Can anyone point me in the right direction to find out what this is? Both connectors have the center and ground connected together and there is a tube inside with a turning knob on top.

 

Can anyone point me in the right direction to find out what this is? Both connectors have the center and ground connected together and there is a tube inside with a turning knob on top.

There was an antenna connected.

 

It is probably a frequency adjustable cavity resonanator .

 

They are often used in repeater installations so that a single antenna can be used for both receive and transmit.

 

I think KeithWalker got it. The adjustment knob is on the box for adjustment or coupling, used on UHF and upwards.

 

It is definitely a tuned cavity bandpass filter. That one looks like it is for the 100 to 200 megahertz range. It may have been used between the antenna and a receiver to avoid interference.

 

Yes it was connected between the antenna and what I believe is a transceiver, I will try to post a picture of it. I was just intrigued by it. As you can tell I am not in this field, I have messed around with communications but I had never seen this.