Mobile Antenna Installation
For quite a while, I had been using an Alinco handheld in the car, along with a little Mirage VHF amplifier. Both of these were powered from the lighter socket. For antennas, I used various luggage-rack mounts and magnetic mounts. No combination of handheld, amplifier, and antenna really worked very well.
About a year ago, I bought an Icom IC2200 to solve the radio problem. However, I still faced the antenna problem. I had seen John’s (AA7UJ) truck with its antennas, but didn’t warm up to the idea of putting a hole in the car until I saw Dave’s (KI7YP) Honda Fit. The installer at Day Wireless in Seatac did a great job on that car. So, I finally made an appointment and took my 2002 CRV down.
The power connection was made directly at the battery, but the cover had to be notched so that it would close over the connector.
Dave the installer (not Dave the KI7YP) used a relay between the battery and the radio. The relay clicks on when the key is on. This way, I can’t leave the radio and run down my battery. I just have to remember to turn off the lights! The power wires are bundled inside a sleeve, and go through the firewall.
The power wires come into the car, and into the console.
Next came the antenna. I decided that if one hole in the car was good, two is better! Dave inspected the ceiling for airbags and the sunroof parts. Once he figured out where they were, he carefully measured to locate the holes so that the antennas would not interfere with the airbags or sunroof. While I went to get some coffee, sneaky Dave drilled two 3/4-inch holes in the roof of my car. The antenna mount comes in two pieces – one piece goes on the inside of the roof and connects to the coax, and one piece goes outside, on top of the roof. Dave had a special tool to position the inside piece without having to disassemble the car’s ceiling. He installed the two mounts, expertly pulled down some trim pieces, tucked the cables out of sight, and neatly reassembled everything.
The cool thing about VHF antennas is that they’re so small, they’re nearly invisible! The back one is invisible, there’s no antenna there (yet!).
WARNING – TECHY, GEEKY STUFF COMING! (but we Hams like this stuff, right?)
The mounts I had installed are NMO-style mounts. Antennas with this mount come in a lot of types, 1/4 wave, 1/2 wave, 5/8 wave, among others. Multi-band antennas may have one wavelength on one band, and another wavelength on another band.
I had originally purchased a short, flexible dual-band antenna, because I was worried about the antenna hitting the roof of my garage.
We installed that antenna, but we could not get a decent SWR. We got about 4.5:1. That just wasn’t going to work. So, we put on that 1/4 wave whip in the picture, and it works great.
The SWR is less than 1.6:1 across the entire two-meter band, and we didn’t even have to trim the antenna. And, to top it off, the antenna just barely hits my garage!
The large ground plane offered by the CRV (or any sport-utility or station wagon) gives the 1/4 wave antenna a pretty low take-off angle. This is great for repeater work, since very little of the signal goes skyward. At two meters, this is good, because VHF signals doesn’t bounce off the ionosphere very well anyway.
Maybe I’ll use that flexible antenna to get the stuff stuck under the sofa…