AMRAD at Winterfest 2014

[wb4jfi at knology.net]

Hey Frank!
Good to hear about your demo.
I've been giving several talks on SDR in the Charleston area the last few 
months.  The big problem is always an antenna.  For HF, I bring along a 
couple of easy to set up verticals (MP-1 SuperAntenna as an example), and 
the Buddipole.  I always put them outside if at all possible.  Again, for 
HF, I have about 125ft of thin RG-174, in 25ft and 50ft sections so I use 
the minimum length of coax.  I've demo'd Softrocks, KX-3, SDR-Cube, Flex 
6500, and several others.

For VHF, I've shown the RTL dongles, using (I think) SDR Sharp, and other 
programs.  I can at least get FM broadcast stations.  I also bring along a 
little cheap FM broadcast transmitter, like for use with iPods and other 
things.  I had one demo where I hooked the Flex 6500 to an antenna and 
laptop, with the Flex demod audio going into the FM transmitter.  Then, I 
had a second laptop with an RTL dongle tuned to the FM transmitter's freq, 
and demoding the HF audio with SDR Sharp through the dongle.  Kind of a 
double-SDR demo!  The small FM transmitter gets around the no-signal issue. 
Otherwise, if you are going to do a demo at a hamfest, or anywhere else, 
plan ahead and put up an external antenna.  The extra time will be worth it!

Remember, the RTL dongles are cute, and a "Cheap Thrill" for sure, but they 
are only 8-bit A/D converters.  I've had many issues where I can't get the 
local 2M FM repeaters because I had to turn the AGC level down quite a bit 
because of local strong FM broadcast stations.  This shows up even worse if 
you try the HF upconverter to receive HF!  You only have about 50dB of 
dynamic range at any AGC setting, and that can be a killer.  Using bandpass 
filters helps a lot with this.  Even our Charleston receiver had a better 
dynamic range (12-bits), but had overload issues at times, without external 
filtering.

I've shown and used the RTL dongles, and cheap USB sound cards for HF SDR, 
with an Acer Iconia W3 tablet, that runs Windows 8, not the RT version. 
With it, you can run all the standard Windows-based SDR software, along with 
Digipan and other digital mode programs.  But, the touch screen is so small 
that an external keyboard is almost a necessity.  And I have small fingers! 
It's more costly, but there is much more software available.  Including 
Microsoft Office!

OFF-TOPIC:
I am about to give up using an iPad for any SDR development.  After two 
years, and $99 per year, I've decided that I'm not lining Apple's pockets 
with any more money for their development tools.  l still like my iPad, but 
I just can't see developing ANY software for it, without charging for that 
software.  The constant updates, requiring minimum hardware to go along with 
those updates, and other time sinks and costs are just too draconian.  You 
need to pay the annual developers fee just to keep your app in the Apple app 
store, even if you don't write another line of code.

I understand that you also need to pay to write for Android, but I don't 
know what their overall model is.  I also don't consider Linux a contender 
for the tablet/small computer world, as I don't see any mass-produced 
tablets that are Linux-based and fairly inexpensive.  I don't consider 
Kickstarter projects as mass-produced, they are often here today but gone in 
six months to a year.

So, I'm seriously thinking of moving to Windows 8-based tablet development 
for the future.  I hate to do that, but it's the only platform that appears 
to have the tools and freedom to create programs where you aren't expected 
to pay dearly for that right.  I'd like any feedback on where I'm wrong on 
the above....

Anyway, congrats again on your demo.  How did the BOAR-net guys do?
73, Terry, WB4JFI


-----Original Message----- 
From: fgentges at mindspring.com
Sent: Sunday, February 23, 2014 9:22 PM
To: Tacos
Subject: AMRAD at Winterfest 2014

The people at Winterfest 2014 were kind enough to provide a couple of
tables out front for AMRAD to set up and demonstrate some of our latest
stuff.

We put together a display of what we called a "Cheap Thrill" receiver
that anyone can build for $121.  The demonstration did not work all that
well as the building blocked a lot of the VHF/UHF signals we can see out
in our houses.  Anyway, here is our Cheap Thrill receiver.

The input uses the RTL-SDR dongle that has an antenna input and a USB
connector output.  These are selling on eBay for less than $10.  It has
an mcx input connector so we add an mcx-BNC adapter so you can add local
antennas.

The processor is an EKEN GC10X tablet computer.  This is an Android
based tablet and is sold by Microcenter for $79.99.  By almost any
measure it is a bargain.  We add a 32 GB micro SD memory card to get
more memory.

We added the Android based SDR Touch software.  The basic software is
free on the Android Play Store.  But for $10 you can get the SDR Key
that unlocks the spectrum display and the ability to save frequencies.
This software is written by a fellow in Bulgaria and Andre has had a
problem getting the key for which he has spent $10 sent to install.
N4TS and I have gotten the key and have it installed without a problem.
  We will try to get Andre installed with it shortly.

But like most things, this receiver is only a start.  There is a web site at

rtl-sdr.com

that has a lot more information and shows a lot of software that the
dongle can run on.  Of particular interest to me is LINRAD that runs on
Linux and Windows.  This has been around for some time and has a lot of
sophisticated features.  The author has optimized a driver for these
dongles and I suspect it will really do some interesting things.  The
author is SM5BSZ.  He has a newcomer guide you can check out at

http://www.sm5bsz.com/linuxdsp/usage/newco/newcomer.htm

He also has some good videos on Youtube under his call sign.

There is some good information specific to RTL-SDR and LINRAD at rtl-sdr.com

So you can start up with the AMRAD Cheap Thrill setup and then grow into
the LINRAD setup if you are interested in performance.  Maybe we will
see a high performance program for Android.

I am going to get some information on the Cheap Thrill up on the AMRAD
web site in the next few days.

Frank K0BRA

_______________________________________________
Tacos mailing list
Tacos at amrad.org
https://amrad.org/mailman/listinfo/tacos