Thanks to inputs from Ted, N9NB, the model was changed where the results are
now in dB showing the additional interference if current Winlink stations
move to RM11708 max bandwidths of 2.8 KHz. The average interference
across the modeled 40 meter spectrum is 3.4 dB. And yes, interference is
the correct term since the stations are all automated and do not have
working busy frequency detectors.
The new graph in dB can be seen at:
http:\\64.128.19.154\Images\RM11708-2.jpg
Two new assumptions were added to the list:
1. The model assumes a linear Power Spectral Density, PSD. That
simplifies the model but it lowers the final results a bit
2. Each 100 Hz frequency bin starts at a count of 1 (rather than 0)
which keeps the dB/power ratio math in check
Terry AB5K
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Taking the existing Winlink stations and transmitting bandwidths and
changing the bandwidths to 2.8 KHz, we can get a idea on the future increase
in consumed bandwidth/interference if RM11708 is approved. Here are the
steps used in this analysis:
1. Take the published Winlink call/frequency/mode list. Determine the
current bandwidth and convert it into a spectral density format where we
total the total number of stations transmitting every 100 HZ.
2. Repeat step one using a 2.8 KHz bandwidth for each station.
3. Import into Excel, sum from 7.060 to 7.100 MHz.
The result is: 3.6 times more spectral bins used if 2.8 KHz becomes the
standard. A graph displaying the results can be found at:
http:\\64.128.19.154\Images\RM11708-1.jpg
The X axis is frequency and the Y Axis is the total stations transmitting in
each 100 HZ bin.
Assumptions:
1. The processing was only ran against US Winlink stations.
2. Only Winlink frequencies were analyzed. Other current and future
digital waveforms (ALE, etc) are not included.
3. Modulation is USB, no offset
4. Current Winlink bandwidths are: Pactor 4: 2.4, Pactor 3: 2.4,
Pactor 2: .6, WINMOR 1600: 1.6, WINMOR 500 .5, and Robust Packet: .5
Terry AB5K
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