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Beginning thread on Radio Installations

2952 Views 41 Replies 9 Participants Last post by  JDBPFLYER
Recently there have been a lot of questions regarding intercom and radio installations. This thread is a start point for some information and tips about the nuts and bolts of getting a good installation for both your intercom and your radio, whichever brand it might be. I will cover things like proper wiring in detail, including noise filters and the how the proper antenna cable makes all the difference and why. I will also cover proper grounding, fuse loads, the actual amount of power your favorite radio uses when transmitting, etc. A few comments about coax connectors, antenna tuning, frequency ranges (especially GMRS), repeater usage, some basic radio programming, etc.

I will do these in separate posts as there is lots of information to cover. I encourage anyone with questions to post them and I will do my best to try to answer them either within the appropriate post topic or specifically within the post.

I am not an expert and I don’t have an electronics degree or anything like that, however I do have years of experience with VHF and UHF specific communications and some formal training from Motorola. I’m an amateur radio licensed operator and GMRS licensed as well (which isn’t saying much) LOL.
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This post will deal primarily with the 12 volt component of your installation. This covers the intercom and the radio. First and foremost, any electrical wiring connection must be soldered and shrink-wrapped for continuity and protection from corrosion. If you are unfamiliar, there are YouTube videos to help you.

Second, wire gauge selection is critical ! That said, here are considerations:

For the intercom, the wires supplied by the manufacturer will do the job just fine (usually 18 gauge wire). They draw very low amperage overall so even a long run of wire (like for a MAX) that gauge will work. That connection must have a fuse somewhere in the circuit on the 12V positive side. Most are 2 amp.

For the radio there are multiple considerations. First is how ,any amps does your unit draw on high power settings? Many do not take this into consideration. Here is an example: A BTECH UV-25x2 radio that has 25 watts of outpouring power draws about 7-8 amps when transmitting on full power. By comparison, a 50 watt Kenwood or similar radio will draw 11-15 amps. Typically the Chinese radios will draw just a slight bit more. So what does this mean? It means you will need to select your wire gauge not only by the amount of amps that wire can draw but how LONG your run of wire will be. There are tons of charts available online to give you guidance on this. It’s not uncommon for longer runs of wire to be 14 or even 12 gauge so that the draw will remain constant. If you undercut the wire gauge, you cause excessive heat (think melting) and the transceiver longevity and power output will be drastically affected. Of course, the radio will need it’s own properly rated fuse on the positive side.

Now for the connection part. Like I stated earlier, all connections should be soldered and shrink wrapped. They MUST go directly to the battery ! I cannot stress this enough. They proper typical connection will be to wire your filter (yes, a filter is required) the best being a Kenwood KLF-2, available on eBay, etc. directly to the battery posts. The single red wire coming out of the filter supplies clean power to your electronics. Both the radio and intercom may be wired to the same red wire. A separate battery ground wire will need to be installed to complete the power and ground to each component. They must be 2 separate wires, do not link the negatives together. It really makes little difference where you run your wiring as through the tunnel is the most common. I suggest protecting them with some split loom to minimize the chance of a short due to rubbing. All of the wires can be run in the same loom. Some may prefer to run a switch of some kind to power off the electronics when not in use. This gets tricky as many of the illuminated switches (especially the incandescent type can introduce “noise” into the system. I prefer to turn them off manually at the component. The key to wiring in the switch is to only use it to cut off the 12 volt positive side, not interrupt the ground as well. In my experience this can be a cause for “ground loop” radio frequency interference (RFI) which is difficult to find and even harder to correct.

In most instances, the chassis on the intercom and the chassis on the radio will need a separate ground, also to dissipate induced RFI. They must be separate as well, no daisy chaining here. This is best terminated at the main chassis ground located on the chassis behind the left seat (or left rear seat on the MAX). It is a single bolt that’s pretty easy to get to and an excellent grounding point.

A note about filters, I’ve tried most of the available offerings out there and the Kenwood is all I use since I’ve spent far too much time chasing whine on the intercom only to find the cheap filters don’t do the job.

The model years that have the 850 Watt stator are the most problematic. Failure to wire they way I suggest will almost certainly result in an intercom whine that changes with RPM and is so annoying you will want to turn it off. Under no circumstances should you be tempted to use the connections in the tunnel. Battery direct only. As to filter placement, the closer to the components the better but I have had good results bolting it to the firewall on the flat section on the left side of the battery bay. The seat will still go all the way back without hitting the filter.

Now that you have power, ground, and chassis ground you can run the intercom cables. These are shielded so running them through the tunnel is fine but run them on the driver’s side of the tunnel away from the electrical wiring whenever possible. Use some split loom to keep them from chafing because as soon as the outer casing gets mangled they lose their shielding. Be careful when using zip ties to not crush those cables ! Just enough to hold the cable in place is all you need. No matter where you decide to mount your radio and intercom, the cabling and wiring need to run through smooth holes for the entire run to keep any damage from happening while bouncing down your favorite trails. There’s pretty much no such thing as too much split loom on these cables or wires.

Now that you have all of that done we will dive into radio antenna selection, coax information, and tuning in the next post coming soon.

I invite any and all questions. Happy wiring !
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Delete if you don’t think these are of value in your thread.


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Might want to clarify that fuses are best served mounted as close to the battery as possible. If the fuse is installed anywhere further, then there is NO PROTECTION should that section of wire get shorted (fire). Chance of wires getting chaffed or shorted are VERY HIGH in a off-road vehicle due to the vibrations/forces.

Also far as the grounding is concerned its important that you ground it all at the same point (anything in the radio/comms/stereo) . This will reduce or remove "ground loops" in your system. don't ground 1 unit here and another there... Run a separate wire for each all grounded at the same point. I know you touched on this, but thought it would be helpful.
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Having a good laundry list put together with some different set-ups would be nice.
EastMT that is great information. I will reference that when we get to the post dealing with diagnosing problems. I would like to keep the information (especially on chokes, ferrites, etc) frequency specific which your link does very well. 2020RR clarified what I said about grounding, chassis grounds should be grounded at the same location whenever possible. This is why I like the main ground I mentioned in my post.
Hollywood can you be more specific with your request? I’m old and slow. LOL
Hollywood can you be more specific with your request? I’m old and slow. LOL
Ummmmmmmmmmmm, I didn’t request anything?😆
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My apologies I meant HPnMORE4J.
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My apologies I meant HPnMORE4J.
You better apologize! Mixing him up with me? Oh the humanity 😂😂😂
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😂🤣😂🤣😂🤣
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Great information.


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Todays post will deal with antennas. Antenna selection, mounting, and coax cable selection is crucial to the quality of your communications as heard by your fellow riders and critical to the longevity of your expensive (or not) radio choice. This post will cover single and dual band antennas since many off-road clubs and the like are transitioning away from the typical “race” frequencies. On that note, if you’re thinking about installing a radio in your car, consider a capable dual band radio that covers all of the VHF (136-174mhz) frequencies as well as the UHF frequencies (400-480mhz).

Back to antennas. Typical antennas come in a variety of flavors, 1/4 wave, 1/2 wave, 5/8 wave, etc. For mobile use to avoid having to worry about overhead damage, we will stick to the 1/4 and 1/2 wave types most typically seen on our cars. A quarter wave antenna is always the shortest in length, or basically a quarter of the wavelength they service. Half wave are longer, typically twice as long. For instance, a quarter wave UHF antenna is about 9 inches while a VHF is about 19. I will refrain from getting into antenna theory here as it gets rather technical and confusing and is of little value to this discussion.
A half wave antenna on UHF is about 19 inches while on VHF it is about 36.

Quarter wave antennas absolutely require a “ground plane”, so what exactly is a ground plane? Simply it is a metal surface that, at the minimum, covers the same distance as the antenna is in height. So, if you have a quarter wave antenna that is 19 inches, the ideal ground plane is a metal roof that has 19 inches of metal as measured from the base of the antenna in all directions. In essence, this ground plane is what gives the antenna its range with low SWR (which we will get into later). A typical OEM BRP metal roof with the antenna placed in the center will more than suffice. The performance you should see is more than adequate for anything you might need, including using repeaters (which we will cover briefly later as well). The problem we run into is most run a plastic roof which will not work. How can we get around this? Well, you really can’t BUT you can minimize signal loss by mounting the antenna into a metal mount and then grounding that mount properly (Rugged has a great video on how to do this) to your chassis. This will give marginal performance with slightly higher SWR but it can be done. I do not recommend this but if you have no other choice, go with it. As always, it will require some tuning (covered later). There are many antennas available from multiple reputable manufacturers. Be sure to choose one with a good spring base to prevent breakage. These are available as dual band and are the best choice for overall performance and cost factor. A good quality antenna from a reputable manufacturer can run around $100-$180 with some more budget friendly offerings around $80-$100. Remember these are dual band and will typically be “center loaded” meaning they have an enclosed coil in the center of the antenna whip.

Half wave antennas work best as a single band (VHF or UHF only), which is why many advertise them as “no ground plane required” antennas. While this is somewhat true, it really is a misnomer because every antenna needs a ground to work at its optimum efficiency. Can you get away with a half wave on a plastic roof? Yes, but just be aware the SWR will be higher and the actual efficiency will be less, meaning less range compared to a properly grounded (think metal roof again) one. They are typically “base loaded” meaning they have an enclosed coil in the base of the antenna. They are longer and will hit trees the quarter wave misses. There are half wave dual band antennas available but they come at a higher cost with the risk of destroying an expensive antenna on overhanging brush. Rugged, PCI, etc all sell the half wave antenna on their respective sites at a reasonable price. Just remember they will not work on UHF despite what their inflated claims say. SWR runs over 2:1 when trying to get it to tune on UHF and even then, they are almost worthless for GMRS frequencies. Don’t do it !
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Antenna mounting is as important as the antenna itself. The easiest and most typical installation is with a “NMO” mount. These typically come with a length of coax so when choosing one, be mindful of the length that comes with it, as well as the connector to be sure it matches with your radio. They are easy to install, whether you drill a hole in your roof, or use some kind of clamp style from Axia Alloys or others. Avoid anything that comes from China here whenever possible. The top threaded mount needs to be brass and not an alloy so choose something made in the US from a reputable dealer like ARC antenna, the antenna farm, etc. As stated above, the best possible mounting is in the center of a metal roof. When that is not an option, a clamp on style mounted in the center of the car as high as possible will give the best results. The rear crossbar on the top of the cage is a great place to put it. If you place it lower and block part of the antenna mast, your SWR and transmit range will suffer greatly. The mount needs to be grounded to the chassis in all cases to at least help with ground plane issues.

Now, on to coax cable. Not all cable is created equal !!! Most will use a standard like RG-58 A/U or RG-58/U. Why? It’s cheap and readily available BUT it has a lot of loss as it travels down the cable. Loss is directly proportional to the amount of power that can be transmitted from the antenna based on your radio. So, let’s talk about that. If you have a 50 watt radio (assuming the antenna is perfectly tuned) and have a length of cheap cable, you may only be able to get 30 watts out of it. Yes ! Imagine spending big bucks on a top of the line radio and having poor performance simply because you cheaped out on the cable. Not good. So, what should we use? For VHF and UHF frequencies the LMR-400 is the gold standard but expensive. We can go a bunch cheaper by using LMR-195. It’s easily sourced and ranges around 70-90 cents a foot while the LMR-400 is easily 3 times that much. The LMR-195 cable has a solid conductor (GREAT) but the foam that surrounds that and the shielding is the real magic here. Want to make sure your digital dash doesn’t freeze up? Use LMR-400. Have an analog dash? Use LMR-195. These cables are very low loss so your power from the radio is not lost before it gets to the antenna. Some loss is to be expected, but nowhere near the level of the RG-58 series cables. Also, as always, made in the US is what you buy. Stay away from anything else as their standards are “looser”. Brands like BELDEN come to mind and are excellent.

Ok, now you’re thinking, can I get an NMO mount with LMR-195 or LMR-400 cable attached already? NO, not that I have found commercially, however, you can get a NMO mount that doesn’t have the cable on it and solder it up yourself. There are several YouTube videos out there that will show how to do this easily. Now that you have the mount attached to the cable, now what? Now you get the bare connector appropriate for your radio, something like a PL-239 or BNC. A google search will show what they look like. They are easy to solder up on the end and work well. A work of caution on the connectors though, the e-bay and Amazon connectors are junk! Go for something made in the USA again, and always. Remember, connectors are sized for the cable so a connector for LMR-400 will not work on LMR-195 as the diameters of the cables are not the same. HOWEVER, connectors for RG-58 WILL work on LMR-195. By the way, the LMR stands for “Land Mobile Radio” in case you were wondering.

When running the coax from your antenna to the radio, be very careful when attaching it to a hard point on the car. If you zip tie it to the point it starts to crush to casing you may ruin the cable. I use split loom on the cable to prevent this. Snug on the zip tie is fine !! Be careful where you run it so as not to cause any pinch points and give yourself plenty of cable for corners. This stuff is not as flexible and most will tell you it requires a minimum of 5 inches for a 90 degree bend. Route it away from anything it could get caught on, especially the steering shaft or the adjustment area. Route it away from the DPS unit especially and NEVER coil up the excess!! Either cut it to the length you need or use large “S” shaped patterns to take up the excess but don’t zip tie it together, leave it loose. Do not run it through the tunnel, instead run it down the driver or passenger side along the chassis below the seat away from the seat rails.

OK, this is a lot of information for today. I invite questions and comments. I’ll do my best to answer whatever I can. In the next post we will talk about antenna tuning as it relates to SWR and why that’s important.
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Good information! I read it twice, and didn’t see it, or perhaps you worded it differently, but you can get antennas “tuned” to a specific channel, for greater reception. I know PCI tunes their Kenwoods with their antennas to Weatherman (Baja channel).
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Hollywood, this is true and I did not cover it for a reason. While tuning to a specific channel (or frequency) has it’s place, tuning for a RANGE of frequencies makes more sense for those who may use different channels in different areas or with different groups. Let’s see how this matters. If you look at all of the race frequencies we have, you can use some simple math and figure out what the “center” frequency is. Take the largest MHz and add the smallest MHz and divide by 2. I have done this and the “rescue” frequency is about as close to center without programming a custom frequency. In this case it is 155.100. If you tune the antenna to this frequency with the lowest possible SWR, then moving up or down in frequencies produces very little change in SWR throughout the range. If you tune the antenna to a specific frequency and it’s either on the low or high end of the range, the SWR will change much more as you move away from the tuned frequency. If all you ever use is one channel, by all means tune for that.

Incidentally, when tuning at 155.100, the dual band antennas will tune nicely between 462 and 467 (GMRS) frequencies as well as the antenna acts as a half wave in that spectrum. I hope this helped.
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Great information! Very informative!

When talking about the ground plane for the antenna, does the flatness of the roof have an effect on tuning/efficiency? Is flatter better? are the RC style roofs going to an issue?
Hollywood, this is true and I did not cover it for a reason. While tuning to a specific channel (or frequency) has it’s place, tuning for a RANGE of frequencies makes more sense for those who may use different channels in different areas or with different groups. Let’s see how this matters. If you look at all of the race frequencies we have, you can use some simple math and figure out what the “center” frequency is. Take the largest MHz and add the smallest MHz and divide by 2. I have done this and the “rescue” frequency is about as close to center without programming a custom frequency. In this case it is 155.100. If you tune the antenna to this frequency with the lowest possible SWR, then moving up or down in frequencies produces very little change in SWR throughout the range. If you tune the antenna to a specific frequency and it’s either on the low or high end of the range, the SWR will change much more as you move away from the tuned frequency. If all you ever use is one channel, by all means tune for that.

Incidentally, when tuning at 155.100, the dual band antennas will tune nicely between 462 and 467 (GMRS) frequencies as well as the antenna acts as a half wave in that spectrum. I hope this helped.
Copy that!
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