Hello Akram:
All that means is that the authors of the article saw higher FM signal strength than you. Maybe their building walls caused less path loss than yours. Maybe they are located in a less-crowded area (less buildings around). Maybe they have FM stations in closer
proximity. Maybe they used different antennas. I don't know, there are just too many possibilities. These power values do not mean anything, unless you control such variables (which is probably not feasible in this case).
True (absolute) power levels are typically measured in milliwatts or in watts. Communication enginners usually convert them to decibel scale and call them decibel-milliwats (dBm) or decibel-watts (dBW). This is the true electromagnetic power level. USRPs cannot
measure this (unless you calibrate them using calibrated analyzers).
USRP N210s sample at 100 MS/s. Therefore, they need to make faster clocks by multiplying that 10 MHz to higher clocks using PLLs. This can leak into your receiver. The easiest way to fix this is... just getting a different radio (with different clock rate).
Or just ignoring it. While (actually) fixing or suppressing it is possible in theory, it's not a simple job (if it was easy, Ettus Research would have done it for you). Such spurious signals are pretty common on cheap radios (and yes, USRP N210s are not considered
expensive.. when compared to other higher-end radios or measurement equipments).
(Also, I added discuss-gnuradio back to the recipient list.)
Regards,
Kyeong Su Shin
보낸 사람: whoppix_tn whoppix <address@hidden>
보낸 날짜: 2020년 3월 30일 월요일 오전 2:50
받는 사람: Kyeong Su Shin <address@hidden>
제목: Re: Issue with USRP N210
보낸 날짜: 2020년 3월 30일 월요일 오전 2:50
받는 사람: Kyeong Su Shin <address@hidden>
제목: Re: Issue with USRP N210
Hi Kyeong Su Shim,
Based on the snapshot from the link below, I was expecting something around -50dB
What does absolute power level mean?
Indeed, it looked odd to me to have that spike at 100MHz. How can I avoid having this kind of leakage? And how come that it's 100Mhz, I thought the clocktamer was configure at 10Mhz...
Regards,
Akram
On Sun, Mar 29, 2020 at 5:35 PM Kyeong Su Shin <address@hidden> wrote:
Hello Akram,
What kind of power levels do you expect, and why?
The observed power level depends on multiple factors, including your environments, antennas, gain settings, and more. Also, USRPs are not calibrated spectrum analyzers and the numbers do not mean much (the numbers are relative to the dynamic ranges of the devices, and are not the absoute power levels).
By the way, please note that the peak that you are observing at 100 MHz is probably not a real FM station. It's probably a clock leakage.
Regards,Kyeong Su Shin
보낸 사람: whoppix_tn whoppix <address@hidden> 대신 Discuss-gnuradio <discuss-gnuradio-bounces+ksshin=address@hidden>
보낸 날짜: 2020년 3월 30일 월요일 오전 1:09
받는 사람: Marcus D Leech <address@hidden>; address@hidden <address@hidden>
참조: address@hidden <address@hidden>
제목: Re: Issue with USRP N210Thank you Marcus and Chris,I figure out that indeed that the ports were not properly labeled. I've moved the antenna to the second RF and it gave a result:
However, I still see that the power is not that high (around -75dB). Is that normal?
Regards,Akram
On Sun, Mar 29, 2020 at 4:38 PM Marcus D Leech <address@hidden> wrote:
Also what daughtercard are are you using?
Sent from my iPhone
> On Mar 29, 2020, at 8:10 AM, whoppix_tn whoppix <address@hidden> wrote:
>
>
> Dear,
>
> I'm starting with USRP N210/Gnuradio, so my first exercise was to test it using uhd_fft. Here is the result I'm getting:
>
> uhd_fft --args "addr=192.168.10.2" -A RX2 -s 10e6 -g 10 -f 102e6
>
> <image.png>
>
>
> It seems to be that the result is not really as expected. In this FM band, I should see plenty of spikes which is not the case. Also, for the one that exists (100Mhz), the power is at -70dB which also seems too little to me. FYI, I'm using the clocktamer 1.2. I appreciate your support to make sure I have everything properly setup.
>
> Regards,
> Akram
>
