[Linrad] Re: Linrad - MAP65 communication

[Edward Cole <acsalaska.net; kl7uw@xxxxxxxxxxxxxxxx>]

At 01:06 PM 7/21/2009, you wrote:
>---snip-----
>Softrock vs SDR I_Q.
>
>Doug and I have done in the past some comparison measurements for the SDR box
>versus one of my softocks. Softrock is runnung with Si570 LO, and has
>a pre-selector. We found the sensitivity on 28 Mhz of the softrock approx
>10 dB better then the SDR I-Q.
>Softrock with a un modified delta44 sound card ( the same numbers with
>Linrad in SSB mode, Winrad and SpectraVue.
>
>I use a little prtable softrock SDR here with the laptop and have to use
>an external soundcard for the I/Q processing ( USB sound card )
>
>Of course, SDR IQ receives 0-30 MHz in one sweep, Sofrock is narrow band,
>and would need a lot extra to have it cover 30 MHz of as one spectrum.
>
>
>73  Rein, W6SZ

Rein,

I found that the SDR-IQ needs a little more gain.  I added 18-dB gain 
in front of my SDR-IQ running at 28-MHz and improved my sensitivity 
16-dB (tested by comparing with spectra-JT traces from JT-65B running 
from a soundcard (my measurements were at most +/- 2 dB accuracy).  I 
used a signal generator with 66-dB attenuation added to get down to 
-166 dBm (this was with a 1-dBNF preamp) feeding both receivers.  Try 
a little IF gain on 28-MHz.


***********************************************************
73, Ed - KL7UW              BP40iq, 6m - 3cm
144-EME: FT-847, mgf-1801, 4x-xp20, 8877-600w
1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60/300W  (not QRV)
http://www.kl7uw.com       AK VHF-Up Group
NA Rep. for DUBUS: dubususa@xxxxxxxxxxx
*********************************************************** 


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