Log periodic dipole antenna - LP
VU2GRM-Mr.Ram Mohan G. Cell-9342187220
This type of antenna is used in places where one needs a wide bandwidth coverage. Example - TV DXing, BC DXing etc. This is normally a multi element array.
It consists of a number of half-wave dipole driven elements of gradually increasing length, each consisting of a pair of metal rods. The dipoles are mounted close together in a line, connected in parallel to the feed line with alternating phase. Electrically, it simulates a series of two or three-element Yagi antennas connected together, each set tuned to a different frequency.
VU2GRM-Mr.Ram Mohan G. Cell-9342187220
This type of antenna is used in places where one needs a wide bandwidth coverage. Example - TV DXing, BC DXing etc. This is normally a multi element array.
It consists of a number of half-wave dipole driven elements of gradually increasing length, each consisting of a pair of metal rods. The dipoles are mounted close together in a line, connected in parallel to the feed line with alternating phase. Electrically, it simulates a series of two or three-element Yagi antennas connected together, each set tuned to a different frequency.
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LPDA antennas look somewhat similar to Yagi antennas, in that they both consist of dipole rod elements mounted in a line along a support boom, but they work in very different way. Adding director elements to a Yagi increases its directionality and gain, while adding elements to a LPDA increases its frequency response and bandwidth.
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It works as a multiple Yagi antenna with different adjacent frequencies. For every dipole, the element in the front of it acts as a director and the one behind it acts as reflector.
Above picture Figure 3 shows the layout of the dipoles. This is achieved by having two booms, with alternate dipoles mounted over one boom forming the Hot end and the other forming the Cold end. Picture below shows the separate booms. They are mounted over each other separated by a spacer.
Above picture Figure 3 shows the layout of the dipoles. This is achieved by having two booms, with alternate dipoles mounted over one boom forming the Hot end and the other forming the Cold end. Picture below shows the separate booms. They are mounted over each other separated by a spacer.
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Figure 5 BoomA Figure 6 Boom B Figure 7Boom A & B
The design details are from OE3MXC Om. Michael Zwinglfrom Austria.
Dimensions for home brewing is given below in centimetres:
The design details are from OE3MXC Om. Michael Zwinglfrom Austria.
Dimensions for home brewing is given below in centimetres:
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Element Length Spacing Boom position
EL-1 53.00 0.00 0.00 EL-2 50.90 12.30 12.30 EL-3 48.90 12.10 24.30 EL-4 46.90 11.90 36.20 EL-5 45.00 11.70 47.90 |
Element Length Spacing Boom position
EL-6 43.20 11.50 59.40 EL-7 41.50 11.40 70.80 EL-8 39.80 11.20 82.00 EL-9 38.20 11.00 93.00 |
They are mounted over a 19mm standard Aluminium square section tubes. The booms are approximately 1 meter in length. Spacing between them is between 5 to 9mm.
Coax RG58 is fed through the Cold Boom A and terminated at the shortest dipole end EL-9. The hot end terminated on Boom Bat the shortest dipole end EL-9. Both are sandwiched over each other by a spacer as shown in figure 7. Elements are of ¼ inch or 6.3 mm Aluminium rods. No special matching is required.
Results are very encouraging a gain of 8.5dBd at 144 Mhz and 10.9dBd at 435 Mhz.
I have been using this for over 3 years and results are very good.
In case you have any clarifications I am available on email rammohang@gmail.com or on mobile no 9342187220.
Ram Mohan G
VU2GRM, Bangalore
For Sale
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Antenna is available in a DIY format at a cost of Rs.4500/-. Kit consists of antenna booms with spacers, mounting plate with clamps and 2meters of RG58 cable terminated with PL259 connector. One needs to mount the elements over the clearly labelled boom. Shipping extra at actuals. Lead time of 10 days.
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