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Old 14th Jun 2018, 11:11 am   #21
Radio Wrangler
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Default Re: Oscilloscope bandwidth

I was saying that there are other limitations than just the Y amplifier. Once you get above 20MHz, the tube does start to be a limitation.

||Good 50 and 100MHz scopes were made without going to the expense of distributed plates, but the short plates needed were insensitive, so the sensitivity was boosted by having an electron lens after the deflectors and before the drift space to the screen. This was in the form of a helical PDA resistor arounf the end of the tube neck into the conical section, and a dome shaped mesh to screen the deflection area from the accelerator field.

Tek sold a distributed plate scope to 1GHz and a storage version as well.

I'd keep the miniscope as it is, as an interesting historic artifact and go looking for a 50 or 100MHz machine from Tek or HP. That's within the comfort and repairable zone for these things.

David
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Old 14th Jun 2018, 5:37 pm   #22
Craig Sawyers
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Default Re: Oscilloscope bandwidth

The 7104 is the 1GHz scope you are thinking of, with an electron multiplier in the CRT so you can see a single shot at 200ps per division in strong sunlight.

Their fastest analogue storage scopes were 500MHz, and could write at 8,800 divisions per microsecond in fastest storage mode (the 7934).

That is not counting the 7912HB transient digitizer, which would store single shots at 750MHz bandwidth using an astonishing internal double ended CRT with a diode array in the middle, and pull the stored traces off via GPIB.

The 7000 series was introduced in 1968 and ran for 20 years plus.
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Old 14th Jun 2018, 10:09 pm   #23
MotorBikeLes
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Default Re: Oscilloscope bandwidth

Many years ago, I bought a batch of scope tubes. In amongst them was a "double ended" tube. We simply called it a "pushmepullyou". Whilst I used quite a few, I sold the rest including the strange one to one of the used valve and tube suppliers back in about 1989.
I have an idea some pushmepullyou types (including mine?) could be visually read obliquely on one side. Did some have built in displays (Alphanumeric).
Les.
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Old 14th Jun 2018, 10:54 pm   #24
PJL
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Default Re: Oscilloscope bandwidth

I have Tek 7S11/7T11 sampling plugin set which claims to work to 14GHz. Would have been ludicrously expensive in it's day but now totally useless as it's missing the sampling head!
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Old 14th Jun 2018, 10:54 pm   #25
Craig Sawyers
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Default Re: Oscilloscope bandwidth

This is the internal CRT in a 7912HB. In its mumetal shield.
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Old 14th Jun 2018, 11:12 pm   #26
radiograham
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Default Re: Oscilloscope bandwidth

Quote:
Originally Posted by Radio Wrangler View Post
I was saying that there are other limitations than just the Y amplifier. Once you get above 20MHz, the tube does start to be a limitation.

||Good 50 and 100MHz scopes were made without going to the expense of distributed plates, but the short plates needed were insensitive, so the sensitivity was boosted by having an electron lens after the deflectors and before the drift space to the screen. This was in the form of a helical PDA resistor arounf the end of the tube neck into the conical section, and a dome shaped mesh to screen the deflection area from the accelerator field.

Tek sold a distributed plate scope to 1GHz and a storage version as well.

I'd keep the miniscope as it is, as an interesting historic artifact and go looking for a 50 or 100MHz machine from Tek or HP. That's within the comfort and repairable zone for these things.

David
Thanks for all the replies and advice,Going to look for a better scope and keep the Miniscope as original. Graham.
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Old 15th Jun 2018, 12:34 am   #27
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Default Re: Oscilloscope bandwidth

I'd be inclined to look for a S/H Tek. 475 - especially one that you can 'test before you buy', since 475s are getting a bit long in the tooth now and many are really starting to show their age. The 475 has a -3dB B/W of approx. 200 MHz.
However, to realise that figure in practice, you do need an expensive Tek. 'scope probe. The effective B/W of any 'scope + probe is determined by the B/W of each: something that is often over-looked.

For myself, my 'scope (a Tek. 2465) is THE most essential item of all my test kit. (Stated B/W 300 MHz; 'flat' to 100 MHz). Now you might not need a high B/W for what you're using a 'scope for today, but in my experience, the day when you will need the 'extra' B/W will almost certainly dawn. Unfortunately, for 'scopes, B/W is expensive.

Al.
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Last edited by Skywave; 15th Jun 2018 at 12:43 am.
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Old 15th Jun 2018, 7:36 am   #28
Craig Sawyers
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Default Re: Oscilloscope bandwidth

Quote:
Originally Posted by PJL View Post
I have Tek 7S11/7T11 sampling plugin set which claims to work to 14GHz. Would have been ludicrously expensive in it's day but now totally useless as it's missing the sampling head!
You've got to get a head. This is an S6 strutting its stuff using a 30ps pulse fall time.
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