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  2. digital modes on 2m 70cm

Re: digital modes on 2m 70cm

Tony
 

Bruce:

Commercial and military aircraft fly through a sea of RF including megawatt radars that track satellites in space without incident. If there was any risk, big-gun 2 meter EME stations would be outlawed : ) Aircraft scatter is probably not what you imagined - we don't point our antennas at the aircraft.

The mode relies on an aircraft crossing the path between stations; when the geometry is right, signal reflecting from the aircraft rises above the noise so the contact can be made. The reflection weakens as the aircraft continues along it's path so the signal doesn't last very long. Range is limited to 400 miles or so.

I produced a demo video that shows what A/C scatter looks like on a spectrogram.

See: https://www.youtube.com/watch?v=vYkaSuJkYrM

Tony -K2MO

On 10/21/2020 12:00 AM, Bruce wrote:
Hi Tony
Interesting subject on Airplane scatter on 2 meters. Bouncing signals off of aircraft could that interfere with electronic systems or communications in the aircraft? If you bounced signals off of military aircraft, could that be tracked and bring a visit by MP's?
Also what antenna polarization works best for the path ? Do both stations need to be using the same polarization? How do you find stations and frequencies being used and arrange a contact?
Thanks for the education.
Bruce WA6DNT@...

On 10/18/2020 7:24 PM, Tony wrote:
Andy:

The most popular VHF modes are FT8 for terrestrial propagation and MSK144 for meteor scatter. You can get an idea what the activity is like by checking out PSK Reporter with the 2 meter filter on.

If you're used to 6 meters, you'll find that Sporadic-E and other long distance propagation modes typically happen less frequently on 2 meters and a lot less on 432 so it pays to get email alerts to let you know when the openings occur.

If you're looking for daily propagation on 2m and 70cm, aircraft scatter is the most consistent mode out to a few hundred miles. It's easily recognizable by the Doppler shifted signals which FT8 usually handles well.

I've attached a PSK Reporter screenshot that shows the distances you might see on 2 meter A/C scatter. The other screenshot will give you an idea what the A/C Doppler is like on 2 meters.

There are several amateur satellites that you can try as well.

Tony -K2MO
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