I look at a coaxial cable in this context as a capacitor with a
polythene dielectric. I guess that even RG174 could withstand 1 kV, so
quite a lot of energy could be stored in a 100 m length. A similar cable
with PET dielectric could store far more (more volts and much more
capacitance).
On 2025-08-13 22:38, Ralph McDiarmid wrote:
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
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Email: [email protected]
Website: http://dsmith.org
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