy having one, I would most likely prefer buying one after it had been restored as I am not so great at spark chasing down issues within circuits. This doesn't mean I can't learn how. Thanks for posting this. 73's

just got one from flea bay and it works great on an old Heathkit IO-4205 Oscilloscope that I'm calibrating. Fun old stuff that STILL works!

In the diagram shown from 2:38 onward, can someone pls try to explain how is Pdummy calculated in the "Output" table ?

Well, I'm impressed with your PCB, but really feel you absolutely need to put a guard, so that someone that is say moving the unit, does not inadvertently slip and put their hands on that PCB which has many places whereby high-voltage is present!

Europe is pretty well tired of AM and gradually shuts down services. Both Norway and Switzerland have shut down ALL FM broadcast stations with little discomfort. Sadly all them crappy solar inverters are now killing the ham fun on HF.

I think if your pre-amp was not going into saturation before, then putting the filter AFTER the pre amp will improve your SNR quite a bit

Common base offers increased input impedance. Cool choice! A common-emitter would have worked as well! However, your design, your choice, sir!

When I saw your original design had a pre-amp with no front-end filtering I assumed you lived somewhere quite rural. Where I am on the outskirts of Denver I put AM and FM filters in the front end of any HF receivers I build. I also use a variable gain pre-amp. That helps a lot. I had to add an AM filter to the front-end of a friends Hammarlund SW because while he lived far up in the mountains at over 9,000 feet it was almost line of sight to the Denver AM radio station's antennas, and you could hear a couple of them splattering all over the SW bands. I added a metal box on his antenna input with 3 simple LC filters to ground with air-variable tuning caps, and tuned out the 3 strongest AM stations. He said it worked great from then on. But I'm just waiting for a 4th big gun AM station to come on the air one of these days. I should have built him a good high-pass filter like yours, but I didn't have the right toroids handy back then. Now I do. Parts is parts. Thank you for the video.

When you have any firm of tape residue or glue on a surface WD40 will remove it. It may take several attempts to get it all up, and you’ll need to clean off the WD40 left on the surface but it does work.

If R12 was replaced with the schematic value of 2000 ohms (2050 used in calculations, measured value of resistor R12?), then current thru R12 would be 1.037 ma (just over meter full scale). Seems like it would be easier to replace R12 than replacing R10 & R11.

Hello, I'm Py7aom, I live here in Brazil, I'm written on your channel, I'm also a technician, how do I get this board kit for my Drake that I'm restoring?

А я делал микрофонный усилитель на двух транзисторах 2n3904 по обычной схеме эмиттерный повторитель с общим эмиттером. Получилось неплохо, но при большом входном сигнале идёт искажение сигнала.

This a great follow up video well done hope to see more.

There was an electronics/ham radio/CB store in Indianapolis called American Electronics. Their logo looked like the logo on your microphone. I bought my first scanner, a Uniden BC100XL, at American Electronics in approximately 1985. They've been out of business for 10 years or more. I noticed "Azden" cast into the interior of the microphone shell, so that's who probably made the mic.

Greetings.. Try to post a comment, with a link to the ebay seller, "look for RF active probe", but is not allowed, that has your option two prebuilt, looks like he took the schematic and made the probe. I have never characterize the probe, could be fun to do ..

What about the riaa circuit at the phono input that will affect the sound i suppose

Excellent! Looking forward to the next video.

This is valuable information. One other consideration that can sometimes be important is the surge capability of the resistor. Carbon composition resistors, due to the quantity of bulk resistive material contained within, can often absorb momentary overloads that might burn up film resistors. When equipment is initially switched on, there can be large transient currents, much larger than steady-state operation, while the filter capacitors are charging. The ceramic composition resistors or other resistors with suitable surge ratings may be required to replace carbon composition resistors in such cases.

super cool! Thanks for sharing!

Hi Daren, the topic of "active RF probes" is exactly what I am currently working on. I am very interested in the next episode. mny 73 Bernd

You dont need a new probe. Your scope is a great SA - with the build-In FFT function! For higher BW switch your Probe to 10:1.

I need to start simple. Direct Conversion Receiver seems a good choice. I plan on building the sections on separate boards so that I can swap stuff. Thanks.

The EU prefix identifies the Heath educational test equipment line, and the W indicates a factory assembled and wired unit. Most of the EU series was EUW.

These were developed by Stash who sold these at the TRW swap meet. It's a nice little kit and good find.

Wonder if you still have the rig? I just got one a month ago (20 meters also) and with help from your video, ran it through its' paces on the bench. Gonna take it out for a POTA activation tomorrow.

The common base input stage has a very low input impedance, far below 600 ohm.

Any chance you can do playlists with this build and the transmitter build for those of us coming in late to the party? Looking forward to watching these!