Re: [Openbts-discuss] USRP/OpenBTS Extending Range/Coverage Help

[Kurtis H. <khe...@cs...>]

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
>
>
>
>
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