[AMRadio] sdr-iq

Brett Gazdzinski Brett.Gazdzinski at verizon.net
Sat Mar 27 21:16:26 EDT 2010

Did you try adjusting the rf and IF gain settings? The IF gain adds a lot of 
noise using spectravue...
Also, what programs did you use with the sdr-iq?
Winrad seems to have much better audio with less noise.

I don't often use the sdr-iq as a receiver, sometimes I use it to listen in 
the den, as its very small and I am using the laptop anyway.

The flex 5000 seems to be a very good receiver.
Maybe its not quite the same as an old tube receiver, but has other 
It can handle 150% modulation with its sync detector,
It can do diversity, and noise null,
The filters are fantastic, and you can set them as wide or as narrow as you 
want, and slide them around to get rid of qrm,
The frequency response can be whatever you want, down below 20 Hz.
You get a great band scope.
You can record audio right off the air without altering it (and play it back 
over the air as well).
Its all mode.

For weak AM signals, the homebrew seems to be just a slight bit better, but 
the homebrew receivers are much better than anything else I ever owned, 
better then the R390a.

I usually use both, the homebrew for audio and scope output, the 5000 as a 
band scope, and sometimes for the filters when things get tight. On the 
flex, you can slide the passband 25 Hz off a carrier and its gone.


----- Original Message ----- 
From: "Bernie Doran" <qedconsultants at embarqmail.com>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Saturday, March 27, 2010 1:13 PM
Subject: [AMRadio] sdr-iq

> well I am going to stir the pot again with my probable final comments on 
> my
> SDR-IQ.  first the good, never had a panadapter or bandscope, it works 
> great
> for that. The filters are very good.  The issues to me are the following, 
> it
> is noisy, to itself and also to a receiver on the same antenna, it lacks
> sensitivity, it has spurs,  and the big one to me is the audio quality, a
> moderate strength AM signal is difficult to understand and when on my 
> hollow
> state stuff it is nearly %100 copy.  The present computer is a 2.2gig quad
> core, no performance change above a single core 1.8 gig.   Numerous
> different audio systems confirm that it is the nature of the beast.
> I have read numerous articles on D-A and A-D processing and believe that 
> 14
> bit is not going to do the job that I want.  I suspect 24 bit and a much
> higher sampling rate, 150 meg?  would just about cure the audio issue for
> me.  I am starting to believe that the glowing reports written about SDR 
> are
> prepared by those that have never used an old VT receiver or have one
> available to run beside the sdr. My FT1000 Mark V had glowing reports and 
> I
> am really disappointed with it.  I have an ever deepening respect for 
> those
> that designed and built the old classic receivers.  Looking at noise 
> figures
> and sensitivity on those old dogs places them very close to theoretical
> limits, pretty amazing.  I have put my money where my mouth, I should, 
> about
> April 10 or so have a completely reman R-390A.   I was going to try the 
> Flex
> 5000, but as I posted earlier they did not see fit to respond to my
> questions, perhaps  thinking the questions were not fit to respond too.
> Earth hour is today, be sure to turn on all of your lights to help save 
> the
> grid and generators.  !  Bernie W8RPW
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