A Ladder Line Slim Jim for 6m.

Started by gil, January 07, 2013, 01:48:45 am

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Ah, I forgot to post this one... Completed before my 6m magnetic loop. It is a simple ladder line Slim Jim made of 450 Ohm ladder line (http://thewireman.com #551), solid copper. I wish now I had chosen the multi-strand 16AWG type (#552) because the #551 is very brittle and breaks easily. Not a problem since I mounted the antenna inside a PVC tube, but it would break soon or later if I rolled it up often for portable operations. So, the next one will be more flexible..

The idea came from: http://www.astromag.co.uk/j-pole/
It's really a Slim Jim, not a J-Pole.
Total length of the ladder line is exactly 14ft.
The quarter-wave length side is 54-3/4"
Gap is 3.15" (easier to measure 80mm).
It is fed 5.6" (14.2cm) from the bottom.

The ladder line wires are soldered together at the top and the bottom.
(If you bend the copper 90deg, it will break, solder a piece of wire between the two..).
The 80mm gap is cut without removing the plastic. I slice it, cut the copper and pull the piece out.

Here is how the antenna is fed:

Here with the Palomar Engineers RF choke kit:
(They don't seems to sell the kit anymore, but they have the ferrite beads: http://palomar-engineers.com)

The PVC tube is 10'+4' joined by a coupler and epoxied.

Here is how I attached the ladder line to the top end-cap:

SWR is 1.6:1 on 50.4, and 1.5:1 below that. I get the same SWR on my 2m copper tube Slim Jim... I haven't heard anyone on the air yet, so I can't give an on-air report. I am sure it works just fine. I will definitely make a "roll-up" model for 6m, and another for 2m, to be used with an HT. I have a 25' RG-174 patch cable that I will cut in two to feed them both. Those two antennas will be great with my KX3, and fit in a small pouch. You can make one in 20 minutes without breaking a sweat...