Half-Wave Dipole Formula Slate Coaster

A beautifully detailed slate coaster for radio enthusiasts, laser engraved with the classic half-wave dipole formula: L(m) = 150 × VF ÷ f(MHz). This formula is used to calculate the total length of a half-wave dipole antenna, where L is the overall end-to-end antenna length in metres, VF is the velocity factor of the wire or material being used, and f is the operating frequency in megahertz.

For ham radio operators and short wave listeners, the half-wave dipole is one of the most trusted and widely used antenna designs. It is simple, effective, and a great starting point for building antennas for HF bands such as 40m, 20m, 15m, and 10m. The engraved diagram shows the dipole split into two equal halves, making it a useful visual reminder that each side of the antenna is approximately L/2 from the centre feed point. Practical, decorative, and full of radio heritage, this coaster is ideal for the shack, workshop, desk, or as a thoughtful gift for anyone who enjoys amateur radio or short wave listening.

These coasters are supplied with four soft adhesive feet so they do not mark surfaces. Putting four or six together would make an ideal gift.

Product Features

• Precision laser engraved design
• Crafted from natural grey slate
• 10cm diameter and 4mm thick slate coaster with a rustic bevelled edge
• Soft sponge feet included

Please note slate coasters are not dishwasher safe.

Design Copyright Notice

All designs are the intellectual property of Primary 9 Designs and are protected by copyright.

These products are supplied for personal use only. The designs may not be reproduced, copied, distributed, modified, or used to create products for resale without prior written permission from Primary 9 Designs.

Purchase of this item does not transfer copyright or grant a commercial licence to reproduce or sell the design in any form.

Large Orders

Looking to order larger quantities? We are happy to provide bespoke lead time and shipping quotations for bulk orders, schools, clubs, care homes, events and organisations. Please contact us and we'll help find the most cost-effective shipping option for your order.