Montana's Ham Radio Forum

Does anyone know of a place in or near Great Falls that will install an NMO antenna mount? I've never installed one and having a hard time talking myself into drilling a hole into a new truck.

thanks
Tim
kf7vut

Hi Tim,

Unfortunately, the only Motorola 2-way radio shop in Great Falls, Falls Communications, closed its doors on 30 June 2008 when the owner retired.

The next nearest full time Motorola radio shop is located down in Helena: Capital Communications. They picked up some of the area radio work previously done by Falls Communications. The owner is Gary Schmidt. He is usually up in the Great Falls area several times a month on service calls for existing customers. Although I would expect he prefers to do installs down at his radio shop, he will make exceptions if he is already in Great Falls for another scheduled service call. It would all depend on his schedule and what other service calls he has that day. You would just have to coordinate on the day and where to meet in Great Falls.

Call Capital Communications at 1-800-662-3662 and ask for Gary Schmidt. He has NMO mounts, cables, antennas, and connectors. If you buy the material from him, he will give you a discount on the installation work.

You will need to have some things already worked out, such as where you want the NMO mount installed on the roof of your vehicle. Usually the best spots for pickup trucks are right in the middle of the roof (above the dome light), or near the back of the cab roof (about 6-inches away from the third brake light). If your vehicle has side or back window curtain air bags, it will complicate matters slightly.

Identify where your radio will be installed, and where you want the connector end of the coaxial cable to end up. If you have not already installed your radio, be sure to ask for a little extra cable length (about 12 inches should be plenty). You can always tuck a little excess cable out of sight, which is far better than coming up short. It is also a good idea in case you switch to a different radio a few years down the road. A little extra cable length is cheap insurance against Murphy's Law...

Also be sure to specify the type of RF connector to be installed on the end of the coaxial cable. The PL-259 connector is not used in the Land Mobile Radio industry anymore. Most business band 2-way radios use the mini-UHF connector now. Gary has PL-259 connectors in stock – just let him know that is what you need.

If you need a dual band antenna, consider the Larsen NMO 2/70B model. It has been around a long time and has a proven reputation as a rugged antenna. Gary Schmidt prefers to install Larsen brand antennas, so that is what he stocks at his radio shop. He would probably need to special order in the dual band Larsen model, as that is something most of his commercial customers do not need. The only drawback to this antenna is the open coil design, which tends to whistle in the wind as you drive down the Interstate at 65 mph or more. The older version had an enclosed coil, which did not generate any wind noise. Because of the new open coil design, I now prefer the Maxrad MDB-1444 dual band antenna (which has the enclosed coil design).

If you have just a 2-meter rig, I'm certain Gary has a Larsen VHF 5/8 wave antenna that will work well for you and really reach out to the distant repeater sites. The short, 19-inch 1/4 wave antenna is good for around town use, and will often fit inside a garage door opening. The longer 5/8 wave antenna provides 3 dB of gain, but with a length of around 52-inches, it is too tall to clear a garage door. Some folks use the 1/4 wave antenna around town, but keep a spare 5/8 wave antenna tucked behind the seat for the occasional road trip when they need longer range. That is the advantage of the NMO antenna mount - swapping antennas takes only a minute. Just don't forget to switch antennas again before parking in the garage.

Otherwise, consider the Maxrad MDB-1444 collinear 2m/70cm mobile antenna. It is 34-inches long with an enclosed coil. George (AA7GS) usually has a few on-hand at his shop in Black Eagle. See his posting under “The Swap Net”, “For Sale (Ham Related Only)” at the bottom of the Forum page.

Thanks for the reply Bruce, I will look into that. Just about got myself talked into(but not quite yet) punching the hole myself and just being done with it. Luckily my wife is a ham also (kg7bfp) and she's ready to get the ft-60 and mag mount out of there and get a clean install in, so we will see. The radio i am ordering is the ft-7900. Read a lot of good things about it and really like the number of memory banks. I travel back east a few times every year and its nice to have a memory bank for each state that we go through. Have you any experience with that radio or other suggestions? As for the antenna, I am looking at the Larsen NMO-2/70sh, we have trees in the driveway and 19" is a good height to clear. I like the idea of a longer antenna for travel though, I had never considered that. Anyway, thanks again for the info, I'll give him a call and see what he has to say.

thanks again,
tim
kf7vut

Hi Tim,

I looked at the reviews for the Yaesu FT-7900 on the eham.net web site. I noticed that it is a "dual band capable" radio, but not actually a true full-time dual band radio. The true dual band radios show the selected VHF and UHF frequencies side-by-side on the display. You can actually monitor a 2-meter frequency and a 70 cm frequency at the same time, since both are active. This is handy when you live in a town with both 2-meter and 70 cm repeaters available. You can monitor the local 2-meter repeater all the time, yet still hear your wife calling you on the far less busy 70 cm repeater (or 70 cm simplex frequency). It allows you to have a second frequency available for chatting with the wife (also helpful if she does not want to listen to all the chatter on the more busy 2-meter repeater.)

The Yaesu FT-7900 can do either 2-meters or 70 cm, but not both at the same time. Sure, you can alternate the memory channels with 2-meter and 70 cm frequencies, then put the radio in scan mode. But while the radio is stuck listening to one conversation, you might be missing a call on another frequency. I noticed the Yaesu FT-8800 is a true dual band radio. However, several folks who reviewed it on eham.net complained that the front panel buttons do not have backlight illumination like the FT-7900. In the end, a lot depends on personal preference. I have an old Kenwood TM-741 dual band mobile radio that I like. If I was to buy a new rig today, I would lean towards the Kenwood TM-V71A.

In general I look for a radio with backlit illuminated buttons so I can see what I am doing at night. I also believe in cooling fans. Some of the Yaesu mobile radios lack cooling fans. Instead, they rely on an extra large heat sink to dissipate the heat. Unfortunately, by themselves heat sinks have their limitations. I know someone who had a Yaesu mobile radio with the "huge heat sink" design that shut down during a bike-a-thon event one summer day. It was simply too hot outside and in the vehicle for the heat sink to keep the radio cool by itself, so the radio overheated and shut down. A cooling fan moves air over the heat sink and helps dissipate the heat, allowing the radio to keep working in hot weather. I don't mind the noise of a cooling fan, when it keeps me on the air.

Due to the small size of the mobile radios and their internal speakers, I always use an external speaker for better sound quality and volume. A speaker with a housing around 4 or 5 inches square works well. There are a variety of "compact" external speakers available. The problem is that they are so "compact" that you end up with an external speaker that is almost the same size as the dinky one inside the radio. This does not solve your audio problem! Some examples of external speakers that I like would be the MFJ-281 and the DAS 302-VS2, both available from the Ham Radio Outlet (HRO) web site. These speakers are basic models without audio amplifiers or digital signal processor circuits added. They have a 4-inch speaker inside, which is double the size of what is inside the radio. You might even find a suitable external speaker in the CB Radio section of a truck stop. The DAS brand speaker is a generic model that shows up on the shelf with an assortment of name stickers attached: "Cobra", "President", "Uniden", etc. Nothing fancy - just a bigger speaker that sounds better.

If you intend to remote mount the radio, an important concern is where the microphone plugs in. Some radios have the mic plugged in to the control panel. If you remote mount the radio chassis, the mic still plugs into the control panel - which is nice. But many radios have the mic cable going through a slot in one side of the control panel, where it then plugs into the radio chassis behind the control panel. You can remote mount the control panel, but the mic is still plugged into the radio chassis. This forces you to buy a mic extension cable so you can extend the mic to where you can reach it.

I happened to check the Larsen web site and noticed their full size NMO 2/70 antenna now has an open coil design. It used to have an enclosed coil design. The open coil design tends to generate wind noise as you drive down the highway. If the whistling noise kept the deer away I wouldn't mind, but it doesn't. About the only thing the open coil design does for you is it allows you to see more of the dead dragonflies and bugs you smacked during the drive home. So for a full size dual-band antenna I would recommend the Maxrad MDB-1444, which has an enclosed coil. It looks like the Larsen NMO 2/70sh "shorty" dual band antenna also has an enclosed coil, so it should be quiet going down the highway.

When I bought our brand new 2002 Suburban I knew that I did not want to use a mag-mount antenna on it, and put up with the cable running through the door. So I had Falls Communications install three NMO mounts along the length of the roof. It was quick and professional looking when they got done. And I did not have to deal with the headliner and snaking the cable all the way to the front dashboard. I just told them where the cables needed to end at and what type of RF connector I needed on the ends. It was simple for me, and the wife was happy. Paying a Motorola technician who installs antennas for a living to do the work for you is money well spent. Especially if you are not comfortable drilling holes in a new vehicle.

By the way, ask Gary if he has any NMO rain caps. They allow you to unscrew the antenna and replace it with a threaded rain cap, so you can drive the vehicle through a car wash without concern. Most automatic car washes would snag an antenna and rip it out of the roof, so the rain cap is nice. I know lots of guys will say they have driven a vehicle through a car wash without any rain cap. There is an O-ring seal around the base of the NMO mount that "should" stop the water. But I like the extra level of safety with the rain cap screwed on. Besides, the space shuttle Challenger relied on O-rings...

Thanks again Bruce. I did look at the FT-8800 and the Kenwood TM-V71a. With the 8800, I thought not having backlight buttons would be an inconvenience plus it doesn’t have the wx alert, which I like while traveling across the country. The kenwood looked really promising except for the fact that I was not fond of the memory management that Kenwood uses and I really didn’t like the fact that the mic attaches to the body of the radio and having to pay an extra $65 for a separation kit didn’t set well with me.
I like the idea of the true dual band/dual receive but the other aspects of the FT-7900 (backlight buttons, memory management, mic attaching to the faceplate and WX alert) outweighed the true dual band of the other two.
I am still on the look though, maybe something else will pop up that I haven’t looked at yet.

73
Tim
kf7vut

I have this Larsen dual-band antenna on both the van and the house: http://www.hamradio.com/detail.cfm?pid=H0-000565 It works great, but the mount on the van is so-so. Having a full-size van, the fact that can fit in my garage is more important than good comm, so a not-so-good antenna location on the van (front fender) had to do. Worse yet, I can't easily get to the inside of the fender so pop rivets hold the antenna bracket in place, not bolts. (Larsen TMB-34 bracket, I think)

The van is slightly taller than I am, and I have about 2" of clearance under the fully-opened garage door.

It does have an open coil but that's easily solved by a length of heat-shrink tube. No whistling here.

KF7VUT, if you decide to drill a hole (and I'd recommend that), sanding will be involved. The paint acts as a resistor, so in order to get the best possible ground plane, the underside of the roof should have the paint removed wherever the antenna mount's bottom bar goes. http://wa8lmf.net/mobile/NMO-HF-Thick.JPG

Drilling the ¾-inch hole required by the NMO mount is best done using a specially designed hole saw made by Antenex. The Antenex model HS34 hole saw comes with a pilot drill already installed. The special design has a shoulder around the outside of the saw blade that limits the depth of cut to 1/8-inch. This means you can cut through the vehicle roof without fear of going too far and damaging the vehicle headliner below. A regular ¾- hole saw can be used to cut the hole, but at the risk that it will cut through the thin metal roof and keep going! It can be done, but you will have to be very careful and go light on the drill trigger so you can stop just as soon as the drill cuts through the roof panel.

An added bonus with the shoulder design of the HS34 hole saw comes into play after you have finished cutting the hole and have removed the resulting metal disc from inside the hole saw. Place the hole saw back into the hole and spin it with the drill while applying light pressure. This lets the shoulder of the hole saw wear down the paint on the vehicle roof until the bare metal is visible. When you install the NMO-mount brass locking ring with the O-ring gasket, it will contact the bare metal and get a good ground connection.

As Bob N7PTM pointed out, most vehicle roof panels are painted with primer on the underside, preventing the two tabs on the bottom half of the NMO mount from making a good ground connection. This requires sanding in order to get good metal to metal contact. If you have small fingers you might be able to stick a strip of sandpaper or emery cloth down the hole and use your finger to sand away the primer on the inside. If you have access from down below with the dome light removed, you can sand down the primer that way. I usually just let the hole saw remove the paint on the outside of the roof panel with only 15-30 seconds of spinning. The small ring of bare metal created around the hole is just wide enough so it is covered by the brass locking ring when it is tightened down. There is no bare metal visible once the NMO mount installation is complete, even before the desired antenna is screwed on.

The center portion of the NMO mount has two small round holes on either side of the center contact. Motorola sells a special wrench that fits into the holes, so you can keep the mount from rotating while you tighten the outer locking ring with a wrench. However, a small pair of needle-nose pliers with tips small enough to fit into the holes works almost as well. Stick the needle-nose pliers into the holes so they form an “X”. Use the palm of your hand between the handles to apply down pressure to keep the tips in the holes. Use your fingers and thumb to keep the pliers from rotating while your other hand tightens the outer locking ring.

As a side note for those not familiar with the NMO mount, it installs from the outside of the vehicle. You pass the coaxial cable in through the hole in the roof from outside the vehicle. Once you have pulled all the excess cable through, tilt the NMO mount to one side and slip one mounting tab in through the hole, then the opposite tab. The center portion of the NMO mount is slightly larger than ¾-inch, so you cannot simply stick it up through the hole from inside the vehicle.

The Antenex HS34 hole saw can be expensive if purchased at retail prices. I have seen it priced at $60 retail, but less than $40 when purchased through a parts wholesaler such as Tessco. If you are going to be installing a lot of antennas on vehicles, it is a wise investment. It makes installing NMO antenna mounts sooo much easier. But if you only have the one vehicle, a trip to the Motorola radio shop would probably save you a lot of time and hassle. It all depends on how comfortable you are drilling holes and snaking coaxial cable underneath the headliner and down a door pillar in a vehicle.

Hi Tim,

Looks like you have done your research well. You hit on all the pros and cons for the various dual band models. I did not know about the problems associated with remote mounting a radio until I read a review on eham.net on a specific radio model. Before then I had not given it much thought. But after reading the review I went and looked at my Kenwood TM-741 and realized it had the same design, where the microphone plugged into the radio chassis behind the control panel - instead of directly into the control panel. I have never needed to remote-mount a ham radio, but if I ever did, I would want the design where the mic plugs into the control panel so one separation cable is all that is needed.

Bob N7PTM has a good and very simple solution to the open coil design wind noise. I will have to remember the heat shrink trick the next time someone complains about the wind whistling through the open coil. KISS!

One of the best tips I give to folks considering the purchase of a new radio is to research the model they are interested in. Thanks to the internet you can go to the Ham Radio Outlet (HRO) web site and get the basic information on features and price. But for every radio listed on their web site, there is a link to the manufacturer's web site. This allows you find and download a .pdf copy of the owner's manual. Read through it and make sure the radio does what you need it to do.

Years ago, before the internet, I purchased a Yaesu FT-5100 dual band mobile rig. The catalog advertisement boasted that it had 46 memory channels per band, just what I was looking for. Unfortunately, until the radio arrived and I could read the manual, I did not know that the 46 memory channels were separated into two groups of 23 channels - and that the two groups could NOT be combined. You could either use one group of 23 memory channels or the other group of 23 memory channels. Since my goal was to scan various ham and public safety channels, this limitation severely restricted my use of the radio as a scanner. Today I always download and read through the manual of any radio I am considering purchasing to catch any problems before I place the order.

thanks Bruce and Bob for the info....

You know i WAS all set and thought i knew for sure what I wanted(ft-7900), then i went back and looked again at that FT-8800 and found i miss read some of the specs....other than no light on keys it is pretty much what i wanted.

Well i work in Law Enforcement (Border Patrol) and have a radio in my truck and just noticed how often i turn the lights on the radio off at night because they bother me...so now I'm thinking that no lights on the radio won't be an issue...so I've decided on the FT-8800 (thanks Bruce for the suggestion). Haven't decided on whether to have the antenna done professionally or myself yet. I want to get the radio and get it installed and go from there.

Thanks again for the info guys. HOPEFULLY i'll get this done before the snow starts to fall.


Tim
KF7VUT

Hey Tim!

How did the antenna install go? Which radio model did you select?

Just wondering...

Hey Bruce,
I ended up get the ft-8800 and love it. As for the antenna, well I'm still using a mag mount. Truck is coming up on a year old so punching a hole in it now won't feel as wrong. I have the antenna and all, just waiting for a nice day off to get it done.

Thanks for asking.
Tim
kf7vut

Hi Tim,

Glad to hear that the Yaesu FT-8800 dual-band mobile radio is working out for you.

If you ever decide you would rather have a professional radio shop do the NMO antenna mount install for you, don't forget Capital Communications down in Helena. The owner, Gary Schmidt, was just up in Great Falls this past Monday taking care of customer needs in this area. Now that the warm weather has returned, there is the option of meeting Gary in Great Falls for a quick 30-minute NMO install. It all depends on his schedule. He is usually up in the Great Falls area several times a month. Give him a call at 1-800-662-3662.

If you have the time, don't forget we have a weekly ARES net for the north central Montana region every Thursday evening at 7:00 PM. The net is held on the 146.740 MHz repeater (100.0 Hz tone) located on top of Highwood-Baldy mountain (which is 35-miles east of Great Falls).