[AMRadio] sdr-iq


Brett Gazdzinski Brett.Gazdzinski at verizon.net
Sun Mar 28 12:40:58 EDT 2010


There is a trick to getting winrad to run, but its worth it for the audio, 
and changing the filters don't cause that racket, plus it does ecss which is 
real nice.

Also, how you listen to the audio likely counts, with spectravue, audio 
output is low and noisy, with winrad or sdr console its much louder and 
cleaner.
With headphones off the laptop, it sounds fine, my laptop does not have a 
line out, only headphone output for feeding into the Marantz amplifier, and 
does not sound that great that way.

The sdr-iq is not great for operational use, since it has a lot of delay in 
the computer, no muting, etc.
It does make a good swl and listen only receiver for the price and size, and 
is great for spectrum analysis of signals, even your own TX signal.

Remember, the sdr-iq is the cheapest sdr you can buy that covers 100Hz to 30 
MHz, they could have made it a LOT better for more money. The sdr-ip is 
better, and costs $3000.00 to start....


The homebrew RX is a simple single conversion, 455 KHz IF no RF amp, for 
160, 80 and 40 meters.
No active stages before the mixer, just very high Q tuned circuits, the 
filters (Kiwa) is right after the mixer, some IF amp stages, a low 
distortion AM detector, agc, s meter, digital freq readout.
All the tubes run off 150 volts, the LO runs off 100 volts.
Its stable, accurate, quiet, has no birdies, image problems, and has very 
good fidelity.

There are a lot of simple receivers that could be made much better, add a 
digital readout, and a kiwa filter board with say 6 and 8 Kc filters, and 
maybe re do the detector and agc, and you would have a very good AM 
receiver.

I always wanted to try changing a 75s1 to hifi AM by adding a good filter 
and a good low distortion AM detector. It would be stable, accurate, with 
good AM filters, small and light, and nice looking, and still copy ssb and 
cw well.
I suppose it could sound and work just as good as an R390a, sp600, and other 
massive receivers, if you feed the detectors into a nice audio amplifier, or 
build a nice hifi audio output stage, maybe using one of those 8 watt 5 pin 
audio output IC chips.

Brett
N2DTS












----- Original Message ----- 
From: "Bernie Doran" <qedconsultants at embarqmail.com>
To: "Brett Gazdzinski" <Brett.gazdzinski at verizon.net>; "Discussion of AM 
Radio in the Amateur Service" <amradio at mailman.qth.net>
Sent: Sunday, March 28, 2010 7:39 AM
Subject: Re: [AMRadio] sdr-iq


> HI Brett: yep I have tried every setting that I can change. I have never 
> been able to get WINRAD to run and I do have the rf-space downloads to run 
> it. downloaded everything several times from different sources.  as I 
> said, the sdr filters work great, there is an anoying pop when you slide 
> the width around.   It is to the point that I have spent hours and hours 
> fooling with it and have seen no improvement since the first 2 hours. 
> sounds "OK" on SSB and its amusing to look at the splatting, residual 
> carriers and poorly suppressed upper sidebands on 80, most are good but 
> some really do not look good.  its best use is for a bandscope, test 
> equipment, or portable use, as you said.  Interested in your home brew rx 
> tell us what you have.
> the 390 will fed its IF to a sync det and outboard audio stage at least as 
> a test.
> ----- Original Message ----- >>
>>> 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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