Electronics > RF, Microwave, Ham Radio

15m long RG-213 with a notch at 450 MHz

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One might even make the argument that toroids, being on the outside, should not effect the impedance at all, unless the shielding was dysfunctional. (in some way)

I actually have some clip on toroids that I leave on my nanovna2's test leads all the time, to decouple the leads from the shields. I dont see any reason to not do that, and several reasons to do it.

I mostly do it because of high RF noise in my area.

Sometimes I squeeze coax between my fingers (not too hard) i order to "see" if I can locate where a fault is by the changed point. But that doesn't always work.

Paul B:

hi just a thought try changing the BNC connectors for TNC this should be an improvement and eliminate
any  bad joint  then repeat experiment without any BNC connectors in the CCT

I don't have any TNC suitable for RG-213; i.e. OD10 mm. I have fitted the same model of BNC connectors to other coax without any issue.

Paul B:

The fault you have is strange but If you do not have TNC you could try N  The reason to change from BNC is 2 fold first from experience BNC connectors are not good at 1 Ghz when the joint is flexed  / moved  this was found out on the in and out of a inter digital filter changing just the outer-cases to TNC fixed the problem
the second is that there are a lot of very cheap BNC connectors and i have herd form others that the insulation can be suspect from memery of the picture assume you have not used screw on connectors Paul 

I don't want to go to the trouble of changing to another connector type, especially one which I don't have a cal-kit for, when the available evidences do NOT point to the BNC connector:
1. I have other cables using the same BNC connector model without issue, including the one which I posted in reply #8
2. Telegartner has been selling this BNC connector model for decades and any problem would have surfaced by now

Thanks to all for the responses!


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