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.

On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
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.

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.

On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
wrote:

>On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>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!

On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom <cd@notformail.com>
wrote:

>On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
>wrote:
>
>>On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>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.

Some of the attenuators are OK, some not so much.

On Sun, 07 Apr 2024 12:08:43 -0700, John Larkin <jl@997PotHill.com>
wrote:

>On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom <cd@notformail.com>
>wrote:
>
>>On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
>>wrote:
>>
>>>On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>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.

>Some of the attenuators are OK, some not so much.

On 07-04-2024 18:57, John Larkin wrote:
> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
> 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.
>
> 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.
>

I did some consulting job recently. One of the guys insisted we buy the
expensive probes, I carried on with my 900ohms 20:1 10 USD probe. By the
way, the resistor on the end probe is not sensitive to pigtails, so in
many cases it's better than the expensive probes

On Sun, 07 Apr 2024 23:11:28 +0100, Cursitor Doom <cd@notformail.com>
wrote:

>On Sun, 07 Apr 2024 12:08:43 -0700, John Larkin <jl@997PotHill.com>
>wrote:
>
>>On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom <cd@notformail.com>
>>wrote:
>>
>>>On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
>>>wrote:
>>>
>>>>On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>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.
>

I TDR test connectors and cables, for impedance and risetime, 30 ps
resolution.

These edge-launches are great

https://www.amazon.com/gp/product/B07BHGM7MF

if you get the pcb stackup right.

>>Some of the attenuators are OK, some not so much.

On 8/04/2024 2:57 am, John Larkin wrote:
> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
> 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.
>
> 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.
>

Which Caddock part number?

On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

>On 8/04/2024 2:57 am, John Larkin wrote:
>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>> 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.
>>
>> 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.
>>
>
>
>Which Caddock part number?

In the zip file.

On 8/04/2024 11:36 am, John Larkin wrote:
> On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
> <lugnut808@spam.yahoo.com> wrote:
>
>> On 8/04/2024 2:57 am, John Larkin wrote:
>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>> 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.
>>>
>>> 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.
>>>
>>
>>
>> Which Caddock part number?
>
> In the zip file.
>

Thanks, I only looked at the pdf before. For usenet posterity the zip
file contains Agilent document 54006-90002 and a photo of a probe made
from a SMA connector with a resistor marked MD1248 950 1%, and a packet
of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model
MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.

On 4/8/24 00:11, Cursitor Doom wrote:
> On Sun, 07 Apr 2024 12:08:43 -0700, John Larkin <jl@997PotHill.com>
> wrote:
>
>> On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom <cd@notformail.com>
>> wrote:
>>
>>> On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
>>> wrote:
>>>
>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>> 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

On 08-04-2024 06:40, Chris Jones wrote:
> On 8/04/2024 11:36 am, John Larkin wrote:
>> On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
>> <lugnut808@spam.yahoo.com> wrote:
>>
>>> On 8/04/2024 2:57 am, John Larkin wrote:
>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>> 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.
>>>>
>>>> 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.
>>>>
>>>
>>>
>>> Which Caddock part number?
>>
>> In the zip file.
>>
>
>
> Thanks, I only looked at the pdf before. For usenet posterity the zip
> file contains Agilent document 54006-90002 and a photo of a probe made
> from a SMA connector with a resistor marked MD1248 950 1%, and a packet
> of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model
> MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.
This is comparison with sub pF probes vs just a resistor/coax. Seems the
performance from the coax is very similar to high end active probe. From:

http://www.sigcon.com/Pubs/straight/probes.htm

Notice, that you can
have a rather long pigtail on the coax probe and it won't affect the
signal.

On Mon, 8 Apr 2024 09:45:03 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 4/8/24 00:11, Cursitor Doom wrote:
>> On Sun, 07 Apr 2024 12:08:43 -0700, John Larkin <jl@997PotHill.com>
>> wrote:
>>
>>> On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom <cd@notformail.com>
>>> wrote:
>>>
>>>> On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
>>>> wrote:
>>>>
>>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>> 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

We get SMA connectors from Shining Star. Excellent.

Custom RF cables from RF Street. Purchasing notes say not to buy from
Lighthorse.

On Mon, 8 Apr 2024 15:30:57 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

>On 08-04-2024 06:40, Chris Jones wrote:
>> On 8/04/2024 11:36 am, John Larkin wrote:
>>> On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
>>> <lugnut808@spam.yahoo.com> wrote:
>>>
>>>> On 8/04/2024 2:57 am, John Larkin wrote:
>>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>> 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.
>>>>>
>>>>> 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.
>>>>>
>>>>
>>>>
>>>> Which Caddock part number?
>>>
>>> In the zip file.
>>>
>>
>>
>> Thanks, I only looked at the pdf before. For usenet posterity the zip
>> file contains Agilent document 54006-90002 and a photo of a probe made
>> from a SMA connector with a resistor marked MD1248 950 1%, and a packet
>> of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model
>> MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.
>This is comparison with sub pF probes vs just a resistor/coax. Seems the
>performance from the coax is very similar to high end active probe. From:
>
>http://www.sigcon.com/Pubs/straight/probes.htm
>
>Notice, that you can
>have a rather long pigtail on the coax probe and it won't affect the
>signal.

We often probe without a ground connection at all, with fet and Z0
probes. You get a bit more noise but you see what's going on.

Critical signals get their own "probe" built into the board, with a
coax connector.

https://www.dropbox.com/scl/fi/jpy8onicfd1yrlzyp8qc2/T660_Phemt_Oscillator.jpg?rlkey=f5uzzmpmc3z6edqz48c47o31q&raw=1

That's the clock from a triggered LC oscillator.

https://www.dropbox.com/s/674b2w56c0q9orn/Burst_1.jpg?raw=1

SMB, when there's enough room.

On 2024-04-08 10:24, John Larkin wrote:
> On Mon, 8 Apr 2024 15:30:57 +0200, Klaus Vestergaard Kragelund
> <klauskvik@hotmail.com> wrote:
>
>> On 08-04-2024 06:40, Chris Jones wrote:
>>> On 8/04/2024 11:36 am, John Larkin wrote:
>>>> On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
>>>> <lugnut808@spam.yahoo.com> wrote:
>>>>
>>>>> On 8/04/2024 2:57 am, John Larkin wrote:
>>>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>>> 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.
>>>>>>
>>>>>> 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.
>>>>>>
>>>>>
>>>>>
>>>>> Which Caddock part number?
>>>>
>>>> In the zip file.
>>>>
>>>
>>>
>>> Thanks, I only looked at the pdf before. For usenet posterity the zip
>>> file contains Agilent document 54006-90002 and a photo of a probe made
>>> from a SMA connector with a resistor marked MD1248 950 1%, and a packet
>>> of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model
>>> MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.
>> This is comparison with sub pF probes vs just a resistor/coax. Seems the
>> performance from the coax is very similar to high end active probe. From:
>>
>> http://www.sigcon.com/Pubs/straight/probes.htm
>>
>> Notice, that you can
>> have a rather long pigtail on the coax probe and it won't affect the
>> signal.
>
> We often probe without a ground connection at all, with fet and Z0
> probes. You get a bit more noise but you see what's going on.
>
> Critical signals get their own "probe" built into the board, with a
> coax connector.
>
> https://www.dropbox.com/scl/fi/jpy8onicfd1yrlzyp8qc2/T660_Phemt_Oscillator.jpg?rlkey=f5uzzmpmc3z6edqz48c47o31q&raw=1
>
> That's the clock from a triggered LC oscillator.
>
> https://www.dropbox.com/s/674b2w56c0q9orn/Burst_1.jpg?raw=1
>
>
> SMB, when there's enough room.

We do that with U.FL connectors. They're minorly fiddly, but seem to
survive OK and work up to 6 GHz, so at the size of a SOT23 and a cost of
only a few cents, they're Good Medicine. We often populate them for
debug and then leave them off on production units.

We use them for I/O connectors in some products, as well--jumpers going
from U.FL to bulkhead SMA are fairly inexpensive.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Mon, 8 Apr 2024 09:45:03 +0200, Jeroen Belleman
<jeroen@nospam.please> wrote:

>On 4/8/24 00:11, Cursitor Doom wrote:
>> On Sun, 07 Apr 2024 12:08:43 -0700, John Larkin <jl@997PotHill.com>
>> wrote:
>>
>>> On Sun, 07 Apr 2024 18:14:25 +0100, Cursitor Doom <cd@notformail.com>
>>> wrote:
>>>
>>>> On Sun, 07 Apr 2024 09:57:13 -0700, John Larkin <jl@997PotHill.com>
>>>> wrote:
>>>>
>>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>> 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

They have some interesting stuff for sure. Shame none of their site
links work.

On 08-04-2024 16:24, John Larkin wrote:
> On Mon, 8 Apr 2024 15:30:57 +0200, Klaus Vestergaard Kragelund
> <klauskvik@hotmail.com> wrote:
>
>> On 08-04-2024 06:40, Chris Jones wrote:
>>> On 8/04/2024 11:36 am, John Larkin wrote:
>>>> On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
>>>> <lugnut808@spam.yahoo.com> wrote:
>>>>
>>>>> On 8/04/2024 2:57 am, John Larkin wrote:
>>>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>>> 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.
>>>>>>
>>>>>> 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.
>>>>>>
>>>>>
>>>>>
>>>>> Which Caddock part number?
>>>>
>>>> In the zip file.
>>>>
>>>
>>>
>>> Thanks, I only looked at the pdf before. For usenet posterity the zip
>>> file contains Agilent document 54006-90002 and a photo of a probe made
>>> from a SMA connector with a resistor marked MD1248 950 1%, and a packet
>>> of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model
>>> MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.
>> This is comparison with sub pF probes vs just a resistor/coax. Seems the
>> performance from the coax is very similar to high end active probe. From:
>>
>> http://www.sigcon.com/Pubs/straight/probes.htm
>>
>> Notice, that you can
>> have a rather long pigtail on the coax probe and it won't affect the
>> signal.
>
> We often probe without a ground connection at all, with fet and Z0
> probes. You get a bit more noise but you see what's going on.
>
> Critical signals get their own "probe" built into the board, with a
> coax connector.
>
> https://www.dropbox.com/scl/fi/jpy8onicfd1yrlzyp8qc2/T660_Phemt_Oscillator.jpg?rlkey=f5uzzmpmc3z6edqz48c47o31q&raw=1
>
> That's the clock from a triggered LC oscillator.
>
> https://www.dropbox.com/s/674b2w56c0q9orn/Burst_1.jpg?raw=1
>
>
> SMB, when there's enough room.
>
>
I do that too, also for all PSU rails. And add resistor in series with
the feedback path of PSUs, then it real easy to do gain/phase measurements

I add 900ohm resistor on the board before the UFL, I guess you do the same?

On Tue, 9 Apr 2024 01:42:22 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

>On 08-04-2024 16:24, John Larkin wrote:
>> On Mon, 8 Apr 2024 15:30:57 +0200, Klaus Vestergaard Kragelund
>> <klauskvik@hotmail.com> wrote:
>>
>>> On 08-04-2024 06:40, Chris Jones wrote:
>>>> On 8/04/2024 11:36 am, John Larkin wrote:
>>>>> On Mon, 8 Apr 2024 11:06:52 +1000, Chris Jones
>>>>> <lugnut808@spam.yahoo.com> wrote:
>>>>>
>>>>>> On 8/04/2024 2:57 am, John Larkin wrote:
>>>>>>> On Sun, 07 Apr 2024 14:51:29 +0100, Cursitor Doom <cd@notformail.com>
>>>>>>> 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.
>>>>>>>
>>>>>>> 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.
>>>>>>>
>>>>>>
>>>>>>
>>>>>> Which Caddock part number?
>>>>>
>>>>> In the zip file.
>>>>>
>>>>
>>>>
>>>> Thanks, I only looked at the pdf before. For usenet posterity the zip
>>>> file contains Agilent document 54006-90002 and a photo of a probe made
>>>> from a SMA connector with a resistor marked MD1248 950 1%, and a packet
>>>> of resistors marked CADDOCK Part No. 0699-2371 (MD1247) Rev B Model
>>>> MG680 Resistance 450 Ohm Date 12-7-88 Date Code 8845 amongst other things.
>>> This is comparison with sub pF probes vs just a resistor/coax. Seems the
>>> performance from the coax is very similar to high end active probe. From:
>>>
>>> http://www.sigcon.com/Pubs/straight/probes.htm
>>>
>>> Notice, that you can
>>> have a rather long pigtail on the coax probe and it won't affect the
>>> signal.
>>
>> We often probe without a ground connection at all, with fet and Z0
>> probes. You get a bit more noise but you see what's going on.
>>
>> Critical signals get their own "probe" built into the board, with a
>> coax connector.
>>
>> https://www.dropbox.com/scl/fi/jpy8onicfd1yrlzyp8qc2/T660_Phemt_Oscillator.jpg?rlkey=f5uzzmpmc3z6edqz48c47o31q&raw=1
>>
>> That's the clock from a triggered LC oscillator.
>>
>> https://www.dropbox.com/s/674b2w56c0q9orn/Burst_1.jpg?raw=1
>>
>>
>> SMB, when there's enough room.
>>
>>
>I do that too, also for all PSU rails. And add resistor in series with
>the feedback path of PSUs, then it real easy to do gain/phase measurements
>
>I add 900ohm resistor on the board before the UFL, I guess you do the same?

450 usually, for 3.3v type signals.

High voltage dividers are another story.