[hpsdr] Selectivity design/measurement

[Bill Tracey]

Here's the measurements Bob McGwier and Rick Hambly did with the Janus/Ozy 
Alpha 1 boards in late October 2006 - rescued from the depths of my email 
archive.   Thanks to Bob and Rick for these.

Cheers,

Bill  (kd5tfd)

>Date: Fri, 27 Oct 2006 14:40:41 -0400
>From: Robert McGwier <rwmcgwier at comcast.net>
>Subject: MDS, IMD-DR, IP3
>
>The Ozy, Janus perform very nicely as a receiver back end for the 
>SDR-1000.  The CPU % is low on a 1.8 GHz laptop (23%).  This all appears 
>to have been completely resolved with sufficient time on sleep to allow it 
>to enumerate again after reset.
>
>The attenuator being inline definitely increases the dynamic range since 
>the noise floor for the system with the SDR-1000 is NOT limited by the 
>Janus,  it is limited by the SDR-1000.  The MDS was within 0.5 dB of being 
>identical (measurement error, etc.) with or without the attenuator but 
>with the attenuator,  we can take a lot more signal before the AKM5394A 
>overloads.
>
>Freq,Preamp setting, MDS:
>
>7.0 , High, -133 dBm
>7.0,  Med, -125 dBm
>7.0,  Low, -120 dBm
>7.0,  Off, -110 dBm
>
>14.2,  High, -137 dBm
>14.2, Med, -126 dBm
>14.2, Low, -118 dBm
>14.2, Off, -116 dBm
>
>At 14.2,  with input tones at -16 dBm and spacings at 2 kHz,  the third 
>order product was 85.5 dBc down.  This means the IP3 is
>-16 dBm + 85.5/2  = 26.75 dBm
>
>We are proceeding to use the fancy audio generator to repeat the Janus 
>only sensitivity tests.  But again,  the extra sensitivity without the 
>attenuator IS NOT USABLE WITH THE STOCK SDR-1000.
>
>More in a bit.
>
>Bob
>
>--
>AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
>TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
>"You see, wire telegraph is a kind of a very, very long cat.
>You pull his tail in New York and his head is meowing in Los
>Angeles. Do you understand this? And radio operates exactly
>the same way: you send signals here, they receive them there.
>The only difference is that there is no cat." - Einstein

And the fancy audio generator results:

>Date: Fri, 27 Oct 2006 14:57:23 -0400
>From: Robert McGwier <rwmcgwier at comcast.net>
>
>With a nice audio generator making 11 kHz at -20 dBm and the PowerSDR 
>calibrated to -20 dBm,  we then removed the signal generator and 
>terminated both inputs with 600 Ohms resistors.
>The MDS was -135 dBm in 500 Hz with the attenuators jumpered.
>
>Bob
>
>--
>AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
>TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair
>"You see, wire telegraph is a kind of a very, very long cat.
>You pull his tail in New York and his head is meowing in Los
>Angeles. Do you understand this? And radio operates exactly
>the same way: you send signals here, they receive them there.
>The only difference is that there is no cat." - Einstein



At 04:56 PM 2/15/2007, Robert McGwier wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>I did all of these measurements on the alpha Janus and Ozy boards.  The
>AKM5394A is  one of the the  best recommendations I have ever given to
>any project or collection of projects and the Phil's and Bill and Lyle
>have a done a great job.   The Janus board lowers the noise floor of my
>SDR-1000 and that system is not SDR-1000 noise limited rather than Delta
>44 noise limited and the "hump" is gone on my set up where I used to
>have a hump with my Delta 44.  I never had one with the Lynx L22 and it
>uses the AKM5394A with balanced inputs.
>
>I am in Boston all week at Mercury computing for Cell processor
>training  and will be at Virginia Tech next week at the wireless group
>but I invite any of the other developers to feel free to publish the
>numbers Hambly and I measured in the lab using the SDR-1000 and with
>with the fancy audio generators.
>
>Bob
>N4HY

.....




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