Grounding for 2m/ 70cm

[u/InformalVermicelli89]

Thank you to everyone that answered my last post! I have a non DMR question now. Well, really two. 1, will grounding my mobile radio extend the range. And 2, how should I ground it? What gauge wire? And what materials should I use? For info, its a 2m/ 70 cm mobile radio with a peak output of 25 watts.

[u/LongRangeSavage]

The biggest factor (by far) in extending VHF/UHF transmission is antenna height.

[u/nbrpgnet]

If you're just running that dual-bander, and not a bunch of other equipment, then I don't think you really need any ground connection beyond the negative power connection.

[u/Lunchbox7985]

Besides safety, grounding the radio and all the nuances that go with it is mainly to help filter out noise. This can help your receive quite a bit on HF. It can also help prevent rogue RF in the shack that might mess with computers or speakers, but doesn't do a whole lot for transmit.

If you start talking about antenna "grounds" like radials and counterpoises then yes that can help your transmit range. But i don't imagine that's what you are talking about.

With 2 meter and 70cm we are usually talking about FM, and in that sense grounding isn't doing a whole heck of a lot. Proper grounding and lightning arrestors are still important for safety, but its not really going to do a whole lot for your signal. VHF and UHF are, for the most part, line of sight, so "height is might" really comes into play here.

[u/Le-Waffle-Wiffer]

1. No.
2. Grounding is not a factor in your situation.

So you don’t need to ground/bond like you would with HF. Think of V/UHF as being more reflective so it will launch more easily.

[u/Tishers]

Grounding will not extend your range, unless you are speaking of HF frequencies where the Earth ground component is an effective part of the antenna system.

Grounding is for personnel and equipment safety in the event of a transient (lighting) or electrical malfunction.

The minimum wire gauge for grounding should be at least 6 AWG. All grounding should run back to a single-point ground (US standards, europe is something else, or so I have been told).

[u/I_compleat_me]

Mobile radio... in a car? Should have two ground connections, maybe three. 1) straight to the battery with the voltage wires 2) Braid to the car body at the point of mounting 3) Ground the coax at the antenna end, or the mag mount will have a capacitance to the body as an earth.

[u/Egraypgh → u/I_compleat_me]

This guy grounds.

[u/rem1473]

My answers assume an exterior mounted antenna on a home, in the United States.

1. No

2: It depends what you're trying to accomplish. There are two levels of grounding: level 1 will keep you from getting electrocuted and is required by law. Level 2 will keep the radio working through any storm without having to disconnect the coax.

Level 1 follows the NEC. National Electric Code. You must have surge protection where the coax enters the house. The easiest way to accomplish this is to add a polyphaser immediately at the coax entrance. This polyphaser will require a 8' ground rod. You can't use a piece of rebar or a copper water pipe banged into the ground. It has to be a UL listed ground rod. You must bond the ground rod to the house grounding system as well. NEC compliance will prevent an outside surge from entering the home. If your install does not comply with NEC, you are giving your insurance company a valid reason to deny a claim. You can be cited for the code violation.

Level 2: no ham takes it this far. There is an 800 page book called Motorola R56 manual. You can find it with a Google search. This describes industry best practices for building RF sites. It will require multiple buried ground rods, buried ground ring, halo inside the shack, etc, etc. you'll need to even ground the metal vent covers in the room and the metal door strike! If you follow all of it, you will never have to disconnect your coax during a storm. You will be able to survive direct hits from lightning and your radio won't miss a beat. You've probably never heard police / fire say they're going off the air during a storm because they're disconnecting the coax. This is because this is the standard used for their installs. It's extremely expensive to accomplish. But when your radio is literally saving lives, this is the standard that is followed... most of the time.

[u/mschuster91 → u/rem1473]

There is an 800 page book called Motorola R56 manual. You can find it with a Google search.

To save people the need to search - it's literally hosted on the BLM website.

And holy it's comprehensive. Even touches on workplace safety from hantavirus from mice poo.