[Lowfer] SDR

[Richard Goodman]

Laurence,

   I've been using the SDR on LF for about two weeks now. If you get one,
you will not be disappointed. I've used it with a fairly large remotely
tuned loop and with the AMRAD E-Field Probe. Works very well with both of
them ... especially the E-Field probe. Compared with the two other receivers
I use (a Ten Tec RX320 and a Yaesu FT920), the SDR seems to be more stable
and seems to have a better front end. With the 920 & the 320, I have
problems with interference with a local AM station ... the SDR is quiet.

	I posted someting about a week ago on the SDR .... I'll include it again
below. Since I wrote this, I've tested the SDR up on 10 MHz. Using ARGO in
the 30 second dot mode, I plotted WWV on 10 MHz for about 25 minutes .... I
could see no detectable drift at all, not even a fraction of a hertz.
http://home.comcast.net/~wa3usg/wwv_SDR.jpg


+++++++++++++++++++++++++++

The SDR-IQ is an amazing receiver! I was fortunate and got one at the
promotional price of $385 out the door including shipping! So far from what
I’ve seen, it does EVERYTHING from about 10 KHz up through 30 MHz extremely
well. I purchased it primarily for LF however and that’s where most of my
experience with it lies.

Here’s what my receiver looks like packaged in a little Radio Shack box:

http://home.comcast.net/~wa3usg/DSC_4821.jpg

I can switch between the two antennas that you see via the link below.

http://home.comcast.net/~wa3usg/DSCF3297.JPG

The AMRAD E-field probe is on the left. My remotely tunable loop is on the
right. The loop has a outdoor utility box under it that contains 9 relays to
switch different capacitors in and out in parallel with the Varactor diode
which is remotely tuned from within the shack. Using this, the loop is
tunable from around 100 KHz up through 500 KHz. I also have a rotor mounted
at the bottom so I can turn it.

http://home.comcast.net/~wa3usg/MVC360X.JPG

I built the E-Field probe because for years, I had 60 Hz related noise on
the loop that I could never quite get rid of. The E-Field probe was much
quieter 
 you could still hear just a little 60 Hz buzz on the Probe but it
was way down in the noise. Solving the noise problem is a totally different
story, but now, both antennas are silent!

The SDR-IQ, as far as I can tell, is absolutely accurate to a fraction of a
Hertz all the way up through 800 KHz (I haven’t tried to determine the
accuracy above that). The front end gain, and gain in the IF are adjustable
from menus on the main control screen on the fly. Likewise, the bandwidth is
adjustable from 100 Hz in the CW mode, all the way up through 20 KHz in the
AM mode. Let me tell you guys 
 this receiver really works well! I have a
strong AM station located about 5 miles from me and until the SDR-IQ, I
always had trouble with it getting in ... no more!!

One of the coolest things about the SDR, is that it has a display that will
let you look at a frequency span of up to 190 KHz around where you are
receiving. The display updates FAST 
 several times per second. The
sensitivity is such that it will display things that are on the threshold of
audibility across the whole span.

When I tune the remote varactor in my loop, you can see the bump in the
noise floor move around and you can put it right where you want it 
 same
way with my tunable preamp 
 I can center the passband of it right where I’m
receiving, If you look at the below display, you can see the loop & preamp
passband is about 25 KHz wide running from about 165 to 190 KHz. Being able
to see & visualize this kinda stuff adds a new dimension to LF reception.
You can also run Argo and the SDR Control program at the same time just
fine. Argo will pick the audio right off your soundcard directly ... no
cables needed.

http://home.comcast.net/~wa3usg/sdr01.jpg


Last night was my first real good night with this setup 
 I’m really anxious
to see what’s around this evening. In case you’re curious about the SDQ-IQ,
I’ll post a link to the RFSPACE website here:

http://www.rfspace.com/sdriq.html

I also wrote a review of this receiver in our Club Newsletter 
 I’ll post a
link to that also (it's 3 Meg):

http://home.comcast.net/~wa3usg/2007_03.pdf

Try it, you’ll like it!

73
Dick, WA3USG

-----Original Message-----
From: lowfer-bounces at mailman.qth.net
[mailto:lowfer-bounces at mailman.qth.net]On Behalf Of Laurence KL1X
Sent: Tuesday, March 06, 2007 9:00 AM
To: lowfer at mailman.qth.net
Subject: [Lowfer] SDR




Anyone any practical experience on using the sdr iq or similar "radio" on
LF/MF and any interference/noize issues from PC noize? Im trying to reduce
the volume and shipping weights of the radio/computing system a bit as I
wander. I know the IQ model is very new so maybe not a lot of experience
yet..

Anyone had any experience on the 897 or 857 for LF with a preamp up front on
LF image/imod etc issues? Not that impressed with 817 on LF as you may
remember even with preamps.

Thanks -

We leave Shanghai for the last time around May 20th and will turn up in
Singapore a few weeks later.

Laurence VR2 /KL 1X
wet and cool Hong Kong

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