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2400 series probes (is p6137 the most optimal?)

 

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Connectors are kind of available, at a very high price. There is Lemo USA in Santa Rosa, CA, telephone listed in my catalog is (800) 444 5366. They also have representatives and distributors, the US plant should be able to direct you. It is over 20 years since I had connectors bought and pricing is just a vague memory, I think something like $25 a piece, not pair. It seems to me it is more viable to pursue the whole supply, 1101, on e bay. Part number system is rather involved, it is best to get catalog and work it from there. The basic type is B series and connector size is 0B. Watch out for pin configuration, it is split, 2 male and 2 female; there is occasional listing on e bay for 4 pin unit, but all that I have seen where for all male or female contacts. I do not remember ever seeing a listing for connector used by Tektronix and I have a search running for several years for 'Lemo 4 pin'.

The 1101A as is seems quite reasonable power supply, it is all linear with reasonable internal heat sink, I do not see what a 'modern' would contribute to operation.

Best of luck,

Miroslav Pokorni

On 3/2/2014 6:38 PM, snmp_4u@... wrote:

?

I did not know the 2400's had this LEMO connector as an option.? where would those mount?

if I plan to go this route, should I spend $100 on the 1101 or just DIY my own?? I'm assuming that low noise is important in this PSU.? I know of a few low noise dual 15 psu's and 5v is probably not signal-path critical so any old 5v reg would do.? do you agree?

how hard is it to get hold of those connectors that mate with the probes, for power?

would it be a good/bad idea to buy a used 1101 and swap out its whole psu and replace with something more modern?
 

if you can believe it, tucker had a psu on sale and it was affordable, too!? tucker?? affordable??? seriously??? lol



so I grabbed that one due to the 'sale' price offered (under $75).

those connectors are hella expensive and the psu was cheaper than 4 connectors, alone.

I've never seen those connectors before, btw.? they must have limited use (tek only?)
 

alright, I now have the PSU and a p6202a on the way.

is there anything the p6201 gives me that I should look into?? if I see one cheap come up, is it worth adding to my collection?? it looks bigger and that's not usually a great thing.? the ones I see on ebay seem to have a good set of tips for them but it seems like such a very old design.? not sure its worth having if I already am getting 6202.? ???
 

Ah, a probe that has no effect on the circuit - a bit like a perpetual motion machine really :-) . ?Well, as high impedance doesn't exist at VHF a high resistance probe (passive or active) does you little good at high frequencies because the shunt capacitance soon becomes dominant and?drags the impedance down to the kilo-ohm level, resulting in a big difference in the attenuation ratio from LF to HF and hence distortion of the displayed waveform. Its main advantage is a higher sensitivity than a passive probe. In?many case you'd be better off with a 10:1, 50 ohm passive probe for HF work. The impedance variation with?frequency is much less with this probe so distortion will be less, but of course you always have to make a small correction for the loading effect on the signal, which is usually from a 50 or 75 ohm environment.?

If you have a critical application and really need to measure with minimal effect on the signal the only practical solution is to build a dummy?plug-in?probe into the circuit?with exactly the same characteristics as the scope/probe combination that will be used for measurement, and replace the dummy with the real probe when making the measurement. As insertion of the real probe does not load the circuit it can be low impedance (typically 50 ohm) and so will feed directly into your 50 ohm scope input. ?As this setup is easily built yourself it is a far cheaper option than an active probe if your circuit can be modified in this way.

If 500MHz scope bandwidth is too low you may want to go to a sampling system instead of getting a 7104. The cost should be no more, you just have to be careful with input signal level. As sampling is inherently 50 ohm it's a great match for the dummy probe system while frequency response and sensitivity are so much better than the 7104, if somewhat noisier. Only good for repetitive signals though - no good for looking at transients or finding glitches.

Peter.
K5MYJ
 

?
I thought FET probes such as the 6201 were made to reduce loading on VHF/UHF circuits?
?
Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"

----- Original Message -----
Sent: Tuesday, March 04, 2014 7:40 AM
Subject: [TekScopes] RE: 2400 series probes (is p6137 the most optimal?)

?

Ah, a probe that has no effect on the circuit - a bit like a perpetual motion machine really :-) . ?Well, as high impedance doesn't exist at VHF a high resistance probe (passive or active) does you little good at high frequencies because the shunt capacitance soon becomes dominant and?drags the impedance down to the kilo-ohm level, resulting in a big difference in the attenuation ratio from LF to HF and hence distortion of the displayed waveform. Its main advantage is a higher sensitivity than a passive probe. In?many case you'd be better off with a 10:1, 50 ohm passive probe for HF work. The impedance variation with?frequency is much less with this probe so distortion will be less, but of course you always have to make a small correction for the loading effect on the signal, which is usually from a 50 or 75 ohm environment.?


If you have a critical application and really need to measure with minimal effect on the signal the only practical solution is to build a dummy?plug-in?probe into the circuit?with exactly the same characteristics as the scope/probe combination that will be used for measurement, and replace the dummy with the real probe when making the measurement. As insertion of the real probe does not load the circuit it can be low impedance (typically 50 ohm) and so will feed directly into your 50 ohm scope input. ?As this setup is easily built yourself it is a far cheaper option than an active probe if your circuit can be modified in this way.

If 500MHz scope bandwidth is too low you may want to go to a sampling system instead of getting a 7104. The cost should be no more, you just have to be careful with input signal level. As sampling is inherently 50 ohm it's a great match for the dummy probe system while frequency response and sensitivity are so much better than the 7104, if somewhat noisier. Only good for repetitive signals though - no good for looking at transients or finding glitches.

Peter.
 

Yes, the key word is "reduce" - not eliminate. You always have some capacitance to worry about, so?as the frequency and z level go up, the probe becomes more of a burden on the circuit.

?

You have to be aware of the relative effects, based on the application and experience. Instinct and on the fly mental processing are usually sufficient to compensate for what's observed when probing around for diagnostic purposes, but not for high precision measurements. Sometimes, the probe just can not work because it upsets the circuit too much. On the other hand, sometimes a circuit will work with the probe attached, but not without it - the effects can go either way, but usually tell you something.

?

Ed
 

They do reduce loading at high frequencies. The recommended 400 MHz P6137 x10
passive probe has a capacitive loading of 10.8 pF but the 500 MHz P6202A x10
active probe has a loading of 2.0 pF. Passive low impedance probes are in the 1
pF range.

The example homemade probe circuits I posted about that use a 2N5486 UHF JFET
have a capacitive loading below even that. Bob Pease said 0.45 pF for his with
a bandwidth of 90 MHz but I wonder how much faster it would be with the RF
transistor output stage that Jim Williams included with his. They achieve a
lower input capacitance because they lack input protection. These would make
for a fun general availability kit project . . . hmm.

On Tue, 4 Mar 2014 07:59:31 -0800, you wrote:

I thought FET probes such as the 6201 were made to reduce loading on VHF/UHF circuits?

Bob Macklin
K5MYJ
Seattle, Wa.
 

On 04 Mar 2014 07:40:20 -0800, you wrote:

If you have a critical application and really need to measure with minimal effect on the signal the only practical solution is to build a dummy plug-in probe into the circuit with exactly the same characteristics as the scope/probe combination that will be used for measurement, and replace the dummy with the real probe when making the measurement. As insertion of the real probe does not load the circuit it can be low impedance (typically 50 ohm) and so will feed directly into your 50 ohm scope input. As this setup is easily built yourself it is a far cheaper option than an active probe if your circuit can be modified in this way.
Tektronix mentions a way to do this in the 7S11 manual on page 2-14. A load or
gain setting resistor which is grounded at one end can be replaced with an R
minus 50 ohm resistor and 50 ohm transmission line going to the 50 ohm
oscilloscope input.

If 500MHz scope bandwidth is too low you may want to go to a sampling system instead of getting a 7104. The cost should be no more, you just have to be careful with input signal level. As sampling is inherently 50 ohm it's a great match for the dummy probe system while frequency response and sensitivity are so much better than the 7104, if somewhat noisier. Only good for repetitive signals though - no good for looking at transients or finding glitches.
If you have a persistent display you can find glitches. The low sampling rate
of the oscilloscope may make the time required impractical though. Digital
storage oscilloscopes with low waveform acquisition rates have the same problem.
K5MYJ
 

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I have a 475 scope. I know the 485 is a 350MHz scope.
?
How do higher frequency scopes work? I have been considering using a converter in front of my 475 to work in the UHF ham band regions.
?
I can use the down converter for lower frequency counters also.
?
I retired as?an EE in 1998 (not voluntarily!)
?
Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"?

----- Original Message -----
From: David
Sent: Tuesday, March 04, 2014 10:03 AM
Subject: Re: [TekScopes] RE: 2400 series probes (is p6137 the most optimal?)

?

On 04 Mar 2014 07:40:20 -0800, you wrote:

> If you have a critical application and really need to measure with minimal effect on the signal the only practical solution is to build a dummy plug-in probe into the circuit with exactly the same characteristics as the scope/probe combination that will be used for measurement, and replace the dummy with the real probe when making the measurement. As insertion of the real probe does not load the circuit it can be low impedance (typically 50 ohm) and so will feed directly into your 50 ohm scope input. As this setup is easily built yourself it is a far cheaper option than an active probe if your circuit can be modified in this way.

Tektronix mentions a way to do this in the 7S11 manual on page 2-14. A load or
gain setting resistor which is grounded at one end can be replaced with an R
minus 50 ohm resistor and 50 ohm transmission line going to the 50 ohm
oscilloscope input.

> If 500MHz scope bandwidth is too low you may want to go to a sampling system instead of getting a 7104. The cost should be no more, you just have to be careful with input signal level. As sampling is inherently 50 ohm it's a great match for the dummy probe system while frequency response and sensitivity are so much better than the 7104, if somewhat noisier. Only good for repetitive signals though - no good for looking at transients or finding glitches.

If you have a persistent display you can find glitches. The low sampling rate
of the oscilloscope may make the time required impractical though. Digital
storage oscilloscopes with low waveform acquisition rates have the same problem.
 

Did you mean option 11, option 22 was two extra probes.
Jeff

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