Your browser is no longer supported

For the best possible experience using our website we recommend you upgrade to a newer version or another browser.

Your browser appears to have cookies disabled. For the best experience of this website, please enable cookies in your browser

We'll assume we have your consent to use cookies, for example so you won't need to log in each time you visit our site.
Learn more

Parabolic story


I was delighted to read of the idea of a direct audio link between England and France (NCE 30 November). However, I would take issue with the reported hemispherical shape of the reflectors described in the article.

A hemisphere does not have a focal point and would lead to a poor signal to noise ratio.

Surely the designers intend to use a parabolic dish which does have the essential focal point.

On the high cost of making moulds, the designers might learn from the world of optical astronomy. Large parabolic mirrors have been made 'simply' by gradually cooling molten glass in an opentopped constantly rotating container.

Any liquid naturally forms a parabolic shape when spun this way. The faster the spin, the shorter the focal distance from the centre of the dish. I am sure this technique could be applied to wet concrete and achieve the desired tolerance.

Peter J Felton, Wilinson Associates, 119 Richmond Road, Kingston Upon Thames, Surrey KT2 5BX.

Have your say

You must sign in to make a comment

Please remember that the submission of any material is governed by our Terms and Conditions and by submitting material you confirm your agreement to these Terms and Conditions. Please note comments made online may also be published in the print edition of New Civil Engineer. Links may be included in your comments but HTML is not permitted.