Also keep in mind in the cellular world they used diversity antennas and pre-amps to make up for the lower return path power budget. Their radios have separate transmit and receive ports and antenna systems, they are not locked in to the one antenna half duplex mentality. Having a separate receive antenna or array that offers more gain than on the transmit side has worked for many years in that space. In the early cellular days when capacity and spectrum reuse was not an issue, it was common deployment practice to have both an Omni for the tower side to transmit and sectors with higher gain for receive to try and balance out the power budgets from the mobile units. The radios at the tower sites had separate ports for TX and RX.
Thank You, Brian Webster www.wirelessmapping.com www.Broadband-Mapping.com -----Original Message----- From: AF [mailto:af-boun...@af.afmug.com] On Behalf Of Adam Moffett Sent: Thursday, July 12, 2018 4:00 PM To: af@af.afmug.com Subject: Re: [AFMUG] How to count amplifiers in link budget Good to know. On 7/12/2018 3:30 PM, ch...@wbmfg.com wrote: > 3dB NF is nothing to crow about these days. Lots of front ends and > preamps are below 2 dB. Even 1.5 is common. > > -----Original Message----- From: Adam Moffett > Sent: Thursday, July 12, 2018 1:24 PM > To: af@af.afmug.com > Subject: Re: [AFMUG] How to count amplifiers in link budget > > Understood. This is 700mhz A-Block, so I'm allowed 1000W ERP in one > direction and 30W ERP in the other. I hadn't thought it through yet > when I talked about amping the 30W side. > > My thinking was to use the higher power channel for downlink. I'm > looking at setting Tx power to +24, adding an amp which says +22 on the > spec sheet, and a 10db omni. That puts me around 400W before cable > losses, might be 300W after cables and connectors depending on the > specifics. The spec sheet claims a noise figure of "<3db", and that > seems reasonable as long as it's not a lie. > > In this configuration the uplink might be up to 12db weaker than the > downlink, but if I have the maximum modulation level down, then I'll > still have something acceptable up. Something like 500kbps x 200kbps > in a 250khz channel. > > -Adam > > > On 7/12/2018 2:57 PM, Brian Webster wrote: >> Remembering also that you will likely need a balanced path so if both >> ends >> of the link don't have the amplification you may have a problem. Amps >> with a >> preamplifier also included have noise figures that don't always give >> you a >> realized gain on the receive side. Using antenna gain over just >> amplification to reach the max legal power is always preferable if >> possible >> as the gain benefits you on both receive and transmit. >> >> Thank You, >> Brian Webster >> Skype: Radiowebst >> www.wirelessmapping.com >> www.Broadband-Mapping.com >> >> -----Original Message----- >> From: AF [mailto:af-boun...@af.afmug.com] On Behalf Of Robert Andrews >> Sent: Thursday, July 12, 2018 2:16 PM >> To: af@af.afmug.com >> Subject: Re: [AFMUG] How to count amplifiers in link budget >> >> But he said he gets 30 ERP not 30 EIRP where EIRP = 1.64 * ERP ( if he >> is actually allowed 30 ERP and not 30 EIRP ). So that would be 49.2 >> EIRP IF he is allowed 30 _ERP_.. so 49.2. watts would be another 2.15 >> db.. 9.85 dbm gain antenna. Still no need for an amp... >> >> Please check my math and assumptions, as I _always_ stick my hand up in >> class and then spit out the wrong answer... >> >> On 07/12/2018 10:30 AM, ch...@wbmfg.com wrote: >>> Yep, that is how you do it. 30 watts EIRP is 44.7 dBm >>> 5 watts is 37 dBm. So 44.7 - 37 = 7.7 dB gain. >>> >>> A 7.7 dBi antenna is pretty common. >>> After adding antenna gain, I don't see much room to amplify. >>> -----Original Message----- From: Adam Moffett Sent: Thursday, July 12, >>> 2018 11:06 AM To: af@af.afmug.com Subject: [AFMUG] How to count >>> amplifiers in link budget >>> I'm looking at an IoT application where we're allowed 30W ERP. The >>> transmitter is 5W, so even with antenna gain I have room to amplify >>> that. >>> >>> How do you count an amplifier in your link budget? Just add the amp's >>> tx gain and subtract connectors, or is there more to it than that? >>> >>> Strangely I've never used an amplifier.....I've never had a legal >>> application for one before. >>> >>> -Adam >>> >>> > > -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com
