Re: [Discuss-gnuradio] why two switches and two Rx in RFX series daughter boards?
Hi Matt, Thanks a lot! So, you means I just need connect between Tx/Rx and leave Rx2 unused for RFX 900. But I want to implement FDD (frequency division duplex), it should use Rx2. Do I need to make change to hardware? how? Thank you! 2007/7/6, Matt Ettus <[EMAIL PROTECTED]>: zhifeng chen wrote: > I am wondering why there are two switches in the RFX series daughter > from schematics. It seems their purposes is different: one for switch > between Tx and Rx, another switch between Rx and Rx2. So, my questions as: > 1. we may use one tx and rx enough, why need to use two Rx? The RX2 port is for those people using external amplifiers who need RX and TX on separate ports. > 2.I follow the python code into usrp.pick_rx_subdevice(u) and the > return value is side and subdev. Since there are two rx there, how may > I know subdev refer to rx or rx2? The subdev is not used on this board. The select rx antenna function is used to choose between the 2 antennas. > 3. if we call set_auto_tr(), it refer to which switch? It controls all switches. > > I also test usrp_fft.py and find both Tx/Rx and Rx2 have signal input > (by using the same usrp_siggen.py), while input from Tx/Rx is stronger > than Rx2. Since Tx/Rx is followed by a filter, it should be less than > Rx2, so, what happens here? The RX2 signal is weaker by about 25dB because it is disconnected. The switches don't have infinite blocking. > > I use two sets of USRP with RFX900 to test a FDD( frequency devision > duplex) by cable connection. According to my experience, the cable > loss should be less than 0.5-1 db, right? (which come with RFX900) So, > If I set the same gain for two RFX900 tx, say -a 100, the received > signal is much smaller than the coupled signal from itself, whatever > the different frenquency is. So, why there are both input signal? it > is coupled signal or intentionally designed? I think it is intentional > designed, and since the tx signal is routed to Rx2 directly, so it is > much stronger than come from its peer end, is it right? > You should NEVER connect the TX output to an RX input without a lot of attenuation in between. You should also not be using RX2 in your situation. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] why two switches and two Rx in RFX
> > Question. What is "a lot of attenuation" (ballpark?) I have a RFX1800 > transmitting at "20" going into (cabled) a dbsrx with gain "40". > Between the transmitter and receiver I have 40dB worth of > attenuators... Would you suggest any different? I learnt the hard way > on the first dbsrx :) The RFX boards can put out as much as 26 dBm. The RF inputs can be damaged by 0dBm. So use at least 30dB. But the frontend isn't linear unless you go even lower. I get this question a lot, and I don't understand it. Attenuators are cheap and they don't charge per dB. Why not just throw 40 or 50dB in there and be safe? Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] why two switches and two Rx in RFX
Message: 2 Date: Thu, 05 Jul 2007 10:10:15 -0700 From: Matt Ettus <[EMAIL PROTECTED]> Subject: Re: [Discuss-gnuradio] why two switches and two Rx in RFX ... I use two sets of USRP with RFX900 to test a FDD( frequency devision duplex) by cable connection. According to my experience, the cable loss should be less than 0.5-1 db, right? (which come with RFX900) So, If I set the same gain for two RFX900 tx, say -a 100, the received signal is much smaller than the coupled signal from itself, whatever the different frenquency is. So, why there are both input signal? it is coupled signal or intentionally designed? I think it is intentional designed, and since the tx signal is routed to Rx2 directly, so it is much stronger than come from its peer end, is it right? You should NEVER connect the TX output to an RX input without a lot of attenuation in between. You should also not be using RX2 in your situation. Matt Question. What is "a lot of attenuation" (ballpark?) I have a RFX1800 transmitting at "20" going into (cabled) a dbsrx with gain "40". Between the transmitter and receiver I have 40dB worth of attenuators... Would you suggest any different? I learnt the hard way on the first dbsrx :) Thanks Jeff ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] why two switches and two Rx in RFX series daughter boards?
zhifeng chen wrote: > I am wondering why there are two switches in the RFX series daughter > from schematics. It seems their purposes is different: one for switch > between Tx and Rx, another switch between Rx and Rx2. So, my questions as: > 1. we may use one tx and rx enough, why need to use two Rx? The RX2 port is for those people using external amplifiers who need RX and TX on separate ports. > 2.I follow the python code into usrp.pick_rx_subdevice(u) and the > return value is side and subdev. Since there are two rx there, how may > I know subdev refer to rx or rx2? The subdev is not used on this board. The select rx antenna function is used to choose between the 2 antennas. > 3. if we call set_auto_tr(), it refer to which switch? It controls all switches. > > I also test usrp_fft.py and find both Tx/Rx and Rx2 have signal input > (by using the same usrp_siggen.py), while input from Tx/Rx is stronger > than Rx2. Since Tx/Rx is followed by a filter, it should be less than > Rx2, so, what happens here? The RX2 signal is weaker by about 25dB because it is disconnected. The switches don't have infinite blocking. > > I use two sets of USRP with RFX900 to test a FDD( frequency devision > duplex) by cable connection. According to my experience, the cable > loss should be less than 0.5-1 db, right? (which come with RFX900) So, > If I set the same gain for two RFX900 tx, say -a 100, the received > signal is much smaller than the coupled signal from itself, whatever > the different frenquency is. So, why there are both input signal? it > is coupled signal or intentionally designed? I think it is intentional > designed, and since the tx signal is routed to Rx2 directly, so it is > much stronger than come from its peer end, is it right? > You should NEVER connect the TX output to an RX input without a lot of attenuation in between. You should also not be using RX2 in your situation. Matt ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] why two switches and two Rx in RFX series daughter boards?
I am wondering why there are two switches in the RFX series daughter from schematics. It seems their purposes is different: one for switch between Tx and Rx, another switch between Rx and Rx2. So, my questions as: 1. we may use one tx and rx enough, why need to use two Rx? 2.I follow the python code into usrp.pick_rx_subdevice(u) and the return value is side and subdev. Since there are two rx there, how may I know subdev refer to rx or rx2? 3. if we call set_auto_tr(), it refer to which switch? I also test usrp_fft.py and find both Tx/Rx and Rx2 have signal input (by using the same usrp_siggen.py), while input from Tx/Rx is stronger than Rx2. Since Tx/Rx is followed by a filter, it should be less than Rx2, so, what happens here? I use two sets of USRP with RFX900 to test a FDD( frequency devision duplex) by cable connection. According to my experience, the cable loss should be less than 0.5-1 db, right? (which come with RFX900) So, If I set the same gain for two RFX900 tx, say -a 100, the received signal is much smaller than the coupled signal from itself, whatever the different frenquency is. So, why there are both input signal? it is coupled signal or intentionally designed? I think it is intentional designed, and since the tx signal is routed to Rx2 directly, so it is much stronger than come from its peer end, is it right? Thanks for your reply! BR, Zhifeng ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
