Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Jeroen Belleman Newsgroups: sci.electronics.design Subject: Re: Scope Probes off Ebay Date: Mon, 8 Apr 2024 09:45:03 +0200 Organization: A noiseless patient Spider Lines: 75 Message-ID: References: <4l851jte21egs8mmkqou4proepifknb7v7@4ax.com> <55j51j5n2p9chajruolqrmqs57smippb5t@4ax.com> <7gk51j5homhambnu4inj9dtsnehvh7v64p@4ax.com> <97661jhod6ppmfrn4uf5ji4be6nimb79ru@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Mon, 08 Apr 2024 07:45:11 +0200 (CEST) Injection-Info: dont-email.me; posting-host="44d8905cc89bb29199d833a569f45b57"; logging-data="3545376"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18SCR+WmmyZ/VKUxZnxAfHc" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.13.0 Cancel-Lock: sha1:ogxi6y4BQIV5NF2MT471C0IBlJc= In-Reply-To: <97661jhod6ppmfrn4uf5ji4be6nimb79ru@4ax.com> Content-Language: en-US Bytes: 5012 On 4/8/24 00:11, Cursitor Doom wrote: > On Sun, 07 Apr 2024 12:08:43 -0700, John Larkin > wrote: > >> On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom >> wrote: >> >>> On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin >>> wrote: >>> >>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom >>>> wrote: >>>> >>>>> I never learn. I bought a used "Agilent 500Mhz probe" off Ebay for 50 >>>>> quid as the highest bandwidth probe I thought I had was a 150Mhz Tek >>>>> one. Anyway, I have a large selection of old probes lying around so >>>>> decided to check to make sure the "Agilent" one was genuine. Not >>>>> surprisingly it turns out it isn't. I haven't calculated what it's >>>>> real bandwidth is. I've established it's not as sensitive as the >>>>> 150Mhz one and that's all I need to know. Whilst I was going through >>>>> this palarva, I tested a old probe I came across that I've never used >>>>> before and was amazed at the improvement in signal I got with it. I've >>>>> just Googled its part number and it turns out it's a 3.5Ghz passive >>>>> probe! I never even knew I had one so fast. I would never have ordered >>>>> the "500Mhz" one if I'd known I had this forgotten-about one already. >>>>> So the fake's going back for a refund and I won't be ordering any >>>>> more probes from anywhere in the forseeable future. >>>> >>>> The HP54006 is a 6 GHz probe, into a 50 ohm scope. >>>> >>>> https://www.dropbox.com/s/lxq4ujmkvo755uy/HP54006_probe.zip?dl=0 >>>> >>>> They show up on ebay now and then. There's one now, asking $150. >>>> >>>> You can make your own with some of those Caddock resistors. The >>>> Caddocks have some magical recipe. And unlike a fet probe, they are >>>> hard to damage. I use them to probe 7 ns 1400 volt spikes in my >>>> Pockels Cell driver. >>> >>> Funny you should say that, but the 3.5Ghz probe I mentioned (a Tek >>> P6056 to be precise) has a fragile resistor assembly in the tip >>> according to the datasheet and it's easily damaged by rough handling. >>> I'd be very interested to know what the secret sauce is in the >>> Caddocks and why they're more robust than whatever Tek used in the >>> P6056. >>>> >>>> And you can do a GHz at least with a 1-cent axial or mini-MELF or 0805 >>>> resistor on the end of a coax. 450 ohms makes a 10:1 probe. Fast >>>> circuits are often low impedance circuits and don't mind a 500r or 1K >>>> load. >>> >>> Many years ago when I was somewhat impecunious, I used to improvise >>> like that, but these days I prefer to just buy whatever I need ready >>> made. Some of those top-end RF patch cables can be ruinously expensive >>> to buy ready-made, but what are you gonna do? No matter how good you >>> are with terminations, you'll never emulate the quality standard of a >>> properly made, high quality patch lead. When you're as ham-fisted and >>> half-blind as I am, it's a no-brainer to buy 'em ready-made! >> >> Amazon has some crazy cheap coaxial jumpers and SMA and SMB connectors >> and adapters. All the ones I've got so far have been fine. For bench >> work of course, not production. > > What do you mean by "fine"? How did you go about characterising them > and what were you looking for specifically? IME you get what you pay > for and cheap connectors are very seldom worth it. Buy cheap, buy > twice as they say. Not necessarily. I used to buy phase-matched sets of SMA cables from Huber & Suhner. Then, one day, because H+S did not reply to a new request for a quotation, I got them from JYEBAO in Taiwan via a French representative. They were cheaper *and* better. Jeroen Belleman