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View all threadsUBX-40 Gain
I wanted to make sure that I understand the UBX-40 gain correctly. It
seems that there is an LNA (one for < 1.5 GHz and one for > 1.5 GHz)
followed by a programmable attenuator. When playing with GNU Radio and
adjusting the gain of the N210, am I simply setting how much attenuation to
add after the LNA? Meaning that at 31.5 dB of 'gain' I am simply not
attenuating the LNA output? And for 0 dB of 'gain' I am attenuating the
output of the LNA by 31.5 dB?
Thanks!
On 02/24/2017 04:24 PM, Dave NotTelling via USRP-users wrote:
I wanted to make sure that I understand the UBX-40 gain correctly. It
seems that there is an LNA (one for < 1.5 GHz and one for > 1.5 GHz)
followed by a programmable attenuator. When playing with GNU Radio
and adjusting the gain of the N210, am I simply setting how much
attenuation to add after the LNA? Meaning that at 31.5 dB of 'gain' I
am simply not attenuating the LNA output? And for 0 dB of 'gain' I am
attenuating the output of the LNA by 31.5 dB?
Thanks!
Yes, that's precisely it.
In fact, there are two layers of LNA, as I recall, and the attenuator
lives between them. This reduces the impact on noise figure.
Thank you!
On Fri, Feb 24, 2017 at 4:42 PM, Marcus D. Leech via USRP-users <
usrp-users@lists.ettus.com> wrote:
On 02/24/2017 04:24 PM, Dave NotTelling via USRP-users wrote:
I wanted to make sure that I understand the UBX-40 gain correctly. It
seems that there is an LNA (one for < 1.5 GHz and one for > 1.5 GHz)
followed by a programmable attenuator. When playing with GNU Radio and
adjusting the gain of the N210, am I simply setting how much attenuation to
add after the LNA? Meaning that at 31.5 dB of 'gain' I am simply not
attenuating the LNA output? And for 0 dB of 'gain' I am attenuating the
output of the LNA by 31.5 dB?
Thanks!
Yes, that's precisely it.
In fact, there are two layers of LNA, as I recall, and the attenuator
lives between them. This reduces the impact on noise figure.
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On 02/24/2017 04:44 PM, Dave NotTelling wrote:
Thank you!
No problem.
I'd also like to point out, for the benefit of the assembled audience,
that when you set a gain like this, you ARE NOT setting the total system
gain, but only the variable portion of it. For example, the mixer
has a fixed conversion gain, and then whatever IF/baseband amplifiers
are in-circuit also contribute some gain. On some systems, the ADC
also has a VGA built-in.
Some folks have been tempted "in to sin" by making assumptions about
total system gain, and using a strictly numeric approach to
estimate signal levels as seen at the antenna port. Just wanted to
point out that's dead-wrong and you need to calibrate with an
external, known, source.
On Fri, Feb 24, 2017 at 4:42 PM, Marcus D. Leech via USRP-users
<usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com> wrote:
On 02/24/2017 04:24 PM, Dave NotTelling via USRP-users wrote:
I wanted to make sure that I understand the UBX-40 gain
correctly. It seems that there is an LNA (one for < 1.5 GHz and
one for > 1.5 GHz) followed by a programmable attenuator. When
playing with GNU Radio and adjusting the gain of the N210, am I
simply setting how much attenuation to add after the LNA?
Meaning that at 31.5 dB of 'gain' I am simply not attenuating the
LNA output? And for 0 dB of 'gain' I am attenuating the output of
the LNA by 31.5 dB?
Thanks!
Yes, that's precisely it.
In fact, there are two layers of LNA, as I recall, and the
attenuator lives between them. This reduces the impact on noise
figure.
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Very good to know, thanks again :D
On Fri, Feb 24, 2017 at 5:06 PM, Marcus D. Leech mleech@ripnet.com wrote:
On 02/24/2017 04:44 PM, Dave NotTelling wrote:
Thank you!
No problem.
I'd also like to point out, for the benefit of the assembled audience,
that when you set a gain like this, you ARE NOT setting the total system
gain, but only the variable portion of it. For example, the mixer has a
fixed conversion gain, and then whatever IF/baseband amplifiers
are in-circuit also contribute some gain. On some systems, the ADC also
has a VGA built-in.
Some folks have been tempted "in to sin" by making assumptions about total
system gain, and using a strictly numeric approach to
estimate signal levels as seen at the antenna port. Just wanted to
point out that's dead-wrong and you need to calibrate with an
external, known, source.
On Fri, Feb 24, 2017 at 4:42 PM, Marcus D. Leech via USRP-users <
usrp-users@lists.ettus.com> wrote:
On 02/24/2017 04:24 PM, Dave NotTelling via USRP-users wrote:
I wanted to make sure that I understand the UBX-40 gain correctly. It
seems that there is an LNA (one for < 1.5 GHz and one for > 1.5 GHz)
followed by a programmable attenuator. When playing with GNU Radio and
adjusting the gain of the N210, am I simply setting how much attenuation to
add after the LNA? Meaning that at 31.5 dB of 'gain' I am simply not
attenuating the LNA output? And for 0 dB of 'gain' I am attenuating the
output of the LNA by 31.5 dB?
Thanks!
Yes, that's precisely it.
In fact, there are two layers of LNA, as I recall, and the attenuator
lives between them. This reduces the impact on noise figure.
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