Marko 100f booster
 

I have an old Marko 100f 40-10 meter am/ ssb booster.
from when it was on a cb , about 25 or 30 years ago, it would reach out and talk, but anyway, what would make it legal to use? I know a radio license, but does anybody know if those were made for cb band illegal, or were they ham boosters that worked on cb or did they have to be modified?
Would anything have to be done different on another radio besides a cb

Amplifiers are legal on ham (amateur radio) bands and yes you must have a license to operate legally. CB is limited by the FCC to 5 watts input and 4 watts output to the antenna. Anything above this threshold is illegal. Hams can legally use amplifiers on any band including the 10 meter band which is right next to the 11 meter CB band. 10 meter amplifiers can be re-tuned to operate on the CB band by those that are technically savvy. When using an amplifier you put out a stronger signal which gives you more transmitting distance. However, unless it is a bi-lateral amplifier such as the old Pace/Pathcom units your receiving signal is still "local". So unless the other person is also using an amplifier he/she may be able to hear you but you may not be able to hear him/her if they are only running stock power.

In my younger years I ran CB. I am now a ham and it is comforting to know that ham communications are reliable and get through. You don't have the typical problems associated with CB. Getting my amateur radio license was well worth the effort.

KG6SLC aka Eugene

Use of the linear amplifier on the CB (11 meter) band is illegal both in your country (US) and up here in Canada. There is no legal way to use it even with an amateur license, give the broad range it sounds like that was set up for it would probably work or was retuned for 11 meters. Frankly though as KG6SLC mentions I would just get your amateur license which is now pretty easy to get vs the old days when you needed to learn morse code.