Is possible to use wave guide to decrease beam width


If I use a normal 1/4 monopole antenna "30 MHz for example" and cover it with metallic wave guide has a narrow beam width, should the gain increasing according to this formula below?

$$G = 10 \; log \Big(\dfrac{32400}{H \times V}\Big)$$

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Best Answer

Rule of thumb: physically larger antennas have narrower beam width for the same frequency.

If you want to make a 30 MHz monopole more directional, you can't just cover it with a piece of metal. One solution would be to get a bunch of antennas and build a linear array, where the array factor would give you the gain. This array will need to be at least several meters long. Adding a reflector behind the antenna would increase the gain a little bit, about a factor of two. Bottom line, if you want a high gain at 30 MHz, you're going to need a REALLY big antenna.