Antenna and coaxial cable

[Chessy68]

Question 1- I've been researching about GMRS antennas for in and around city's, homes and trees saying i should get a low gain antenna for this type of area. I live between Houston and Galveston, would a low gain or hi gain antenna be better for this environment. 2nd question is how much coaxial cable is to much if it even matter's when installing a home antenna, I have a 25 foot collapsible flag in my yard that's 25 yards away from the house and is that too much coaxial cable for a home radio GMRS or ham. Just starting out on amateur Radio and researching it.

[kidphc]

Real quick. Loss in coax at uhf and above is a real issue and can be a big loss. Cheap cable and the wrong spec cable, are usually the culprit. Don't get cheap with connector they will only add more losses.

For flat areas, high gain antennas as reasonably high as you can get it. I always recommend collapsible flag poles.

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[WRVR303]

 How much loss you have in your cable is very dependent on what type of cable you use. There are many online cable loss calculators out there. One is https://kv5r.com/ham-radio/coax-loss-calculator/

Personally, after looking at several manufacturer's antenna radiation patterns, I concluded that about 7 dBi of gain was ideal,  because it put most of the energy out concentrated in about a 40* pattern, or 20* going up above horizontal, and 20* below. I live in a hollow, and the ridgeline is 10* above horizontal, so there's a good bit of power getting out over the hill. A 9dBi or greater antenna would put most of the energy into the hill, while 3-5 dBi would hit the ground below the antenna and the birds above, but might not reach the local repeaters.

[WRYZ926]

Remember that most coax loss calculators, including the kv5r calculator, use dBd  in their calculations when figuring loss. Most antenna manufacturers advertise in dBi. To get dBd , you subtract 2.14 from the dBi value.

So an antenna listed as 6 dBi will actually have a gain of 3.86 dBd. A 9 dBi antenna will have 6.86 dBd of gain. It does make a difference on which value you use.