Friday, March 13, 2020

Mobile HF/VHF/UHF Install

Icom IC-7100 install I did in my 2013 Chevy Impala LTZ covering 2m/70cm, and HF.

My main sources of information were:
  • K0BG.COM - dedicated to mobile amateur radio operators, ABCs is a good starting page.
  • Mobile Radio Systems (QRZ forums) is a good place to search for info, and post questions.

Choosing a Radio

K0BG has a good page called Miniature Radios which covers all the usual suspects.

The Icom IC-7100 is my choice for mobile, covers 160m thru 2m, and 70cm, all modes. DSTAR is an added bonus.

It's well worth spending a few bucks on rtSystems programming software, you can buy it and download it directly from them and use the supplied Icom USB cable.

Icom made the QST July 2014 review of the IC-7100 freely available at

KV5R wrote a review covering both the good points and annoyances at

Several more Icom IC-7100 reviews can be found online.

Daughter investigating the IC-7100

Radio Mounting

Radio mounted under the center console where it meets the dash, my 2013 Chevy Impala has an ideal space for a radio of this size to fit in there and easy access for the cabling. I also got the optional mounting bracket to maintain an airspace around the radio.

Control head mounting took some research, in the end I settled on a Ram Mounts RAM-B-102-UN10U. The "large phone/phablet" grip will hold the oddly shaped IC-7100 control head, makes it easy to remove and reposition.


Power Cabling

K0BG covers the important details in Wiring & Grounding.

I used the following items from Powerwerx:

Finding a way through the firewall in a 2013 Chevy Impala, the 2000-2005, and 2005-2013 W body Impalas use the same chassis, they have a rectangle rubber plug that can be pulled out in the passenger footwell just under the top of the carpet.

I poked a hole in the top right corner through the rubber boot with a screwdriver, then taped the power cable and coax to a piece of wire and fed it through.

Where it exits in the engine bay is close to the power steering pump pulley, I was able to cable tie the power cable and coax to the factory loom, there is enough space to freely run it between the factory loom and the firewall following the loom up with out coming into contact with anything.

Once I had the cables through, I cut a notch out of the rubber plug to allow room for the new cables and reinstalled it, I later realized I should have put a blob of RTV silicone around where the cables pass through the boot to seal it..

Pictures, note the pics of the cable passing through the firewall into the engine bay I took when pulling the cables through, as noted above they are neatly cable tied to the firewall side of the factory loom.


Antennas and Mounts

Coax I used is LMR-200, it's the same size as RG-58 but dual shielded and lower loss. HRO sell LMR-200 per foot at a reasonable price. I used silver plated crimp PL-259 connectors.

  • Larsen NMO 2/70 antenna I've had for a few years.
  • The NMO Mount from Amazon, this one appears to good quality. I sealed where the coax is crimped with some RTV silicone and heat-shrink tube over the top.
  • I mounted this one on the rear left (passenger side) with an NMO L bracket.

  • I used this Firestick 3/8 x 24 stud and mount from Amazon. Mounted this on the left front/fender of the car. The shape of the bracket had to be modified slightly by reducing the bend in the bottom L and the next bend up so that it would lean outwards allowing the hood to close and be level. Not having a vice I gave it a couple light taps with a sledgehammer and got lucky. I also had to level the bracket by packing one end with 3 thick washers and use a longer (than supplied) stainless sheet metal screw. I coated the screws with "Jet-Lube SS-30 Pure Copper Anti-Seize 12555" to prevent rust and maintain a good electrical connection. 
  • Single band Hamsticks - HRO sell MFJ and Shark Antenna versions of these, I got the Shark!
  • At the antenna end 9 turns of coax through a pair of 3/4" mix 31 clamp on ferrites from Palomar Engineers. No common mode currents here!
  • Grounding braid to bond the hood and trunk lid, HRO sell ABR industries 233/2-G4-10 - 10ft 1/2 inch braid with nickel grommets. 
  • K0BG covers bonding and grounding in detail.
  • I'd like a screwdriver antenna, my choice would be the Little Tarheel HP.

The SWR with the ham sticks is high, I'll need to make an matching coil as K0BG suggests in Antenna Matching. I made a temporary one out of some bare #14 copper wire I had and got 1.2:1 match on 40m (bandwidth is narrow as expected), 20m has been a problem to get matched, I suspect part of the issue might be that I have not yet bonded the hood hinges with the braid. I'm planning on making the coil removable so it's only installed when I have an HF antenna on the car.

As you can see the power cabling and coax is neat and out of the way cable tied to the factory loom that passes through the firewall.

Disclaimer: None of this is an endorsement of specific items, suppliers or manufactures, it's what I decided to use based on available information, personal preference, and/or what I already had.