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2m omidirectional aerial

 

2m Omnidirectional  Aerial  Project

 

This design is based on the talk Bob Nash G4GEE gave some time ago based on the article below

Look at this article.....

kf3g25cw.altervista.org/Images/6mHorizOmni.pdf

This article related to a 6m omnidirectional aerial.  Pictures below show original  ( taken from above website )

 

Tonight you are challenged to build a 2m version of this.

The end result should be an aerial that operates through the 2m band with a low SWR ( less than 1.5:1)

To test the aerial I used  an FT851 tuned over the range 144.00 to 146.00MHz switched to AM ( to give 50W carrier ) with an accurate SWR meter in series to the antenna feed.  In addition I added a coil balun just below the aerial/ coax connection.

My design was originally based on a centre frequency  of  145 MHz with loops 2% above and below this frequency.

 

Note...loop length is approximately  wavelength of chosen frequency. 

Below are the measurements of the loops ,  height = 2x width

 

          smaller loop = higher frequency                                           larger loop = lower frequency

 

                                   34 cm                                                                                                      35 cm              

 

 

 

 

65cm                                                                                             70 cm

 

 

 

 

 

 

It is important that the two loops are at right angles to each other and that the centre lines of the loops are the same.

 

See working aerial for construction details

Leave short tails of wire from the loops to allow loop interconnection to terminal block

Loops are connected in parallel

Some final adjustment may be needed to get the lowest SWR.

Bob's challenge is using USB  on the 2m band i.e. in the range 144.00 to 144.30MHz

You may want to try to build other similar aerials based on this design..

Have a go !