Has anyone any experience of making 2.4GHz antenna more directional? I need about 90 degrees, rather than 360. I've seen the "Pringles" DIY projects *, but they are all to produce a beam.
I was thinking of a tin cut in half lengthways, any thoughts?
There are other options. I have seen flat plates used - not sure what the princoles are, but some kind of dipole and reflector I think.
Mail me for some suppliers of ready built aerials if you like...
Hum not quite sure I understand how you can have a "more directional" aerial without "a beam" but anyway something like:
Some examples of those here:-
I've seen aluminium plates being used for something like this. They couldn't be fitted directly to the ground plane, but you could insulate it from the main antenna and place it in the opposite side of where you want to point to.
The aluminium plate was convex to wrap around the area to be shielded, and I think it also reflected some of the signal back against the aerial as well. I don't go in for all that techie stuff any more. :-))
As someone else in the thread has said, the best directional antenna is a beam though.
Yes, and this can be an advantage (it redirects the signal) but also a problem (it increases the SWR).
Perhaps this isn't the best group for this q, sorry.
A beam is *too* directional, I need about 90 degrees.
That's why it must be insulated away from the antenna and the ground planes though. I've seem them wrap a piece of rubber around the stick and then clamp the bottom of the reflector plate to it with a big elephant clip (tension band, jubilee clip)
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You mean it alters the feed impendance ?
Dave
The Telex 2405 is 85 degrees or the 2401 72/60 degrees...
Links previously posted.
Sorry, should have said. I've already bought a 12dB antenna, I just need a little more gain over a 90 degree area.
Think your stuffed. You can't have more gain and wider acceptance angle the physics doesn't work like that.
Oh dear, I'm not explaining very well. I've got a 360 degree omnidirectional antenna (it's 7dB not 12), and I want to increase the gain in one quadrant, at the expense of the other 3; a narrower angle.
pam is missing e-mail Bit puzzled by OP Is it; a) A matter of making the signal stronger within a certain beam width/direction OR. b) A matter of shielding the antenna in certain direction/s from undesired signals other than the 90 degree arc desired. I respectfully suggest that; (a) requires some form 'beam' antenna which adds 'gain' to the strength of the signal coming or going in the desired direction. Often/usually obtained by increased or greater forward to back ratio. This also diminished the signal of the other undesired directions. An antenna with a not too narrow a beam width will be required. One with 12dB sounds like it might be TOO directional? (b) Might only require shielding to prevent transmission or reception from/to certain direction other than the desired 90 degrees. This shielding should be far enough away to not affect the electrical performance of the antenna itself. However at the frequency of 2.4 GHz (and much lower) reflections of signals from other objects is quite possible! These reflections can add to or cancel the strength of the signal; particularly if a metal object and it's moving like a car, plane etc. e.g. The wow/flutter on a TV receiving an off-air signal when a plane flies over? These reflections can come from almost any direction! Suggestions? But a news group more dedicated to radio antennae might be helpful e.g. < alt.radio.amateur.antenna > ?
So look again at the telex 2405, 2417 2443, 2444, 2445.
The last three are sector antennas with gains/width of 12dbi/120deg,
14.5dBi/90deg and 12dbi/90deg (horizontal polaristation). They all have pretty narrow elevation beamwidths (As others have said you cannot change the basic laws of physics! In your case I think you are going to have to consider two antennae each covering a sector of some 45 degrees or so. Also remember that quoted antenna gain figures are seldom realised in practice and the signal polarisation can have a big effect. Likewise the received signal strength is affected by the gain and orientation of the receive antenna. Once you get away from a point to point link with fixed antennae pointing at one another then the mathematics become unbelievably complex and you need to adopt a suck it and see approach rather than pure theory!
gee six jay en snipped-for-privacy@spamcop.net
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Lots of good stuff on 2.4GHz here
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