It depends on which dongle you have. TS9, MCX and SMA are the most common connectors I've seen.
I use this adapter on mine to connect to my QFH antenna with RG-6 coax and standard TV F connectors.
And when you need a break from /r/rtlsdr , head over to /r/adsb and check out the fun plane spotting you can do. You'll need one of THESE for adsb and at least 25ft of regular old cable tv coax. You'll want to look up coax-colinear antenna too.. Super easy.
I am sorry, I have never used a dish. I did use an adapter so I could use coax cable with the dongle. This one: http://www.amazon.com/gp/product/B00CKG6T9I/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1
I had made the coat hanger HD antenna (look it up if you like) and had supplies for cutting it and adding ends/connectors.
As an affair of convenience I ordered other things that would let me use things I have on hand. I cannot tell you if this makes a big difference or not, but the the coax I got locally is all 75 ohm. There is 50 ohm too, but It is less common here. I am not sure it will make much of a difference. Maybe to some,but for us newbs, just get the cable man.
I bought the dongle and got it going with the mess of instructions above. Once it was working, I made the different antennas and checked them out. It seems like a lot, when you try to suck it all in. But if you go one step at a time, it is really not so bad. Go slow friend. It can work, and you will learn a bit along the way. Best wishes, I should never be considered an expert, but I have no problem talking about it all with you. I am sorry if it causes more confusion too, but we should be able to get you set up! I will try.
It looks like this person soldered coax directly to the pans.
I soldered an 18 gauge wire to the center of RG6 coax and one to the shielding. Then electrical taped the exposed connections. I crimped ring terminals on the ends of the 18 gauge and mounted them to the pans with sheet metal screws. I had no luck trying to solder directly to the pans.
Then I used this connector to plug it into the radio. No balun. Maybe a couple of ferrite beads.