Thanks to all for the quick responses to my SOM question. I really appreciate it!
I learn much from this list!! EN --- Moebius <[EMAIL PROTECTED]> wrote: > eyeball [bleck] -or- > Ohm meter [ok] -or- > SWR Bridge and transmitter [better] -or- > Really expensive antenna analyzer [drool] > > ----- Original Message ----- > From: "Mike at Satel-West Radio Modems" > <[EMAIL PROTECTED]> > To: "Jeff Liebermann" > <[EMAIL PROTECTED]>; > <[EMAIL PROTECTED]> > Sent: Wednesday, April 09, 2003 5:37 PM > Subject: Re: [BAWUG] Respectable SOM > > > > BTW, if you have a tower with a bunch of different > antennas, open cables > on > > the ground: > > How could i tell which cable is/is not connected > to one or open at the > > tower, without climbing the tower? > > Mike > > ----- Original Message ----- > > From: "Jeff Liebermann" > <[EMAIL PROTECTED]> > > To: <[EMAIL PROTECTED]> > > Sent: Tuesday, April 08, 2003 6:16 PM > > Subject: Re: [BAWUG] Respectable SOM > > > > > > > On Tue, Apr 08, 2003 at 03:49:13PM -0700, Casey > Halverson wrote: > > > > 23dBm is perfect. I wouldnt have any worries, > it'll be up more than > > your ISP probably ;) > > > > > > > > You can actually convert a SOM, link distance, > and frequency into an > > availability percentage. > > > > > > > > Here's a good guide to follow for 2.4GHz: > > > > > > > > Margin 100 meters 1 kilometers 10 > kilometers > > > > > ------------------------------------------------------ > > > > 0dBm 99.7% 62.1% > 38.0% > > > > 3dBm 99.8% 81.0% > 74.0% > > > > 6dBm 99.92% 90.5% > 84.5% > > > > 10dBm 99.97% 92.2% > 95.4% > > > > 20dBm 99.997% 99.6% > 97.2% > > > > 30dBm 100% 99.96% > 99.1% > > > > > > > > > >From my scribblings on the back of my notebook: > > > > > > Fade margin Availability Downtime Downtime > > > % per year per cent > > > 8dB 90 876 hrs 10 > > > 18dB 99 88 hrs 1 > > > 28dB 99.9 8.8 hrs 0.1 > > > 38dB 99.99 53 minutes 0.01 > > > 48dB 99.999 5.3 minutes 0.001 > > > 58dB 99.9999 32 seconds 0.0001 > > > > > > This assumes a perfect demodulator and a 1 error > bit > > > in 10^5 BER (bit error rate) reference. > > > > > > I keep a 10dB, 6dB, and 3dB N-N pad in my junk > box. > > > When I setup a link, I add attenuators, until > the > > > link dies. That's my fade margin and sanity > check. > > > If it doesn't match the calculations, less about > 6dB > > > for a "mushy" demodulator, I look for path > obstructions, > > > water in the coax, crappy crimps, mangled > antennas, > > > and defective hardware. > > > > > > > > > -- > > > # Jeff Liebermann Liebermann Design 150 Felker > St #D Santa Cruz CA > > 95060 > > > # 831.336.2558 voice 831.421.6491 > digital_pager AE6KS > > > # [EMAIL PROTECTED] > http://www.LearnByDestroying.com > > > -- > > > general wireless list, a bawug thing > <http://www.bawug.org/> > > > [un]subscribe: > http://lists.bawug.org/mailman/listinfo/wireless > > > > > > > -- > > general wireless list, a bawug thing > <http://www.bawug.org/> > > [un]subscribe: > http://lists.bawug.org/mailman/listinfo/wireless > > > > -- > general wireless list, a bawug thing > <http://www.bawug.org/> > [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - File online, calculators, forms, and more http://tax.yahoo.com -- general wireless list, a bawug thing <http://www.bawug.org/> [un]subscribe: http://lists.bawug.org/mailman/listinfo/wireless
