| William H. Magill on Tue, 3 Jun 2003 23:48:09 -0400 |
|
On Monday, June 2, 2003, at 02:06 PM, Molnar, Bradley wrote: An unfortunate side effect of living in a pre-depression era house (other I live in a big old Victorian which has quite an assortment of "live" and dead spots easily attributable to the various construction materials. There are two major issues -- construction materials and antenna. If you have hot air heat, hot water heating or air-conditioning, that is your culprit. Hot air (aka forced air) heating uses BIG rectangular metal ducts -- typically 6 inches by 12 inches to convey the hot air upwards from the furnace in the basement to the "grills" in the baseboards of the 2nd and 3rd floors. These typically run up inside the walls, usually inside walls if at all possible. Return air ducts on the other hand were usually "constructed," by simply tacking a layer of sheet metal across two of the floor joists so that one could put the "return" in the middle of a room and duct it across the floor to the down duct in the wall. "Whole House" air-conditioning employs this same ductwork. Ok... so you've got hot Hydronic (hot water) heating (radiators). ... Same situation exists. Back in the early 1900s, they knew how to build such systems... the "risers" and the "returns" are typically 4 inch cast iron pipes. Again they are run "up" the inside walls and the horizontal distributions (1.5 or 2 inch pipes) run across the floor to the radiators on the outside walls. These things make very good signal dampers. The other factor in a pre-1940s house is that it is probably made of plaster-lath construction. There is a 10% possibility that you may also have "concrete board" - similar to wall board, but much, much denser. Both of these construction materials do a very good shielding job. And lastly, there is the question, "what is the floor made of?" "Back in the good-old days, Floors were A) built on 12 inch joists B) had a full sub-floor, probably 1/2 thick C) covered with a finished wood floor... frequently a dense parquet type material. Repairs were often made by inserting a layer of "masonite" between the sub-floor and the finish floor to "level things out." This was very true if a tile or "linoleum rug" was installed. Then there is always the possibility of "ball-and-tube" wiring issues in a house of that vintage. The Antenna orientation is the other major issue. Antenna polarization is normally either horizontal or vertical. A box like the Link-Sys has "moveable" antennas which make it pretty obvious which way they are polarized. The antennas may be "omnidirectional," but that just means they radiate equally in 360 degrees relative to their polarization. Signal propagation is normally NOT spherical, with the antenna as a point source. It is a flattened sphere, with the center at the antenna being "shorter" than the distance to the outside radius. The signal moves at right angles to the orientation of the antenna. So if you want the signal to "go far" horizontally, you make the antenna "point up." If you want it to "go far" vertically, make the antenna point sideways. The reason Apple's Airport looks like a Hershey's Kiss is because the antennas are built into the 45 degree sloping-sides of the unit... a compromise between a vertical and a horizontal orientation. But that is only half the answer. The receiving antenna is the other half. WHERE is that antenna in your laptop? In the frame (like the iBook)? in the frame like the TI-book? On a little antenna sticking out of a PCI card? The Titanium Power Book, TI-book, has a problem that the "window" which covers the antenna is not "RD invisible" the way it is on the iBook. Consequently, the iBook has MUCH greater signal sensitivity than the TI-book. T.T.F.N. William H. Magill # Beige G3 - Rev A motherboard - 768 Meg # Flat-panel iMac (2.1) 800MHz - Super Drive - 768 Meg # PWS433a [Alpha 21164 Rev 7.2 (EV56)- 64 Meg]- Tru64 5.1a magill@mcgillsociety.org magill@acm.org magill@mac.com _________________________________________________________________________ Philadelphia Linux Users Group -- http://www.phillylinux.org Announcements - http://lists.netisland.net/mailman/listinfo/plug-announce General Discussion -- http://lists.netisland.net/mailman/listinfo/plug
|
|