Re: [Discuss-gnuradio] Confusion, help please

[Ali Riaz]

Hey Marcus,

Thank you for replying back! Absolutely, I've posted my flowgraphs on imgur.com now.

Here's the link: http://imgur.com/a/a0KCX

Also, for some reason, I think it could be because I'm using the Spectrum analyzer's tracking generator?

P.S I've done a couple of changes since my last email:

1) My sample rate is now 10M

2) My filter taps for the channelizer are being calculated as you told me earlier: firdes.low_pass(1.0, samp_rate, samp_rate/(nchan*2.15), samp_rate/(nchan*4.5))

3) Assuming that the tracking generator is at fault, and everything else in the design is good, it works perfectly fine for a 2M sample rate, but when I try using a higher sampling rate say 10MHz, I get strange results which leads me to believe that there's something wrong in my design, though I just can't put my finger on it. One of the pictures is when I'm asking the channelizer to make a total of 8 channels, and the other one is where I'm asking the channelizer to create 20 channels. (Only 6 of which are being plotted in both cases). Is the way I'm calculating my filter taps at fault here or is it perhaps something else?

Best,

Ali

Date: Tue, 03 Mar 2015 09:42:19 +0100
From: Marcus M?ller <address@hidden>
To: address@hidden
Subject: Re: [Discuss-gnuradio] Confusion, help please
Message-ID: <address@hidden>
Content-Type: text/plain; charset="windows-1252"

Hi Ali,

that's interesting.
Would you mind sharing the flow graph that you use?

Greetings,
Marcus

PS: Although using adblock plus, before I see every other picture on
tinypic, I get stuff like casino advertisment, and similar.
Could you use any image hoster that doesn't block view on the pictures
with advertisement? I found imgur.com to work fairly well.
On 03/03/2015 12:27 AM, Ali Riaz wrote:
> Hello all,
>
> I just had a quick question regarding the polyphase channelizer. As a
> start, I'm trying to divide an input spectrum into 6 channels of equal
> width. My sample rate for now is 5 MHz and the way I'm calculating the
> taps as follows:
>
> firdes.low_pass2(1.0, samp_rate, samp_rate/(nchan*2.15),
> samp_rate/(nchan*13.8),

attenuation_dB = 10, window = firdes.WIN_HAMMING)
>
> The channels are being divided equally now, but the first channel
> behaves very different from the rest, it becomes super wide for a
> moment, and then shrinks back to normal just like the rest of the
> channels and this happens repeatedly. I'm honestly stumped as to what
> the reason could be, so would really appreciate if anybody can point
> me in the right direction or at least clarify why this is happening.
>
> You can find the images here: http://tinypic.com/a/3e8so/4
>
> Thank you,
>
> Best,
> Ali
>
>
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