On Jun 25, 1:17*pm, Roy Lewallen wrote:
There can be substantial radiation from an OCF dipole feedline even with
an effective choke in place. The asymmetrical positioning of the
feedline relative to the antenna results in a net induced common mode
current, while a choke only stops the current at one point. Effective
reduction of induced current can require two chokes placed about a
quarter wavelength apart, which isn't practical for a multi-band
antenna. In practice, you might have to fiddle with the feedline length
(since some lengths will result in more current than others on
particular bands) in addition to using two or more chokes in order to
drop the feedline radiation to a tolerable level. I think that with an
OCF dipole you've just about got to expect some feedline radiation.

Roy Lewallen, W7EL

Thanks Roy. You've pretty much confirmed what everyone else is saying
regarding feedline radiation. Hadn't thought about the induced
contributor from the asymmetrical configuration. So a 90 degree
feedline takeoff in this situation would still result in induced
current it would appear. I added a wire simulating the radiating
feedline conductor in my EZNEC model. It appears from the FF patterns
it may be helping in some directions.

While I've got you, is there any way in EZNEC to add an RF ground
counterpoise at the source end of my model? I have a long wire at my
common equipment ground point to better enable RF grounding on my
equipment and would like to see if EZNEC can tell me anything about
its effectiveness. I can't figure out how to tie the wire in to only
the ground side of a source. I read up on split sources but still
can't be sure I'm doing this correctly.

73
Dykes (AD5VS)