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does wavelength determine height of antenna
- Thread starter bhuvanesh
- Start date
354 what?
I know that 144MHz corresponds to a wavelength of around 2 metres, so on that basis 850MHz would be about 350mm.
That's wavelength, and while that helps inform you about the length of an element of an antenna, it doesn't tell the whole story.
Primarily, it informs you about the length, but not the height of an element. For an antenna like a yagi or similar, many elements may be placed in parallel, with the longest dimension possibly orthogonal to the elements themselves.
Other antennas stack elements end on end, with the total length a multiple of the size of the element.
Another consideration is that the individual elements might be 1/4, 1/2, or 5/8 of a wavelength in length. For a dipole you can double this (two 1/4 wave elements are typical).
For multi element antennas, other elements will differ in size, something I'm sure you've seen.
When you speak about height, you may be referring to an antenna with a vertically oriented element. In this case, the minimum height will be that of the element, assuming it starts at ground level.
However, at higher frequencies you probably want to place the relatively smaller antenna on a mast to lift it clear of obstructions. In this case the height is probably more determined by topography and financial resources than frequency.
For horizontally polarised antennas it is also often best to ensure the antenna is separated from rooftops, other antennas, etc, by some reasonable portion of a wavelength.
I know that 144MHz corresponds to a wavelength of around 2 metres, so on that basis 850MHz would be about 350mm.
That's wavelength, and while that helps inform you about the length of an element of an antenna, it doesn't tell the whole story.
Primarily, it informs you about the length, but not the height of an element. For an antenna like a yagi or similar, many elements may be placed in parallel, with the longest dimension possibly orthogonal to the elements themselves.
Other antennas stack elements end on end, with the total length a multiple of the size of the element.
Another consideration is that the individual elements might be 1/4, 1/2, or 5/8 of a wavelength in length. For a dipole you can double this (two 1/4 wave elements are typical).
For multi element antennas, other elements will differ in size, something I'm sure you've seen.
When you speak about height, you may be referring to an antenna with a vertically oriented element. In this case, the minimum height will be that of the element, assuming it starts at ground level.
However, at higher frequencies you probably want to place the relatively smaller antenna on a mast to lift it clear of obstructions. In this case the height is probably more determined by topography and financial resources than frequency.
For horizontally polarised antennas it is also often best to ensure the antenna is separated from rooftops, other antennas, etc, by some reasonable portion of a wavelength.
Last edited:
signalman72
- Jan 26, 2014
- 57
- Joined
- Jan 26, 2014
- Messages
- 57
IIRC, frequency ÷ 300 = wavelength.
no its 300 / freq in MHz = wavelength in metres
or conversely
300 / wavelength in metres = freq in MHz
Dave
signalman72
- Jan 26, 2014
- 57
- Joined
- Jan 26, 2014
- Messages
- 57
Yes you are correct. I mistakingly forgot to include that it's frequency in MHz
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