I am attempting to validate and update.
I understand there is a reciprocal operating agreement with the US but I am still guessing it is necessary to inform and request a permit/license from the Grenada NTRC. I did go to their website and investigated what might be required of me. It appears that I need a copy of US ham radio license, and perhaps a fee of about $25 (is that US or Grenada currency). The website gives some information but the details are usually where any problem might occur.
United States
Examples: a Canadian Amateur would use VA3RAC/W4 in the US 4th call area. A US Amateur would sign as K8HI/VE3 in Ontario.
The main difference for Canadian Amateurs operating in the US is that, unlike Canada, the US has a mandatory band plan which specifies modes and sub-bands. Canadians in the US must operate in accordance with FCC Part 97 Rules using the appropriate modes within their designated sub-bands. For detailed information see https://www.arrl.org/band-plan.
The countries with which arrangements are in effect are: Antigua and Barbuda, Argentina, Australia, Austria, The Bahamas, Barbados, Belgium, Belize, Bolivia, Bosnia-Herzegovina, Botswana, Brazil, Chile, Colombia, Costa Rica, Croatia, Cyprus, Denmark (including Greenland), Dominica, Dominican Republic, Ecuador, El Salvador, Federated States of Micronesia, Fiji, Finland, France [including French Guiana, French Polynesia (Gambier, Marquesas, Society, and Tubuai Islands and Tuamotu Archipelago), Guadeloupe, Ile Amsterdam, Ile Saint-Paul, Iles Crozet, Iles Kerguelen, Martinique, New Caledonia, Reunion, Saint Pierre and Miquelon, and Wallis and Futuna Islands], Federal Republic of Germany, Greece, Grenada, Guatemala, Guyana, Haiti, Honduras, Iceland, India, Indonesia, Republic of Ireland, Israel, Italy, Jamaica, Japan, Jordan, Kiribati, Kuwait, Liberia, Luxembourg, Macedonia, Republic of the Marshall Islands, Mexico, Monaco, Netherlands, Netherlands Antilles, New Zealand, Nicaragua, Norway, Panama, Paraguay, Papua New Guinea, Peru, Philippines, Portugal, Seychelles, Sierra Leone, Solomon Islands, Republic of South Africa, Spain, St. Lucia, St. Vincent and the Grenadines, Surinam, Sweden, Switzerland, Thailand, Trinidad and Tobago, Turkey, Tuvalu, United Kingdom [including Bermuda, British Virgin Islands, Cayman Islands, Channel Islands (including Guernsey and Jersey), Falkland Islands (including South Georgia Islands and South Sandwich Islands), Great Britain, Gibraltar, Isle of Man, Montserrat, Northern Ireland, Saint Helena (including Ascension Island, Gough Island, and Tristan Da Cunha Island), and Turks and Caicos Islands], Uruguay, and Venezuela.
http://www.arrl.org/select-countries-e-h
United States FCC Ham Amateur Radio Reciprocal Operating Arrangements
https://www.fcc.gov/wireless/bureau-divisions/mobility-division/amateur-radio-service/reciprocal-operating-arrangements
How to Apply for an IARP (Canadian citizens only)
https://www.rac.ca/operating/international-amateur-radio-permits/
Citizens of Canada holding an amateur service license granted by the Government of Canada and citizens of countries holding an amateur service license granted by a country with which the United States has made reciprocal operating arrangements are authorized by 47 C.F.R. § 97.107 to be the control operator of an amateur station transmitting from a place where the Amateur Radio Service is regulated by the Federal Communications Commission (FCC)1.
FAQ Frequently Ask Questions
https://grenadaamateurradio.blogspot.com/p/faq-frequent-ask-question.html