SDR Receiver table and SDR servers on the Internet

[Terry Fox]

Here are a few links to info I mentioned on the technical discussion 
tonight.

The first is a link to Rob Sherwood's table of HF receiver performance for 
various radios.  His table is listed in order of narrow-band blocking 
dynamic range, which he feels is probably the most important factor in 
modern HF receivers.  He and others have suggested that receiver sensitivity 
id no longer as important, as most modern HF receivers have a better 
sensitivity than the band noise, especially on frequencies below 20M 
(14.35MHz).  Note that the new top-dog on his list is the Flex 6700 SDR, 
followed by Hilberling (analog) radio, which may or may not be purchasable. 
Then comes the Elecraft KX3, which is basically an SDR rig with a hardware 
controller.
http://www.sherweng.com/table.html

The above is partially why I totally disagree with the recent presenter at 
Vienna Wireless when he said in a slide that analog radios will always be 
better than SDRs.  As always, that discussion depends on many factors, with 
cost being a major one.  Also, HF radios are much easier to implement in SDR 
now, thanks to faster and deeper A/D converters.  For VHF/UHF, the analog 
radios may still win out, but a look at how many new cell phones are still 
analog (none) versus SDR-based (all) brings another aspect as well.  I 
wonder how much actual experience the presenter has had with higher-end HF 
SDRs versus high-end analog radios, and how recent that experience is.

All I know is that for some of the more esoteric HF problems, my Flex 6500 
can run circles around my Elecraft K3 (which may also be considered by some 
an SDR rig with a hardware/firmware controller).  And the Flex 
software/firmware is just now reaching acceptable usability.

Another point I should mention is that your average analog radio is either 
fixed in design at the point of manufacturer (without user modifications of 
course), or is upgradable via firmware/software IF THE MANUFACTURER ALLOWS 
THAT AND IS INTERESTED IN DOING THAT.  An SDR CAN BE UPGRADED CONTINUOUSLY, 
to the limits of the hardware used.  Flex has shown how this can be done, as 
has the openHPSDR group, the ANAN group, RFSpace, and other SDR 
manufacturers.

Here are a few web sites that have lists of SDR servers available around the 
world via the Internet.  Note that there are a LOT of hardware variations. 
These are just a few lists, and may require different SDR client programs.
http://websdr.org/
http://v2.sdrspace.com/
http://www.sdr-radio.com/central/ViewList.aspx

These programs generally give you control of the SDR hardware and DSP, then 
demodulate the audio at the server and ship it to you.  They also calculate 
the FFT for the spectrum display (if available), and send that date to your 
client, which then displays it on your computer.

There are also servers for listening to VHF/UHF using the RTL dongles and 
cheapie computers such as the Raspberry Pi.  Here are a couple of examples:
http://zr6aic.blogspot.com/2013/02/setting-up-my-raspberry-pi-as-sdr-server.html
http://www.hamradioscience.com/raspberry-pi-as-remote-server-for-rtl2832u-sdr/

And some basic RTL dongle SDR info:
http://sdr.osmocom.org/trac/wiki/rtl-sdr
http://www.rtl-sdr.com/big-list-rtl-sdr-supported-software/

GNU Radio Companion (GRC) is a VERY cool tool that allows you to build the 
DSP part of an SDR literally block-by-block.  I have used is with Softrocks, 
David Brainerd (WB6DHW) boards, the SDR-IQ, and our own AMRAD/Charleston SDR 
(Digilent FPGA board and AFEDRI8201 board).  A nice way to learn about the 
DSP part of SDRs.  Some Linux experience will help.
http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion
http://www.csun.edu/~skatz/katzpage/sdr_project/sdr/grc_tutorial1.pdf
http://www.joshknows.com/grc
http://en.wikipedia.org/wiki/GNU_Radio_Companion

The GRC can also be used with RTL dongles, along with a lot of other SDR 
front-end hardware.
http://www.instructables.com/id/RTL-SDR-FM-radio-receiver-with-GNU-Radio-Companion/

I would say that SDR technology is moving more and more into mainstream 
Amateur Radio, primarily because I hear more and more SDR rigs on HF on the 
air these days.  Of course there are still many, many amateurs that don't 
like any radio that doesn't have a bunch of knobs, or doesn't weigh over 40 
pounds, or that doesn't have a single tube in it.  That's fine.  But, I like 
to be constantly learning and pushing the technology envelope, and SDR is 
where it's at!

Along with digital amateur television, and other new-fangled things.
73, Terry, WB4JFI