Thanks a lot for your reply, lots of very useful information! A few questions:
* When you say a max gain of 89 dB, that is the gain you set in GNU Radio on the USRP block right? * With a 30dB attenuator, regardless of what I set the gain to on either the rx/tx blocks in GNU Radio, and regardless of how far apart I position the antennas I won't be able to damage the rx side will I? * One thing I'm wondering also is how you calculated the dBm value for 49 dB tx gain? Cheers Chris On Sun, Mar 4, 2018 at 6:00 AM, Gilad Beeri (ApolloShield) < gi...@apolloshield.com> wrote: > B200 has a max output power of ~ 15 dBm (give or take) in max gain (89 > dB), depending on the frequency, and a max input power of 0 dBm. To be on > the safe side, you can and should take a 10 dB backoff, so for the sake of > discussion, assume the max input power is -10 dBm. > > You can use the Free Space Path Loss formula (calculator: https://www. > pasternack.com/t-calculator-fspl.aspx) to get a sense (the formula is for > the free space) of how much power you "lose" by using a wireless channel, > the results depend on your choice of frequency and distance between > antennas. You need to make sure the antennas are "far" enough to be on the > far field of each other. > > You can also take into account the attenuation the SMA cables add on both > sides, or, to save you all of the trouble, > you can just transmit with a gain low enough such that the transmitted > signal is weaker than the max input power (i.e., if 89 dB tx gain is ~ 15 > dBm, then 49 dB tx gain is ~ -25 dBm, so you're good), and/or you can put a > 30 dB attenuator either in the tx or rx port, that way you'll know that > even if you make a software mistake, you're on the safe side. > > On Sun, Mar 4, 2018 at 3:38 AM Christopher Richardson via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Hi, >> >> I'm just wondering if anyone could give me some advice, I'm using the USRP >> B200 with GNU Radio with a simple FM example to transmit and receive on >> the same frequency. >> >> I made use of telescopic whip antennas on the Tx port and another on the >> Rx port, I had the antennas tilted away from each other, but I've been >> informed this could still be a bad idea and could overload the receiver? (I >> had also played with different Rx/Tx gain values while testing this). >> >> I'm just hoping I haven't damaged anything. >> >> I'm planning on now getting 2x 3 metre SMA cables to separate the >> antennas by around 6 metres, does this seem sensible? >> >> Cheers >> >> Chris >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >
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