# Re: Max Output Power from the LFTX

**URL:** <https://www.ruby-forum.com/t/re-max-output-power-from-the-lftx/233733>\
**Category:** GNU Radio\
**Created:** [January 6, 2015, 6:23pm UTC](https://www.ruby-forum.com/t/re-max-output-power-from-the-lftx/233733 "2015-01-06T18:23:39Z")\
**Posts on this page:** 4\
**Page:** 2

<div class="post-metadata">

**Author:** ![khalide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/3bc359/32.png) [@khalide](https://www.ruby-forum.com/u/khalide)\
**Post date:** [January 16, 2015, 9:07pm UTC](https://www.ruby-forum.com/t/re-max-output-power-from-the-lftx/233733/21 "2015-01-16T21:07:22Z")

</div>

I see. Is there someone we can contact at Ettus for this?

Khalid

---

<div class="post-metadata">

**Author:** ![khalide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/3bc359/32.png) [@khalide](https://www.ruby-forum.com/u/khalide)\
**Post date:** [January 16, 2015, 9:11pm UTC](https://www.ruby-forum.com/t/re-max-output-power-from-the-lftx/233733/22 "2015-01-16T21:11:44Z")

</div>

On 01/16/2015 03:06 PM, khalid.el-darymli wrote:

> I see. Is there someone we can contact at Ettus for this?
> 
> Khalid

Send a note to [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)

If the card is within waranty period, you’ll likely get a replacement.  
Otherwise, the NI repair policy kicks in, and it wouldn’t be worth  
getting it  
repaired.

---

<div class="post-metadata">

**Author:** ![khalide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/3bc359/32.png) [@khalide](https://www.ruby-forum.com/u/khalide)\
**Post date:** [January 19, 2015, 8:10am UTC](https://www.ruby-forum.com/t/re-max-output-power-from-the-lftx/233733/23 "2015-01-19T08:10:24Z")

</div>

We are using almost the same IC in our product, as a driver for a  
transmitting coil in industrial environment, for material test, and we  
had never ever fail one of those. Must be around 4k or 5k of those ICs  
we have out in the field, and the only failures were two or three that  
came dead from the PCB manufacturer. Even a hard short never was able to  
kill one.

Ralph.

From: [discuss-gnuradio-bounces+ralph=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+ralph=removed_email_address@domain.invalid)  
[[mailto:discuss-gnuradio-bounces+ralph=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+ralph=removed_email_address@domain.invalid)] On Behalf Of  
Marcus D. Leech  
Sent: Friday, January 16, 2015 8:12 PM  
To: khalid.el-darymli; Michael R.  
Cc: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Discuss-gnuradio] Max Output Power from the LFTX

On 01/16/2015 02:08 PM, khalid.el-darymli wrote:

Hi All,

Just to update you in case somebody else comes across this problem.  
Following Mike’s advice, we replaced the LFTX daughterboard with a new  
one. We’re getting now 1 V p-p. This is around 4 dBm.

Thanks very much for your help.

Best regards,

Khalid

Interesting. The driver chip that’s used, as a unity-gain  
differential-to-single-ended driver, is, according to the datasheets,  
pretty robust. So, it would  
be interesting to know exactly what the failure mode is.

On Tue, Jan 6, 2015 at 2:38 PM, Michael R. \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

Hi Khalid,

I had a similar issue with an LFTX that I had been working with for  
about two years. I actually had two boards running on separate USRP2’s  
and both were working fine for quite a while, but I recently noticed  
that one had a drastically lower output range. I ended up replacing the  
LFTX and all is working well now, so I’m assuming it was a hardware  
issue that came up at some point.

I didn’t take the time to look for the problem, but I figured I’d share  
this info since what you’re seeing might be a hardware issue rather than  
something you can resolve with settings.

-Mike

On Tue, Jan 6, 2015 at 12:59 PM, khalid.el-darymli  
\<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

> > Output power is determined largely by baseband signal magnitude in that case.

Yes, I understand. And I noticed that for baseband signal with an  
amplitude \> 1, the pass-band signal gets clipped off. So I assume that  
an amplitude of 1 for the baseband signal should deliver the maximum  
output power (for the pass-band signal).

My question was, what is the maximum power one can get for the pass-band  
signal output from LFTX? In your earlier reply, you said it is around  
+7dBm, am I getting this right? In my case, for a baseband amplitude of  
around 1, I am only getting -28.13dBm, much less than what you said, I  
am not sure, why?

Thanks,

Khalid

On Tue, Jan 6, 2015 at 1:56 PM, Marcus D. Leech \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

Thanks Marcus for your reply.

> > Probably somewhere in the neighborhood of +7dBm, maybe a little more.

> > The LF/BASIC series have _no_ gain in either path, so you’re just looked  
> > at buffered ADC ouput.

So, ~ +7dBm is the max output power I supposed to get from the LFTX  
daughterboard? How do I get that?

Since I am only getting -28.13 dBm, does that mean I have some issue  
with my LFTX daughterboard?

Khalid

Output power is determined largely by baseband signal magnitude in that  
case.

Message: 2  
Date: Tue, 6 Jan 2015 10:13:45 -0330  
From: “khalid.el-darymli” \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
To: "[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) "  
\<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
Subject: [Discuss-gnuradio] Max Output Power from the LFTX  
daughterboard  
Message-ID:  
\<CACdmG=zCHATiwrtv=wBVLwG0\_

[5GQr0y=removed\_email\_address@domain.invalid](mailto:5GQr0y=removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
Content-Type: text/plain; charset=“utf-8”

Hi,

What is the maximum output power from the LFTX daughterboard when used  
with  
the USRP N200?

According to this datasheet [1], the N200 with the WBX daughterbaord  
provide an output power of 15 dBm. However, when using the LFTX  
daughterboard, I am getting a much less output power.  
[1]  
[http://www.ettus.com/content/files/07495\_Ettus\_N200-210\_DS\_Flyer\_HR.pdf](http://www.ettus.com/content/files/07495_Ettus_N200-210_DS_Flyer_HR.pdf)

In GNU Radio with the USRP N200, we use a sinusoid with a frequency of  
150  
kHz and an amplitude of 0.98, fed into the LFTX daughterboard for a  
center  
frequency of 5 MHz. When the output of LFTX is plugged into a scope  
terminated with a 50-ohm terminator, the scope reads 24.8 mV  
(peak-to-peak). This is around -28.13 dBm.

Is this the max power one can get out of the LFTX daughterboard?

Thanks.

Best regards,  
Khalid  
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Message: 3  
Date: Tue, 06 Jan 2015 08:48:08 -0500  
From: “Marcus D. Leech” \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
To: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Discuss-gnuradio] Max Output Power from the LFTX  
daughterboard  
Message-ID: \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
Content-Type: text/plain; charset=UTF-8; format=flowed

On 01/06/2015 08:43 AM, khalid.el-darymli wrote:

> Best regards,  
> Khalid  
> Probably somewhere in the neighborhood of +7dBm, maybe a little more.

The LF/BASIC series have _no_ gain in either path, so you’re just looked  
at buffered ADC ouput.

–  
Marcus L.  
Principal Investigator  
Shirleys Bay Radio Astronomy Consortium

> **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org/)**
>
> Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami.

–  
Marcus L.  
Principal Investigator  
Shirleys Bay Radio Astronomy Consortium

> **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org/)**
>
> Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami.

---

<div class="post-metadata">

**Author:** ![khalide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/3bc359/32.png) [@khalide](https://www.ruby-forum.com/u/khalide)\
**Post date:** [January 19, 2015, 8:11am UTC](https://www.ruby-forum.com/t/re-max-output-power-from-the-lftx/233733/24 "2015-01-19T08:11:41Z")

</div>

Usually you just see, the IC is defective, that’s all, and this is what  
we already know anyway 🙂

Ralph.

From: [discuss-gnuradio-bounces+ralph=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+ralph=removed_email_address@domain.invalid)  
[[mailto:discuss-gnuradio-bounces+ralph=removed\_email\_address@domain.invalid](mailto:discuss-gnuradio-bounces+ralph=removed_email_address@domain.invalid)] On Behalf Of  
Marcus D. Leech  
Sent: Friday, January 16, 2015 8:59 PM  
To: khalid.el-darymli  
Cc: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Discuss-gnuradio] Max Output Power from the LFTX

On 01/16/2015 02:54 PM, khalid.el-darymli wrote:

I see. If you would like to diagnose the problem, we can ship you the  
malfunctioned daughterboard?

Thanks,

Khalid

Thanks. I personally wouldn’t have time/equipment to really diagnose  
it. So it would be up to Ettus R&D as to whether they want it back to  
see  
what the failure mode is.

I’ve been doing Ettus support for 6 years, and LF\_TX are not generally  
items that show up with RMA requests very often.

On Fri, Jan 16, 2015 at 4:17 PM, Marcus D. Leech \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

On 01/16/2015 02:42 PM, khalid.el-darymli wrote:

We were using only one Tx channel with the Subdev Spec in the USRP Sink  
is set to A:AB

Could the failure be due to that the other (idle) Tx channel is left  
open circuit (i.e., not terminated by 50 ohms)?

That seems quite unlikely. These aren’t “precious princess” RF power  
transistors, but reasonably-robust differential-to-unbalanced drivers.  
I’d  
be very surprised if they couldn’t handle an open-circuit condition.

Khalid

On Fri, Jan 16, 2015 at 3:41 PM, Marcus D. Leech \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

On 01/16/2015 02:08 PM, khalid.el-darymli wrote:

Hi All,

Just to update you in case somebody else comes across this problem.  
Following Mike’s advice, we replaced the LFTX daughterboard with a new  
one. We’re getting now 1 V p-p. This is around 4 dBm.

Thanks very much for your help.

Best regards,

Khalid

Interesting. The driver chip that’s used, as a unity-gain  
differential-to-single-ended driver, is, according to the datasheets,  
pretty robust. So, it would  
be interesting to know exactly what the failure mode is.

On Tue, Jan 6, 2015 at 2:38 PM, Michael R. \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

Hi Khalid,

I had a similar issue with an LFTX that I had been working with for  
about two years. I actually had two boards running on separate USRP2’s  
and both were working fine for quite a while, but I recently noticed  
that one had a drastically lower output range. I ended up replacing the  
LFTX and all is working well now, so I’m assuming it was a hardware  
issue that came up at some point.

I didn’t take the time to look for the problem, but I figured I’d share  
this info since what you’re seeing might be a hardware issue rather than  
something you can resolve with settings.

-Mike

On Tue, Jan 6, 2015 at 12:59 PM, khalid.el-darymli  
\<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

> > Output power is determined largely by baseband signal magnitude in that case.

Yes, I understand. And I noticed that for baseband signal with an  
amplitude \> 1, the pass-band signal gets clipped off. So I assume that  
an amplitude of 1 for the baseband signal should deliver the maximum  
output power (for the pass-band signal).

My question was, what is the maximum power one can get for the pass-band  
signal output from LFTX? In your earlier reply, you said it is around  
+7dBm, am I getting this right? In my case, for a baseband amplitude of  
around 1, I am only getting -28.13dBm, much less than what you said, I  
am not sure, why?

Thanks,

Khalid

On Tue, Jan 6, 2015 at 1:56 PM, Marcus D. Leech \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \> wrote:

Thanks Marcus for your reply.

> > Probably somewhere in the neighborhood of +7dBm, maybe a little more.

> > The LF/BASIC series have _no_ gain in either path, so you’re just looked  
> > at buffered ADC ouput.

So, ~ +7dBm is the max output power I supposed to get from the LFTX  
daughterboard? How do I get that?

Since I am only getting -28.13 dBm, does that mean I have some issue  
with my LFTX daughterboard?

Khalid

Output power is determined largely by baseband signal magnitude in that  
case.

Message: 2  
Date: Tue, 6 Jan 2015 10:13:45 -0330  
From: “khalid.el-darymli” \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
To: "[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) "  
\<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
Subject: [Discuss-gnuradio] Max Output Power from the LFTX  
daughterboard  
Message-ID:  
\<CACdmG=zCHATiwrtv=wBVLwG0\_

[5GQr0y=removed\_email\_address@domain.invalid](mailto:5GQr0y=removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
Content-Type: text/plain; charset=“utf-8”

Hi,

What is the maximum output power from the LFTX daughterboard when used  
with  
the USRP N200?

According to this datasheet [1], the N200 with the WBX daughterbaord  
provide an output power of 15 dBm. However, when using the LFTX  
daughterboard, I am getting a much less output power.  
[1]  
[http://www.ettus.com/content/files/07495\_Ettus\_N200-210\_DS\_Flyer\_HR.pdf](http://www.ettus.com/content/files/07495_Ettus_N200-210_DS_Flyer_HR.pdf)

In GNU Radio with the USRP N200, we use a sinusoid with a frequency of  
150  
kHz and an amplitude of 0.98, fed into the LFTX daughterboard for a  
center  
frequency of 5 MHz. When the output of LFTX is plugged into a scope  
terminated with a 50-ohm terminator, the scope reads 24.8 mV  
(peak-to-peak). This is around -28.13 dBm.

Is this the max power one can get out of the LFTX daughterboard?

Thanks.

Best regards,  
Khalid  
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Message: 3  
Date: Tue, 06 Jan 2015 08:48:08 -0500  
From: “Marcus D. Leech” \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
To: [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) [mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
Subject: Re: [Discuss-gnuradio] Max Output Power from the LFTX  
daughterboard  
Message-ID: \<[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
[mailto:removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) \>  
Content-Type: text/plain; charset=UTF-8; format=flowed

On 01/06/2015 08:43 AM, khalid.el-darymli wrote:

> Best regards,  
> Khalid  
> Probably somewhere in the neighborhood of +7dBm, maybe a little more.

The LF/BASIC series have _no_ gain in either path, so you’re just looked  
at buffered ADC ouput.

–  
Marcus L.  
Principal Investigator  
Shirleys Bay Radio Astronomy Consortium

> **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org/)**
>
> Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami.

–  
Marcus L.  
Principal Investigator  
Shirleys Bay Radio Astronomy Consortium

> **[Live Draw HK Tercepat | Result HK | HK Pools | Live HK | HK Prize Hari Ini](https://www.sbrac.org/)**
>
> Temukan live draw hk tercepat melalui halaman hk pools yang resmi dan dapatkan result hk prize melalui live hk secara langsung di situs kami.

* * *

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