I'm going against the grain again *cracks knuckles* :) This one is a good story, with a very interesting premise and fantastic production values - but had more than its fair share of issues.

While I've not seen any official note or comment referencing it, there's definitely a close relationship between Signal and a US movie called Frequency released in 2000 where an NYPD detective in modern day is able to use an old radio set to communicate with - what transpires to be his father back in the 60's and he tries to prevent his fathers death by warning him of events to come. So - I come to Signal having watched both this and the TV series of the same name, both of which were absolutely fantastic, and with that premise and a really strong cast I had high hopes.

High Points:
Production quality is outstanding, the visuals are superb. The simple effect of styling and colour grading the scenes in the past and present differently was superb and enabled you to instantly tell what was going on as well as providing a dated feel to the visuals (imagine you're watching it on a VHS tape perhaps). The cast were superb and I really enjoyed their performances and the music was good too - though I have yet to listen to the OST properly.
The story does keep moving at a decent pace, there are numerous cases that are covered so it's not like you're in the mire on one case the entire time, which helps keeps things interesting too.

There is one section with Kim Hye Soo where she is involved in one of the cases that was one of the best performances i've seen, knowing a little about how actors prepare themselves for roles to be able to create their characters I hate to think what she put herself through to be able to capture the intense and raw emotions portrayed as this sequence comes to a close.

Low Points:
Fundamentally the core element of the show - the radio being used to communicate between past and present - is totally underused. Where in the "normal" run of events people clearly didn't solve cases, this time around they are figuring things out even without sharing that information on the radio. When the radio is used other than a small number of times where it IS used effectively, it's almost only used as if a couple of buddies catching up and then that's it, radio is off again, and meanwhile everyone carries on solving murders and figuring things out at the same time anyway.

There is one time where the bad side effects of tampering with the timeline are covered brilliantly and devastatingly and I thought that was one of the highlights of the whole story. It was crushingly saddening and definitely one of those rare moments in any show where you're sitting there open mouthed thinking "what the heck are they going to do now?", but at the same time it also then cripples the characters from taking certain actions and ultimately was the turning point for the story going down hill for me as the story largely turns into a fairly normal crime thriller and the radio becomes a bit-part.

I felt the ending to be extremely weak. On reflection I have to admit that they do wrap up a lot of the main elements of the story but they leave some key ones open and even suggest at some new elements, this has all the hallmarks of "let's leave room for a season 2", though I don't feel as cheated as say "Vagabond", enough was wrapped up to mostly conclude the main story elements it just wasn't a truly satisfying end for me. Yes, I do like things wrapped in a pretty bow darn it.

It's definitely not a 9 or a 10 for me, but it's definitely kept me entertained. I wouldn't see myself watching it again based on the poor ending however.