On 01/10/10 05:06, Dave D wrote:
On Sep 30, 12:28 am, wrote:
On 30/09/10 15:23, Dave D wrote:

Thanks guys... I've never had that problem before. Any tips for what
clamp-on ferrites might work best, or how many? Or the best way to
configure them?

I meant also to ask how you dressed the coax away from the feedpoint.

I often see pics of coax tie wrapped to one leg of the transmission line
spine of the LP. Guaranteed to create common mode current.


Thanks Owen,

In this case I had it down the middle between the haves, through clips.

Does that disturb the characteristic impedance of the spine transmission
line? If so, does that contribute to the problems you observe?

If this LP is mounted to a mast somewhere forward of the rear element, I
would consider dressing the feedline away from the feed point at right
angles to the spine, installing a common mode choke near the feedpoint,
and bringing the feedline to the mast some distance below the spine.

If you were to perform a test where the LP is mounted a wavelength or
more above ground, pointing to the zenith, feedline falling downwards
from the feedpoint, common mode choke near the feedpoint, it would
reveal whether the array is working as intended. If your actual mounting
causes it to work differently, you know where the problem is.

Owen