Products > Test Equipment

Another radio amateur about to buy a DSO ...

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tggzzz:

--- Quote from: Mike99 on November 16, 2023, 12:29:32 am ---
--- Quote from: ebastler on November 15, 2023, 01:13:17 pm ---
--- Quote from: 2N3055 on November 15, 2023, 01:02:43 pm ---Anyways, it shows 50Ω path is not made by simply putting 50Ω terminator in parallel with 1MΩ/20pF input...

--- End quote ---

This would be a nice opportunity to demonstrate the difference.
@Mike99, any chance you could repeat the measurement with the scope's input set to 1 MOhm and an external 50 Ohm pass-through terminator? Thanks!

--- End quote ---

I don't have a pass through terminator, only a 6dB BNC attenuator.

Mike

--- End quote ---

A 6dB passthrough attenuator followed by the imperfect internal attenuation will be better at reducing VSWR than an external terminator. That technique is frequently used inside equipment where components/subsystems have poor impedance matching.

Basic principle: gain is easy and cheap, wideband matching is difficult and expensive. But don't stick an attenuator in front of a low-noise front end, of course :)

Mike99:
I have made some more measurements.

First was the 50 ohm input bandwidth, measured using an RF millivoltmeter:



Next was input VSWR. The graph compares the 50 ohm input with the 1Mohm input, the latter using a T piece with a 50 ohm load.



Finally, the impedance of the 1Mohm input.



Mike

Orange:
Hi Mike,

An impedance plot for 50 Ohms would make this information complete :-)

Mike99:

--- Quote from: Orange on November 16, 2023, 12:52:39 pm ---Hi Mike,

An impedance plot for 50 Ohms would make this information complete :-)

--- End quote ---

OK I'll do that later today.

Mike

dshorthill:
I use this device to monitor the RF output of  a 1 kw ham amplfier on my 1204xe Siglent scope.  I have a bnc t with a 50 ohm termination on the scope end.  Works great.

https://www.ebay.com/itm/193686855709

Dave
k1xd

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