hamradio11

MOBILE HAM RADIO ANTENNAS

I really enjoy tweaking mobile antennas. I am always looking for the better mouse trap, thus I purchase and test lots of mobile antennas. I also tend to break the occasional mobile antenna and I plan to discuss the whys along with potential solutions to this problem. From the actual antenna to the mount, coax and connectors this is one of my favorite subjects.

A VIRTUAL ANTENNA FARM ON THE RAM

AN ASSORTMENT OF MOUNTS ALL WITH STANDOFFS TO KEEP THE

TOOL BOX LID FROM HITTING THE ANTENNAS WHEN IT IS OPENED

THE STRESS OF WINDLOAD ON THE TOOLBOX CAN OVERWHELM THE

ALUMINUM STEPTREAD SO I WELD REINFOCEMENT PANELS TO THE INSIDE

The antenna mounted on the drivers side is a Diamond NR770NMO. This antenna is designed for use on the 2 meter and 70 centimeter bands. On 2 meters it is a 1/2 wave with 3.0 dB gain and two 5/8 wave on 70 centimeters with 5.5 dB gain. It is rated at 200 watts with a VSWR of less than 1.5:1. The overall height is 40.2 inches and uses a NMO mount.

I have tried taller antennas at this location on this truck but they tend to drag on every drive-through window I go through. This antenna provides good performance, without being so tall that it hits too much stuff, and is very sturdy with no fragile loading coils to break. It also has a fold over feature for quick and easy ability to resolve temporary clearance issues such as parking decks.

The center antenna on this truck is a Comet UHV-4 quad band designed specifically for the Yaesu FT-8900 radio that is mounted in this truck. It is pretuned for 2 meters and 70 centimeters and had independent tuning for the 6 and 10 meter bands. On the 6 and 10 meter bands it operates at 1/4 wave, on 2 meters and a two 5/8 waves in phase on 70 centimeters. The maximum power ratings are 120 watss on 10 meters and 200 watts on 70 centimeters, 2 meters and 6 meters.

The overall length is 54 inches and has a PL-259 connector. This antenna also has a fold over feature to make it easy to get it out of the way when driving under low objects. The top loading coil is very fragile and I broke it within a week of installing this antenna. Replacement coils are about 18 bucks each from Comet and I went ahead and purchased three of them to have spares. The Comet representative told me that they used to make these coils much stronger. He said a while back a ham in California forgot to lower his antenna before driving into his garage and damaged his home with the antenna. He sued Comet for the damages and actually won in court. Thus they have redesigned much of their mobile line to break before causing damage to what they hit. My personal thought are that any too dumb to lower their antenna and then blame someone else deserves what they get. But in our society I have to suffer because some moron decided to sue Comet over his ignorance.

I have the Diamond and Comet antennas fed into a selector switch and then into the back of my Yaesu 8900. The Comet is selected for all of my 6 and 10 meter contacts on this radio and some of my 70 centimeter and 2 meter work. At times I switch the VHF and UHF work over to the Diamond. With the differing gains and radiation patterns due to mounting locations on the truck I can quite often switch from on antenna to the other and work contacts that I couldn't hit otherwise.

The antenna on the passenger side is a Wilson "Silver Load". It is a 5/8 wave antenna and is 60 inches long. It is used with my Galaxy 99V and is used for both 10 and 11 meter work. I have a manual antenna tuner between the radio and antenna so that I can fine tune the SWR for each frequency. This antenna is very durable. It has been mounted on this truck for most of its 11 years without any issues other than vibrating loose every once in a while. If all antennas were this tough it would be a good thing for all concerned.

THE ANTENNAS ON THE DAKOTA

On my 1993 Dakota the FT-7800 dual band radio sends and receives through a Comet SBB-7NMO 2 meter and 70 centimeter antenna. This antenna is a 5/8 wave center load on 2 meters and has 4.5 dB of gain. On 70 centimeters it is a three 5/8 wave and has 7.2 dB of gain. The VSWR specs at 1.5:1 or less and will handle up to 70 watts. The overall height is 55 inches and has a fold over feature.

I originally purchased this antenna for use on my 1997 Ram but its position on the drivers side had it at a height the was interfereing with getting under the awning of the drive through at the only fast food joint in town which serves vegetarian food. Getting out almost daily to fold the antenna over just for a vegi-burger was driving me nuts. On the shorter Dakota it gets through the window with inches to spare so antenna height on the drivers side has determined the antennas used on these two trucks.

The antenna that is mounted on the glass is a Radio Shack scanner antenna that is attached to a Uniden Bearcat scanner. The antenna on the passenger side is a carbon copy of the 1997 Rams equipment on the same side. It is a 60 inch tall, 5/8 wave Wilson "Silver Load" that can be tuned for either 10 or 11 meters.

THE TOP KICK ANTENNA FARM

My 1997 GMC Top Kick with a 43 foot High Ranger bucket is slowly being turned into a bug out vehicle for emergency operations and field day events. Currently it has three radios and I am going to add at least two more. The Yaesu 2800 2 meter is run through a Diamond NR770NMO as described above. The Vertex UHF rig transmits and receives through a Comet SBB2NMO dual band antenna. This antenna has 2.15 dBi gain on 2 meters and 3.8 dBi gain on 70 centimeters which is the only band in which it is currently being used. The cool thing about this antenna is that it is only about 18 inches tall and does not interfere with the operation of the boom.

I have a second generic external dual band antenna mounted that terminates inside the truck with an SMA connector on its coax so that a handi-talki can be connected to an external antenna if necessary. The scanner receives through a Radio Shack wide band through-the-glass mount antenna. The Galaxy 99v transfers its 10 and 11 meter signal through a Wilson "Trucker 2000". It goes through a antenna tuner so that the SWR can be optimized for each band.

I am also working on an assortment of secondary antennas for each of these radios that will attach to the bucket that I can raise once on a location for extended range. I am still mounting switches, running the 50 foot coax cables and tweaking the antennas. The end goal is to be able to roll onto a location and be able to raise an assortment of large omnidirectional and directional antennas along with an inverted V dipole to a 40 plus foot height, rotate them for maximum efficiency, flip a few switches and be transmitting in 5 to 10 minutes. This is still a project so check back for how it all works out.

THE HANDI TALKIE ANTENNAS

The three antennas pictured above are all used on my SMA mount handhelds. The antenna at the bottom of the photo is a Maldol MH510. It utilizes an SMA mount and and is 20.75 inches tall. This antenna can handle up to 10 watts and it has a gains of 0/0/.32 dBi respectively. While it does not have great numbers in the gain department it does work much better than a factory rubber duck which is the center antenna in the photo.

The top antenna is my favorite antenna that I have ever used on a handi-talkie. It is a Prime

COOL DXING NAVIGATION