Monday, 14 September 2015

A Super J-Pole Antenna for the 4m (70Mhz) Amateur band.


A Super J-Pole Antenna for the 70Mhz (4m) Amateur band.
The Vortex ‘Super J-Pole’ Antenna consists of a five eighth wave vertical radiator, a half wave tuning section and a half wave top section. At the base, a quarter wave matching stub forms the classic ‘J Shape’. The addition of the extra half wave top section boosts the gain over a standard J-Pole. The Super J-Pole has an added advantage that tuning can be varied over a fairly wide frequency range by moving the feed-point location up or down. This also gives the user finer control over the impedance and match. The antenna is end fed and has an omni-directional radiation pattern and requires no ground plane or radials. The antenna has a nice low angle of radiation, typically 8 degrees when mounted at 4m in height. This angle reduces further the higher the antenna is mounted. A typical installation with the antenna at 8 meters above ground sees the angle reduce to 5 degrees and the gain increases to 7.29dbi when ground reflections are added.


J-Poles should include a 1 to 1 ‘Choke Balun’ close to the feedpoint, which prevents feedline radiation. A simple and cost effective solution is to wind a small length of coaxial cable around a former. Vortex can also supply this if required in commercial grade ®Westflex 103 Coaxial Cable .
A Vortex Antenna Systems premium ‘Ferrite Core 3kw Choke Balun’ (Sealed to IP67 rating) is also available as an optional extra.


The 70Mhz antenna is pre-tuned from the factory and all set-up measurements are included. However the system is fully adjustable should the user require to finely tune the system for their own requirements. A full set-up instruction sheet with each antenna.


All Vortex Antenna Systems Super J-Poles use heavy duty components and hardware including M10 stainless hardware, heavy duty Stauff polyamide and aluminium clamps as also used in the lower frequency base antennas. The main element section of this antenna is 5 sections of genuine VORTEX 6082-T6 or **AA6082-T6 Aluminium each section telescoping into its counterpart. 16mm tube is used for the adjacent matching section. The feed from the SO239 socket is twin 6mm 762 strand
low-loss oxygen free copper flex to minimise losses. The half wave tuning section is supported with 2mm Mastrant professional synthetic guying line and marine grade (316) stainless fittings.




See info below for mechanical and electrical details:

Band:
70Mhz (4m Amateur Frequencies).

Element Material:
6082T6 or AA6082T6 Aluminium Tube (VORTEX).

Gain:
Freespace 4.15dbi. Typical over 6.1dbi when mounted 4m above ground.

Matching:
None – Direct Twin Line to Feedpoint. Twin Line is positioned for best match.

Feed:
Via SO239 Socket.

Hardware:
All stainless steel hardware.

Element Clamps:
Heavy Duty Polyamide and Aluminium.

Antenna Weight:
5kg.

SO239 to Antenna Feed:
6mm 762 Strand Oxygen Free Multistanded Copper Twin Conductors.

Mounting Plate:
6.35mm 6082-T6 Aluminium Plate and kit to mount antenna to 2 or 2.5 inch mast.

Height:
4.8m.

Power Rating:
2kw.


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