I personally find very difficult to understand which radios support full duplex operation and (given the comments I saw in the other newbie questions topic) among the ones that do, which ones can effectively isolate crossband interferences while transmiting in full duplex.
Another thing is the "all mode" radios. Will I want to use SSB? Given the price of the all mode V/U radios I can only imagine that therer are very few operators using it. Is this the case?
Regarding antennas (maybe the most important part), I'm thinking something directional like a yagi-uda should be the way to go. But what about polarisation? Should I go with something with circular polarisation? Switchable RHCP/LHCP? Single or two independant coaxial connections?
My scenario of operation will most likely be portable as I live in an appartment.
List of full duplex radios (click the tabs for HTs / Mobile / Base)
https://www.dropbox.com/sh/v3byggtuqw33fkk/AAAamatWbd9657AQfXhM6-wPa/Articles/Full-duplex_radios_for_satellites.xlsx?dl=0The "linear birds" have less operators, but in the US this is a GOOD thing. The FM birds are so crowded here, it is currently almost impossible to make a QSO on some passes. For linear birds, the most common portable setup (which I use) is a pair of FT-817 radios. Next to that, but more difficult to transport, would be the older IC-820/821 radios.
If you are portable, go with a handheld antenna. In the US, the by far most popular is the Arrow:
https://www.arrowantennas.com/arrowii/146-437.htmlNext to that is the Elk:
https://elkantennas.com/product/dual-band-2m440l5-log-periodic-antenna/Or you might try building one:
http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf(I have a regular Arrow, an Alaskan Arrow (longer) and two Elks, one to hold by hand and one I have on a tripod.)
A hand held antenna allows you to rotate the antenna to match the polarity of the satellite in the moment. So, no need for circular polarity. (Circular polarity is sometimes used with home stations where the antenna is fixed and not able to rotate to match the satellite.) Most satellites use linear antennas now (whips) and the polarity changes as the satellites 'tumble' in orbit. Watch this video for a demonstration of polarity and rotatng the antenna:
https://www.youtube.com/watch?v=XTqjQ9xIQQEAs for number of antenna connections, it varies with radio(s) and antenna design. I chose to have single connections and use a duplexer to separate the bands, which adds the extra benefit of some filtering and helping to eliminate the crossband interference you mention. (as long as the interference is not
inside the radio)
As for Doppler shift. You shouldn't need to be concerned with Doppler shift for the FM ISS Repeater or any of the FM single channel satellites. There of course is a Doppler Shift on the FM Satellites but the FM filtering is wide enough to handle Doppler Shift without you needing to adjust your frequencies.
I would have to disagree with this... doppler does not matter that much on the 2m uplink/downlink but DOES on the UHF side. On my full duplex HT, I will have about 5 frequencies in memory on the UHF side for each satellite and start off on the higher ones for downlink, lower one for uplink. You start off at one end as the satellite rises gradually, adjusting to the middle frequency when the bird is highest, and going to the other end as it goes back down to the horizon. It is MUCH easier to adjust with UHF downlinks as you listen to the signal get 'noisy/off frequency', you click to the next channel and it comes back in clear again. On UHF uplink, if the satellite is busy, you cannot be sure if you do not hear yourself because you are off frequency or because someone else is also trying to transmit. So for uplinks, just have to make an educated guess.
One thing to note, while Baofengs have been used to make satellite contacts, my personal experience is that they do not work very well. The nature of the 'radio on a chip' design makes them susceptible to interference, and missing the signal due to 'scanning', etc. I have an older IC-W32a... I am told the Yaesu FT-530 is a good HT as is the Kenwood TH-72a. BUT there may be some differences between US versions and EU versions that would affect things. (Like allowed transmit frequencies, etc.)
Some notes... you need to have an OPEN squelch. The signals are often so weak they will not break the squelch even on the lowest setting. I would recommend that you try out the FM birds first to get the 'hang' of things. The linear (SSB/CW) birds are a bit more to learn with regards to doppler, etc. and the radios are usually more expensive. (Antennas are the same though.) Besides it may take you a little while to figure out what will work best for you... there is no 'one way' to operate satellites in regards to which radio, antennas, etc. I always tell people to 'find what works for you'. I have some pictures of my portable gear on this webpage:
https://www.qrz.com/db/N4UFO/P But I am experimenting with trying an antenna mounted to a tripod with a very adjustable swivel base (to allow for polarization adjustment). Most satellite ops detest tripods, but some have figured it out...

Again, find what works for you.
I have long ago taken down and sold my home satellite station that I had at a former QTH... once I completed the 488 CONUS grids for the Gridmaster Award. (Took just over 5 years.) After moving across the country, I don't quite see wanting to start over and do that again! Now, I would just like to work Hawaii so I can finally complete the WAS award. You will hopefully find it fun to talk to people, maybe chase grids, Pedro. When I was on the East Coast of the US, talking to ops in France and Europe was a lot of fun! Often I had to be awake in the middle of the night here to do it though.

Find what you enjoy!
Hope this info helps! 73, Kevin N4UFO