Mobile HF Installation – Part 2/4 (Bonding and Choking)

Transceiver Ground

Transceiver Ground

This article will cover the second phase of our Mobile HF project – bonding and grounding.The following is a summary of the phases of the project:

We have been having fun with our new Mobile HF installation in our 2009 Ford F-150 Pickup Truck. We are currently using a simple HAMStick antennas to operate on the 20m and 40m bands. The initial installation focused on getting the radio installed in the truck and working and while this was successful, we have had to work around quite a bit of electrical noise when the vehicle is running. The noise was S9 without the Icom IC-7000 Transceiver’s Noise Blanker turned on and about S3-S4 with the Noise Blanker on. Most of the noise sounded like ignition or fuel injector spikes (it was engine speed dependent) and I understand that this is quite common with the Ford F-150 Truck. This past weekend, I set about solving the noise problems via a combination of Bonding and Choking techniques. An excellent source on how to approach this can be found on the K0BG Mobile HF website.

The first step in the process was to ground my radio to a solid point on the truck’s body. I used 3/4″ wide ground braid from DX Engineering (picture above) for this purpose. I was fortunate that my F-150 had Truck had good ground straps installed between the body and the frame at the factory (although I do plan to supplement these with heavier straps in the future).

Power Connection Choke

Power Connection Choke

Next, I added Type 31 choking material to the transceiver’s power and antenna leads. I added a total of three beads on the power leads (one in the engine bay close to the firewall and two on the interior side of the firewall). I also installed choking material on the antenna coax near the radio. The correct way to install these beads is to coil the cables through them as many times as possible to form an effective RF choke. With these initial steps, my noise fell from S9 to about S6-S7 without the Noise Blanker.

Hood Bonding

Hood Bonding

The next step was to bond the hood of the vehicle to the rest of the body via 1″ wide ground braid. These were made from material that I purchased from DX Engineering and they were installed on both hood hinges.

Body Bonding

Body Bonding

I also installed two bonding straps between the cab and the bed of the truck (one on each side).

Exhaust Bonding

Exhaust Bonding

Finally, I used kits from DX Engineering to bond my exhaust system to the frame of the truck. This needs to be done in three places – at the exhaust pipe section which is connected to the engine, on the mid-pipe which leads to the front of the muffler (shown above) and at the tail-pipe which leads from the rear of the muffler to the rear of the truck. Exhaust system bonding is probably the most effective technique for reducing electrical noise in most installation and mine was no exception.

With these additional steps, I my noise level was reduced to S0! While I still have a faint amount of engine electrical noise, I can operate without the Noise Blanker on and with a lower level of Noise Reduction than before the steps outlined here. My installation is much quieter overall and I find that I am hearing many more stations than I did before. There is still more work that I plan to do in the future including bonding the truck’s bed to the frame at all four corners, improving the existing factory grounding between the body and the truck’s frame, and bonding the four doors to the body. For now, my Mobile HF operating experience has been improved considerably.

The next stage of our Mobile HF project will be the installation of a Screwdriver Antenna. We also plan to install a mobile HF amplifier for high-power operation as well as other upgrades.

– Fred (AB1OC)

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12 thoughts on “Mobile HF Installation – Part 2/4 (Bonding and Choking)

  1. Great write up Fred. I am planning on a similar setup in my Subaru Impreza using the MFJ HF mini stick and IC-7000.

    You say that you “installed choking material on the antenna coax near the radio.” My understanding is that the choke was inside the vehicle near the passenger side kick panel. Am I right? I ask because K0BG insists that you need to install the choke outside the vehicle.


  2. Fred, thanks very much for taking what must’ve been a lot of work to document your installation. Fine job! It’ll prove very beneficial to me as I install my own mobile rig into a 2006 F150. I’ll be using a TS-480hx and a Tarheel 75a screwdriver, but the fundamentals are certainly the same.

    Great job and 73,


  3. I’m trying to get my setup into a 2001 ford ranger. I’v installed a 30amp noise filter.
    But reading about the bonding sounds more in line of what I need to do. My noise sounds like ignition plugs and wiring . But I done a tune up using resister plugs and wiring. And it’s not the fuel pump. bonding is my next trip. And reading a coil or two would help. Ford ranger’s are bad for this kind of noise !
    thanks .. Steve

  4. Just found your blog. Great info. I’m starting to install ft 857 in a 2010 GMC Sierra. Did you Bond body to frame? If so what method did you use to attach to frame. Was cab to bed sheet metal a body to body bond.

    • Hello Jeremey. Thank you for reading our Blog. Yes, I did bond both the body and the bed to the frame. In general, its best to bond everything to the frame if you can reach it with reasonable length straps. Sometimes, all you can really do is to bond body parts together. An example would be a hood or trunk lid bond. I hope that this helps you. BTW, the exhaust pipe and the motor block bonding steps did the most good in our installation.

  5. I was directed here from the Scorpion antenna site. Nice blog! I am in the process of installing a screwdriver antenna in my Ram Pickup. The placement of your mount is what prompted me to read the blog. I do have a few questions.
    First, the mix#31 beads just clamp around you power and control leads? I was under the incorrect assumption you had to wrap the leads around them. Second, do you find the DXE RG8X working well for your installation? How much coax is needed for the 7 turn wrap through the bead? Thanks Bert KD8JSE

    • Hello Bert,

      Thank you for reading our Blog! You do need to wrap as many turns of your control and power leads as you can around the ferrites. See the pictures in the following post –

      I custom made the RG-8X coax cables for my installation so I don’t have an exact length for you. As long as you keep the cables reasonably short and don’t exceed 500W you should be OK with RG-8X.

      Good luck with your project!


      Fred, AB1OC

      • Thanks Fred! Sorry for my confusion, but I did see these pictures and from the angle it looks like the leads just pass through the center of the bead. Also, in another post there is a picture of the power lead where it enters the firewall. It appears to have no wraps.

        I did read K0BG’s very informative write up on RFI and Bonding. In his description of making the chokes he mentions using only 60 inches…

        So am I correct in saying you ran the sheathed motor and control wire back to where the antenna was, stripped off 60 Inches of outer sheath and wound that through the bead then terminated it at a connector? …and did this for each pair?

        I will be staying well below 500W so the RG-8X will be my first choice!

        Thanks for your time! Bert KD8JSE

      • Correct and don’t forget to place a second set of chokes where the control cables exit the cab.

        Fred, AB1OC

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