Mobile hf radio grounding

Grounding and Receiver Noise

Forums New posts Search forums. Media New media Search media. Classifieds New listings. Log in. Search titles only. Search Advanced search…. New posts. Search forums. For a better experience, please enable JavaScript in your browser before proceeding. Mobile antenna grounding. Status Not open for further replies. I've always heard that "grounding is grounding" except when it comes to lightning but is that always the case when it comes to a normal ham radio antenna setup? I'm wanting to ground my vehicle ham radio antenna to improve 6 meter transmission and transmission. The antenna mounted on a luggage rack crossbar that is painted. Neither the mount nor the antenna is grounded because of that coating on the crossbar. Would it be better to run a ground wire from the antenna mount to a ground point, probably following the same path as the coax, or, would it be permissible to ground the PL connector where it plugs into the radio using a more convenient ground point from inside the vehicle? The radio is mounted under the passenger seat with the control head attached to the side of the side of the console. I have this antenna mounted on a trunk lip mount. It requires a good ground plane to work correctly. That needs to be at the feed point not at the radio. I would suggest looking at a different type of mount. It's pretty long for a luggage rack mount anyway. Do not confuse DC grounding which is best done at the radio with RF grounding which needs to be done at the feed point. You want the car body to be the ground plane. To make this work well sometimes it's necessary to place copper braid between the trunk lid and the car body. You may have to experiment. I've used mine on the low end of the band for sideband, but it's not too efficient for DX. The sound plane is most critical for 6 meters, but also necessary for 2 meters and 70 cm. I understand the necessity for grounding 6 meters. That's why I'm wanting to ground the antenna. I have an SUV so obviously, the trunk mount is out.

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If you do the grounding before you install the antenna it will make the antenna installation go a lot smoother. On vehicles that are more composite than steel, bonding hinges on doors and hatches to the frame will also help. Bonding is one of the most important aspects of mobile radio. There are several reasons for this. First is noise abatement. Bonding minimizes the leakage of RFI into and out of the various bolted on parts of the vehicle. It is not uncommon to see a 20 to 30 dB drop in noise levels once they're properly grounded. Bonding engines, hoods, and in some cases radiators, is important for the same reason. The best mobile antenna money can buy, isn't any better than the ground plane it is mounted over. Maximizing the available ground plane is what bonding is all about. On the HF bands, our vehicles act more like a capacitance to ground, rather than a ground plane. The bonding of doors and trunk lids has a lesser effect on noise, but does aid in maximizing the ground plane. If ground losses are high, it doesn't make much difference how good the antenna is, because ground losses will be the largest factor in determining efficiency. If ground losses are low, the difference in efficiency between a cheap antenna and a good one become very apparent. One of the most misunderstood concepts is the difference between DC and RF ground neither one is a ground plane. A ground strap may work perfectly as a DC ground, but at some frequency that same ground strap will make a perfect antenna! We all know that an inductor can provide a good DC ground, but look like an open circuit to RF. A capacitor can provide a good RF path to ground, but not a DC path. Ground strap, like any piece of wire, has both inductive and capacitive reactance. These reactances change as the frequency changes. For any given value of reactance, as the frequency goes up, inductive reactance also goes up, but capacitive reactance goes down. When inductive reactance and capacitive reactance in any given piece of wire are equal, that wire will become an antenna, and ceases to be an RF ground. One is to use flat braided wire. RF flows at the surface rather than through the wire, and flat braid has more surface area for any given current carrying capacity. It has more capacitive reactance which increases the self resonant point. Flat braid is also much more flexible and less likely to fail due to repeated flexing. For longer lengths, one inch wide braid is a better choice. But keep the length as short as possible. Remember, the ground strap must present a low impedance connection to effectively shunt RF to ground. Good connections are also important to provide both a DC and RF ground path. Crimping and soldering are mandatory. Crimping provides a good mechanical connection, and soldering a good electrical one. Good quality lugs and connectors are a must too, as the cheap ones do not solder well. There are few things to be aware of before you start drilling and attaching ground straps. Vehicles have dozens of wire looms placed throughout the superstructure. This includes the A, B, and C pillars, under both doorsills, inside the doors, under the carpet, and behind almost every piece of trim.

grounding a mobile radio


Knowing how to ground an antenna properly can make significant improvements to its performance, whereas a poor ground or earth connection can mean that its performance is greatly impaired. Grounding an antenna properly makes the antenna safe to use and also enables the best to be made of the performance of the antenna. There are several aspects to grounding an antenna. When looking at how to ground an antenna it is necessary to look at what is required and then proceed accordingly:. Whatever the reason for needing to ground an antenna, there are many instances where this is required. When grounding an antenna it is necessary t undertake it knowing how to ground the antenna properly. How to ground antenna There are several aspects to grounding an antenna. Balanced antennas like dipoles do not need an RF ground for their correct operation as long as common-mode currents are kept off the feeder. However many vertical antennas and many end fed wires use their RF earth connection as an integral part of the antenna. For system like these it is imperative that a good ground connection is made. As conductivity of the ground is relatively low, a good surface area must be presented by the conductor to the ground. The volume in which conduction can take place is huge, and therefore once a good connection has been made to the ground, the actual resistance can be low even though the resistivity of the ground material is high. Read more about the antenna RF ground. This is a simulated ground made from a sheet of conductor which typically extends out to a quarter wavelength from the antenna. Often the conductor is simulated by a number of radials, often a quarter wavelength long. Read more about the antenna ground plane. It could be as a result of being connected to equipment that becomes defecting and puts a live voltage onto the antenna. It could be as a result of the accidental of live power lines. These have all happened in the past and could be a danger. There are many dramatic photographs of lightning striking tall buildings or even just striking the ground. The lightning strike can have a very destructive effect. With typical current levels rising to anywhere between about 3 and amps, it is hardly surprising that anywhere that receives a direct strike is damaged. Even if a direct strike is not experienced, induces voltages can be very high.

Mobile antenna grounding


QRZ Forums. Nothing in the manual says anything about how to ground the radio. I read all over the place that I should ground the radio yet the manufactorer says nothing about how. So how does one ground a mobile radio? If you have connected the black lead to the negative side of the battery and the antenna feed line coax is connected tot he antenna and the antenna is connected to the body of the car, this is usually the only grounds you are going to get. HF rigs have a ground lug. You can take a wire from this ground lug and connect it to the chassis of the car. Sometimes this helps limit or reduce noise. K8YSAug 9, VHF Okay. What about the mobile VHF radio in the house as a base station? My antenna is in the attic and thus not grounded. If your power supply has a lug for ground, ground the power supply via that lug. Word of advice on the mobile. Either run both wires from the battery and fuse them both at the battery, or use the shortest ground lead you possibly can. This is to prevent your radio from becoming the whole car's ground if the body ground wire should come loose under the hood. This is known to happen and is not good, therefore most factory power leads have a fuse on each polarity. I chose to ground my radios with about 10 inches of the ground wire to a body bolt on the passenger seat base. This helps eliminate the resistance of two long skinny wires all the way to the battery. And grounded this way, if the body ground is lost, the radio among other things will act up, but won't become the ground path for the whole car. Low-voltage DC-powered equipment like yours can be totally ground isolated in all ways and function perfectly. There will always be an ESD ground provided by the negative lead that connects to the power supply and its impedance is very low for that application. And for an indoor antenna, a lightning ground isn't a good idea, since it would route lightning energy inside the home, which isn't where you want to conduct it.

Mobile antenna grounding

There is a serious flaw with the suggestion mobile radios be wired across battery terminals. The negative radio lead should actually not have a fuse, and not be wired to the battery post. Early vehicles had both positive and negative grounds. USA passenger vehicles evolved, standardizing on "12 volt" negative ground systems. The resting voltage was around Many large commercial vehicles, however, retained positive grounds. Non-standardization of systems meant two-way radios and other add on equipment was generally designed to operate with either negative or positive grounds. This was accomplished by floating the internal negative supply buss, while grounding all normally accessible external user ports to the case or cabinet. These early systems started the trend of negative fuses, with both power leads directly attached to the battery. This was not harmful, because the equipment had a completely isolated internal "ground " that was electrically isolated from all other leads leaving the device. Once any other lead common with the negative bus leaves the case, it is no longer safe to conned the negative to the battery post. It is also not safe to fuse the negative lead. In most early CB and commercial two-way radios, the negative buss inside the unit fully floated from the cabinet and any external ports. This included commercial two-way radios like the Motorola Motrac, Micor, and other expensive, high-quality, radios. The floating negative was universal across brands including, but not limited to, GE and RCA land mobile equipment. The floating negative allowed use of radios in either negative or positive ground vehicles. It also solved ground loop issues, allowing direct connection to battery posts without fire or equipment damage hazards. Equipment manufacturers had no way of knowing if the final installation would be in a negative ground vehicle or a positive ground vehicle. As a result, systems with a floating negative buss were shipped with both negative and positive power line fuses. The floating negative buss system inside the radio allowed safe direct connection to the battery posts, and safe shutdown if either the positive or negative fuse opened. The floating negative power buss made it impossible for starter or charging currents to flow through antenna cables, microphone, or speaker leads. All exiting connections, as well as the case, were electrically isolated from the negative lead. Over time, vehicles with positive grounds disappeared. As this happened, manufacturers stopped using the more-expensive and more-complicated floating negative power bus system. Many vehicle manufacturers, and most aftermarket equipment manufacturers, never re-thought the systems others were using. Manufacturers carried over the acceptable negative fuse idea appearing in ground independent power buss systems, which could also use a negative battery post connection. Manufacturers misapplied the allowable fused negative battery post connection to equipment with internally grounded negative bus systems. Not realizing the safety hazard, they continued to fuse both negative and positive radio power leads and often advised direct battery post negative connections.

Mobile HF Grounding Basics



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