I am a ham with a handheld radio (HT) and a desire to do emergency volunteer work with the Amateur Radio Emergency Service (ARES). My HT transmits 5 watts of power. I have a cheap mag-mount antenna for the car. In the exercises with my local ARES group I had trouble communicating with more distant stations. In my case, I could hear (receive) stations, i.e., repeaters, but could not be heard (transmit). The obvious answer is more transmit power. However, the common wisdom is that the antenna is the most important factor in transmission and reception, so before spending money on a more powerful transmitter I decided to get a better antenna.
After doing some research I settled on the Diamond NR-770HB antenna. I realized I also needed a mount for the car. A little more research provided an example of mounting on a 2012 Prius (see [1]). More research brought me to the Diamond 400S antenna mount. The mount is one of the most sturdy mounts. I wondered about NMO versus non-NMO mounts but selected a non-NMO mount (see [2] and [3]). In this article I document the installation of the mount.
First let’s see what we get in the kit. There is the mount. There is also the cable. One end has the threaded antenna connector and and the other end an SMA connector (which is perfect for my HT). A PL-259 adapter is included. Allen wrenches for the base and antenna positioning are provided. Stick-on cable clips are also provided.
I spent some time getting familiar with the parts. The base is attached to the hatch by four screws.
The adjustment bracket has two axes of adjustment which allows the antenna to stand straight up on the angled hatch door.
The antenna connection hardware has a threaded part that the antenna screws into. There is a threaded collar and a nut. I played around with the collar and the nut and found that I probably don’t need the nut for the threaded part to fit snugly into the mount and the collar to lie flat on the mount.
Moving to the car we survey the situation. The space under the hatch gets debris from the trees which I vacuum out.
In attaching the mount to the hatch there is the issue of proper grounding to the car’s body. Some believe it is necessary to remove the paint prior to installation. In this case the mount was screwed onto the hatch and then electric continuity was measured to see if that was sufficient.
We measure the resistance between one of the position adjustment screws and a ground on the car, i.e., the metal loop that catches the door. The resistance is less than half an ohm so the paint can be spared.
The next step is to install the threaded antenna receiver, make sure it is reasonably level, and place the antenna cable.
The space between the hatch and the car is cleaned-up and the cable clips are installed.
Now comes the moment of truth. The antenna is attached to the mount. The HT is attached to the cable and powered-up. No one is out there to answer my calls, but received signal strength from various repeaters is noticeably improved.
The antenna is 40″ tall. The antenna will be connected when I participate in ARES exercises. I replace the antenna with the cap provided when it is not in use.
References
[1] Prius Radio Install. https://www.youtube.com/watch?v=khuxSOzfqBk
[2] http://ravtrack.com/GPStracking/the-versatile-nmo-antenna-mount/
[3] https://blog.solidsignal.com/tutorials/what-is-an-nmo-mount/
Dan's Thoughts and Musings 