Yes, Jim, but: "It's also the kind of destructive failure that the use of MOV surge protectors can CAUSE".
MOV can be used even in AC power applications (50/60Hz) , but only if the potential thermal run away effect ( drawing more leakage current after energy absorption/exposure or by aging ) is controlled by a series connected high impedance (no-fire mode) spark gap. What is however critical under non-fire RF conditions (MOV -ZnO has big nF capacitance and is a semiconductor) is the nonlinear diode effect. This can lead to RF rectification (harmonics, emission issue) before the firing level is reached. 73 Andy HB9CVQ -----Original Message----- From: [email protected] <[email protected]> On Behalf Of Jim Brown Sent: Montag, 18. Januar 2021 19:16 To: [email protected] Subject: Re: [Elecraft] Automatic lightning protection for radios, .... an off the wall idea On 1/18/2021 9:09 AM, Bill Frantz wrote: > While serious lightning protection for structures and other robust > things must be done outside the building, I have heard reports of K3S > USB chips being fried from currents induced in the USB cable attached > to the radio, with the suggestion of disconnecting the cable to > protect the chip. I don't see how to do this disconnect outside the building. Right. That is the kind of failure that proper grounding and bonding are able to protect against. It's also the kind of destructive failure that the use of MOV surge protectors can CAUSE. > When I consider a direct strike on my shack's lighting rods, I see > massive currents flowing down the thick aluminum cables from the rods > to the grounding system. I see these currents inducing currents in any > wires in the house, including the USB cable. The lightning rods are > the first level of protection, but may not be enough to protect > sensitive electronic equipment. Remember, when we work on these > radios, we have a grounding wrist strap and a conductive mat on the work surface etc. That's another thing the proper grounding and bonding protect against. But lightning induces current not only on that external wiring, but also wiring within the building. IEEE studies show that up to 3kV can be induced on internal wiring by a strike! 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
