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Re: [Discuss-gnuradio] Merge multiple complex streams]


From: Imre Biacsics
Subject: Re: [Discuss-gnuradio] Merge multiple complex streams]
Date: Tue, 13 May 2014 13:15:07 +0200
User-agent: SquirrelMail/1.5.2 [SVN]

Thanks a lot, it really got me going! This is part of my learning process,
if it's leading to nothing at all; that's okay.

Somewhere I red about feeding multiple dongles from a single signal
source, interesting....

A possible configuration:

1. Upconverter & 30 Mhz low pass filter
2. Cheap wideband amplifier / splitter ( 75 Ohm tv splitter ?)
3. Rig dongles with usb hubs

I fiddled around with Mike's example had a hard time to figure out the way
to merge the FFT outputs. Found the solution in the 'Streams to Vector
block' Setting the vector length to the FFT size.

Result: http://www.livep2000.nl/code/grc/

Let's test the frequency border(s)


On Tue, May 13, 2014 10:13 am, Martin Braun wrote:
> On 12.05.2014 17:49, Imre Biacsics wrote:
>
>> Playing around with GRC for a few months now, sorry if this question is
>>  from a dummy.
>>
>> I've a bunch of rtl dongles laying around, and wonder if it's possible
>> to combine more then one to a single baseband signal.
>>
>> The goal is to create a super cheap full HF band web reciever like or
>> for ' websdr'
>>
>>
>> I managed to create multiple channels, where the 2nd dongle is tuned to
>> an offset, equal to the samplerate of the first. (for example 2 x 2 Msps
>> = 4
>> Msps baseband)
>>
>>
>> Is such a thing possible with GRC?
>>
>
> A couple of things, on top of what Mike said:
>
>
> - HF bands go lower than the frequency of the dongles. Keep that in mind.
>  - As Mike said, clocks aren't sync'd. So, if you're using data from
> multiple dongles, that'll most likely be corrupt. - To make things worse,
> they drift differently too. So, little chance in fixing things. - If all
> you want is an (inaccurate) "spectrum analyzer" for more than 2 MHz, then
> this is actually not a bad idea. If you have N+1 dongles, you can use N of
> them to monitor N*2MHz of spectrum, and the other one to receive at
> frequencies you're interested in.
>
> M
>
>
>
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