[TowerTalk] A DC in Coax Question

[Dan Zimmerman N3OX]

> There haven't been any problems YET. I'm concerned that at some frequency I'll end up with a series resonant circuit shunting lots of RF to ground.
>
> How can I check for such a situation? And can I check just the unit connected to a dummy >lod or will each antenna /feedline combo have to be checked?

Putting a dummy load on the output of the feedline carrying DC and
sweeping the whole frequency range of interest with an SWR analyzer
will work fine.  If the coil used has any series resonances on its
own, or via capacitance to the shielding box, you'll see them.

Dan