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And that's where the NEC and Ampacity tables have their largest differences. In radio work, at least with the radios we are dealing with on this site, wire lengths don't come into play so there is no regard to the internal resistance of the conductor and any losses that result from length. I believe the NEC formulas are set to keep the insulation temperature below 60C where the ampacity tables allow temps up to 130C. The most common PVC coating will withstand a temp of 160C while silicon will allow a temp of 600F which can light paper. Additionally, we are normally dealing with amp draws of 16 - 18A max as the radios are limited to 50W. 100W amateur radios will draw 28A which can be run on 14Ga wire, but I build all my harnesses with 12Ga silicon.

I'm not that good with the math. I cheated and got the information on the Internet from several different sources.

I wouldn't worry about the wire on the plug. 12 ga wire will handle 30A with no issues. In fact, 14 ga silicon insulated wire will handle 30A but PVC or rubber insulated wire can get over 200 degrees Fahrenheit when carrying that much current.

GMRS/FRS isn't as popular or widely used as CB. As the service is still growing, there are a lot of "holes" in the service area. Unlike CB, GMRS won't work for long distances as the frequency dictates line-of-sight communications. Unlike CB, you can use repeaters in GMRS, but each repeater is privately owned, and the owner of the equipment has control over who is allowed to use it. As to equipment, for mobile use anything over 25W is unnecessary as higher power doesn't equate to longer distances because of the line-of-sight characteristics. The biggest improvement for any installation is centered around the antenna. The location and height are the two biggest elements. Installing something as short as a 1/4 wave whip (about 6") on the roof of your vehicle will give you all the range possible with a 25W or higher watt radio.

I believe Maryland has a law against using a police scanner in a motor vehicle. The law is on the books to protect motorists from pirate tow truck drivers and companies responding to assistance calls by the police. The motorist also has to affirm to the police officer they accept the uninvited tow operator over the police contracted service,

It's the default value.

He would have to have been violating a regulation that a state or other federal agency had on their books for them to take action. Forestry can't enforce FAA regulations unless they have a similar regulation within their rules. Without specific regulations against causing interference or impeding radio communications they have to defer to the FCC as the agency with the jurisdiction to take action.

That will always be an issue with crowd sourced information. As ham and GMRS repeaters aren't licensed and funded there is no guarantee they will be live from one day to the next.

Yup, making the plug is fully seated is the only fix. A lot of times it's the boot around the plug that's the problem.

The EFJ's were a popular alternative to the Moto's for many public safety agencies using P25 phase 1

At GMRS frequencies almost any power supply will work with no interference coming from the switching circuit in any FCC registered supply. Mean Well, available on Amazon has some good ones under $40.

Change Tone Mode to TONE. If the repeater is on the air and you can reach it you should hear the squelch tail from pressing and releasing the PTT on your radio. If you don't hear the squelch tail just monitor for any traffic and then ask for a radio check.

If you buy a radio made for GMRS it will have only FRS/GMRS frequencies programmed from the factory.

You can pick up a decent miniature VNA (Vector Network Analyzer) for less than $100 that will tell you many things about your installation. VNAs can measure the SWR, tell you what the resonant frequency of your antenna is and show you what must be done to get the antenna at its lowest losses at the frequencies you use.

Coverage area from a radio varies little when you use 15W or more up to the 50W maximum allowed. The biggest gains aren't in how much power is fed to the antenna, but how well the antenna performs. The two key things in your antenna choice are location and loss. Because the radiated signal from the antenna travels in a virtual straight line, the higher on the vehicle the antenna is mounted, the better the range. The second is signal loss due to both the antenna and the coax cable feeding the antenna. Your antenna has a resonant frequency where it works the best. Going above or below that frequency introduces loss as the antenna isn't as efficient. The coax used to feed the antenna is also a source of loss. No coax is highly efficient at GMRS frequencies but different cables perform better than others. The piece of equipment needed to measure loss most use is an SWR/Power meter. SWR or Standing Wave Ratio is the amount of power reflected back to the transmitter from the antenna and this increases the further you go from the resonant frequency. This loss is added to the loss from the coax meaning a decrease in the amount of power put into the radiated signal. Loss is measured on a logarithmic scale stated in dB or decibels. In practice, you want the SWR to be as low as possible at the frequencies you use, usually less than 1.5:1. SWR measurements of up to 2:1 is considered acceptable but the lower the better. There are numerous calculators on the Internet that will show you the loss from both SWR and coax.

No. America refers to a single country while the word when combined with North or South refers to a continent.

You need to be a little more explicit about which settings you want to know about. We can guess you are talking about tone settings, and if that's the case then the simple explanation is tones act as filters. If you have a tone set, then everything not sent with a matching tone is rejected. Some radios can use two tones, one transmit and another receive. This is called Split Tones. Split tones do not have to be the same but your radio has to specifically support using tones in this manner. In programming tones you are often given a choice as to the manner in which the tone is used. A setting of TONE means you will transmit the tone when you press the PTT key. TQSL means the same tone is needed for both transmit and receive. Not using a tone sets the radio to CARRIER SQUELCH which means it will activate on any signal received and not send one with the PTT.

Depending on how deep you want to dive you have a choice of attending a college to study Electrical Engineering with an emphasis on wireless communications or perhaps picking up a couple ARRL manuals. ARRL Handbook 2022 (Softcover) The ARRL Handbook for Radio Communications is your complete guide to radio experimentation, discovery, and innovation. It is the Handbook, written by radio amateurs for everyone with a desire to advance the pursuit of wireless technology. ARRL Antenna Book 24th Edition The ARRL Antenna Book for Radio Communications is a single resource covering antenna theory, design and construction, and practical treatments and projects. This book contains everything you need to understand how radio signals propagate, how antennas work, and how to construct your own antenna system.

By this line of reasoning you rely on life because your diaphragm moves.

OOC, where was his truck in relation to you? If he was in front of you then the body of the truck would affect the transmission range because of the antenna placement.

The experimental license expired last year (Aug 2021).

The top green banner on the login page shows where you select GMRS.

Phone, CW or digital? I've only had success with digital (FT8).

If the radio has been sitting unused for several years, it may be some of the wet (electrolytic) capacitors have dried out. It may be cheaper to buy a new radio than to send that one in for checkout and repair if needed.

Unless the receive tone of 74.4 is specifically listed for the repeater change the tone mode from TQSL to TONE. That will transmit a tone only but not require a tone for receive.