Hi Leif ... first let me apologize for mis spelling your name ("Lief")
... is there any advantage to combining these two streams in the
frequency domain (after fft) or doing it in the time domain just as good
... my gut feel is that frequency domain would be best ...
Jim KI6MZ
Leif Asbrink wrote:
> Hi Jim,
>
>
>> needing an excuse to buy a dual
>> core CPU, my thoughts turned to SDR and writing a program that can
>> handle TWO or more separate IQ streams from a 4 or more channel sound
>> card (or 2 cards) and summing them together ... if each stream has its
>> unique digitizing noise, a potential 6 db of noise floor improvement
>> could be had ... and with SDR front ends so inexpensive, this dual
>> channel could be extended to the antenna ... just a thought ... anyway
>>
> This feature has been present in Linrad from start with 4 audio
> inputs and the WSE hardware has the 2 RF channels needed:-)
>
> The two channels are combined for optimum S/N in the computer. In
> case both channels are fed from the same antenna, the signals will
> add coherently to increase by 6 dB while the random noise from
> digitation process as well as from amplifiers in the radio hardware
> will increase by 3 dB. This means that the dynamic range increases
> by 3 dB.
>
> You do not need a dual core computer for this:-) Linrad was designed to
> run on a Pentium III....
>
> On a single core Pentium IV you can run several issues of Linrad
> simultaneously if you wish. The modern computers are fantastic:-)
>
> 73
>
> Leif / SM5BSZ
>
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>
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