NVIS Dipole, Coax choke vs Nothing 

thx for your thoughts. distance wasnt far... about 20km but about 150m hill in between. the station at home has a vertical antenna. not sure about the vertical radiation from the cable...could be. I could test that theory by changing the coax cable from hanging down to going horizontal/perpendicular away from the feed point...or even better reduce the cable length to 1m or something like that.

afterthought...the SNR were higher with the choke at the feedpoint than without. that would contradict your theory imho. also keep in mind there was a second choke at the transceiver connected.

@@CrazyChekov maybe, but not necessarily. I think the point is that the radiation pattern will be modified from the textbook dipole pattern (even more than it already is by virtue of being in a low, real-world environment). The extent to which NVIS (on a low dipole) and ground wave are more effective will also vary by frequency and time of day. If your coax alters your radiation pattern by having the coax dangling from a horizontal dipole, it will almost certainly increase the proportion of vertical polarization. Whether that’s beneficial or not will vary based on the circumstances of both stations. You’ll get more radiation from the coax if your feed point is off-center. And if you’re going for NVIS, which sounds like maybe is your case given the hill/mountain between you and Wien, you’d probably rather want to keep as much of your radiation on the dipole elements as possible. Ultimately, you’d expect the same amount of total power radiated from either choked or unchoked, only with a modified pattern. But if your unchoked coax runs on the ground, you’d probably expect some ground loss. Having the chokes may also make the receiver quieter, in some cases. But perhaps less so when out in the field. You might be curious to look at the New Carolina Windom coax-fed off-center-fed OCFD antenna (which purposefully avoids choking at the feed point and rather chokes the coax a specific length away from the feedpoint). On its fundamental frequency, in particular, it adds that vertical radiation quite a bit. It’s not exactly your experiment, but it’s an interesting implementation.

will add a test to my list with nearly no feedline at all that should clarify it. we need more accurate real world tests to verify all these theories....systematically.

I didn’t realize that the feedpoint is low enough that you’re able to eliminate the coax completely. The length that’s dangling will make a difference, and will also be band dependent. There is a reason people like Dave Cassler (sp?) will say “with antennas, everything affects everything.” If you’ve got really consistent signal paths that you want to work reliably/consistently, then the systematic tests are quite viable. But I’m afraid you’d almost need an unviable number of empirical tests in order to generalize greatly beyond that, and would have to fall back on more of a ‘systematic review’ of many published results and/or modeling. But I think it’s great that you’re publishing your findings, and will be interesting to hear about where you think theory and practical measurements seem to differ. Nice chatting with you a bit and 73!

for a dipole thats what I try to figure out. other antenna types can be a pain in the ass without them.

If you have a greater imbalance on your dipole (due to either environmental or design/execution factors), you’ll probably see more benefit. The benefit will probably arise from less than ideal/textbook setups for a horizontal dipole, but could be useful for a dipole in other orientations etc.

I just doesn't pay to over think a dipole.