SDR-Audio : CQ WW DX SSB Contest.

With the CQ WW DX SSB contest in full swing, I captured some interesting callsigns audio clips on 15, 20, 40 this weekend. 
Receiving station:
Rig: Softrock SDR
Ant:  Wire vertical over salt water.

15m 1815Z

DSP, $5 Linux server, cognitive radio and more...

Well, it's been a while since posting here, mainly because I've been investing some time in educating myself in the world of DSP s/w.

Some new pieces of SDR gear made it past the bench and into the shack  The latest Softrock Ensemble rx is now online,
and I must say the new pcb design is much cleaner and compact from a constructor's perspective.  It's performance on par with the previous v9.0.

The next step was to dedicate a Linux system for SDR  experimentation. As the good fortune would have it, I was lucky enough to pickup a desktop PC, in immaculate condition at the local swap meet.  It became the dedicated Ubuntu platform and now serves as my main development platform.

Ubuntu desktop installation is a snap, and with the added dev-tools a scap PC is transformed into a capable development platform.  Ubuntu's S/W manager makes things really easy.

SDR and Cognitive Radio
Experiments around the automation of decision making for the purpose of detecting information via rf sensing technologies can cover a wide range of topics.  For the Amateur Radio experimenter, there are several benefits and utility to this exciting field.  Propagation studies are among the very useful outcomes of cognitive radio.  In the context of two-way communications, ionospheric path optimization could be another interesting outcome of path discovery/and auto selection between two/more terrestrial locations.

H/W:
As the chip manufacturers push the A/D envelope and DSP integration becomes more affordable, we have access to a level of instrumentation sophistication which has never been available before. 

S/W
Unix/Linux is of course a very capable networked O/S - which is perfect for radio work, as well as a powerful s/w development platform for doing DSP development work.

Design considerations.
To approach the problem of concurrent decoding of multiple digital data streams, and adding a level of control logic to make decisions about decoding activities over time, an understanding of a few key concepts are necessary.  Here is an interesting write-up on the general progress and concepts of SDR.

DSP concepts.
With the advances and adoption of SDR technology, the technical components for cognitive radio are in place today.

• First, a reasonable understanding of DSP is needed when tinkering with S/W methods for signal processing.  The several phases of processing a signal undergoes through digital acquisition, digital processing and filtering and subsequent decoding, are all significant in laying the basis for S/W DSP.
• Secondly, DSP happens in real time, and therefore the processing speed becomes a consideration when selecting a O/S platform - when done right, interesting opportunities await - eg. dx-spotting, "steering passive antennas" by means of S/W phase shift, diversity reception, etc.  

Hopefully you will find some of this information interesting, perhaps entertaining, but most of all, somewhat useful in your own experimentation activities.

Useful references:
The Scientist and Engineer's Guide to Digital Signal Processing  is a good starting point for DSP concepts.
Do you understand the SDP concept?

SDR Reports

Using PSK Reporter is a really helpful system for tracking propagation.
Here is a sample of what my 20m SDR receiver sees during a 24 hr cycle.

Softrock : Miles per watt.

With recent propagation, 20/40m has been really great for grayline dx.  A very active QSO party weekend added some more long distance QRPp Qs.
Rig: - Softrock txrx 6.3 running at max 1W,  - (300-500mW just for fun) 
Antenna: was wire vertical over salt water (somewhat sloped config


(Distances in miles)

Date        Start    Station  Band  Mode My Power Distance   QTH
5/2/2010  04:48    K1TTT   40m    CW    1W    2,478.45    PERU
5/2/2010  04:44    W7POE   40m    CW    1W    1,065.37    BURIEN
5/2/2010  04:42    K7LFY   40m    CW    1W    1,090.35    ADDY
5/2/2010  04:34    KK7S    40m    CW    1W    1,071.44    MEDINA
5/2/2010  04:32    N7BV    40m    CW    1W    1,118.16    PORT ANGELES
5/2/2010  04:30    W7UG    40m    CW    1W    906.60      SALEM
5/2/2010  04:22    W7GKF   40m    CW    1W    1,084.23    Snohomish
5/2/2010  04:21    K7ZSD   40m    CW    1W    961.20      SCAPPOOSE
5/2/2010  04:11    K7MI    40m    CW    1W    826.58      BANDON
5/2/2010  04:10    W7AR    40m    CW    1W    929.78      WEST LINN
5/2/2010  00:36    KX7L    20m    CW  300mW   1,085.29    BOTHELL
5/2/2010  00:22    K7HBN   20m    CW  300mW   1,088.06    BOTHELL
5/2/2010  00:19    AB7R    20m    CW  300mW   1,122.27    OAK HARBOR
5/1/2010  23:43    W7RN    20m    CW  500mW   487.45      VC HIGHLANDS
5/1/2010  23:38    N7BV    20m    CW    1W    1,118.16    PORT ANGELES
5/1/2010  23:26    KI7MT   20m    PSK31 1W    1,015.82    HELENA
5/1/2010  23:17    W1KM    20m    CW    1W    2,594.23    MARSTONS MILLS
5/1/2010  23:10    WG7Y    20m    CW    1W    1,020.32    GILLETTE
5/1/2010  23:06    W7GKF   20m    CW    1W    1,084.23    Snohomish
5/1/2010  22:11    K7QQ    20m    CW    1W    1,064.91    Olalla
5/1/2010  22:09    NZ1U    20m    CW    1W    2,525.26    E KILLINGLY
5/1/2010  22:03    KN7T    20m    CW    1W    1,088.06    BOTHELL
5/1/2010  21:58    AC7T    20m    CW    1W    1,075.91    REDMOND
5/1/2010  21:57    N7TT    20m    CW    1W       965.01   LA CENTER
5/1/2010  21:53    KK7S    20m    CW    1W    1,071.44    MEDINA
5/1/2010  21:41    K7SS    20m    CW    1W    1,070.89    SEATTLE
5/1/2010  21:40    W7VP    20m    CW    1W    1,081.45    WOODINVILLE
5/1/2010  21:30    KK7OO   20m    CW    1W    1,157.75    BELLINGHAM
5/1/2010  21:25    K7BG    20m    CW    1W    1,081.01    POWER
5/1/2010  21:24    W7AC    20m    CW    1W      942.16    ALOHA
5/1/2010  21:20    NG7Z    20m    CW    1W    1,085.29    BOTHELL
5/1/2010  21:18    K9SG    20m    CW    1W    1,808.46    GREENFIELD
4/25/2010 03:09    NV5E    20m    PSK31 750mW 1,163.11    ARLINGTON
4/25/2010 02:52    K5JJR   20m    PSK31 750mW 1,147.25    HASLET
4/25/2010 01:16    WA5MS   20m    PSK31 1W    1,165.94    HIGHLAND VILLAGE
4/25/2010 01:12    W5GT    20m    PSK31 1W    1,157.56    N RICHLAND HILLS
4/10/2010 09:37    JS1NDM  40m    CW    1W    5,576.71    Noda City Chiba
4/10/2010 09:07    JA7DLE  40m    CW    1W    5,379.44    Hanamaki
4/10/2010 08:30    JA1XMS  40m    CW    1W    5,600.02    Chiba City
4/10/2010 08:17    JF2QNM  40m    CW    1W    5,752.96    My shack :CHITAGUN 
4/10/2010 04:31    KI7MT   40m    PSK31 1W    1,015.82    HELENA

2010 ARRL CW DX Contest - portable operation

Another edit of some of the activities during the recent 2010 ARRL CW DX Contest.  Events such as this are really useful for tweaking your station configuration.  With a low power portable station, the dx contest is especially helpful, because of the test requirement to "work dx only".
Here is a view of some of the weekend activities, which I conducted from the hills just east of San Diego.
It was a cool day, with the temp hovering around freezing - (31F)

ARRL CW DX Contest - portable.

Here's the next challenge.  Portable, CW contesting.

Dec 2009 - Africa - Portable Operations.

Located about 100 miles north-east of the coastal city of Cape Town, our base camp is at 32.871954S, 19.084239E.
This time, we are exploring the mountainous region of the Ceder Mountains, adjacent to the Great Winterhoek Mountain Nature Reserve.
The base cabin is visible in the middle of the picture. A freshwater stream (which provides drinking water as well as a refreshing break from the daytime heat) runs about 100ft from the cabin.


Traveling here is easy by car (we bring 4X4 just in case), and at elevation of about 1500 MSL, we are surrounded by lots of mountains.
The cabin offers sleeping facilities for 6x. No electricity or water supply - just the way we like it. Well - ok - plenty of running water from the nearby river which serves as fresh water supply as well as a welcome relief from the baking southern sun.
At this location, the air is clean, there is no light pollution and at night, the Milky Way lights up the skies. While around the campfire, stargazing consumes the better half of the evening.
(No visible International Space Station pass during our stay unfortunately)

The "Green" Inverted V goes up - Mast is a sturdy piece of 30ft straight timber we found close to the cabin.

QRV / QRP - Of course no electrical infrastructure for miles, also means no rf pollution, and virtually "no" noise floor. With an inverted V for 40/20m, we light up the 706 (battery power). 20m dx sounds fill the quiet evening and even S1 signals are booming in Q5. What appears to be 20m short path to the U.S. comes alive around 20:00 UTC. No dx luck at QRP power levels, unfortunately, due to the high noise floors at the remote stations.

On 40m, local stations (< 1000 miles) provide for fun rag-chew QSO's during the daylight hours.

 Working local stations on QRP power offers quite a bit of activity during the daytime, with several fixed base and mobile stations from as far as Namibia and the Kruger National Park on 40m.

Stateside dx on 40m around 04:00 UTC are 5/9++. W1AW code bulletins are as clear as local stations during this window. 40m Gray line propagation shuts down around 06:30 UTC. Unfortunately we did not work any dx on 40m this time.

The rock formations in this area are truly spectacular, with a variety of freshwater streams feeding into the Elephant river. Easy hikes from base camp provide access to great vistas, waterfalls and freshwater mountain pools for cooling off during the summertime heat.

This time of year, the temperatures average about 30C. During our stay, we were lucky with some overcast days reaching 28C.

HF A/B linear on 20m - 15W PSK

With the LPF inline and on higher bands, such as on 20m this amps' performance drops a little but still delivers 15W easily with 1W drive.

Homebrew 40W WA2EBY linear amp.

After soldering in the header to support LPF/plug-ins the homebrew Hf-packer amp finally made it into an enclosure. Nothing permanent for now, but at least it'll keep some of the rf inside the box. The 2 x IRF510 MOSFETS are visible mounted on heatsink.
The amp delivers 40W output with 1W drive - at 24 Vcc.

The heatsink is pobably a little overkill, but it works! The IRF510's are heating up quite a bit at 20W.
This al enclosure (designed for rf use) was a find at the local surplus store for $5. It came with pre-drilled openings for DB9-style panel mounts - which now double as BNC mount slots.

The lid + heatsink still sitting loose on-top...and I'll have to do better job of running shielded cable to the MOSFETs. (hidden from view here under the heatsink)

ARRL CW SS : 40m

Zooming into the activity shows the signal spacing around 100Hz
Detecting light signals on this busy band is no problem - Rocky S/W, (with narrow filters still usable to around 35Hz on CW.)