Wireless Challenge

You must consider that you may also cause interference to the plane. Please check your equipment as interference can cause havoc.

In SA we have this problem, our frequency allocation differ from America and cheap equipment from you know where does not restrict themselves to the allocated frequencies. The result is that Com's on restricted channels are interrupted by a typical data transfer.

You might want to rent a spectrum analyzer and see if there's a patch of spectrum that is quiet and then park your communications there. Hendrick is right of course, if you are interfering with their comm's there could be big trouble.

You could be suffering from receiver overload from the DME or ILS systems. Those typically respond to signals transmitted from the plane which would account for you only having problems when a plane is on approach. I think the DME may use a 1 KW transmitter with a directional antenna. You may be right in the beam.

If RX overload is your problem, a band pass filter for your 900 MHz signal on the trancievers on the cranes and your server may help remove the interference without attenuating your signals too much.

This could be a cheap fix. http://www.microwavefilter.com/rfmicrowave/RF-PDF/capabilitiescatalog.pdf

If you can determine the frequency of the interfering signal, you may be able to get away with a high or low pass filter which may be considerably cheaper than a band pass design.

Gents,

Thank you for your assistance on this, I will let you know how this turns out.

If you weren't hopping I'd say use a cantenna. You could run much lower power and greater reliability as well as less risk of interfering with flight systems. A spectrum analyzer can be an expensive one time expense. IDK if there are people who offer that as a service.

I have installed a high gain antenna, and it has helped the situation. The polling of the information seems to have recovered quicker. The spectrum analyzer is expensive, but if I could rent one, that would certainly be my best bet. The system is currently set up as point to multi-point, I have thought about installing another modem as a repeater.

What type of antenna's are you using? Is the antenna in your maintenance shop outside or is it a whip antenna on the radio inside? You didn't describe the orientation of the flight path relative to the cranes. What might be happening is that you are getting a reflected signal from the plane such that it is causing fading at your receiver. Fading is caused by multiple signals arriving at the antenna that are out of phase with each other. The net result is that the signal is partially cancelled or can be completely lost in the background noise.

I am using a high gain antenna, which has seemed to help. The final approach of the aircraft is directly overhead. Depending upon direction of the wind. The cranes run along stacks east and west and the final approach of the aircraft is south to north.

The base antenna is mounted on top of the maintenance building. Antenna length is 6.0".

I have located an inexpensive spectrum analyzer, I need to see where the traffic is in that range.

If the antenna is 6 inches long it sounds like you're using a whip antenna. What type/diameter and how long is the cable between the radio and antenna? It might be benneficial to get an OMNI with 6 DB gain. OMNI and gain seem like an oxymoron since the gain of a true OMNI is 1 but what is happening is they give it gain in the horizontal plane at the expense of the vertical and this may, in itself, be a boon because, it this is a fading issue, the reflected signal will have a reduced signal strength relative to the signal coming directly from the crane and the fading would be reduced.

maybe you can use AAPSK technology which is described by patents held by Aerotelesis Inc. (AOTL) -- this is a sub-micro-penny stock. However, i think the technology can be important so I hold some shares in it, and am keeping my fingers crossed. perhaps if you look into it, you can see if their technology is appropriate for your application. I do not have the technical understanding needed. Good luck though!