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DIY active probe - another approach (BUF802)
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IAmBack:

--- Quote from: luudee on November 23, 2022, 12:35:39 pm ---
Is this a regular FR4 ?

May be something like a Megtron-6 would be a better choice?

luudee

--- End quote ---

It's thin (1mm) FR4.
colorado.rob:

--- Quote from: luudee on November 23, 2022, 12:35:39 pm ---Is this a regular FR4 ?

May be something like a Megtron-6 would be a better choice?

--- End quote ---

Wouldn't this turn a $3 PCB into a $300 PCB (minimum)?
nctnico:

--- Quote from: colorado.rob on November 23, 2022, 07:35:31 pm ---
--- Quote from: luudee on November 23, 2022, 12:35:39 pm ---Is this a regular FR4 ?

May be something like a Megtron-6 would be a better choice?

--- End quote ---

Wouldn't this turn a $3 PCB into a $300 PCB (minimum)?

--- End quote ---
And it is not really necessary. With a good PCB design, the traces will be very short anyway. Lots of designs run several GHz over FR4.
Berni:

--- Quote from: colorado.rob on November 23, 2022, 07:35:31 pm ---
--- Quote from: luudee on November 23, 2022, 12:35:39 pm ---Is this a regular FR4 ?
May be something like a Megtron-6 would be a better choice?

--- End quote ---
Wouldn't this turn a $3 PCB into a $300 PCB (minimum)?

--- End quote ---

Yep FR4 is perfectly fine for it and it is dirt cheep from china. You can do most high speed things on it, especially on 4 layer boards that let you keep a ground plane nice and close.

Excuses for fancy PCB core materials might be very large loads that make short traces impossible but need very stable conditions or when building various filter and coupler structures into the PCB as distributed elements. The sort of designs where you do an EM simulation before even manufacturing the board.
nctnico:

--- Quote from: Berni on November 24, 2022, 06:08:40 am ---
--- Quote from: colorado.rob on November 23, 2022, 07:35:31 pm ---
--- Quote from: luudee on November 23, 2022, 12:35:39 pm ---Is this a regular FR4 ?
May be something like a Megtron-6 would be a better choice?

--- End quote ---
Wouldn't this turn a $3 PCB into a $300 PCB (minimum)?

--- End quote ---

Yep FR4 is perfectly fine for it and it is dirt cheep from china. You can do most high speed things on it, especially on 4 layer boards that let you keep a ground plane nice and close.

--- End quote ---
Having a 4 layer board is not always a blessing for RF stuff. First the stackup needs to be controlled as in the PCB needs to be build according to the dielectric thicknesses you specify. Otherwise the impedances may be off. Secondly, with a thinner dielectric, the traces get thinner so variation in width of the trace gives you a larger relative error. For my 1.4GHz differential probe design I have used a 2 layer board; it is good enough and keeps things simple.
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