Thanks for the insight. Is this publicly documented anywhere? The USRP web manual (https://files.ettus.com/manual/page_calibration.html) still explicitly states to leave RF ports disconnected for calibration. Updating that page ASAP could save folks out there a lot of grief…
From: Michael West <michael.w...@ettus.com> Date: Thursday, April 19, 2018 at 9:20 PM To: "Stanley, John P." <john.stan...@jhuapl.edu> Cc: ROBIN TORTORA <ti...@comcast.net>, "Stanley, John P. via USRP-users" <usrp-users@lists.ettus.com> Subject: Re: [USRP-users] DC Offset Calibration Issue for Rev. C UBX-40 daughter cards Hi John/Robin: The calibration utilities rely on leakage across the RF switch. The newer UBX boards (rev C and later) have RF switches with much higher isolation. The benefit is a lot less leakage from TX onto RX. The drawback is that the calibration utilities will only work if you connect the TX/RX to the RX2 port with a 30 dB attenuator in line. Regards, Michael On Thu, Apr 19, 2018 at 11:12 AM, Stanley, John P. via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> wrote: While uncalibrated LO leakage has never been great in the UBX for us, the dc offset calibration procedure has given us adequate enough improvement. We’re generally using offset tuning, but we still need that extra 15-20 dB suppression we get from the calibration procedure. The issue we’re seeing with these newer Rev C boards, though, is that the calibration doesn’t just fail to improve LO suppression; it actively makes it worse. Offset tuning is pretty fruitless when the LO spur alone is >0 dBm at the mid-point of available RF gain. From: ROBIN TORTORA <ti...@comcast.net<mailto:ti...@comcast.net>> Reply-To: ROBIN TORTORA <ti...@comcast.net<mailto:ti...@comcast.net>> Date: Thursday, April 19, 2018 at 1:44 PM To: "Stanley, John P. via USRP-users" <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>>, "Stanley, John P." <john.stan...@jhuapl.edu<mailto:john.stan...@jhuapl.edu>> Subject: Re: [USRP-users] DC Offset Calibration Issue for Rev. C UBX-40 daughter cards _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com<mailto:USRP-users@lists.ettus.com> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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