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Re: Discuss-gnuradio Digest, Vol 217, Issue 10

From: Moses Browne Mwakyanjala
Subject: Re: Discuss-gnuradio Digest, Vol 217, Issue 10
Date: Mon, 9 Nov 2020 18:26:53 +0100

The flowgraph contains a sinusoidal source and a USRP sink. You may notice that the sample rate is quite high. It is part of the requirements. 

On Mon, Nov 9, 2020 at 6:19 PM <discuss-gnuradio-request@gnu.org> wrote:
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Today's Topics:

   1. Re: Measuring transmission power from USRP B210 (Marcus D. Leech)


Message: 1
Date: Mon, 09 Nov 2020 12:01:24 -0500
From: "Marcus D. Leech" <patchvonbraun@gmail.com>
To: discuss-gnuradio@gnu.org
Subject: Re: Measuring transmission power from USRP B210
Message-ID: <5FA975E4.9020000@gmail.com" target="_blank">5FA975E4.9020000@gmail.com>
Content-Type: text/plain; charset="utf-8"; Format="flowed"

On 11/09/2020 11:39 AM, Moses Browne Mwakyanjala wrote:
> Hello everyone,
> I'm in the process of testing a GNU Radio transmitter. The transmitter
> will be connected to a solid-state power amplifier (SSPA) for
> near-Earth satellite communications. The SSPA expects an input of 0dm
> from the USRP TX port.
> The first step is thus to measure the power from the USRP. To that
> end, the flowgraph generates a complex sinusoidal signal with a unit
> magnitude. The UHD:USRP Sink block is set to maximum gain (i.e.
> normalized gain of 1.0). Unfortunately, the maximum power I can see
> from the spectrum analyzer is around -6.93 dBm as shown below. To my
> understanding, the USRP can transmit up to 20 dBm as reported in the
> "External Connections" section at this Ettus link :
> https://files.ettus.com/manual/page_usrp_b200.html.
> Could anyone explain why I can't achieve a 20 dBm (or anything around
> it) power level?
> IMG_3475.JPG
> Thanks in advance,
> Moses.
Could we perhaps see a minimal flow-graph that demonstrates the issue?

Generally, setting the baseband magnitude to 1.0 at the same times as
setting to MAX gain can cause linearity issues.

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