## [Aironet] Re: power output reduction.. (sigh)

 [Aironet] Re: power output reduction.. (sigh) From: Jean Tourrilhes - 2000-02-18 23:31:27 ```Samudra wrote : > hi, > > I am dissapointed that just as things were getting interesting, Harris > prism chipset was newly issued and the power output from the PCI4800 > cards went down to 30 mW from 100 mW. Which is significant since I use > them always almost in WAN applications. But I am confused by the > following statement: > > 4800B sensitivity at 5.5 Mb/s is -87 dBm, whereas 4800 is -83 dBm (so > 4800B is more sensitive by 4 dBm). And of course the power output is > less by 5 dBm from 22 dBm (4800B < 4800 power output). So, just how does > the "the power reduction is a loss of 5 dB for you, sensitivity is a > loss of 3 dB" statement fit. You may personally be interested in 5.5 Mb/s, but when you want to make a 25 km link (as Elmer does), you need the greatest range, therefore go to 1 Mb/s. At 1 Mb/s, this statement make sense. > would that not be: a LOSS of power output by 5 dBm, while a GAIN of > sensitivity by 4 dBm, so therefore, the link budget using a 4800B > compared to a 4800 would be equiv. of a LOSS of 1 dBm ??? @ 5.5 Mb/s only > By the way isn't -5 dBm equivalent to 0.316, so... would 5 dBm reduction > in the RF power output level mean that the previous power output of 100 > mW is now.. 31.6 mW ? > > I guess, 1 dB = 10 * log (Pi/Po) comes in handy. Picky on the decimals, isn't it ? Ok, so 30 mW = +14.7712125472 dBm, and not +15 dBm. Mea culpa, I was totally wrong. Happy now ? By the way, with the natural fluctuations and calibration of the power aplifier, won't make any difference. Add the fluctuations of the channel... > I'm defintely not a mathematics person, and have never studied > electrical engineering and by all means am a layman when it comes to > analog radio black magic and RF power ... mea culpa in advance if I > screwed up but I would surely like to know where I did and how I can > learn my mistake and use the 4800B cards in a better fashion. > > -samudra haque Regards, Jean ```

 [Aironet] Re: power output reduction.. (sigh) From: Jean Tourrilhes - 2000-02-18 23:31:27 ```Samudra wrote : > hi, > > I am dissapointed that just as things were getting interesting, Harris > prism chipset was newly issued and the power output from the PCI4800 > cards went down to 30 mW from 100 mW. Which is significant since I use > them always almost in WAN applications. But I am confused by the > following statement: > > 4800B sensitivity at 5.5 Mb/s is -87 dBm, whereas 4800 is -83 dBm (so > 4800B is more sensitive by 4 dBm). And of course the power output is > less by 5 dBm from 22 dBm (4800B < 4800 power output). So, just how does > the "the power reduction is a loss of 5 dB for you, sensitivity is a > loss of 3 dB" statement fit. You may personally be interested in 5.5 Mb/s, but when you want to make a 25 km link (as Elmer does), you need the greatest range, therefore go to 1 Mb/s. At 1 Mb/s, this statement make sense. > would that not be: a LOSS of power output by 5 dBm, while a GAIN of > sensitivity by 4 dBm, so therefore, the link budget using a 4800B > compared to a 4800 would be equiv. of a LOSS of 1 dBm ??? @ 5.5 Mb/s only > By the way isn't -5 dBm equivalent to 0.316, so... would 5 dBm reduction > in the RF power output level mean that the previous power output of 100 > mW is now.. 31.6 mW ? > > I guess, 1 dB = 10 * log (Pi/Po) comes in handy. Picky on the decimals, isn't it ? Ok, so 30 mW = +14.7712125472 dBm, and not +15 dBm. Mea culpa, I was totally wrong. Happy now ? By the way, with the natural fluctuations and calibration of the power aplifier, won't make any difference. Add the fluctuations of the channel... > I'm defintely not a mathematics person, and have never studied > electrical engineering and by all means am a layman when it comes to > analog radio black magic and RF power ... mea culpa in advance if I > screwed up but I would surely like to know where I did and how I can > learn my mistake and use the 4800B cards in a better fashion. > > -samudra haque Regards, Jean ```
 Re: [Aironet] Re: power output reduction.. (sigh) From: Elmer Joandi - 2000-02-19 00:16:13 ```On Fri, 18 Feb 2000, Jean Tourrilhes wrote: > > You may personally be interested in 5.5 Mb/s, but when you > want to make a 25 km link (as Elmer does), you need the greatest > range, therefore go to 1 Mb/s. At 1 Mb/s, this statement make sense. btw, nope, here you have to see the noise and legalese stuff. For wan link you have to provide a certain amount of quality of service. Now, if to leave aside my super-ideal-conditions 25km link (where 100mW signal goes easily @11Mbps), everything else goes worse, unless I want to start walking across the city with expensive equipment and put all fellows having even more powerfull and less sensitive devices, to jail. And I have to put all of them there, to get the noise level down. now, there are lots of old arlans at city, with valid for some years non-ETSI licenses and PC4800 too, non-etsi licenses valid for 4+ years. while now comes 4800B under ETSI regulations, it is going to be beaten in city. That would be no harm if they either would freewillingly replace all links or force ETSI on older or Aironet would still produce PC4800. (not directly my problem, my links are countryside, no probs) (btw, anyone knows a price on such scanning equip for 2.4Ghz ?) Coming back to that 25km link - how to get, besides signal, those packets also trough ? My deep theory is that i need 1. random backoff time longer 2. point2point link 3. rate limiter to send packets one-by-one at intervals to avoid collision. elmer. ```