Sal M. Onella Inscribed thus:

On Jul 15, 12:33Â*pm, Baron
wrote:
Peter Inscribed thus:

Hi all

I have just modelled both the Slim Jim antenna and J Pole antenna
using MMANA-GAL at the same frequency (145MHz) all other parameter
equal and was some what surprised that they appear exhibit the same
gain and radiation pattern. Based on an article I read in a English
magazine many years ago I have always believed the Slim Jim had a
slight edge over the J Pole. Wonder if others had a similar view
and if my modelling is correct are there any advantages with the
Slim Jim design?

The difference is negligible. They both suffer from unbalanced feed
currents and thus feeder radiation. Â*There is or was a commercial
design that attempted to reduce that.

73's
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Best Regards:
Baron.

I only did it once but the j-pole design papers often call for the
feedline to be coiled tightly -- a few turns -- just below the feed
point. I have made and used several of these "choke baluns" for HF
because failure to use a balun seems to screw up my VSWR readings.
Does this strictly apply to 2m j-poles, too? I don't know.

"Sal"
(KD6VKW)

A few (2 - 4) ferrite beads, the sort used on the glass computer monitor
video lead, works very well slipped over the co-ax just below the
bottom of the J. Best of all you can get them for free...

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Best Regards:
Baron.