Menu

Slim Jim v J Pole

Search this Thread

Previous Post

Next Post

#11

Report Post

Old

July 17th 10, 06:56 AM posted to rec.radio.amateur.antenna

Owen Duffy Owen Duffy is offline

Owen Duffy is offline

external usenet poster

First recorded activity by RadioBanter: Dec 2006

Posts: 1,169

Default

Slim Jim v J Pole

"Sal M. Onella" wrote in news:cc6de1f9-fa1d-4a1c-bf7f-
:

Does the velocity factor of the coax come into play when locating the
second
choke or does the outer shield behave like an open wire, VF ~ 1.0?

Perhaps I am slicing the baloney too thin for an average sandwich ;-)

You will often see emphatic advice as to which side of the thing to
attach the shield, and which the centre conductor.

In fact, the antenna structure lends itself to an effective integral
balun. If you take the feed coax through the bottom wall of the U
section, bonding the shield to the tube, and up one side (doesn't
matter), exiting at the appropriate point. At this exit, trim the shield
and bond it to the tube, and take the inner horizontally across to the
other tube and connect it.

If physical symmetry is very good, the balun will be very good.

Nevertheless, as Roy observes, the feedline and supporting structure
below the U section is coupled and there is still potential for some
level of common mode current.

(To preempt Roy, the velocity factor of the outside surface of the shield
clad with a thin layer of vinyl will be close to 1, close enough for the
purpose at hand.)

Owen

Reply With Quote

Reply With Quote

Thread Tools	Search this Thread
Show Printable Version	Search this Thread: Advanced Search
Display Modes
Switch to Linear Mode Switch to Hybrid Mode Threaded Mode

Posting Rules
Smilies are On [IMG] code is On HTML code is Off Trackbacks are On Pingbacks are On Refbacks are On

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Help with slim jim nec model	[email protected]	Antenna	23	April 17th 13 05:54 AM
J-Pole vs Slim Jim?	Ian Jackson	Antenna	4	February 10th 07 02:55 PM
Slim Jim vs. EZNEC	RST Engineering	Antenna	9	January 24th 07 12:55 AM
Helical wound slim jim?	John Smith	Antenna	103	April 22nd 05 04:08 PM
Anyone here of a "SLim Jim" antenna?	[email protected]	Antenna	9	January 19th 05 08:09 PM

All times are GMT +1. The time now is 09:42 AM.

About Us

"It's about Radio"

Contact Us RadioBanter forum home Privacy Statement

Copyright © 2017