Is the input impedance of your scope 1Mohm or 50 ohms? You sure you have
the voltage multiplier (1x/10x) set correctly?
On Tue, Jan 6, 2015 at 11:01 AM, khalid.el-darymli <khalid.el-dary...@mun.ca
> wrote:
> >> Trying setting a gain in your sink block of, let's say, 20dB, with a
> magnitude of 0.9. What power output do you get? How are you measuring
> power?
>
> This gives me 23.2 mV (peak to peak). This is the reading I get from a
> scope connected to a T. For the input ends of the T, one end is connected
> to a 50-ohm terminator and the other end is connected to the output from
> LFTX. This gives a power of: 30+10 log_10[{23.2e-03/[2*sqrt(2)]}^2/50]=
> *-28.711* dBm.
>
> >> What is your flow-graph actually doing? Have you tried both connectors
> on the LFTX?
>
> Simple, a signal source (Sine) block directly connected to a USRP Sink
> block.
> Yes, both connectors on the LFTX daughterboard give the same voltage
> reading.
>
> Thanks,
> Khalid
>
>
>
>
>
>
>
>
>
>
> On Tue, Jan 6, 2015 at 2:34 PM, Marcus D. Leech <mle...@ripnet.com> 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
>>
>> For a magnitude of ~1, you should see maximum amplitude signals coming
>> out of it.
>>
>> You could try setting gain, but on any platforms with VGAs in the DAC,
>> there's only about 6dB of gain range settable. Trying setting a gain in
>> your
>> sink block of, let's say, 20dB, with a magnitude of 0.9. What power
>> output do you get? How are you measuring power? What is your flow-graph
>> actually doing? Have you tried both connectors on the LFTX?
>>
>>
>>
>>
>> On Tue, Jan 6, 2015 at 1:56 PM, Marcus D. Leech <mle...@ripnet.com>
>> 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" <khalid.el-dary...@mun.ca>
>>> To: "Discuss-gnuradio@gnu.org" <discuss-gnuradio@gnu.org>
>>> Subject: [Discuss-gnuradio] Max Output Power from the LFTX
>>> daughterboard
>>> Message-ID:
>>> <CACdmG=zCHATiwrtv=wBVLwG0_
>>> 5GQr0y=wksequrcajrtuv5...@mail.gmail.com>
>>> 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
>>>
>>> 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" <mle...@ripnet.com>
>>> To: discuss-gnuradio@gnu.org
>>> Subject: Re: [Discuss-gnuradio] Max Output Power from the LFTX
>>> daughterboard
>>> Message-ID: <54abe798.5060...@ripnet.com>
>>> Content-Type: text/plain; charset=UTF-8; format=flowed
>>>
>>> On 01/06/2015 08:43 AM, khalid.el-darymli wrote:
>>> > 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
>>> >
>>> > 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
>>> 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 Leech
>>> Principal Investigator
>>> Shirleys Bay Radio Astronomy Consortium
>>> http://www.sbrac.org
>>>
>>>
>>>
>>> --
>>> Marcus Leech
>>> Principal Investigator
>>> Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org
>>>
>>>
>>
>>
>>
>>
>>
>> --
>> Marcus Leech
>> Principal Investigator
>> Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org
>>
>>
>
>
>
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