Offline KevAmiga

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HF Radio Signals, Propagation and DX.
« on: April 15, 2019, 11:16:21 AM »
Morning all :)

Have had a few spare hours this weekend so have been performing some HF Radio experiments, mostly looking at time of day propagation however this lead me into thinking... How would the FE guys explain what i'm seeing here. In the RE model its pretty straight forward.

So to set the picture, 7.074mhz is the frequency in use, using a mode called FT8. What FT8 is, in a nutshell, is a Data mode where radio transceivers controlled by PC's (doesnt need to be connected to the internet) exchange information back and forth, signal strength, location, etc. This can then be seen using a website called PSK Reporter (https://pskreporter.info).

So anyway, the question. At the moment, the HF "bands" are pretty flat, meaning comms are difficult due to the sun spot cycle. We are at flat bottom at the moment, causing Ionospheric "lulls" (Can read about it here : https://www.electronics-notes.com/articles/antennas-propagation/ionospheric/hf-propagation-basics.php if interested). What this means is, to best of my understanding, the ionosphere isn't reflecting HF frequencies well.

So - my observations. Using FT8 this weekend I can see my signal being picked up, mostly around Europe. Nothing local, nothing much further. I can put this down to the fact that, as the earth is a globe, my signal cannot "bend" and relies on reflection back down to earth. If the earth was indeed flat, I would not require any bouncing of signals as such? The only thing in the way would be mountains, buildings etc but being on a high ASL myself, this would help. But what REALLY adds the heat to the fire with this one, is all of a sudden, boom, i can be heard in the states, Russia, Antarctica, etc due to changes in the atmosphere. And then... as quickly as it comes,,, it goes.

Anyone else have any thoughts or experiences themselves? Happy to go further into FT8 if anyone is interested, or provide some times / my callsign for anyone wanting to see how the propagation works on PSK Reporter.

Kev

Offline KevAmiga

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Re: HF Radio Signals, Propagation and DX.
« Reply #1 on: April 17, 2019, 08:44:18 AM »
Did a bit more FT8 last night, chasing the shadow (certain bands work better in the evening)... still hard to think how this would happen in the FE world.

Some good contacts from the UK down to Australia, Portugal, all on low power :)

Offline JCM

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Re: HF Radio Signals, Propagation and DX.
« Reply #2 on: April 17, 2019, 04:44:05 PM »
I think you may be surprised by the FE reaction to this.  This will be used as evidence for flatness, not a globe Earth.  The justification is that obviously a curved Earth you shouldn’t be able to conceptually bounce the signal far at all.  On a flat Earth the bounce makes a lot of sense you will hear.  As far as differences in sunspot that difference is the same for both models and proves nothing as different conditions allow a further bounce.  Again, this will be used against the globe Earth, the farther the bounce the stronger the flat Earth argument, after all, how do you bounce a signal the other side of a globe?!   It also props up the idea that satellite signals are bounced off the ionosphere and aren’t coming from actual Earth orbiting satellites.

Offline KevAmiga

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Re: HF Radio Signals, Propagation and DX.
« Reply #3 on: April 19, 2019, 07:01:58 AM »
Hey JCM, thanks for the reply.

So, my thoughts are :

1. I don't see why on a FE the bounce would make more sense? On a FE you wouldnt need to, you could aim your signal at the "horizon" and your away, no need for angle of attack at all.
2. Bouncing around the globe is based on the fact the layers within the atmosphere are also round, and thats where the bouncing occurs. (Read : "https://www.sws.bom.gov.au/Educational/5/2/2 ), 

3. Bouncing generally only affects HF and below. Satellite signals are generally in the GHZ range and require line of sight to work. 1575.42 MHz for GPS for example. Those signals, if sent from the ground would simply penetrate straight into space.

So here's another example of how we know this happens. When working modes like FT8 on HF, i'm in the UK and my signal was being received in Australia, and Iran, all sorts. But people in Scotland cant hear me. Neither can those in London, and the signal passes directly over them (in the F or E regions of the atmosphere, not at ground level). Hence the curve :)

Cheers!

Kev

Edit : So here's a quick propagation report based on stations receiving my signal this morning.



Signals again received in Australia... but shot directly over everyone else?
« Last Edit: April 19, 2019, 07:10:56 AM by KevAmiga »