David wrote:
Hi,

I have a design for a Yagi antenna at 436MHz and would like to scale it
to 921 MHz. The calculations I used from the understanding I have
obtained from reading various articles appears below.

Would someone be kind enough to advise me if this procedure and values
look correct ?
[...]

Regards

David Huisman


The basic principle of scaling antennas according to wavelength is that
you must make an *exact* scale model. That means scaling every
dimension, and not adding any new or different 'features'.

Often that isn't practical for mechanical engineering reasons, so then
you need to apply corrections. However, you should still aim to keep
those corrections as small as possible. For example, simple scaling is
likely to produce odd, unavailable values for the element diameter, so
it's OK to use corrections to change to the nearest commercially
available diameter. But if you also decide to double the diameter, the
correction is more risky - you're entering the territory of a completely
new design.

Sorry that I don't have time to check your particular dimensions in
detail, David, but you can find resources for scaling and constructional
techniques on my 'VHF/UHF Long Yagi Workshop' pages. There is a
downloadable program which leads you through the relevant questions, and
also a link to an online Javascript version.

(From about 1200utc I will not have access to this newsgroup for the
next few days, so I hope the above will keep you going.)


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek