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No, no it wouldn't.

These are directional antennas, and directionality is achieved by focusing.

If you used something like this for indoor coverage, you would have one small corridor of great signal, and more dead spots than you started with.

If you want great indoor coverage use this stuff: http://www.andrew.com/products/trans_line/radiax/d efault.aspx

--e

http://www.andrew.com/products/measurement_sys/inv ex_system.aspx

is the info on the system they use to gather the data

> I'm not sure if this is really true. Currently, cell phones operate
> totally without any line of sight component in a multipath
> envirinment (ie, a Rayleigh signal model).
> I haven't see a a Smith chart for a cell tower antenna in a
> while, but while the main lobe is basically horizontal, there
> will be a side lobe pointing up.

You're correct in that multi-path governs cellular communications, particularly for spread spectrum systems like IS-95 CDMA. However, wouldn't the fact that the device is flying above the skyline with no objects for the signal to bounce off of minimize multi-path effects? It's almost free air space with no obstructions when you're pointed at an airplane.

The airplane would offer an unobstructed path to the cell site, which could help things, but you'd still have a problem with the main lobe (on the vertical axis) pointing away from the airplane. You'd have to rely on a lobe pointing up or even on the back lobe in the case that the antenna is really tilted (like in an urban environment).

They've got some Smith charts on Andrew's web site that indicate the problem. I pulled a pattern for what I think is a typical cellular sectored antenna 854DG90VTESX running at ~824 MHz. If the top lobe is pointed at the plane (and there's no multi-path), along the blue vertical axis you're going to get a node 20 dB down from the main lobe. Thus, the line of sight coverage from the base station will be much lower than one would expect, and both the base station and mobile station will have to increase their power levels to make up for the lack of coverage.

> I'm not sure if this is really true. Currently, cell phones operate
> totally without any line of sight component in a multipath
> envirinment (ie, a Rayleigh signal model).
> I haven't see a a Smith chart for a cell tower antenna in a
> while, but while the main lobe is basically horizontal, there
> will be a side lobe pointing up.

You're correct in that multi-path governs cellular communications, particularly for spread spectrum systems like IS-95 CDMA. However, wouldn't the fact that the device is flying above the skyline with no objects for the signal to bounce off of minimize multi-path effects? It's almost free air space with no obstructions when you're pointed at an airplane.

The airplane would offer an unobstructed path to the cell site, which could help things, but you'd still have a problem with the main lobe (on the vertical axis) pointing away from the airplane. You'd have to rely on a lobe pointing up or even on the back lobe in the case that the antenna is really tilted (like in an urban environment).

They've got some Smith charts on Andrew's web site that indicate the problem. I pulled a pattern for what I think is a typical cellular sectored antenna 854DG90VTESX running at ~824 MHz. If the top lobe is pointed at the plane (and there's no multi-path), along the blue vertical axis you're going to get a node 20 dB down from the main lobe. Thus, the line of sight coverage from the base station will be much lower than one would expect, and both the base station and mobile station will have to increase their power levels to make up for the lack of coverage.

Do they drive their plows on vacation trips with the family? It's not like truckers carrying missles or hazardous materials take their rigs on vacation. And even if they do, I'm sure there's a way to turn off the system when they're off duty.

All you need is a big old satellite antenna, a spectrum analyzer, a frequency generator capable of tuning to a stable 6 or 14 GHz (C or Ku) signal, an amplifier capable of amplifying that kind of signal up to about 100 watts, some waveguide... hmmm. It would probably also help to have a fast car for when the FCC arrives 30 minutes later.

This is sort of like saying that flying to the moon is easy - all you need is a big metal tube and some propellant.

2Mbps at 1km point p-t-p is not much - we do that at work all the time (I'm working for a wireless ISP).

Linksys WAP11 is one of the worst pieces of HW I have seen (I haven't even looked at the worse ones). You need a trained monkey to monitor it (no SNMP - try using Cricket or MRTG) and have to reboot it once a week. Even if you have the monkey, the box won't tell you anything - no signal strength, no retransmission counter, just the packet counters (at least in version 1.009).

If you intend to build such a link, use either decent FHSS devices (but those are quite expensive), or something like SparkLAN (sorry, no URL, try google) - a friend of mine is using those for 5km 8Mbps links (under ideal conditions, of course). These are about $200 in Slovakia, don't know about US (or Egypt).

It is also better to use high-gain (like 24dBi) antennas - have a look at Andrew. Do not use omnidirectional antennas.

Also try to keep the HF cables as short as possible (the guy could have made them some 2ft shorter) and water-proof your connectors - or your link will go down anytime the rain coes (and will not come up after some months due to rust)

The company I used to work for, Andrew Corporation, produced an active transponder that was aimed at improving cellular telephone reception in buildings- it was a panel you placed in a window and had flat antennas on each side. We had an experimental version in our office (our group didn't make these things). You can't just place two antennas with an amplifier between them because amplifiers only go one way, and if you have a return path really close, it is highly likely that they will oscillate.

I have seen passive re-radiators- essentially just a pair of antennas with a cable in between- which might help, but you need to get some pretty high quality cable between the antennas, because the cable losses at the PCS frequencies (up near 2 GHz are pretty high). (I'm guessing this is a PCS or some other non-traditional-cellular (800-900 MHz) cellular phone, since building construction is much less friendly to letting the PCS frequencies through).

For a passive re-radiator to work well, you need to place an antenna outside (not behinid a window- many windows have metallic coatings that will kill RF), preferably in full view of your local cellular phone tower. Run the absolutely shortest cable you can to your inside antenna. Both antennas must be tuned to the frequency of interest. Unfortunately, since celluar phones are frequency agile or spread spectrum, you want antennas that have a somewhat wide band around the frequency band- don't forget that transmit and recieve from the tower may be on separate frequency bands.

-OR- work hard and get a window office. This is probably the most effective solution to your problem.