If the effect is real, not hokum, I assume it would be extremely subtle and easily “reset” with a tiny a.c. current. In other words, it would disappear the next time you put the cable into use. From: Gert Gremmen F4LDP <[email protected]> Sent: August 13, 2025 6:57 AM To: [email protected] Subject: Re: [PSES] Shielded cables at dc Well the theory is not that well evolved yet, but it might be parametric storage (memory) in the dielectric (Indeed) that gets re-triggerd once the cable is at rest. If not connected, the QRM cannot leave the cable (SWR=infinite) and "polarizes" the dielectricum. Rinsing it a sufficient amplitude DC will iron out the storage, and make the cable suitable for its purpose. Everytime i drink a beer the mechanisme shows crystal clear, the day after its gone ....
May be our friend Doug has some enlightening ideas on this ? (sorry Doug, not Dough as i inadvertently wrote). On 13-8-2025 14:50, John Woodgate wrote: Hi, Gert. Can you please explain a bit more? Do you mean stored charge in the dielectric? I suppose that if the cable is non-uniform, either due to construction of damage in usage, there might be separated charges in different places along the cable? I can't see that any alternating voltages or currents could occur. On 2025-08-13 13:40, Gert Gremmen F4LDP wrote: In EMC world it is of utmost importance to rinse coaxial cables with clean DC before using them as a snesituve measurement cable. It's what i learned my customers before a beer (or was it after the beer ? not sure) You never know what QRM is left over from a previous measurement/ application! Is that what you meant to address , Dough ? On 13-8-2025 7:07, doug emcesd.com wrote: We all know that coaxial cables have some pretty amazing properties for ac signals. But at DC they also have different but still amazing properties. Anyone here use coaxial cables for dc power, nothing to do with ac "noise" shielding like we usually use them? Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 Email: [email protected] <mailto:[email protected]> Website: http://dsmith.org _____ This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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