With EmComm being one of my main interests with Amateur Radio, I found that I had a need to fill a gap in my mobile setup. While at home, I can talk to just about anyone almost anywhere in the world. When mobile, I had a gap from about 20 miles away to about 150 miles out.

With my base station and my portable antenna systems, I cover this gap with HF and an inverted V using NVIS propagation, but setting up the inverted V while doing portable operations is very time consuming. Especially if there is wind and it needs to be guyed. Plus, who want to spend an hour doing a setup and tear-down if you only need to operate for a few minutes to either have a voice call or send a quick email/text message? I know I don’t. So, I got a little creative.

I want to share this because, while extremely simple to accomplish, I haven’t seen this anywhere. When I have something that works that doesn’t seem to be too well known or at least not well published, I like to share. I hope it helps someone else get where they need to be on their EmComm or entertainment setup.

The short of it (I know, too late), I used a hamstick to make a single element NVIS mobile mounted antenna. Digital testing was conducted with 2 Winlink Peer to Peer messaging sessions and a connection to an RMS. I also conducted voice tests.

The Winlink testing was mobile to base at distances of 145 miles, 96 miles and 87 miles. All well outside of LOS propagation and too close for traditional reflection and refraction of low-angle skywave propagation. NVIS propagation was also confirmed by placing the antenna fully vertical and there was zero signal reception on either end.

Additionally, voice testing was conducted with multiple stations at 20 miles, 35 miles and 190 miles. The plus side is, there is a little more to it than NVIS, as I was also able to speak to people well outside the NVIS coverage area, as far as 746 miles. This is a good indication that there is still significant low-angle skywave propagation occurring at the same time NVIS propagation is occurring. Providing a bit of flexibility in communications.

Another advantage of the design is, though you cannot drive while the antenna is fully deployed, you can swing the antenna over the cab and drive. When you get to where you need to operate, you can simply swing the antenna out, lock the jam nut and start transmitting.

If you would like to replicate what I have, it’s fairly inexpensive. The total cost was about $70 and an hour of work. The parts are…

A UHF mount to the bed of the truck (for flexibility with other antenna options)

MFJ PL259 to 3/8x24 adapter

Wilson 10" Replacement CB Antenna Shaft (actually 12 inches long)

Two jam nuts

One 3/8x24 barrel connector

A 75m hamstick with a 3/8x24 detachable upper whip

One 102 inch steel whip 3/8x24 antenna

To get the angle I needed for the antenna, I used a press to bend the antenna shaft to about a 40 degree angle (the weight of the antenna sags to the correct position). I mounted the MFJ adapter to the antenna connector, put jam nuts on each end of the antenna shaft and spun the bent antenna shaft onto the adaptor. I put the barrel connector on the top of the antenna shaft and locked it in place with the top jam nut.

Once the foundation was in place, I screwed the loading coil from the 75m hamstick on the end of the extension. From there, I used the steel CB whip as the main element, since the 75m whip is too short for the bottom end of 80m. I cut the whip to about 2 feet longer than the whip that came with the hamstick, and then used my antenna analyzer to cut the whip to the proper length to be resonate on 3.58 MHz with the best possible SWR.

So, I know the first question I have been asked by several people already is, why not just use an 80m hamstick? Good question… and the answer is simple. Using a 75m coil and a CB antenna style 3/8x24 whip gives you less coil and more straight radiating element, being a slightly more efficient antenna. Also, the whips that come with 75m and 80m hamsticks are flimsy and sag over too far when the coil is at the proper angle. The steel whip stays straight for a better performing antenna that provides a more consistent/stable SWR.

I found that the closer the whip is to the vehicle, the worse the performance was and it harder to get a good SWR. The best performance and SWR is when the antenna is perpendicular to the bed of the truck. You see in the images and video that the antenna comfortably hangs off the side of the vehicle. You can operate while the vehicle is in motion with the antenna trailing behind the body of the vehicle. However, performance is less than optimal and there is highway safety law that need to be obeyed, relating to items extending beyond the rear of the vehicle. For example, Code of Virginia § 46.2-1121. Flag or light at end of load.

Let me know if you have any questions!