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[KE6TDT]

Mine looks exactly like this below. It's worn and the housing is not cracked appears to be in good condition, clean contacts etc.. 

The whip on this is approximately 48". Is this designed for 2 meters and do I need to trim the antenna? Was this how the MX-270 were shipped where it requires it to be trimmed for the correct frequency? I have no problem doing that if this is the case.

My concern is I looked up the MX270 but it shows a 36" whip...

Thanks for any advice.

[WB6BYU]

Without the photo, it is difficult to tell.

But many manufacturers reuse the same parts on different
antennas.  For example, a 48" whip may be a 5/8 wave
antenna for 2m, or designed for CB or other frequencies,
depending on the coil inside the base housing.  The same
housing could be used with a 36" whip as a 2m half wave,
or for some other band.

So if there is no markings on the antenna itself, the only
way to know for sure is to put it on a mount and check the
SWR.

[KE6TDT]

I was afraid of that. I used a magnifying glass to look for any identifying product numbers but found none. The only thing I have to go by is the housing. Looks like I will put it on 2 meters and check the swr.

Thanks, I do appreciate the response.

[K0UA]

A dollar says that baby resonates on 27 Mhz.

[WB6BYU]

There should be some way to open it up and look at the matching
assembly inside the case. 

I've converted several CB antennas with 36" whips to 2m half wave
antennas, just by rewinding the coil and adding a trimmer capacitor.
With a 48" whip you could make a 5/8 wave antenna.

But a glance at the innards would go a long way to identifying the
design frequency.

[KD6VXI]

Throw the load in the freezer for an hour or so.

See if you can read it then.  Sometimes this will let you make out old lettering.

Works on tubes great.  Other things I've found to be hit or miss.  Either works, or doesn't help at all.

--Shane
WP2ASS / ex KD6VXI

[K0UA]

OK.  so you bought this at a yard sale.  Knowing the number of Ham band antennas vs. the number of 27 Mhz antennas manufactured, AND knowing the whip length is incorrect for the ham band model, what are the chances? A million to 1? Of course this is a CB antenna. Why is there even any doubt?  If this is a 2 meter antenna, I will eat your hat and pay you that dollar.

Of course one simple test is worth all the conjecture in the world. Not to mention looking for numbers, not to mention freezing, and not to mention taking it apart. a 2 minute test will show you beyond the shadow of a doubt that this unit was made for 27 Mhz CB band.

[K1KIM]

NanoVNA

[K0UA]

NanoVNA

Wouldn't take long to find out would it? Or for that matter about any old antenna analyzer. OR get this, Just a simple old $5 SWR meter designed for CB.

[KEOWRU]

Mine looks exactly like this below. It's worn and the housing is not cracked appears to be in good condition, clean contacts etc.. 

The whip on this is approximately 48". Is this designed for 2 meters and do I need to trim the antenna? Was this how the MX-270 were shipped where it requires it to be trimmed for the correct frequency? I have no problem doing that if this is the case.

My concern is I looked up the MX270 but it shows a 36" whip...

Thanks for any advice.

its a cb antenna a mx has a load in the middle n about 27 inches tall