[RTTY] Estimating increase in bandwidth/interfeerence from Winlink if RM11708 is approved

RTTY rtty at contesting.com
Thu Apr 17 22:03:17 EDT 2014


Terry,

One other issue ... PACTOR III is 2.2 KHz not 2.4 KHz.  That change
will further increase the additional interference by at least 0.5 dB.

73,

    ... Joe, W4TV


On 4/17/2014 9:36 PM, RTTY wrote:
> 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
>
>
> ------------------------------------------------------------------
>
> 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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