On an Ethernet cable you can’t use an inductor because it would block the Ethernet signal. So you use a ferrite tuned to specific frequencies you want to block. The other thing is you typically put all 8 wires through the ferrite, so it is only blocking common mode signals.
DC cables give you a lot more leeway to block everything except DC. Including fast risetime surges. You could think of the inductor and the distributed capacitance of the cable forming an LC filter. That does however make you wonder what you are protecting, and from what. From: AF <[email protected]> On Behalf Of Adam Moffett Sent: Wednesday, May 28, 2025 7:00 PM To: AnimalFarm Microwave Users Group <[email protected]> Subject: Re: [AFMUG] Tarana power cable with inductor I recall we were having problems on an AM tower, and after consulting with the station engineer we added ferrite cores on all of our cables that were tuned for AM frequencies. He told us that as a side benefit the ferrite core would help us stop blowing ethernet ports during thunderstorms (which had been happening). I don't claim to understand all the magic, but that engineer was right and we did stop losing ethernet ports. Incidentally, all of the ferrite cores we installed on our cables on the AM tower were warm to the touch, so I guess they were soaking up the AM radio signal off of our cables. I'm not sure if this is what you meant by inductor, but I think a ferrite core is technically an inductor, and you sometimes see them built into DC power cables. If that's what it is, it won't hurt and from my anecdotal experience it might help. -Adam On Wed, May 28, 2025 at 7:44 PM Adam Moffett <[email protected] <mailto:[email protected]> > wrote: By inductor do you mean a ferrite core? On Wed, May 28, 2025 at 6:01 PM castarritt <[email protected] <mailto:[email protected]> > wrote: Tarana is telling everyone to switch to a DC power cable for their radios that has a big inductor for surge suppression. Is that really a good idea though? We use a Transtector DC Defender (SASD based) SPD at each BN, and they want the inductor in between the SPD and the radio. If the only surge event that we needed to worry about was a voltage spike on the DC line, this might make sense, but that's not what happens when the tower is struck by lightning, right? The whole structure and the radio chassis/ground is getting energized when the site is struck, and my understanding is that the DC lines need to be brought to the same potential by the SPDs to avoid damage. Wouldn't putting an inductor on the DC line between the SPD and the radio be counter productive? -- AF mailing list [email protected] <mailto:[email protected]> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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