I will start by saying that I have always believed in ghosts but never thought I would experience anything, until recently.
The biggest experience I had started after my brother unfortunately passed away. I think he visited me a few times after he died for the following reasons.
1) I let my brother live with me for a few years. I would find the light on in the room that was his. I hadn't been in that room for six months so I know it wasn't me. Even if it was me I would have noticed that it was on at some point. This happened multiple times. I would turn it off just to find it on the next day.
2) I would wake up in the morning to find the living room tv was on. I had the tv set to turn off after one hour of inactivity so it could not have been on that long, I am also really good at turning things off after myself. My brother had the habit of never turning lights or tvs off.
3) I would find my car keys on the kitchen table where he would leave then on the occasion I let him borrow my car. I never put them there.
4) After he passed I got his xbox1. While I am aware that the system does have a glitch that causes it to turn itself on there are a few things I cannot explain. The first being the system turned on 5 times in a row. If its the glitch its one time and its done for a few days. In the instance I would turn it off get two steps away and it would turn back on. I said hi to my brother and the instance stopped. The following morning I unplugged the system. I got home from work the system was plugged back in and turned on.
Things stopped after a month or so.
I have a radio from 1928 I wonder if it has a spirit attached to it. It has doors on it that lock. The doors occasionally open themselves even if locked. My pet birds act spooked whenever I carry them passed it.
I also had on occasion to wake up to someone yelling HEY right in my face. I have also heard what sounds like sneezing coming from the living room. I live alone so I cannot explain why this would be.
I suppose that your brother is just trying to say HI and let you know that he is around, as for the radio, I do believe that objects can be haunted, perhaps the person it belonged to previously has an attachment to it.