It is important to remember that 'improved' often is intended to mean higher gain which itself means more directionality.

Directionality (high gain) is a bad thing for certain, typically mobile, applications (GPS for example) where the signal might be coming from almost anywhere.  If the orientation can be controlled, then +3dBi gain can be achieved for hemispherical coverage (assuming that there is no signal emerging from underground - a safe asumption for most applications...).

Active steering can provide both high gain and automatic tracking - at a cost.

1) Yagis for cell phone - these are still available and are useful for remote cottages and off-shore islands, etc.  I've read about people using them to deselect their local over-priced British Virgin Islands cell phone provider and use the cheaper American Virgin Islands provider several miles across the sea.

2) It only takes a couple of dB to make a huge difference in pixelization breakup for any digital TV signal. Same thing applies to satellite TV dishes where an extra couple of inches diameter can provide much much better reliability during heavy rain storms.

3) GPS is mostly about signal processing tricks.  The antennas must be low gain, although perhaps an array of antennas could be used.  The present approach is to use fancy DSP tricks to make a better GPS mousetrap.

4) There is the 4-element Luneburg Lens array to provide mobile DBS with about 4" height.  This is how they bring DBS TV to large aircraft or RVs.  For RVs, the signal still drops out under overpasses and behind buildings - so the travelling rock stars reported spend more time playing video games than watching TV.

The 'Next Big Thing' will be mobile Wi-Max (56Mbps, 35km range) which brings high speed Internet to your car.  Imagine what happens to your local AM/FM radio station when you can listen to anything you want from the Internet on your car stereo or your Wi-Max enabled walkman.

Cheers.

I would be interested in industrially rated, (ruggedized for harsh environments), 2.4 Ghz and 5.2/5.8 Ghz directional and omni-directional antennas. You would be surprised how difficult it is to find a 2.4 Ghz antenna that will stand up to being mounted in the middle of a chemical plant.

You can make one using appropriate (low loss) coaxial cable, a length of plastic pipe, and glue.  Basically, make a sleeve dipole from the coax and enclose it in the plastic pipe. Quick, cheap and rugged.  Weatherproof too.

Maybe an obvious question regarding chemical plant antennas, but are present units being destroyed by your chemicals, and if so how long do the antennas last and how much to they cost? How are the cables that are attached to the antennas fairing? Please describe the physical situation a bit.

I'd be inclined to use a material named PEEK. It's very chemical resistant.

For reference, here is a sample antenna set from http://www.itelite.net/

Frequency 2400-2483 MHz
Gain 9 dBi
Polarization vertical
Beamwidth deg vertical 12°
VSWR 1.2
Impedance 50 Ohm

Frequency 5170 - 5320 MHz
Gain 17 dBi
Polarization horizontal
Beamwidth deg vertical 12°
VSWR max. 1.7 Impedance 50 Ohm

Frequency 5700 - 5850 MHz
Gain 19 dBi
Polarization horizontal
Beamwidth deg horizontal 90°
Beamwidth deg vertical 10°
VSWR max. 1.7 Impedance 50 ?

kch

...how long do the employees last?

OK, you want a challenge?

We need a transmitting antenna for a long-range ground penetrating radar. Needs to be a reasonable match to 50 ohms, gain of -10dB (yes negative, including losses!), 3MHz to 30 MHz, and "easy" to move. The antenna to beat is a bowtie thrown on the ground. Remember, the ground detunes it by the square root of the dielectric constant, so it's about a third of the in-air size.

OK, what’s the problem with the bowtie?

When it comes to a scientific or industrial application, a pretty blue anodized finish isn’t an improvement.

To quote an old professor of mine “Don’t reinvent the wheel”…or to quote my Grandfather “If it ain’t broke, don’t fix it.”

If you could enumerate the improvements needed for your ground penetrating radar antenna, it would be a great help.

As far as the -10dB gain, Any old wet noodle could get you that!

I remain ,
The Old Soldering Gunslinger

Jim,
Sounds like a good challenge.
to be efficient and relatively small you'll need an active antenna that tunes with cue's from your transmitter/reciever.

We just completed an efficient air dielectric antenna 70-200 MHz and it's 48" long.
What size requirements do you have to limit yourself to?

Any other Spec's available.
If this is a real program, give me a call at 805 685 1482 and we can get going on it.
Kevin C. Higgins.