On Fri, 4 Nov 2005 10:17:45 -0000, "Christian McArdle"
wrote:

Need a new TV aerial; I note Screwfix sell different models for 'strong'
and 'weak' signal areas. AFAIK we're in a fairly OK area, but my
question is, is there any disadvantage in fitting the 'weak signal' type
if it might not be necessary? Otherwise it's clearly not worth even
considering paying two quid less for the 'strong' variety?

Disadvantages I can think of:

The weak signal aerial may be larger and more intrusive visually. It may
overload your set unless you insert an attenuator (easily obtained and
cheap). It may have a tighter frequency band which makes it less suitable
for digital reception on certain transmitters. It may not, but you need to
check. Get a wideband version if possible.

However, it doesn't increase the noise as well as the signal. That's the
whole point of it. It takes the signal from a smaller segment of the sky, so
you get more of the available signal (which can be regarded as a point
source) without swamping it from the noise you get from a less directional
aerial that takes in the noise from a larger area.

The higher the gain, ie the more directional, the more likely it is to
have "side lobes", which means that it picks up signals from the
_side_ as well as ahead. If you do have a high gain aerial and large
metallic structures at certain angles to your line of fire, you risk
ghosting (with analogue reception anyway).
Some experimentation is often required.

--
Frank Erskine