How to use the USRP2920 as CW transmitter

[HB-EUM]

Hi

For a simple application, I would like to use the USRP2920 as a CW transmitter.

I'd like to generate a cw-signal around 101MHz, and the frequency as well as the signal amplitude will change during the execution of the program.

My first idea was to use the AM-modulation with zero amplitude. That way, only the carrier signal was generated. I could have also simply defined a complex I/Q vectors as zeros.

But I didn't find the way to change the amplitude of the carrier.

Any suggestion ?

By the way (...), I need a solution till tomorrow...

Thanks for any comments

HB-EUM

[Sarah_Y]

Hey HB-EUM,

There is an example that ships with the NI-USRP 1.1 driver that should work for what you are trying to do, niUSRP EX Tx Continuous Async Reconfig on the Fly.vi.  You can find this example by going to Start » All Programs » National Instruments » NI-USRP » Examples.

If you set the tone frequency parameter on the front panel to 0 and the carrier frequency to 101M (or whatever your desired frequency is) you will generate a CW wave at 101 MHz.  If you need to change the amplitude of the tone, you can adjust the gain setting, which will update as soon as you update the gain parameter on the front panel.

[HB-EUM]

Thanks, I found it.

I guess, this would also work with the version 1.0.

best regards

HB-EUM

[HB-EUM]

Well, I was too optimistic....

First, I got some error messages when I try to change the gain in the loop: code -1074118632. This attribute cannot be modified while the driver is in the running state.

Is there a difference between 1.1 and 1.0 in that respect?

Best regards

HB-EUM

[Anthony_F]

Hello HB-EUM,

If I recall correctly, the ability to change the carrier frequency "on-the-fly" (otherwise known as "in a running state") was added in the USRP 1.1 update.

Yes, the readme does say this:

NI-USRP 1.1 includes the following features:
...
...
Support for reconfiguring gain, carrier frequency, and active antenna while an acquisition or generation is in progress

[HB-EUM · Accepted solution]

Hallo Anthony and Sarah,

first , thanks Anthony, that was my first question at the beginning of this thread.....

Now, everything is working fine since I could at last make a update of the image and firmware!

with my best regards

HB-EUM