A few weeks ago I decided to reinstall a dual-band transceiver in my wife’s car. It had been removed while her car was being repaired and had been repurposed for another project. Since we were going to be leaving for a vacation and using her car for the trip, I figured it would be a good time to put it back in service.
The last time a radio was mounted in the car, the main unit was mounted in the trunk and a special bracket was designed and installed to hold the control head and external speaker just in front of the bench seat in the Mercury Gran Marquis. I never really liked the setup because the control head was too low and the seat would press on the speaker if my wife adjusted the driver’s seat to fit. I decided to start with a “clean sheet of paper” and see if the shortcomings of the old installation could be overcome. For starters, I planned on mounting the main body of the radio under the front passenger seat instead of the trunk. For one thing this eliminated having to basically gut the rear seat area to get the various wires and cables from the trunk to the area of the front seat. This was a major simplification from the previous installation. I also wanted to be able to remove the radio from the car without a lot of hassle if it was needed elsewhere.
The antenna would be a relatively small dual band unit with a very small magnetic base. The new magnet technology has shrunk the mag-mount to the size of a chocolate kiss. Even though the mount is quite tiny it holds tightly to the vehicle roof even at speed. A BNC to PL-259 adaptor took care of the connection to the FT-7900R and the RG-174 sized coax was easily tucked into the trim around the rear passenger side door. It is worth noting that the RG-174 coax has a max power rating of 50 watts and since the coax is less than 9 feet long the losses, even at full power, are relatively minor.
The next consideration was where to mount the control head. The powers that be said “No drilling any holes in the dashboard!” I freely admit that while I might think differently where it concerns my car, I had no desire to drill any holes in the Merc’s dash either. Another solution would have to be found. I noted that the Mercury’s dash had a pull-out section that contained the ashtray and cigar lighter and two cup holders. The front of this pull-out section was a metal stamping painted the same color as the rest of the lower dash panel and there was about one-half inch of clearance between the top of this stamping and the contents that it fronted. If I could come up with a way to hang the control head from the top of the front of the pull-out section the control head would be perfectly placed for use and not be in the way of any of the normal dashboard controls.
The solution came in the form of a small block of 1 x 2 pine about ¾” thick and the same length as the mounting plate for the control head. A couple of small wood screws attached the mounting plate to the wood block and a couple of cup hooks that I padded with heat shrink screwed into the top of the wood block to hang it and the control head from the pull-out portion of the dash. It was a simple matter to attach a small external speaker to the bottom edge of the wood block and I fabricated a little L-bracket out of a mending plate from the hardware store to hang the hand mic on. The bracket is screwed onto the driver’s side of the wood block and extends far enough beyond the control head so that the hand mic is not jammed in place at all. A trio of self-stick felt pads on the back of the block dampen out the occasional rattle and also keep anything from scratching the paint on the dash. The yellow tape on the back of the block was a first attempt to protect the paint. I decided to add the felt pads after a shakedown test, no pun intended.
The next consideration was power. I have always been a proponent of wiring the radio directly to the car battery (with fuses at the battery of course) but in this case I took a different route. In order to allow for the quick removal and replacement of the installation, I chose to utilize the auxiliary power port under the dash. This port is fused by the manufacturer for 20 amps and the FT-7900R does not draw more than 10 amps under the most strenuous of conditions. I am fully aware of the risks of RFI by using the vehicle’s wiring to power the radio, but so far there have been no problems with RFI at all in either direction. That is, the car does not get any RFI from the radio and the radio does not get any RFI from the car. Because there is only one auxiliary power port under the dash of the Mercury ( My Chevy Blazer has two) I built a plug in splitter with two more cigar lighter sockets plus a power-pole equipped lead for the FT-7900R. My wife and I use an aftermarket GPS for long trips and/or unfamiliar destinations and the extra sockets allow for the GPS plus the transceiver plus one extra spare for “just in case”. The splitter plugs in securely to the power port under the dash and has shown no indications of working its way out so far. There are plenty of two and three way splitters on the market in auto part stores and big box stores but I built my own because the wire gauge of the commercial units was too light for a 10 amp draw and the reliability of the commercial units has not been up to the usual standard in my experience. All connections are soldered and covered with heat shrink. The feed to the radio is 12 gauge and the feeds to the two sockets are 16 gauge
. The entire set-up can be removed from the car in less than 5 minutes if necessary and can be reinstalled in less than 10 minutes. On reinstallation, one does have to tuck the coax and power wires neatly out of sight, after all. During the entire installation, not one hole was drilled anywhere in the car and yet the radio and control head have not moved in over two thousand miles of driving so far. For the amateur operator who does not want to drill into a new car or who cannot for various reasons, (company car, leased or rented vehicle, etc.) this method of installing the transceiver may make a lot of sense. A temporary install during a disaster is easily possible with this method even if an operator is assigned to a fire vehicle or other municipal response vehicle. The power-pole connection between the radio and the power splitter means that the radio remains ARES compatible at all times. The cigar lighter type plug on the splitter allows the operator to power the radio from almost any source such as a jump-start power pack or any one of several different power supplies that have a matching socket on the front panel of the supply. While a permanent and “bolted down” installation is always the preferred method, this more temporary approach can also be useful.
N1GY- The simple Approach to Ham Radio