Re: [multipsk] Digital modes and Propagation - Part-II


Sep 19, 2012

 


----------------------------

#15205 Sep 19, 2012

All:



This video shows how HF radio waves are manipulated by the ionosphere in

greater detail.



www.youtube.com/watch?v=pN5oZJwl2qA



The signal is a mixture of single and double-hop rays; each with it's

own X / O components. You can see how the amplitude of the signal

changes as the multiple ray paths move in and out of phase.



In the previous video, the 10 MHz signal had the least amplitude

variation so it would appear that the rays were in phase. Fading can

also be caused by ionospheric motion, polarization, variation in

absorption, ray focusing / defocusing etc.



Tony -K2MO



-------- Original Message --------

Subject: .[digitalradio] Digital modes and Propagation

Date: .Tue, 18 Sep 2012 23:28:11 -0400

From: .Tony dxdx@...>

Reply-To: .digitalradio@yahoogroups.com

To: .digitalradio@yahoogroups.com, multipsk@yahoogroups.com







All:



It's interesting to see how fading characteristics vary from one HF band

to the next. I made this strip chart recording of WWV on 2.5, 5, 10, 15

and 20MHz to illustrate this (see below). Samples from each band were

taken minutes apart.



I think it demonstrates why band selection is such an important factor

when it comes to digital mode throughput. It gives one an appreciation

for those robust digital modes when operation is limited to only one or

two bands.



www.youtube.com/watch?v=opMdR3N8oLI



Tony -K2MO



----------------------------

#15206 Sep 19, 2012

That was not only interesting but very informative as well. To actually see the signal and the E and F layers in action was nothing short of fantastic! Thank you Tony!Very 73, Glenn WB2LMV

On Wed, Sep 19, 2012 at 9:18 PM, Tony DXDX@...> wrote:

All:



This video shows how HF radio waves are manipulated by the ionosphere in

greater detail.



www.youtube.com/watch?v=pN5oZJwl2qA



The signal is a mixture of single and double-hop rays; each with it's

own X / O components. You can see how the amplitude of the signal

changes as the multiple ray paths move in and out of phase.



In the previous video, the 10 MHz signal had the least amplitude

variation so it would appear that the rays were in phase. Fading can

also be caused by ionospheric motion, polarization, variation in

absorption, ray focusing / defocusing etc.



Tony -K2MO



-------- Original Message --------

Subject: . . . .[digitalradio] Digital modes and Propagation

Date: . Tue, 18 Sep 2012 23:28:11 -0400

From: . Tony dxdx@...>

Reply-To: . . . digitalradio@yahoogroups.com

To: . . digitalradio@yahoogroups.com, multipsk@yahoogroups.com







All:



It's interesting to see how fading characteristics vary from one HF band

to the next. I made this strip chart recording of WWV on 2.5, 5, 10, 15

and 20MHz to illustrate this (see below). Samples from each band were

taken minutes apart.



I think it demonstrates why band selection is such an important factor

when it comes to digital mode throughput. It gives one an appreciation

for those robust digital modes when operation is limited to only one or

two bands.



www.youtube.com/watch?v=opMdR3N8oLI



Tony -K2MO



















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