Regular reports of my grabber activity and that of others, plus information on QRSS software, hardware and technique that comes my way

Thursday, July 3, 2014

Using Google Analytics to Track Usage of Your Grabber

I used to have one of those cute little Maps on my grabber page that shows who's using it.  These apps are provided free and I read that they are a means of collecting user data, including IP addresses.  The provider can then sell this data to advertising companies, etc.  When I learned this I immediately removed the apps from my web page at

I really wanted a way to see if my grabber was being utilized since I rarely get feedback indicating it is.  I ran across a reference to Google Analytics which allows a web site operator to collect the data without obtaining personal data and IP address.  I've found it to be a useful and safe tool to monitor site activity and the most detailed info I get is rough geographic location and how many times my web page is accessed.   Here is what the info looks like:

I chose to watch on a daily basis but you can also select hourly, weekly or monthly.  In the graph above I can see that the peaks occur on weekends and the minima at mid-week.  Country information is also available.  There is also an option to monitor in real time so I can see who is accessing the web page now.

To install the app just to to Google Analytics and set up an account then follow the instructions.  You can also get reports for other web sites you may operate.

de w4hbk

Friday, May 30, 2014

One Billion Miles per Watt on 20m

Back in 2011 Dave, WA5DJJ, and I became interested in just how low we could go in power and still be able to copy his call letters, which is our definition of QSL for QRSS work.  On 30m we were able to make it down to 8.51 uW using image stacking technique.

Since that time we have kicked around the possibility of going down to 1 uW and last November started a new campaign to do so.

By early May of 2014 we had reached 15 uW on 30m after months of trying but could go no lower.  We need long periods of time free from interference in order to obtain a sufficient number of 10 minute grabs to use image stacking to extract the signal from the noise. Activity has increased since 2011 both from QRSS and other digital modes.  The notorious OTHR from Akritori, Cyprus is a regular visitor also.     In addition, this was a most unusual Winter here in North Florida with frequent thunder storms related to the infamous Polar Vortex which plagued the East Coast this year.

At this point we decided to try 20m to escape the QRM and hopefully see less QRN.  The difference was amazing.  Not only did we have the spectrum all to ourselves but the QRN dropped almost to nothing.  We started at 100 uW and came down rapidly in 3 dB steps to 5.8 uW.  After that the difficulty with each 3 dB step increased exponentially with the final step from 2.5 uW to 1 uW requiring 12 days until all the variables lined up in our favor.  Here's a 3-day stitched image showing our approach to the 5.8 uW level:

Note that the WA5DJJ signal was still drifting a bit until Dave installed the MEPT in a thick-walled styrofoam box.

On the night of May 17 the 1 uW signal was visible in and out on the 8 hour grabber from 0430z to 1040z.  Thirty-eight 10 minute grabs over this time period were processed with the stacking software Rot'n'Stack to produce a barely discernible image in which I could read all the letters of Dave's call.  That's 1 uW over a distance of 1164 miles/1873 km.  If you do the math that's over one billion miles per Watt for a signal propagated via the ionosphere.

Here is the results of the image stacking:

Note the use of a second signal from WA5DJJ from an older MEPT feeding a vertical.  It was not stable in time thus preventing stacking.  We used this to give some idea of propagation.  KB5R also joined in for the same purpose.  The cw signal from IK6ZEW was strong but not stackable.  The 1 uW signal eminated from a QRP Labs U2 mept feeding a Cushcraft A3 triband Yagi.  The receiving antenna at W4HBK was a 30/40m inverted V with the apex at 18 meters.

For comparison here is one of the better 10 minute grabs:

It's fun to compare our miles/Watt to that of the NASA's deep space probe Voyager 1 which at a distance of 11.8 billion miles from Earth running a 20 Watt transmitter which gives 590 million miles per Watt.  Of course they are sending HiDef images and telemetry compared to our 6 scratchy letters but on the other hand they are using a 70m dish at the receiving site.

Here is the story from Dave's point of view:

de w4hbk

Friday, April 18, 2014

Frequency Scale Calibration for QRSS Grabbers

Spectrum Lab provides two methods of frequency calibration which can be utilized to set the frequency scale accurately on all bands.  The first applies to calibration of the sound card by injecting a known audio frequency and comparing it to the frequency measured by SL.  Figure 1 shows the Audio I/O screen for entering these values in the "Correct Frequency" and "Displayed Frequency" boxes on the right.  After entering click on the "Calibrate Input SR" and the sound card's Sample Rate will be determined and entered in the "Sound Rate Calibration Table".  I generally use a nominal SR of 11025 Hz and in the actual value is 11099.8922552 Hz which is now applied to the SL measurement.  At this point Spectrum Lab is reading audio frequencies accurately.  I used the standard tones of 500 and 600 Hz provided on the WWV carrier when listening in AM mode.

Figure 1.  Spectrum Lab Audio I/O Screen

The second frequency adjustment is via the "Radio Frequency Offset" value found on the Spectrum(2) screen, Figure 2.  This is the frequency to which the radio is tuned and adjusts the scale to read in units of the actual frequency being received.  For example, on 30m, my rx dial is set to 10138.70 kHz to produce an audio tone of 1300 Hz for 10140 kHz.  If the master oscillator were perfect then the frequencies measured by SL would also be perfect.  However, even the best receivers are off by at least a few Hz (unless locked to GPS or an atomic standard) so a little extra correction is needed.  This can be applied by adding or subtracting the appropriate value to the rx display.  My rx on 30m reads low by 7 Hz and I add this to the offset value as 10138.707.

Figure 2.  Spectrum Lab Radio Frequency Offset 
The offset can be determined in general by measuring the error for several know frequencies and applying a linear regression.  This is possible because the frequency my TS-440 and as far as I know all modern transceivers is controlled by a single crystal.  I used the standard frequencies of 5, 10, 15 and 20 MHz from WWV in Colorado to generate the curve shown in Figure 3.  The linear regression for this data is:

            F(offset), Hz = -0.2 + 0.672*F(rx), MHz,

where F(offset) is the offset needed to correct the received frequency and F(rx) is the receiver frequency.  Ideally the intercept value should be zero but the value of -0.2 is easily attributable to measurement error.  The offset values for each band are also printed on Figure 3 for quick reference.

Figure 3.  Offset Graph and Table
Use of WWV for frequency calibration can be tricky due to Doppler effects caused by motion of the ionosphere.  I made my measurements on a day when ionospheric conditions were settled and at a time when the night-to-day movement should have been completed.  I confirmed this by monitoring the Doppler shift for several hours.