# Signal level **URL:** \ **Category:** GNU Radio\ **Created:** [June 5, 2014, 4:35am UTC](https://www.ruby-forum.com/t/signal-level/230215 "2014-06-05T04:35:15Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 4:35am UTC](https://www.ruby-forum.com/t/signal-level/230215/1 "2014-06-05T04:35:15Z")
Hi, In GRC is it necessary that we give a signal to any sink having an amplitude greater than 1? Regards, Ali ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 5:15am UTC](https://www.ruby-forum.com/t/signal-level/230215/2 "2014-06-05T05:15:20Z")
Hi Ali - some sinks care about the amplitude, and others do not. For example, the instruments built into gnuradio (Scope, Frequency display, etc.) can examine a signal of almost any amplitude within floating-point range because you can adjust the display scale factor. However other sinks, such as a physical transmitter (USRP, HPSDR, etc.) are constrained in the amplitude that they can accept. Normally this must be less than one, and hitting or exceeding 1.00 (even just on the peak) can cause problems. Also a physical transmitter might have only 12 or 16 bits fixed point dynamic range, so there may be a minimum signal amplitude as well. – Tom, N5EG ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 9:56am UTC](https://www.ruby-forum.com/t/signal-level/230215/3 "2014-06-05T09:56:30Z")
On 05.06.2014 05:17, jason sam wrote: > Hi Tom, > Can you tell what is the constraint for USRP B210? Stay _well_ within +/-1. M ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 5:18am UTC](https://www.ruby-forum.com/t/signal-level/230215/4 "2014-06-05T05:18:17Z")
Hi Tom, Can you tell what is the constraint for USRP B210? ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 10:02am UTC](https://www.ruby-forum.com/t/signal-level/230215/5 "2014-06-05T10:02:24Z")
What will happen if i exceed this limit?Actually with this amplitude the TX power is very less…Is there any other solution? On Thu, Jun 5, 2014 at 12:54 PM, Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 10:10am UTC](https://www.ruby-forum.com/t/signal-level/230215/6 "2014-06-05T10:10:40Z")
Hi Ali, > power is very less… > Of course, since power is proportional to amplitude squared. > Obviously, if you try to drive an DAC with more than it’s maximum > amplitude, you will get clipping. > This is a nonlinear thing and has very bad effects on your spectrum, and > that’s why you usually avoid it. Greetings, ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 1:29pm UTC](https://www.ruby-forum.com/t/signal-level/230215/7 "2014-06-05T13:29:58Z")
On Thu, Jun 5, 2014 at 3:54 PM, Martin B. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > On 05.06.2014 05:17, jason sam wrote: > > > Hi Tom, > > Can you tell what is the constraint for USRP B210? > > Stay _well_ within +/-1. Is there any way to tell whether clipping had happened, says from warning message etc ..? ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 1:14pm UTC](https://www.ruby-forum.com/t/signal-level/230215/8 "2014-06-05T13:14:38Z")
On Thu, Jun 5, 2014 at 4:09 PM, Marcus Müller [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Hi Ali, > > > power is very less… > > Of course, since power is proportional to amplitude squared. > > Obviously, if you try to drive an DAC with more than it’s maximum > > amplitude, you will get clipping. > > This is a nonlinear thing and has very bad effects on your spectrum, and > > that’s why you usually avoid it. Dear Sirs, There is a parameter “Ch0: Gain(dB)” on both UHD Source and UHD Sink. Does this gain apply before or after the ADC? Meanwhile depends on daughtercards, sometime there are some built-in “auto-gain” mechanism, is this correct? ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 3:34pm UTC](https://www.ruby-forum.com/t/signal-level/230215/9 "2014-06-05T15:34:56Z")
Well, clipping _definitively_ will occur when you leave the ±1 range; below that, clipping can happen in the analog part, which the USRP can’t warn you about. ---
**Author:** ![jason\_sam](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/7993a0/32.png) [@jason\_sam](https://www.ruby-forum.com/u/jason_sam)\ **Post date:** [June 5, 2014, 2:23pm UTC](https://www.ruby-forum.com/t/signal-level/230215/10 "2014-06-05T14:23:37Z")
On 05.06.2014 13:13, Activecat wrote: > Dear Sirs, > > There is a parameter “Ch0: Gain(dB)” on both UHD Source and UHD Sink. > Does this gain apply before or after the ADC? > > Meanwhile depends on daughtercards, sometime there are some built-in > “auto-gain” mechanism, is this correct? That sort of wraps it up. However, setting the gain to max can also give you nonlinear distortions. M