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I saw this article but I can't imagine the power output, (eight watts max) would be enough to be picked up by the ISS at 200 miles above me.

Similarly, I don't know if the preamp on the receiver would be sensitive enough to pick up the signal, unless they put up the full 1,500' ERP for it to be picked up.

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  • $\begingroup$ Isn't the UV-5R only 5W output, though? The BF-F8HP is 8W (claimed, and widely believed to be less). $\endgroup$ – Zeiss Ikon Oct 28 '19 at 12:12
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In theory, yes.

In practice, "probably not". In my experience, the front end on Baofengs is not very good. We have a UV-82, and it just did not work when we tried to use it for amateur satellites (AO-91, AO-92, etc). When we replaced it with a Yaesu FT-60R we were finally able to receive the "birds".

So while theoretically you should be able to receive LEO (low earth orbit) satellites (and the ISS), in reality your Baofeng is being overloaded by everything surrounding you. The same goes for cheap "RTL SDRs", which need some filtering to get a usable signal: Baofengs ARE SDRs, and cheap ones at that.

I haven't tried it, but maybe in the "middle of nowhere", far from broadcast stations, you would be able to receive the ISS. Or maybe if you use a suitable filter.

But if you want to experiment with ISS, amateur FM satellites, and NOAA APT (while they last), you should get a second hand "traditional" (analog, superheterodyne, etc) receiver, which will save you a lot of headache.

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  • $\begingroup$ What antennas were you using? $\endgroup$ – Mike Waters Oct 28 '19 at 1:45
  • $\begingroup$ My dad built them. One was a IOio , and the other I'm not sure, but I think it's a dual-band Moxon. $\endgroup$ – hjf Oct 28 '19 at 1:46
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You definitely can, but would benefit a lot from a dual band directional antenna. There are plenty of examples of self-built yagi antennas that are perfect for satellite work (such as https://hackaday.io/project/25143-wa5vjb-ultra-portable-dual-vhfuhf-yagi but there are lots of others in varying degree of sophistication and effectiveness). I particularly like the idea of using tape measure parts since you can easily fold them (see https://www.instructables.com/id/The-Tape-Measure-Antenna/ for an example). The idea is the same as above. For an "ideal" antenna you would probably want the wire version instead of the flat metal but you are trying to have fun and not make a commercial product.

The front end of those radios is not great, but you can quite easily make a filter yourself for that. It all depends on how much you want to make things yourself and experiment, or rather buy a product that you know (should) work...

In any case, have fun with it...

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You don't need to imagine it, because it's true. Many amateur satellites have around half a watt of output, and they're easily received on the ground with only a modest antenna (a 3-element yagi helps, but I've worked AO-91 and AO-92 with quarter-wave verticals). 8 watts is far more than enough. It doesn't take that much power to get above the noise floor even at hundreds or thousands of miles of distance. The reason terrestrial VHF/UHF are distance-limited is because some obstruction (like the earth itself) always gets in the way sooner or later, but satellites are conveniently located in the sky, where there is generally a whole lot of nothing between us and them.

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Radio waves will travel for billions and billions of miles through space if they're not interfered by matter. Consider the New Horizons Interplanetary Space Probe that did a fly-by of Pluto in 2015. I am not sure how far that was but Pluto is about 2.6 Billion miles from Earth at its closest.

The transmitters have a power of 12 watts! One of the antennas on the probe has a gain of 42 dBi with about a 1 degree beam width. Earth bound antenna dishes used for communications though are huge, 70 meter dishes part of the NASA Deep Space antenna network.

You can use the Friis transmission formula to compute the free-space path loss of the signal and get an estimate of the power of the signal when it reaches the earth. I have not done the computation but you can do it as a homework assignment. Of course, there are likely unknowns that you will merely have to guess at to fill in the blanks of the formula. Or, maybe a diligent internet search can find the necessary parameter values.

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I've received the ISS during a school contact as described in the linked article on my UV5R using its supplied helical antenna. Copy was good from a high pass but held up for a long time. A beam should give better results for a low elevation pass. The ground station was 150 miles away so I couldn't hear that, of course. I've not tried sending to the ISS e.g. to the packet node.

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