Thread by @4o4a

So, you have only one radio and restrain yourself from LEO sat operations because you don't know how to deal with Doppler?

Or you have two radios and would like to find clear frequency to call, or to find exact frequency where that rare station is listening?

#amsat #dxcc

1/6

You know math, right?

And you already have ISS Detector for Android, with those valuable information about passes, paths, Doppler shift for your location?

How to calculate on what frequency you have to call, to be heard exactly where you heard someone calling?

2/6

Take a look at ISD Detector info. All you need is there.

Where to transmit? Where to set second VFO or second radio, without hola-holing or whistling around?

Let's say, you found a clear frequency on 435.630, and you would like to call CQ.

3/6

Imagine that there is no Doppler.

You want to listen on 435.630 USB - you need to TX on 145.975 LSB. If RX is 20 kHz from lower edge of RX transponder, TX is 20 kHz from upper edge of TX transponder.
Add Doppler information to this.

TX freq will be sum of all freqs.

4/6

TX = 145.975 + TXd + RXd
TX = 145.975 + 0.97 - 2.91
TX = 145.973.06

You can do it even more faster, you don't need to use decimals, you cannot be so much wrong even without it.

TX=145.975 + 1 - 3
TX=145.973

You cannot miss more than 1 kHz, and it will be easy to correct.

5/6

A few guys will remember that I was not exactly on the frequency when I called them on their extra valuable activations (grid borders, new DXCCs).

Take a deep breath, do your math quickly. Point the antenna and call.

Happy new year to all, and happy LEO SAT DXing!

73!

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