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6M BAND RINGO ANTENNA

Reworking of an old 2m band ringo antenna for the 6m band    Under development


Having a small amount of radio equipment for this really interesting band, but not having any antennas, it was time to put this right. 

The antenna is constructed from an old Cushcraft 2m band co-linear ringo antenna and converted to the 6m band by reconstructing the matching ring and adapting the 2m band co-linear main element to a single 0.548 wavelength (3.61m) element. The length of the radiating element was determined from modelling the antenna in MMANA and optimising the antenna for best horizon radiation pattern and best SWR match.

 

Construction

The antenna is constructed from an old 2m band Ringo antenna with only radiator mounting hub and matching ring mounting hardware being retained. Some of the aluminium tubing from the main radiating element was reused with an additional 1.8m length of 10mm diameter aluminium tubing to make the new 3.61m length main radiating element. The below table along with Figure 1 Ringo drawing shows element dimensions for a selection of bands.

  

Band:  6m 4m 2m
Frequency MHz:  52.0 70.0 146.0
Main Element Length in mtr 'A' :  3.162 2.306 1.105
Ring Diameter in mtr 'B' :  0.321 0.239 0.114

  

Figure 1 Ringo element dimensions

 

Photo 1 Matching Ring assembly

 

Figure 2 Radiation plot for 52MHz were produced using MMANA antenna modeller and optimiser.

 

Figure 3 MMANA antenna model showing the a suitable 3d radiation pattern.

 

Antenna testing

With the antenna assembled on an easily accessible test mast well clear of the ground and surrounding metallic objects, the antenna was connected to an AIM 4170C antenna analyser to ascertain how the antenna loaded up.

The goal here is to find the lowest SWR for the operating frequency of 52.0MHz and ideally have the resonant frequency as close as is possible to the same frequency

The AIM 4170C produces a display of all relevant data and most importantly it can project it's analysis to the antenna end of the coax giving a truer picture of the antenna.

With modest adjustment of the matching ring tap an SWR of 1.7 was realised at 52.0Hz with a resonant frequency at 52.0MHz. The SWR was acceptably low across about 2MHz of the 6m band with only maximum of 3.0 at 50.0MHz. The phase angle shown in purple displays a shallow zero angle crossing at 52MHz indicating the resonant frequency of the antenna.

AIM 4170C antenna analyser explanation;

 

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Page last revised 17 July 2019  
 

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