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Re: [Openbts-discuss] USRP/OpenBTS Extending Range/Coverage Help
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From: Kurtis H. <khe...@cs...> - 2013-07-23 17:24:12
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Ralph knows his RF better than I do, so ymmv! On Tue, Jul 23, 2013 at 7:28 PM, Ralph A. Schmid, dk5ras <ra...@sc...>wrote: > Believe me, this crosstalk problem is nothing but a rumor from someone who > did not understand the difference between crosstalk when using one > frequency vs. using two frequencies. In fact I cover 200 m with a standard > WBX and two directly attached small antennae without any problems when > using GSM1800 with its large uplink/downlink spacing. At a demonstration a > few weeks ago it was no problem to cover three floors of a conference > center with only a few mW of output power.**** > > ** ** > > The OP must have some error in his setup, maybe mixing up downlink/uplink > or input/output. Or some bad cable, bent connector pin, whatever. **** > > > Ralph.**** > > ** ** > > *From:* Kurtis Heimerl [mailto:khe...@cs...] > *Sent:* Monday, July 22, 2013 6:52 PM > *To:* Derek Wells > *Cc:* ope...@li... > > *Subject:* Re: [Openbts-discuss] USRP/OpenBTS Extending Range/Coverage > Help**** > > ** ** > > Oh this is one daughterboard? My understanding is that there's a lot of > crosstalk on the board with one daughterboard, that's going to limit your > coverage a lot. Also may explain why the duplexer does so little. **** > > ** ** > > On Mon, Jul 22, 2013 at 9:49 AM, Derek Wells <der...@gm...> > wrote:**** > > John, > > Can you discern whether you are uplink or downlink limited? > > That is, is your range limitation due to a transmitter problem or a > receiver problem? And furthermore, is it the on phone end (unlikely) or > the USRP end of the up or downlink? > > It sound like you are working off of one daughterboard, is that correct? > -99 dBm sounds pretty low at 15 meters with a Yagi (like Kurtis said). > Consider using the "noise" and "power" commands from the CLI and providing > some numbers back to the forum. > > And because I've done it before with other systems...check each RF > connection and cable to make sure you have a male pin mated with a female > socket at every connection, and not two female sockets...it happens. > > Derek**** > > > > > > **** > > On Sat, Jul 20, 2013 at 1:37 AM, Kurtis Heimerl <khe...@cs...> > wrote:**** > > There's something wrong with your USRP, you should certainly get more than > 15 meters with a USRP1 and a 12db Yagi. **** > > ** ** > > On Sat, Jul 20, 2013 at 1:20 PM, john wake <dag...@ho...> > wrote:**** > > Hello guys, > > We are having trouble extending the range of our USRP1 which is running > OpenBTS I really hope someone can help our current setup is as follows > > RX = Antenna -> Duplexer -> LNA -> USRP > TX = Same antenna -> Same duplexer -> Power Amplifier -> Fullband Transmit > Filter -> USRP > > When we try running the USRP with just the antenna we get a range of > around max 10-15 meters the phone showing -99dBM when we add the power amp > the range increases by a few meters however when we also add the LNA so we > have both the LNA + power amp connected at the same time > this is when the range decreases to around 5 meters. > > We would be happy if we were able to cover 1/2 mile or anything near this > range we do have a temporary license to transmit in our frequency however > this expires in 2 months. > > There has been quite a bit spent on equipment so far trying to extend the > range with no luck it seems the USRP is made only to work at a very short > range so any help on how to do this would be very much appreciated. > > Also would adding a bandpass filter to the RX side make any difference? > > The spec of equipment we are using is as follows > > 900 Mhz 12 dBi Yagi antenna > > Frequency（MHz）824~960MHz > Length:55cm > SWR ≤≤1.5 > Input Impedance-Ω: 50 > Horizontal Beamwidth -° :54/48/40/36/30 > Vertical Beamwidth -° :48/40/36/32/30 > Maximum Power -W :100 > Bandwidth-MHz :154/154/154/140/120 > > Duplexer > > 30 W GSM Duplexer TX RX > Pass Band 925 - 960 MHz 880 - 915 MHz > Insertion Loss 1.0 dB 1.0 dB > Passband Ripple 0.2 dB 0.2 dB > Rejection 50 dB @ 80-850 MHz 50 dB @ 80-800 MHz > 50 dB @ 1-3 GHz 50dB @ 1-3 GHz > Return Loss minimum 20 dB > Impedance 50 Ohms > Coupling Port -30 dB (+/- 1.5 dB) > Power 30 W average RF poewr > > > LNA > > Parameter Unit Minimum Typical Maximum > Frequency Range MHz 850 950 > Small Signal Gain dB 40 41 > Output Power Pout @ Pin = 0dBm dBm +40 > Saturated Power Psat @ Pin = +5dBm dBm +42 > IP3 dBm +50 > Reverse Isolation dB -75 > Efficiency at Pout = +40dBm % 38 > VSWR Input 1.4:1 > DC Power Supply V +12 > > Power Amp > > 775-950 Mhz > 40 dB gain > +18 dBm > > Filter > > Passband: 925-960 MHz > Passband Insertion Loss: 1.5 dB maximum > Rejection: > DC-915 MHz 80 dB minimum > 1000-2880 MHz 60 dB minimum > Passband Return Loss: 15 dB minimum > Maximum Power Handling: > CW 10 watts > Peak Instantaneous 40 watts > Intermodulation Products: -110 dBm maximum > with two +34 dBm carriers > > **** > > ** ** > > > ------------------------------------------------------------------------------ > See everything from the browser to the database with AppDynamics > Get end-to-end visibility with application monitoring from AppDynamics > Isolate bottlenecks and diagnose root cause in seconds. > Start your free trial of AppDynamics Pro today! > http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk > _______________________________________________ > Openbts-discuss mailing list > Ope...@li... > https://lists.sourceforge.net/lists/listinfo/openbts-discuss**** > > ** ** > > > > ------------------------------------------------------------------------------ > See everything from the browser to the database with AppDynamics > Get end-to-end visibility with application monitoring from AppDynamics > Isolate bottlenecks and diagnose root cause in seconds. > Start your free trial of AppDynamics Pro today! > http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk > _______________________________________________ > Openbts-discuss mailing list > Ope...@li... > https://lists.sourceforge.net/lists/listinfo/openbts-discuss**** > > ** ** > > ** ** > > > ------------------------------------------------------------------------------ > See everything from the browser to the database with AppDynamics > Get end-to-end visibility with application monitoring from AppDynamics > Isolate bottlenecks and diagnose root cause in seconds. > Start your free trial of AppDynamics Pro today! > http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk > _______________________________________________ > Openbts-discuss mailing list > Ope...@li... > https://lists.sourceforge.net/lists/listinfo/openbts-discuss > > |
