A Long 5 element LFA Yagi for 50MHz with a 4.9mtr boom

Premium commercial versions of this antenna at Innovantennas

If you suffer with noise from living in the city, this is another low-noise antenna from G0KSC

This antenna has been designed in order to minimise the upward and downward lobes typically seen the the EL plane on Yagi antennas. By doing this, a drastic reduction in pick up of unwanted noise in City locations is the result. The double bonus is the likelihood  of reducing transmitted interference too. However, this version is not a model with optimum suppression which would see a reduction in forward gain of 1dB. If you suffer with very bad noise on 50MHz and have room for an antenna of this size, Email me for details of the very high suppression version.

This antenna can be built with Metric or Imperial sized tubing:

The 4.9m lonf 5el LFA at JA2DDN

The 4.9m 5el 50MHz LFA at EI7BA - above this is a 8el 2m LFA Yagi

Performance

Gain: 11.01dBi @ 50.150MHz

F/B: 19.37dB @ 50.150MHz

Peak Gain: 11.04dBi

Peak F/B: 19.98dB

SWR: Below 1.1.1 from 50MHz to 50.600MHz

Construction

For full details of how to make the LFA, read here: http://www.g0ksc.co.uk/making-the-lfa-loop.html

Email for different tube sizes, for 12mm loop reduce to 1.238mm

Antenna Dimensions for 10/13mm tube

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.484                                             10mm or 3/8 inch

DE1                      .319                          1.239    (1.240 for 12mm Tube)        13mm or 1/2 inch

DE2                      .864                          1.239    (1.240 for 12mm Tube)         13mm or 1/2 inch

D1                       1.543                         1.390                                             10mm or 3/8 inch

D2                       3.055                         1.342                                             10mm or 3/8 inch

D3                       4.865                         1.299                                             10mm or 3/8 inch

Antenna Dimensions for all elements in 12mm with 10mm loop ends

Spacing                      Half Element Size  in Metres              Element Diameter

Reflector                0                              1.4855                                            12mm

DE1                      .288                          1.2455              feedpoint                 12mm

DE2                      .823                          1.2455                                            12mm

D1                       1.471                         1.3835                                            12mm

D2                       3.014                         1.3285                                            12mm

D3                       4.900                         1.2775                                            12mm

The ends of DE1 and DE2 are connected together with 10mm or 3/8 inch tube. The Feed point is the centre of DE1.

NOTE: SWR will not read as per the graph below if you use a package with mininec or nec2 the swr graph is correct and confirmed within nec4 and through building this antenna.

Any questions, please ask!

Justin G0KSC

A 11el 12.5 Ohm 50MHz Optimised Wideband Low impedance (OWL) Yagi

Revised  February 2010

Premium commercial versions of this antenna at Innovantennas

The OWL by G0KSC provides the benefits of both OWA (Optimised wideband Array) 50 Ohm antennas with those of traditional low impedance antennas. More information on the OWL can be found here

Visit HERE to learn how to make the OWL Match/Balun

Do not look at the gain figure of this antenna and compare with other 11 element 50MHz Yagis. Compare the gain, F/B and bandwidth together against other antennas of a similar boom length. With almost 15.16dBi and a boom less than 16.6M long, this antenna will be a winner for field days and the rural Ham radio operator.

 

PLEASE NOTE:

 

• Special attention should be taken in ensuring the element spacing and sizes are absolutley correct upon a 12.5 Ohm Yagi
• If SWR is not perfect, D1 may also need to be adjusted. An analyser is reccomended for use when finalising 12.5 Ohm OWL Yagis
• Visit 'Making the OWL Match' for more information on the recommended matching methods
• Please add 2mm to each element to allow for insulator correction if using G0KSC Insulators for thru-boom and element insulators add 3mm

 

 

The Force12 17.9m long version of this antenna with 15.3dBi at KK5O - Details www.texasantennas.com

 

 

A close-up shot of the KK5O 11el fitted with the G0KSC 'Antenna Balun' - More info HERE

 

 

The G0KSC Antenna Balun fitted on this FORCE12 11el OWL from another angle

 

 

VE1JF also installed the 17.9m Force12 inc version at 255' above salt water, awsome !!

 

 

 

Performance UK/USA Version

Forward Gain:                           15.16dBi at 50.250MHz

Front to Back Ratio:              24.84dBi at 50.250MHz

Peak Gain:                                 15.2dBi

Peak F/B:                                24.88dB

Bandwidth:                               500KHZ below 1.13:1

 

Build Dimensions for UK/USA Version

Element           Spacing (m) - Half element length (m) - Element Notes

Reflector               0                1.4965             12.7mm 1/2 inch Diameter tube

DE                       .301            1.446               12.7mm  1/2 inch tube

D1                       .884            1.398               12.7mm 1/2 inch Diameter tube

D2                     1.653            1.325               12.7mm 1/2 inch Diameter tube

D3                     2.711            1.3495              12.7mm 1/2 inch Diameter tube

D4                     4.619            1.329                12.7mm 1/2 inch Diameter tube

D5                     6.871            1.307                12.7mm 1/2 inch Diameter tube

D6                     9.322            1.288                12.7mm 1/2 inch Diameter tube

D7                     11.822          1.270                12.7mm 1/2 inch Diameter tube

D8                     14.424          1.2645              12.7mm 1/2 inch Diameter tube

D9                     16.598          1.288                12.7mm 1/2 inch Diameter tube

Build Dimensions for European Version

Element           Spacing (m) -  Half element Length (m) - Element Notes

Reflector               0                  1.4975                            12mm Diameter tube

DE                       .301              1.447                              12mm Diameter tube

D1                       .884              1.399                              12mm Diameter tube

D2                     1.653              1.326                              12mm Diameter tube

D3                     2.711              1.3505                            12mm Diameter tube

D4                     4.619              1.330                              12mm Diameter tube

D5                     6.871              1.308                              12mm Diameter tube

D6                     9.322              1.289                              12mm Diameter tube

D7                     11.822            1.271                              12mm Diameter tube

D8                     14.424            1.2655                            12mm Diameter tube

D9                     16.598            1.289                              12mm Diameter tube

 

 

 

Fantastic Azimuth plot of this 11el 50MHz OWL Yagi

 

The Elevation plot is really clean too. A quiet antenna compared with most!

 

This SWR plot is taken with the Coaxial stub embedded within the EZNEC model Ever seen a 12.5 Ohm antenna like this one before? Watch how many now appear on the Internet but remember where you saw them first!

 

The G0KSC OWL element layout. Note the close spacing of the first 3 elements which give the OWL its extra gain and wide bandwidth.

 

As always, or if you have difficulty tuning, please Email me!

 

Justin G0KSC