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[Linrad] Re: Linrad - MAP65 communication

On Jul 22, 8:12 am, Edward Cole <kl...@xxxxxxxxxxxxx> wrote:
> 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: dubus...@xxxxxxxxxxx
> ***********************************************************

Hi Ed,

Thanks for your experiences
with the SDR I-Q.

The point of discussion was a SDR I-Q box versus a
Softrock V9 on 28 Mhz, As I use a Si570 and the Si570
produces quite a number of higher order harmonics, I
added the pre selector  more as a band pass filter at
the front end than for sensitivity reasons.

I guess the ideas vary whether SDR I-Q and all the
other SDR boards need pre-amps or not. The old
argument about too much gain before mixing or not
though in with ADC in the front th eargument is a little

Thanks anyway I love to hear about experiences with SDR I-Q
or other SDR radio's

73 Rein W6SZ

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