On 2/4/21 12:00 PM, Thomas Kerns wrote:
Thanks for the help. I don't remember exactly what I was doing at the moment it quit, but I had been measuring a long run of coax, and I had also measured the swr of an outdoor antenna (a 160 meter dipole). That is a lot of wire in the air, with the potential to pick up static, I suppose. I wonder the best way to protect my vna in the future.
I see someone mentioned a drain resistor. Would this be something I would do only when testing? ie make a coax pigtail with a drain resistor across from the shield to the center? would that affect measurements?
It's a good practice in general to "permanently" have a leakage path to ground.? A 100k or 1 meg resistor in a Coax T is one way. If you get a big transient, it will probably fail, so that makes an ohmmeter a useful diagnostic tool <grin>
Some people use a RF choke that has high Z at the operating frequency, but lower DC resistance to bleed the charge faster.
?Standard 0.405" coax (RG-8, RG-213) is about 40 pF/meter, so a 100 ft/30meter run is 1200pF.
