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1

The effect you have observed has nothing to do with transmission lines. You need to consider 'skin effect'. You'll find it in any good RF textbook, such as Terman, Radio Engineering. Basically, as the frequency increases, the main current flow moves further from the conductor's centre, ie, the current flows in the skin of the conductor. The higher the ...


25

Your tooling seems to be the cause there, not the cable. From https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=1428419&nid=-32775.536879654&id=1428419 The 4294A extends its measurement frequency range up to 110 MHz by terminating each measurement terminal with 50 ohm in order to eliminate the resonance of test leads (...


1

Consider the cable (I assume coax) as a string of small inductors with capacitors at the junction of each pair of inductors to ground (the shield). At low frequencies the inductors act as they would with near DC signals (a wire) and the capacitors would be near opens at the near DC signals. As the frequency goes up the inductors have more reactance and the ...


20

Something as simple as a cable does not have discontinuities like that. There may be a clue in the fact the problem occurs at a nice round number, 5MHz. Is this a place where your test set changes ranges? Maybe it changes output amplifier, or filter, and one of them is broken or damaged. The fact that you've quoted measurements at 4.99MHz and 5.01MHz ...


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