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

Wednesday, March 9, 2011

A new toy

I have experimented off and on with the "Watch Window" feature in Spectrum Lab which lets you plot a graph of signal intensity vs time.  Up to 10 signals can be view at once and plotted on the same graph in different colors.  Each signal is selected from the Waterfall Display by setting the lower and upper frequency.  For a square wave type QRSS signal this is just below and above the Mark and Space frequencies.

While I was doing this, Dave (WA5DJJ) was developing a way to compare antennas by having two stations transmit on the antennas using the same power level, 100mW in this case.  We had not been coordinating our efforts in any way but when I heard from Dave about his experiment  it occurred to me that the WW feature might allow us to view the relative signal strengths directly.  So, with both of the signals bracketed I began recording and here is my first image:

Figure 1 - Plot of Signal Strengths from WA5DJJ and KE5OFK

Both stations are located in the same neighborhood in Las Cruces, NM and I am 1164 mi/1873 km to the west.  OFK was using an inverted V,  DJJ a Butternut HF6V vertical and my receiving antenna was an inverted V broadside to them..

First thing I noticed is the slow QSB....then how the two stations fade 180 degrees out of phase. The inv V has the edge on peaks by several dB but much deeper fades.

                     Figure 2 - Same parameters as in Fig 1 but Nine hours later

The next image was taken about 9 hours later, near my sunrise.  Notice now that the two stations are now fading together and that the inv V is better than the vertical by about 7 dB.  I've seen this kind of signal strength differences on the Las Cruces stations before but could only judge which was stronger by the brightness of the traces.  Window Watch puts this into numbers though I haven't used it enough to have confidence I'm doing everything correctly....more testing and experimenting is needed.

Not only does this technique provide information about the antennas but also about the Ionosphere, but this is where things get really complicated because of all the phenomena which effect the amplitude and phase of a radio wave passing thru the Ionosphere.  With more observations and lots of reading maybe some of this will become apparent.  Your comments would be welcomed.  But for now I'm just showing some pretty pictures :>)

One final note....I cannot disable the AGC on my rx and I think this is why the Noise trace is fluctuating as strong signals cause pumping.  You can also see this on VK6JY's signal and it may be possible to correct for AGC effect by just subtracting off the noise level.

73 bill w4hbk

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