CB Part Identification

I bought a Midland CB unit secondhand, and it came with an unmarked black box:

It appears to be labeled as if it were directional, there's no significant resistance through the center conductor, and the connections are the same size and thread pitch on either side.

Aside from extending my coax cable 2.5-inches...  what might this thing do?

Maybe some kind of a matching box for a specific antenna, or a choke intended to stop reflected RF coming back into the radio. No other markings?

IIRC those were sold as a booster for antenna.

Yeah, no other markings at all...

i was thinking it might be a filter of somesort but figured amplification was out of the question since there were no power wires going to it...

I guess i'll have to open her up and see what we can see 

NOT A TA said:

IIRC those were sold as a booster for antenna.

Were those boosters legit, or more along the lines of snake oil?

If there are no other wires to it and it's billed as a booster, definitely snake oil.

If you see coil-like things when you open it up, it's some sort of match box used to tune up the interface between transmitter and antenna.

It's possible that a match box would get more power out the antenna, so maybe they billed that as 'boosting'. But a good 1/4 wave antenna is already close to the 50 ohm impedence that your radio circuits want, so there is little or no benefit from matching.

Awesome.  Sounds like it's headed for the bin.

Thanks everyone!

You could get an SWR meter, try it with and without the box, see if it makes a difference.

CB radio is still a thing?

10-4 Good Buddy

Bandpass Filter.  Only let's CB frequecies get to the radio.

Cactus said:

You could get an SWR meter, try it with and without the box, see if it makes a difference.

That's what I was thinking.  I've been meaning to order one anyways, now is a good time.

GeddesB said:

Bandpass Filter.  Only let's CB frequecies get to the radio.

Interesting!

That would explain why it was directional.

ShawnG said:

CB radio is still a thing?

 

I wonder - My motorhome has one of those "all in the handset" cobra radios.  Had it on all across the country one time and never heard another voice other than the marine / weather channel.

Truckers must be using an app on a tablet or something?

GeddesB said:

Bandpass Filter.  Only let's CB frequecies get to the radio.

Good call. Could also be to keep a transmitter from interfering on other bands. TV at 54MHz would be interfered with by a crappy 27MHz transmitter (or a decent transmitter with a crappy amplifier).