When on a road trip, I usually monitor the 2m FM calling frequency, 146.52 MHz. For the most part, that frequency is pretty quiet but sometimes a fellow traveler, camper, SOTA activator or random ham shows up on frequency. I don’t usually bother with tuning into local repeaters as that requires frequent adjustment of the radio while cruising down the highway.

Our RV has an Icom IC-2730A transceiver that covers the 2m and 70 cm bands. This radio has two receivers, so one receiver is set to 146.52 and other one is set to “something else.”  Sometimes, I’ll go ahead and put one of the local repeaters in the other receiver, especially if we are going to hang out in one location for a while.

When driving near coastal areas, I often put the second receiver on the VHF Marine Channel 16 (156.80 MHz). This is the International Hailing and Distress Frequency for marine radio. You will hear boats calling each other on this channel, then switching to another working channel. It is also common to hear the U.S. Coast Guard come on the air with an announcement. (The USCG may say switch to Channel 22 to hear the announcement.)

Some other useful marine frequencies:

Channel 22   157.100 MHz   Coast Guard Liason Channel
Channel 68   156.425 MHz   Non-Commercial Working Channel

The complete list of VHF Marine frequencies are available here:

U.S. VHF Marine Radio Channels and Frequencies

Just another frequency to listen to when on the road.

73 Bob K0NR

[My apologies. I fumble-fingered WordPress and published a draft version of this article that was incomplete. This is the corrected version. ]

Sometime during the 20th Century, I learned that fuses (or circuit breakers) are used in electrical circuits to prevent catastrophic failure. Fuses open in response to an electrical fault that causes excessive current to flow. The job of the fuse is to minimize the damage and keep things from catching on fire. When I started installing amateur transceivers into vehicles, I learned that you should connect wires directly to the car battery (or darn close) and you should fuse both the positive and negative power leads. I was surprised by the need for two fuses, but there are technical arguments for it. Besides, the transceiver manufacturers recommend it in their manuals. (See figure below.)

I am focusing this discussion on a typical 2m/70cm FM transceiver installation – that is what I have the most experience with and that is the most common ham mobile installation. Such a radio typically draws ~10 A on transmit, so the DC power is usually fused with something like a 15 A (or 20 A) fuse. Keep in mind that a 15 A fuse is not going to protect delicate circuitry but might stop more serious damage or fire.

Connect To The Battery?

Alan/K0BG has an excellent website that provides guidance on mobile radio installations. He points out that modern vehicles usually have an Electrical Load Detector (ELD) inserted into the negative lead of the battery, so that the vehicle control systems can monitor the state of the battery. It is important to connect your radio on the “other side” of the ELD, near where it connects to the vehicle chassis. Oh, and never use the existing vehicle wiring to power your radio (especially not the 12 V accessory plug).

One Fuse or Two Controversy

Recently, I became aware of controversy with regard to proper fusing. Some people are questioning the practice of fusing both DC power leads, while others are vigorously defending it.

For example, there is a lively eham.net discussion here.  Ed/W1RFI provides some useful insight on the ARRL forum.  Alan/K0BG covers the topic of DC power on his wiring and grounding page.  Tom/W8JI argues for the one fuse approach on his website.

What Do The Manufacturers Say?

Generally, you should follow the advice of the manufacturer on any equipment installation, so I took a look at a few owner’s manuals. Most (or all?) of the manuals for the amateur gear show the two fuse method. See the ICOM example below. (Note that they don’t show the presence of the ELD.)

I also took a look at some commercial land mobile radio manuals. Motorola shows the single fuse approach.

Hytera also shows a single fuse in its land mobile manuals.

ICOM makes both amateur and commercial land mobile gear, so I wondered what they recommend for their land mobile product line. Ha, funny thing, they show two fuses, with a comment that says, “Depending on version, the fuse holder may not be attached to the black cable.” Well, isn’t that special?

So is the two-fuse thing some kind of ancient amateur radio practice and the land mobile industry has gone a different path? Sometimes industries adopt “standard” approaches and then forget why with time.

Some Circuit Analysis

After reading through all of the arguments, I tried to distill them down to their essence. I created a wiring diagram that may help explain the concepts. Or maybe not. An automobile is a complex electrical and electronic system, so any practical diagram risks oversimplifying the situation. But here’s my best shot at it.

The center of the diagram shows the body/chassis of the vehicle which is connected to the negative lead of the battery, through the ELD. The transceiver is directly connected to the + terminal of the battery (via Fuse 1) and the chassis side of the ELD (via Fuse 2).  The engine starter is connected to the battery with heavy cables and is also connected to the body/chassis.  While there are a large number of other electrical devices in a modern vehicle, only one is shown here as an example (with a switch and fuse).

The circuit shows the antenna connected to the radio with a coaxial cable. The shield of that cable is almost always grounded to the vehicle chassis at the antenna. (Magnetic mount antennas are one exception and I am sure there are others. Update: Ron/N0IVN pointed out that the on-glass antennas are not grounded.) I can say that every mobile installation I’ve ever done had the coaxial cable connected to the chassis. This is an important point because it provides a chassis connection for the transceiver at point C (whether you wanted it or not). There may be other ways that a transceiver is connected to chassis (point B), including the mounting bracket, external speaker, microphone or other accessories.

Arguments For and Against

The argument for fusing the negative lead is to protect against return current from other devices that find its way back to the battery through the transceiver’s negative power lead.  For example, the starter could have a fault in its negative cable, causing the current to flow through the chassis to the transceiver and back to the battery.  The starter current can be hundreds of amperes which would likely overload the radio wire which is sized for 15 amperes. The fuse will open and protect the negative lead (and maybe the radio, to some extent).

The argument against fusing the negative lead is that if the fuse opens up, it could cause problems. Suppose Fuse 2 opens up due to some transient condition. If the transceiver is completely isolated, Fuse 2 would remove power from the transceiver. However, the return path at the antenna coax (point C) will most likely allow the radio to continue functioning using the coax as the negative return. Typically, this is RG-58 or similar cable, which is not intended to carry significant DC current and may fry under the load. If the current is coming from a fault in the starter wiring (big current), this is going to be a bad day for your mobile.

My Conclusions

I think both arguments have merit but choosing one fuse or two requires estimating which problem is most likely and judging the overall impact of the fault. The negative lead fuse can do only one thing well: protect the negative lead. It might provide some protection to the transceiver but there are a lot of sensitive circuits inside the radio that will get destroyed with 15 A flowing. Again, the connection at point C means that the radio will be connected to chassis and current can flow.

If Fuse 2 is eliminated it allows for the flow of high currents through the negative lead of the transceiver. This is not desirable but is it better or worse than the current flowing through the coax shield? Probably better. If a high current device (the starter) has a wiring failure that dumps large currents into the chassis, it may find a number of return paths. Lots of current is going to flow somewhere and potentially cause damage, with or without a negative lead fuse.

I will note that bonding the transceiver to the vehicle chassis has some benefit (point B in the diagram). You may or may not have this connection depending on how you mounted the radio. This electrical connection can shunt any currents away from the coaxial cable, hopefully doing less damage that way.

What am I going to do? My future mobile installations will have only one fuse in the positive lead.  I’ll also bond the radio body to the vehicle chassis, with a hefty, low-resistance connection.

My existing mobile installations all have two fuses. I won’t be changing them out because the risk of inducing a problem with the negative lead fuse is rather low. I don’t see the negative lead fuse as a big risk. If you choose to follow the amateur radio manufacturer’s two fuse recommendation, I understand.

A Request

The amateur radio equipment manufacturers need to give this issue a fresh look. At a minimum, the presence of ELD’s needs to be addressed and the common recommendation of wiring directly to the battery is obsolete. But the one-fuse-or-two issue should also get a careful look by the manufacturer’s engineering teams.

That’s my analysis. What do you think?
(Runs and ducks for cover.)

Note: This article is my technical opinion but my attorney says to tell you that you are responsible if you destroy your vehicle while wiring up your transceiver.

Some of my ham radio habits are focused on operating mobile.

Some of this probably came from watching the Andy Griffith show when I was a kid.
Deputy Fife is a great role model.

Click here to watch the video.

This recycled post from 2008 is still accurate, but I do have my HF antenna up and recently used it for the CQ WW SSB Contest.

I was looking out the window the other day and noticed that my wire HF antenna is laying on the ground. Hmmm, probably doesn’t radiate very well that way. But if I put a long, lossy coaxial cable in line, the SWR will still be good at the transmitter. And I can tell my buddies that it works just fine because “I can work everyone that I hear.” (What a dumb thing to say.)

This made me realize that most of my ham radio activity lately has been on 2m FM. Actually it has been on 2m and 70cm FM, as I tend to lump these two activities together. These days, my VHF/UHF FM rigs have at least 146 MHz and 440 MHz in them (FT-7800, FT-8900, etc.). I cruise down the road and flip on the rig, talk to the locals, talk to the XYL, etc. It is just too easy and too convenient. It fits the mobile lifestyle, whether it means operating a mobile rig in the car or grabbing an HT to take along on a business trip. (I used to run HF and SSB VHF mobile but found that the rigs were rarely used, so I removed the gear from my vehicle.)

Of course, I need to apologize to the rest of the ham community for this failure to act according to accepted social norms. You know how it is…Real Hams operate HF, weak-signal VHF, microwaves, etc……almost anything that is not 2m FM. Every so often I hear that comment about “well, those techs just hang out on 2m FM,” implying that those guys are permanently stuck in ham radio middle school, unable to graduate to the next level. Or sometimes the FM operators are referred to as having “shacks on the belt” which are dependent on the “box on the hill.” The main message is that 2m FM is just too easy, too plug-n-play, too much like an appliance….too convenient. We certainly can’t have that!

Don’t get me wrong…I enjoy HF, DXing, contesting, digital modes, almost anything to do with amateur radio. That’s the cool thing about the hobby…so many bands, so many modes. One of my favorite activities is operating the major VHF contests. (I’ve even been known to make a few CW contacts.) But on a day-to-day basis 2m FM just seems to fit in better.

Some people call 2m FM the Utility Mode, because it is the mode that gets the job done. Last week, we had a weather net activated to track thunderstorms and a few tornadoes. Did this happen on 40m? I don’t think so. Two meters carried the load. Where do most of the ARES and RACES nets meet? Two meters. How is most public service communications handled? Two meter FM. Even some hard core HF DX enthusiasts are known to flip over to 2m FM to tell their buddies that the DXpedition to a rare country is on the air. It is the Utility Mode.

Over the weekend, I was driving through the mountains and heard an aeronautical mobile working stations simplex on 146.52 MHz…lots of fun. Another time, I heard a station calling about 80 miles away (I was in a high spot) and I had the pleasure of making that contact….again, on 2m FM. A few weeks ago, I operated in the Colorado 14er Event from the summit of Pikes Peak. Since many of the mountaintop stations had hiked up, the most popular mode of the day was (you guessed it) 2m FM.

So sorry, I have been hanging out on 2m FM. I’ll try to get that HF antenna back in the air one of these days.

73, Bob K0NR

After acquiring a Ford F-150 truck last year, I’ve been working on getting a ham radio installed in it. At times, I have loaded up my vehicle with multiple radios covering HF through 70 cm but lately I am content with just having a reasonable dualband 2m/70 cm FM rig in the mobile. Actually, I used a Yaesu FT-8900 that does FM on 10m, 6m, 2m and 70 cm but just set it up for the two bands.

One of the most critical questions for a mobile installation is what kind of antenna to install and where to put it. In the end, the antenna is going to be the main determinant of mobile performance. Ideally, I’d like to have the antenna on the roof of the cab but the truck will not fit in my garage in that configuration. Another option I considered was mounting a longer dualband antenna using one of the stake pocket mounts from Breedlove. I prefer NMO mounts for VHF/UHF antennas and the stake pocket looked like a good way to go. However, a little measuring revealed that a 1/2-wave or 5/8-wave 2m antenna on the stack pocket was not going to clear my garage door. So it seemed that I was limited to a shorter antenna. I may still use the stake pocket mount for an additional antenna for road trips or to add 6m and 10m antennas.

At this point, the F-150 bracket offered by The Antenna Farm looked like a good option. They have a number of these brackets made specifically for various vehicles, so check them out. This made the antenna installation quite simple. <click on any of the photos for a larger view>

The antenna is an NMO-mount dualband that I had laying around the hamshack. I don’t recall the exact model number but these are very common, about 19-inch long for 1/4-wave operation on 2m and a small loading coil to make it work on the 70cm band.

The F-150 has several precut holes for passing wires through the firewall. I used one that is on the passenger side just  below a large module, as shown in the photo. It took a stiff wire and some force to punch my way through the rubber plug and into the cab compartment.

I don’t have a photo of the battery connection but I connected the positive lead right onto the battery terminal while the negative lead was attached to the truck chassis near the battery. You may have been told to always connect directly to the battery terminals but that advice no longer applies to some newer cars because there is a current monitoring device in the negative battery lead. To avoid confusing the vehicle battery monitoring system, the negative connection to your transceiver needs to be on the chassis side of the current monitor. Alan K0BG explains this issue on his web site. Actually, Alan has a wealth of information on mobile installations on his web site: www.k0bg.com. Oh, of course, I used inline fuses on both the positive and negative power cables.

I mounted the FT-8900 transceiver on the floor under the back seat. To route the power cables and antenna coax, I pulled up the flat plastic trim piece that runs along the floor at the passenger door. I started from the front and did some careful prying (and praying) to remove the trim without breaking it. This exposes a trough with a factory wiring harness in it but there’s room for more. A few other plastic trim pieces were removed to get access to the wires coming through the firewall. All in all, this was not that difficult. (Yea, Ford!)

The photo to the left shows the FT-8900 radio installed under the passenger side rear seat. I drilled holes through the floor and mounted the radio with hefty sheet metal screws. The screws go right through the metal floor and and can be seen from under the truck. (Check that out before drilling!) Because the radio body is under the rear seat, I am using a small external speaker mounted near the drivers seat.

The radio control head is mounted inside a little door/shelf that normally pops open to reveal the USB port for plugging in a smartphone. (Note that Ford has multiple seat / dashboard configurations.)

The FT-8900 control head just fits inside this little shelf, even when the door is closed (see photo). The microphone does have to be removed to close the door. I mounted a microphone hanger with a couple of sheet metal screws, as shown in the photo. I don’t like the crappy little hanger that usually comes with a ham transceiver so I bought some higher quality hangers on Amazon.

Overall, I am pleased with the radio install. The antenna location is clearly a compromise and I notice the performance is not as good as my previous vehicle (which was a small SUV with an NMO mount antenna in the middle of the roof.) But the antenna is “low profile” and sufficient for “around town” mobile operating. I am getting a little noise on the 2m band which needs some investigation. The 70cm band is very clean and is the band I use the most.

73, Bob K0NR

One of the things I try to do is monitor the National Simplex Calling Frequency for 2 meter FM: 146.52 MHz, especially when mobile. It is fun to see who might show up on 2m simplex: SOTA operators, hikers, mobile stations, campers, etc. See these two posts on operating ideas: A Simple Wilderness Protocol: 146.52 MHz and The Use of 146.52 MHz.

It is also fun to say hello to another ham when you pass them on the highway. While you may see their call letter license plates or notice their mobile antenna, you may not know what frequency they are monitoring. The Noise Blankers Radio Club has solved this problem — just put this sticker on your vehicle.

After poking around cafepress.com, I found some additional options for indicating your radio frequency:

The 2meter SSB calling frequency:

The APRS frequency:
And there’s this magnet for your refrigerator:

And then there’s this option, 73 the coolest number …

If you don’t like any of these, cafepress.com makes it easy to create your own. Go for it!

73, Bob K0NR

I encourage newly licensed radio amateurs to go ahead and get a dual-band FM rig…handheld, mobile or both. I think the additional cost of the dualbander with both 2 Meters (146 MHz) and 70 cm (440 MHz) is justified by having the ability to operate on the additional ham band. I have noticed that the price of the single-band 2 Meter mobiles are pretty low, less than $200… a real bargain in terms of technology. This made me wonder what the price premium for the second band (70 cm) really is.

I pulled all of these prices from the same major ham radio web site, trying to keep some consistency among the price of the various models. (I ignored specials and coupon pricing.) I looked at a basic 2 Meter FM rig and any comparable dual band models from the same manufacturer. I tried to stick to the basic transceivers and not include models that had advanced features such as D-STAR and APRS in them.

The data is captured in the table below. Note that I differentiated between a single receiver (one frequency at a time) dual-band radio and a two receiver dual-band radio, since the latter variety is much more expensive. I calculated a percent premium for each of the dual-band transceivers, calculated as the percent increase in price over the single-band radio from the same manufacturer. I think this is the most objective way to describe the extra cost of a dual-band radio.

It is worth noting that only Yaesu and Alinco offer a single-receiver dual-band rig. These two radios are 78% and 88% more expensive than their single band counterparts (less than twice the cost). The two-receiver dual-band radios are consistently more expensive, with a price premium ranging from 149% to 172%. While these rigs are often described as having two radios in one, they are more than twice as expensive as a single-band radio.

Although I appreciate the extra utility of the two-receiver radios, it looks to me like the best value is with the single-receiver dual-band rigs.

What do you think?

73, Bob K0NR

We recently sold the old white Jeep and bought a 2012 Wrangler (JK). After quite a bit of researching and experimenting with antenna mounting options, I finally got the ham gear installed in it. My objective is to get 2 Meter and 70 cm FM capability into the vehicle, using the Yaesu FT-7800 that I pulled out of the old Jeep. The big question was what to do about the antenna. The fiberglass hardtop does not make for a good antenna ground plane. Even if it did, during the summer months, we’ll sometimes take the top off to enjoy the open air ride.

Initially, I planned to use the Arizona Rocky Road NMO antenna mount with a Diamond dualband antenna that is a 1/2 wave on 2 Meters. The 1/2 wave does not need a ground plane, so the performance is usually better with irregular mounting structures. However, I found that this antenna combination did not clear my garage door. I don’t like to have to remove or tilt a vehicle antenna to get in/out of the garage — my experience is that it usually just gets left in the “down” position. I tried a shorter 19-inch dualband whip antenna but its performance was dismal due to these factors: lack of a ground plane, being blocked by the vehicle body and poor grounding on the spare tire carrier. By the way, the grounding issue on the tire carrier (and many other technical topics) are discussed in these online forums: WranglerForum, JK-Forum. I think the Arizona Rocky Road mount would have been my preferred way to go (with the longer Diamond antenna), except for the garage issue. One problem I ran into with that mount is that the standard NMO mounts I have (the basic mounts with the cable attached) did not handle the thick steel of the mount. I had to purchase special NMO mounts made to handle thicker metal (see TheAntennaFarm.com).

I abandoned the Arizona Rocky Road approach and decided to use a simple NMO mounting bracket (Laird SBTB3400) on the driver’s side hood.  Like all Wrangler antenna installations, this is a compromise. It is lower on the vehicle than I would like but it does not block the driver’s view. Other people have used a variety of “trunk lip” mounts to accomplish the same thing but be sure to check out the driver’s view before installing. Installing the mount was easy, just three holes drilled and three sheet metal screws.

The next question was where to install the radio. I took advantage of the FT-7800’s detachable control head, mounting it on the dash, while placing the radio under the driver’s seat. I attached the radio’s mounting bracket to the floor of the Jeep with two heavy sheet metal screws. This keeps the radio up off the floor in case water gets into the Jeep. However, it only provides about 1 inch of water clearance, so you hard core Jeepers that are used to flooding the interior of the vehicle during stream crossings may find this inadequate.

I have to admit that I ran into a significant problem at this point. There was not enough clearance around the radio mounting bracket to get all four of the screws installed that attach the radio to the bracket. In the end, I unbolted the drivers seat and tilted it back, which gave me room to insert and tighten the screws. More careful positioning of the radio mount might have saved me from this hassle.

It is always a bit of an adventure to find a way to route the power cable from the engine compartment to the vehicle interior. Fortunately, Jeep has made this very easy, but it is not obvious just by looking around. Fortunately, the folks on the various online forums have scoped this out and provided good advice.

I popped off the small side panel of the dash on the driver’s side, to expose a hole filled with foam (see photos).

A stiff wire or coat hanger can be poked into this hole and the foam easily gives way.

And the coat hanger comes out the other side, right next to the antenna mount.

I routed the power cable and the antenna cable through this hole. I connected the power cable directly to the battery, which is the recommended approach to avoid alternator whine and other problems. I understand there is a similar routing hole on the passenger side but I did not verify that.

The last thing to figure out was where to mount the control head. Although it is a tight fit, I mounted it in front of the gear shift. (I have the 6-speed manual transmission…the automatic transmission gives you more room here.) The control head is very light, so I used stick-on Velcro (about an inch wide and four inches long) to attach it to the dash. This seems to work OK but I will admit that the attachment is just a bit wobbly…fine for turning volume and VFO knobs but the not so good for pushing buttons. Also, I’ll have to see if it shakes lose on bumpy 4WD trails.  If so, I’ll fabricate a small bracket to provide better attachment.

In the process of exploring, I did take the dash apart to figure out what my options were. In retrospect, it was probably unnecessary due to where I eventually mounted the radio and control head. I found this youtube video to be very helpful in dismantling the dash.

Initial checkout shows that the radio installation is working fine. I was pleasantly surprised that the antenna SWR was quite good (<1.5) over the bands of interest. I will use the short 19-inch whip most of the time but I can swap out other NMO mount antennas (including the Diamond dualband antenna I mentioned earlier.)

I appreciate all of the info out on the interwebz concerning JK radio installs and I am passing along what I learned to assist other folks with their Jeep installations.

– 73, Bob K0NR

Update 20 June 2012:

It turns out that the Velcro (hook-and-loop fastener) approach did not work. The Velcro attachment itself was pretty reliable but the stick-on adhesive failed after a few weeks. I used a couple of L-shaped brackets to attach the control head to the dash and it seems to be working fine. I have used Velcro successfully in past installations but in situations where the control head was positioned on top of the center console so the main purpose of the Velcro was to prevent horizontal movement. In other words, the Velcro did not have to support the entire weight of the control head, just keep it from moving around.

Update 8 June 2014:

A number of people have emailed me to ask about the sturdiness of the antenna installation. The vehicle sheet metal that the mount attaches to is not all that thick, so they are worried about putting stress on it and having metal fatigue over time. I have inspected this several times now and it is not showing any signs of wear. The antenna I use is small and lightweight so it does not put much load on the antenna mount. I would be more concerned if the antenna was massive, so keep that in mind when you choose your NMO antenna.