It seems like it was correct before and wrong now. It's always been said
that baseband levels must be restricted to -1.0 to 1.0. Now it's
something different?
I consider this issue to be the same as a patch to the Linux kernel that
breaks user space. And you know how Linus feels about that.
Ron
On 09/10/2018 07:26 PM, Marcus D. Leech via USRP-users wrote:
On 09/10/2018 10:21 PM, Ron Economos via USRP-users wrote:
I have to reduce the baseband amplitude from 0.96 to 0.67 to achieve
the same IMD.
This is a very annoying issue for me, especially since I've set
levels in the Gnu Radio gr-dtv example flow graphs based on previous
behavior.
Ron
I think it was Michael West who worked on the scaling issues in
B2xx. The internal implementation had been wrong for a long time,
from what I understood. This has the unfortunate side-effect that
previous carefully-set baseband levels may no longer work properly.
Unfortunately, there's no "set the baseband magnitude and RF gain as
loud as you can without producing excessive IMD" operator in UHD.
On 09/10/2018 05:37 PM, Marcus D. Leech via USRP-users wrote:
On 09/10/2018 08:34 PM, Ron Economos via USRP-users wrote:
I'll try that. It's going to take a while though since I have to
rebuild.
Ron
Understood. Sorry for the PITA....
On 09/10/2018 05:30 PM, Marcus D. Leech via USRP-users wrote:
On 09/10/2018 08:27 PM, Ron Economos via USRP-users wrote:
No change with 3.13.0. Haven't tried 3.14, since it's not
released yet.
Ron
Is this effect independent of baseband magnitude?
On 09/10/2018 05:21 PM, Marcus D. Leech via USRP-users wrote:
On 09/10/2018 08:17 PM, Ron Economos via USRP-users wrote:
I had previously noted that the B210 TX power had increased by
about 5 dB going from UHD 3.11.1.0 to UHD 3.12.0. Today, I was
doing some two tone IMD testing and noticed that the IMD
performance has degraded *severely* from UHD 3.11.1.0 to UHD
3.12.0.
Here are the spectrum analyzer plots at roughly the same power
level. The 3rd order two tone IMD level changes from almost -50
dB in 3.11.0.1 to a hideous -20 dB with 3.12.0. Something is
terribly wrong.
I know that there had been some "futzing" with scaling in the
B2xx at around that time. What about 3.13 or 3.14?
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