OUTY565,
We don't know where you are located, but since you mention "GMRS", I assume you're in the US?
I'd like to help you out / save you some money and effort.
And, the good news is it's doubtful you'll need any ham radio antennas / ham radios, at all!
(actually ham radio is opposite of what you need for your application....and what you do need is probably less expensive, too.)Your application here is best suited for MURS, CBRS (27mhz Class D Citizens Band / CB Radio), or GMRS, (and maybe even FRS, for short ranges), but the Amateur Radio Service (ham radio) is the least suited for your application!
https://www.fcc.gov/wireless/bureau-divisions/mobility-division/multi-use-radio-service-murshttps://www.fcc.gov/wireless/bureau-divisions/mobility-division/citizens-band-radio-service-cbrshttps://www.fcc.gov/wireless/bureau-divisions/mobility-division/general-mobile-radio-service-gmrshttps://www.fcc.gov/wireless/bureau-divisions/mobility-division/family-radio-service-frsFRS (for very short-range comms) and CBRS / 27mhz CB, are both designed for personal/family communications, without licensing (as well as MURS). This allows personal comms without need for public infrastructure, etc., nor needing any public concern, assistance, etc. This allows personal "selfish" comms, to coordinate, assist, and protect yourself, and family, without care for others.
GMRS and MURS can also do the same, although the range of GMRS may depend on repeaters (infrastructure) and/or decent antennas at all of your family's locations, and as GMRS freqs are shared and whether using repeaters or simplex, you may find others using "your pre-defined" freqs, that could interfere with your comms (of course this can happen with almost all radio comms).
MURS is VHF simplex only (no repeaters, no infrastructure), with radios limited to 2 watts, but no restrictions on antennas...so, depending on what comms range you need, MURS may be your best choice here! (and, fyi, MURS is very lightly used, so doubtful you'd have any interference / shared users, as might be the case with GMRS....oh, and MURS is also "license-free", like CB Radio....but unlike GMRS)
But, in general, MURS and GMRS, etc. does not require you to have any concern for others, nor provide any public service, etc.
Some MURS info:
Connecting a MURS radio to an external antenna can extend the range to ten miles or more. MURS stations are not allowed to be interconnected with the public switched telephone network. A station identification announcement is not required to be transmitted.
https://www.fcc.gov/wireless/bureau-divisions/mobility-division/multi-use-radio-service-murshttps://www.fcc.gov/wireless/bureau-divisions/mobility-division/citizens-band-radio-service-cbrshttps://www.fcc.gov/wireless/bureau-divisions/mobility-division/general-mobile-radio-service-gmrsThe Amateur Radio Service (ham radio) on the other hand, is specifically designed for selfless, public service communications, especially in emergencies (or as you wrote when the "SHTF")!
As well as being US Federal Law, it is also international law and codified by most western/developed (and many developing nations, as well) nations' governments. https://www.fcc.gov/wireless/bureau-divisions/mobility-division/amateur-radio-servicePlease read this here, it is the very first part of our US FCC rules, governing the Amateur Radio Service (ham radio):
FCC Part 97.1
97.1 Basis and purpose.
The rules and regulations in this part are designed to provide an amateur radio service having a fundamental purpose as expressed in the following principles:
(a) Recognition and enhancement of the value of the amateur service to the public as a voluntary noncommercial communication service, particularly with respect to providing emergency communications.
(b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.
(c) Encouragement and improvement of the amateur service through rules which provide for advancing skills in both the communication and technical phases of the art.
(d) Expansion of the existing reservoir within the amateur radio service of trained operators, technicians, and electronics experts.
(e) Continuation and extension of the amateur's unique ability to enhance international goodwill.
As you can see, ham radio is not what you want here.
What you want is probably CB Radio and/or MURS, and/or GMRS (sort of depends on where you're located, the comms ranges you require, and your average terrain...if we knew that, we could be more specific).
So, I hope this helps you out.
Wishing you good luck and fair winds.
73,
John, KA4WJA