I've actually bought one of these recently to use for our main TV which is hooked up to a Mac mini. The second input does actually use a coax cable, but the plug on the end is an MCX plug, which is a bit unusual. Even Maplins didn't have any appropriate adapter, but there is a guy in Hong Kong who is selling adapters on ebay that a lot of people have recommended (search ebay for "RF Coaxial to MCX Plug Antenna Rooftop Adaptor DVB-T" to find them).

Alternatively there is the quick and dirty method which is to simply cut the cable of the supplied secondary antenna and solder that to a coax cable with a normal RF connector on the other end. That's what I did and it's fairly easy. I just used a splitter then to take the feed from our roof and then plugged that into both inputs. Then I was getting great signal for both tuners and the dual tuner mode works marvellously.

The Elgato Diversity works much better if you use external antennas - and that's true of any Freeview device. The problem is the second antenna's connector - the first is the usual Belling-Lee coaxial found on all TVs, but the second is the much rarer MCX. Elgato would do well to provide in the box a MCX to RF coaxial connector; I eventually found one on Ebay for £2.99, but I should not have had to look....

The article mentioned that the Freeview signal was not yet as strong as it should be, well it's a lot worse than that in some areas of the UK

On the south coast, the area around Eastbourne, East Sussex receives it's Freeview signal from Heathfield, but due to the signal causing some distortion to the French airwaves, the signal's strength was reduced, thereby preventing most of the area around the South Downs from receiving it. My parents for one, still cannot receive ANY Freeview signal at all.

Which has STILL not been resolved, after years of trying to get the signal increased.

I wonder if it EVER will.