More Changes to Ham Radio

If you follow my Facebook page, then you may remember that I relocated my Icom ID-5100A ham radio display to its third home about a year ago. It started in front of the gear shift in 2016, moved to the center vents in 2018, and then to the driver’s side vent in 2019. This location has been working well for me. However, I wanted to address the limitation of being able to use only use a tiny UHF antenna whenever I have a rooftop cargo box or basket mounted (see photo below). I devised a plan to remedy that. In the process, I decided to make other changes since I was already digging into things…

I had quite a mobile ham setup on my Mk3. It was packed with electronics and had a crazy “antenna farm” on the trunk lid. I worked the HF bands during my 330-mile weekend commutes. I decided to pare down to a single antenna when I moved to a Mk6 Jetta TDI. I continued to maintain the sleek look by mounting just one antenna on my “StealthGTI” as well. I used the existing sharkfin antenna hole to mount a very sturdy and reinforced NMO mount on the roof. It will accept any antenna with an NMO mount, and others by using an adapterClick here to see how I did it.

I was happy with this setup for a few years. However, I wanted to be able to use the workhorse 2-meter band (144-148 MHz) when carrying rooftop cargo. An idea came to me when I was making a DIY awning for my roof rack. It was the first time I had cut the rubber strip on my Rhino Rack to use t-slot mounting bolts. If t-slot bolts worked for an awning, then why not use one for some sort of antenna solution?

First, I had to find a way to get the coax out of the car and to the crossbar. I did something unorthodox for the first 12 inches of coax: I attached an NMO-to-SO239 adapter to my existing Breedlove NMO mount, followed by a right angle adapter to point the coax toward the front of  the car. The coax enters the crossbar through a small hole that I cut in the rubber topper (see photo below). Next, I needed a way to mount an antenna to the end of the crossbar, clear of the rooftop cargo box.

I chose Laird’s SBTB3400 NMO mounting plate. I bored out the center mounting hole to accept the M10 t-slot stud that I used on my Rhino Rack. I use Diamond’s C101NMO mount, which features six feet of RG-316 cable. I raised the mounting plate about ¾” with black spacers to clear the bottom of the antenna mount, then placed a black cap on the M10 nut. I had planned to tie wrap the coax to the crossbar. Surprisingly, I was able to hide the excess cable in the vacant areas of the t-slot channel. It’s completely hidden!

My 38-inch Comet SBB-5NMO antenna is almost perfectly impedance-matched at 147 MHz, just as it is when attached directly to the roof, and still reads 1.3:1 at 144 MHz. My other antennas will mount to this location, too. However, they don’t tune as well since the roof rack is not electrically tied (bonded) to the body of the car; nor, do I intend to do so. Half-wave antennas work well without a ground plane. All of this planning and work had me wondering, “Why don’t I gather my Yaesu FT-857D parts and to get this car on the HF bands?” I’ve never been a huge HF user. But I am a fan of maximizing the capabilities of any car I own. I saw no reason why I couldn’t at least get the radio installed and working while stationary.

First, I had to find a way to mount a second display to the dash. The outboard ProClipUSA vent mount is tall enough add a second Icom MBA2 display mounting plate, which would hold my FT-857D display. I routed both display cables through the vent. As you can see in this photo, I also glued a second external speaker to the dash. Next, I installed speaker, RJ-11, and RJ-12 cables to mimic Yaesu’s YSK-857 separation kit. A total of six cables connect the displays, microphones, and speakers to the electronics panel in the cargo area. The microphones hang on the driver’s door. I also added a homemade microphone connection box that enables me to conveniently remove the microphones when parked in public areas at night.

The FT-857D’s display is a cozy fit above the ID-5100A. But it fits and visibility is excellent. I can reach all of the controls very easily. Even if I couldn’t, the DTMF microphone has most common functions built into its keypad. The FT-857D’s chassis is mounted to the electronics panel in the trunk. This panel holds my ham radios, audio equipment, and a 12-volt distribution network. It includes a total of 13 quick release cable connections at the front, just in case I need to remove the entire panel for maintenance or recreation without having to unfasten any wiring from the panel. I have addressed the physical attributes of the electronics panel, my subwoofer upgrade, and a sophisticated 12V power distribution network on separate pages. All are complex enough to warrant their own pages.

I use a Comet CF-706 duplexer to connect just one antenna to two separate radios. The duplexer automatically routes 1.8-54 MHz signals to/from the FT-857D and 75-550 MHz signals to/from the ID-5100A. Most of the time, I have my Comet SS-460SBNMO VHF/UHF antenna mounted to maintain the car’s discrete looks. That limits me to using only the ID-5100A. But, when I travel or have time to work HF, mounting my Yaesu ATAS-120A gives the FT-857D a useful antenna while still providing VHF/UHF service to the ID-5100A. Without a doubt, the ATAS-120A is a “compromise antenna,” ideal for neither HF nor VHF/UHF. What it is, however, is a relatively compact screwdriver antenna that performs adequately and is easy to mount, tune, and dismount. I’ve talked with people up to 5000 miles away via skywave propagation when solar cycles were favorable. Sure, there are plenty of better antennas out there. But they are not as convenient as the ATAS-120A. Click this image to see a photo that shows my GTI with each of the antennas I use.

I’ve included a photo album with photos of THIS project below. See the photo album on my updated Communications Page for details about the comms system as a whole.



About Scott

I grew up near Houston, TX and served in the U. S. Coast Guard for over 30 years. I have an electronics background and continue to work in the electronics engineering field. I taught myself the basics about automotive systems as well as how to perform some of my own maintenance (cars and bicycles). I became involved with Amateur Radio and computers in 1995. The explosion of technology has made my job and several of my hobbies quite interesting. My hobbies include Volkswagens, bicycling, photography, electronics, amateur radio, web management, and reptiles. Visit my websites to learn more.
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