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Unless the repeater owner states differently you only need to transmit the code to open his receiver.

Shielding the cable is worthless unless the shield is grounded. You have to have the shielded sockets and those must be connected to a ground. In LAN cabling systems the ground is through the cable to the patch panel and then through the rack which is connected to electrical ground.

Yeasu FT-4XR and FT-65 will also meet your need. The mod to allow out-of-band isa simple key code entry for either.

You set the TX-CTSS to transmit a tone, leave the RX-CTSS blank to receive any transmission. Setting a value in RX-CTSS means you only receive from radios transmitting that tone.

The glass in the building may also limit RF signals as some glass has filters to limit radiation.

Michael, it's you who is not understanding. The FCC has stated what emissions are allowed and if it isn't one of the listed emission types it is not allowed. You are reading the rule incorrectly by stating "It doesn't say it's not allowed" instead of seeing what is allowed.

You will need an SWR meter for the VHF/UHF bands (135 MHz - 470/512 MHZ) to set the antenna for optimal performance. The Surecom 102 is digital and used by many. It's less expensive than many ham meters and the analog pointer is usually more difficult to read when you are close to resonance. The table you posted shows typical values for a receiver. The 25 uV fgure is typically used and the 12 dB SINAD is a decent ratio of signal to noise. You want the adjacent channel and rejection numbers to be higher as in larger absolute values but those come with higher cost radios. And yes, the antenna along with height are the key pieces. As you start putting the pieces/parts of your system together you'll need to calculate your actual power being radiated. You will need to figure the amount of loss in the coax and subtract that from the gain of your antenna. You also need to convert the dB gain numbers from dBi to dBd by subtracting 2.15 from the antenna figures. Now you can subtract the cable loss from the antenna gain to get the correct number (or just read the power from the meter to see what is getting to the antenna). As to the need to adjust the SWR when changing devices, you probably will need to. You should at least check and be certain things have not changed significantly as the feed from the handheld and the mobile may have slightly different impedance values (50 ohms is something strived for but not always met). I would set the SWR using the Base/Mobile and let the HH run with it as it isn't as important.

The antenna gain will limit the frequency response across the full range of channels available as it will maintain a low SWR for 5 MHz on either side of the tuned frequency. As far as a unit to use for the base, I'd go with one that is rated at 50W on the UHF frequencies. Brand isn't as important as are the specs for receiver sensitivity, the higher the value of the number the better. -115 is better than -110 or lower absolute value. The bandwidth affects transmit primarily as SWR has little to no effect on receiving.

Building a repeater that will work reliably is an expensive proposition. Repeaters sell for between $1,000 and $1,500 for good, solid units. Adding an adequate power supply, coax, wiring and an antenna is several more $100s. Purchasing a couple mobile units with the needed accessories will also set you back a couple hundred but you will get a better feel for how the system meets your need. The key point to remember is that height means distance more than raw power. Having a higher antenna with 15 watts of power often means better range than 50W at ground level.

Also try changing channels. BTECH is good with tech support so drop an email to them and see what they say.

Repeater owner uses odd codes/settings for the repeater and you pay a subscription fee for access.

Michael, receiver antennas don't need tuning as they are all band from one quarter inch stubs to mile long wires. Yes, the length matters in that a longer wire is more sensitive; but length doesn't affect the frequency range. You can prove this to yourself by using a simple piece of coat hanger or any wire connected to your radio and listening to the various stations on different bands.

If the radio is GMRS transmit only I wouldn't buy a dual band antenna but one for GMRS. You can receive on almost anything as an antenna.

To make a complicated subject a little clearer, the intelligence in an FM signal (GMRS is FM) is carried by the shifting of the frequency within its channel. Wide band signals can shift a total of 5 kHz while narrow band signals can shift only half that amount. The result is two-fold, the signal sounds softer and additional channels or paths for transmission can be created between the wide band channels.

The application requires certain personal information and the person submitting the application certifies they are the applicant so no; you can't buy a license for another person. That does not mean they couldn't make the application and then you use your credit card to pay for it. It's the statement where the applicant certifies all the statements are true. Falsification is a federal offense.

Could also be something as complicated as the volume knob....

440 MHz refers to the ham 70cm band which is below the GMRS frequencies. A J-Pole cut for the 440 band would need to be shortened by a small amount to put it into the middle of the GMRS band.

Why not ask your Ham club if they want to install it?

Truly the best solution is a rig built as a repeater rather than a home-brew setup. The key piece is the duty cycle of the repeater transmitter. It has to be active for both people and that means it is transmitting throughout the entire conversation. Your typical base station is designed around a 20% duty cycle which means you spend 80% of the time listening and less than 205 of the time talking. A 5 minute conversation is only a couple minutes for each radio but double that for the repeater.

You can use this to calculate the RF exposure. It's now required by the FCC. RF Exposure Calculator (arrl.org)

Narrowbanding was mandated for the VHF frequencies below 174 MHz.

PL-259 will mate with the female SO-239. This is the same connector pair used on mobile radios.

Welcome Tim. GMRS/FRS is a viable solution for your situation. A small mobile unit set up as a base station at your home with an attic antenna would guarantee communications between the two houses. A 20 to 25W mobile is all that's needed (actually 5 watts on an attic antenna would probably work). Midland makes a 15W unit that would be perfect. Look on Amazon for a small 12V DC power supply with at least 15A of output and you're golden for the base. A J-Pole antenna is what I'd use, there are several different ones available. Here's one made from copper pipe rather from twin-lead plastic cable: 462 MHz Land Mobile (GMRS) J-Pole Antenna - KB9VBR Antennas (jpole-antenna.com)

I believe it's called the ping-pong effect when one repeater starts keying another and they bounce back and forth. Other than different codes or powering down there isn't a way to stop it. Cell companies had the problem when private repeater nodes started appearing. Thet could shut the feed down to an antenna and then send the FCC to cite the repeater operator for an illegal transmitter.

Comet, Diamond, Nagoya are just a few that make replacement/upgrade antennas.