Sigma 4 / Vector 4000

[Marconi]

That is interesting. Now I have to figure out why I need a choke on my 4k.

STM, do you have a perfect match to your feed line on your NV4K?

Do neighbors tell you they hears you talking on their phone, toaster, and/or washing machine?

 

[Shadetree Mechanic]

STM, do you have a perfect match to your feed line on your NV4K?

Do neighbors tell you they hears you talking on their phone, toaster, and/or washing machine?

When I first put it up, I was able to get a good match (swr) but I would turn the lights on and off in the china cabinet. I got reports that something is terribly wrong with my station. RF in the audio, Spark Plug played back my audio to me, and it had a loud buzz almost covering up the audio. I ended up winding a choke of 240 flex at the feed point and grounded the equipment in my shack and that took care of my problem. I am also running a low pass filter now. I have no idea what the reactance of my antenna is though. I plan on getting one of those Nano anaylizers soon.

 

[Shockwave]

Steve, I don't believe I've ever heard this idea on Common Mode Currents explained this way before. This thread is about the S4/Vector4K. Does your idea here work the same with other CB vertical antenna designs, or is this idea unique with the S4/V4K design?

To elaborate further, with my VHF version, if the antenna is operated with noticeable reflected power, I can hold the feedline at various points and shift that VSWR and bandwidth just as noticeably. With a match close to perfect, nothing I can do with that cable can shift the bandwidth unless it's pulled horizontal, directly under the antenna and in its pattern. I will say, with the shorter cone that did not shield the entire 1/4 wavelength inside of it, CMC could be detected even when the gamma was adjusted for a good match. This may have more to do with having the phase between the cone and the center radiator aligning up so that they are perfectly inverted rather than the impedance match itself.