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 Previous: Radio Amateur to Spearhead DERA Relief Mission to Haiti |  Next: Conference Provides BPL Industry's Perspective |
By Allen Baker, KG4JJH
September 29, 2004
Mobile radio has always interested me, but figuring out how to install a system with good performance and appearance had me discouraged for a while. After reading K5LXP's "No Holes HF Installation"1 and reviews of the Icom IC-706MKIIG2 and Yaesu FT-857,3 I decided to take another look.
Requirements
My mobile rig consisted of a handheld transceiver feeding
a homebrew J-pole antenna mounted to a 2 by 4 in the bed of my pickup. I hit
most local area repeaters but discovered I was missing the excitement of HF. I
came up with the following wish list:
The size and mounting schemes of the IC-706 and FT-857 convinced me that I could satisfy requirements 1, 2 and 6--provided I could come up with suitable brackets. Having no SWR meter and external speaker posed some problems, however. Most screwdriver antennas are manually tuned with a toggle switch while watching the SWR meter. Mounting the transceiver in the rear compartment also meant the speaker would be in a place where I couldn't hear it.
Gathering Ideas
Riding with NG4T to a local hamfest, I examined his mobile system and was impressed with the setup, particularly with his sound system. The audio output was fed to a cassette deck with an adapter and excellent sound was coming out of the car stereo system. This helped solve the third requirement. I also examined the other mobile antennas and mounts in the parking lot. Of the small screwdrivers that caught my eye, one in particular looked promising. The Yaesu ATAS-120 is designed to work with the FT-857 by automatically tuning the antenna without an external switch or SWR meter--these features are built into the rig.
My truck has an aftermarket radio with CD player and no cassette. Searching the internet, I discovered a FM modulator. These units connect to the vehicle's FM radio antenna jack and modulate external audio inputs to the FM radio band. The JVC model KS-IF2004 appeared capable of doing the job at minimal cost with the ability to choose from eight preset FM frequencies, stereo or mono audio input and automatic source switching. I started my installation by purchasing the least expensive item first.
 The JVC KS-IF200 FM Modulator. |
Putting the System Together
While waiting for the FM modulator to arrive, I began to look at mounting a remote head in the desired location. Detailed dimensions of these heads and brackets were nonexistent, so I made scaled pictures from published ads and dimensions. I printed and cut out the images to see if they would fit.
The IC-706 faceplate cutout fit but its height would
prevent it from clearing the hinged Radio/CD door above. The FT-857 faceplate
was actually smaller than the Radio/CD and would easily fit. By removing the
plastic pocket (mounted below the Radio/CD) I was able to see how much space I
had and how to mount the FT-857 faceplate to the existing radio/CD bracket. I
bought a couple of Stanley brackets and some 2 x 36 x 1/8 inch aluminum stock
at Home Depot. The aluminum was cut to a length of 6-1/2 inch and #6
thread-cutting screws were used to fasten the brackets. I needed the FT-857
remote head bracket and faceplate depth dimension to complete this part of the
installation. There are several informative articles in the ARRL Lab Notes5
as well as General Motors6 and Ford7 installation
tips and should be followed as closely as possible to minimize interference.
 The FT-857 remote head bracket. |  Top view of the FT 857 remote head attached to the mounting bracket. |
Radio Installation
Placing the FT-857 remote head bracket on my homebrew bracket, I began the project. I drilled screw holes and spray painted the assembly flat black to reduce its visibility. Power is wired with 12 AWG wire. The FM modulator is so small and light, I fastened it to the bottom of the radio/CD using double-sided foam tape.
Wiring Installation
I routed all the wiring away from the electronic control module (ECM) to reduce the possibility of interference. Removing the driver side floorboard trim, I looked for a convenient grommet in the firewall. The only penetration was full of wiring and I could not force the two #12 AWG wires through without cutting the grommet. I drilled a small hole in the firewall and use one of the new grommets. Keeping the wires near the chassis, I routed them from the battery area toward the firewall and cut the harness several inches away from the new grommet. I stripped the insulation back and soldered the new #12 AWG wires, adding electrical tape and heat shrink tubing for insulation. These harness extension wires were routed to the rear seat compartment where I reattached the other end of the harness in the same manner. While the path was open, I installed the remote head, speaker, and microphone cables from the compartment back up to the remote head in the dash. To keep from breaking the delicate clips on the RJ-45 plugs, I fished a stiff wire through any tight openings. Looping the cables around this stiff wire and temporarily fastening them with electrical tape, I gently pulled them through one at a time. I closed the floorboard trim, made all connections in the dash, and reinstalled the Radio/CD and FT-857 remote head in the dash. Soldered ring terminals to the fused end of the harness wires are attached to the battery.
 The one and only hole drilled for the entire installation was this feed through the firewall for DC power. |  The Yaesu FT-857 tucked away in the rear seat compartment. |
Antenna Installation
Installing the antenna is the most challenging part of the installation. The decisions made here will affect how well the antenna radiates. The trade-off is between optimum antenna location and what is practical. I thought about the antenna mount for several weeks and looked at most commercially available units. None of them appeared suitable for clamping anywhere in or on the truck bed. A rear bumper meant a very low mounting height. Turning again to the truck bed, I discovered the tie-downs screwed into each inside corner.
Grabbing a screwdriver, I removed one and noticed the screws were fairly large and threaded into the bed frame. I cut one 7-1/4 inch and two 3-7/16 inch pieces of 1 inch square x 1/8 inch wall aluminum tubing. To get the required spacing, I cut three 3-7/16 inch long pieces of 1 x 1/8 inch aluminum then transferred the 65 mm truck bolt spacing to all six pieces and drilled clearance holes for the 8mm mounting bolts. A 3/4 inch hole punch on one side of the 7-1/4 inch piece provides clearance for a socket wrench.
The other end of the square aluminum tubing is drilled to accept a Lakeview 276 bracket and attached with stainless steel screws and nuts. Removing the Lakeview connector, enlarge the hole to 5/8 inch, and installed a SO-239 double-female bulkhead connector. To provide more stability, add a 1-1/2 inch OD x 7/8 inch ID x 5/32 inch thick washer around the SO-239 nut to increase the contact area at the antenna base.
The final assembly is bolted to the bed frame with 8 mm x 75 mm long bolts. The result is sturdy, rustproof, requires no bending or welding and places the entire antenna whip above the cab. The bed mounted J-pole was often in the way so I added a Comet CF-706A duplexer to the FT-857 to allow the ATAS-120 to be used for 2 m/70 cm.
 The Yaesu ATAS-120 antenna and bracket attached at tie-down point in the truck bed. |  The mounting bracket for the ATAS-120 antenna. |
RFI Mitigation
The noise blanker and DSP filters on the FT-857 work well and provide the user with the ability to remove most receiver noise. At full power 2-meter FM, a squeal would result when keying the microphone. I resolved this with snap-together RFI chokes installed on all cables near the transceiver. The HF bands had some radiated RFI impulse noise that took time to reduce. I attempted to add grounded copper braid over the spark plug wires8,9 but the braid (stripped from RG-8) was too small to fit over the plug boots. I shielded the three coils and plug wires with 3M 1181 copper tape (with conductive adhesive) and grounded them to the engine block. I also grounded the engine block, hood, muffler, and antenna mount to the frame. This reduced the RFI by 4 to 5 S units. I now hear other sources of noise (windshield wipers, heater fan, etc).
 3M copper tape shielding the ignition coils. |  The sparkplug wires covered with 3M copper tape. |
Test and Checkout
 The wiring diagram for the complete mobile installation. |
After putting the system through a complete checkout, one problem surfaced. I had previously set the JVC FM modulator to automatically detect audio and turn on. This works fine for SSB, but in FM mode the squelch turns the FM modulator off after 10 seconds of inactivity. I have to use the FM modulator "remote mode" to turn the modulator on whenever the FT-857 is on. This requires fishing another wire from the FM modulator to the +13.8 V pin on the FT-857 CAT connector. The RadioShack 6-pin mini-DIN plug will fit into the 8-pin CAT socket if you cut the plastic tab off of the plug. I soldered the new wire into the plug and reset the FM modulator for remote power detection.
Tuning the ATAS-120 is a joy. Just press the rig's TUNE button and the antenna
automatically moves to the lowest SWR without taking your eyes off of the road.
It gets confused on which way to go sometimes, but it resets in a minute and
then travels to the correct length. The stock whip is 0.078 inch OD and is very
flexible but bends a bit too much in the wind during interstate driving so I
enlarged the hole and replaced it with a whip from an Iron Horse antenna.
 The finished project almost looks like original factory equipment. |  The remote head removes easily with only one connection to worry about. |
Conclusion
All of my goals were met with the exception of having to drill one hole in the firewall. For safety, the equipment is securely attached to prevent flying objects in the event of an accident. All wiring is installed to minimize hazards and interference. The dash-mounted remote head looks like a factory installation. The transceiver is hidden from view and there are no meters or speakers hanging from the dash or console. The controls are within inches of the gear shift, coupled with automatic antenna tuning, it's easy to operate while keeping both eyes on the road. The rig and antenna can be removed and used for home or portable use in several minutes. The FT-857 and ATAS-120 provide continuous coverage on all bands from 6 through 40 meters and 2 m/70 cm. I am very happy with the performance, operation and appearance of the system.
You may contact the author at kg4jjh@arrl.net
Notes 1M. Brueggemann, "K5LXP's No Holes HF Installation". 2"Icom IC-706MKIIG HF/VHF/UHF Transceiver," QST, Jul 1999. 3"Yaesu FT-857 MF/HF/VHF/UHF Transceiver," QST, Aug 2003. 5E. Hare, KA1CV, "Mobile Installations and Electromagnetic Compatibility," Lab Notes, QST Mar 1995. 6"Radio Telephone / Mobile Radio Installation Guidelines," GMNA Engineering Centers, General Motors Corporation. 7"Mobile Radio Installation Guidelines," Ford Motor Company. 8S. G. Downs, WA6PDP, "Automotive RFI Elimination," QEX, Jan/Feb 2000. 9B. Johnson, K2BJ,"Noise Suppression Techniques". |
| Previous: Radio Amateur to Spearhead DERA Relief Mission to Haiti | Next: Conference Provides BPL Industry's Perspective |
