I had a long weekend commute on quiet highways from 2006-2009. So, surfing the HF bands was a great way to help the drive pass. I was using a Yaesu ATAS-120A. Performance-wise, it can be described as “adequate, but  not great.” With my Yaesu FT-857D, tuning the ATAS was as simple as pressing a “TUNE” button… or what could be called an “EASY” button.  😉  I made some distant contacts with that antenna, even toward the bottom of the solar cycle. I took a break from HF when I was stationed closer to home; my interest in ham radio comes and goes. Eventually, I decided I wanted a better antenna. Some say the Scorpion SA-680 is the best mobile HF antenna money can buy. I decided to find out.

The Scorpion SA-680 comes standard in stainless steel. I paid extra for the “Black Widow,” which is powder coated in gloss black. Each antenna is made to order. So, I paid and waited. I got my antenna in about six weeks. It was packaged in a manner that would allow it to endure almost anything… VERY impressive. I ordered a capacity hat, too, which came in its own PVC pipe packaging. My setup is for part-time use. So, everything is easily removed when not in use. I had originally planned to mount my Scorpion on a roof rack. Setting up the rack isn’t necessarily fast, but it is easy enough to call “temporary.” Mounted on the roof rack, the SA-680 is obnoxiously tall, but still within the highway-legal limit of less than 13’6″ with the cap hat mounted (the whip would exceed max height allowances). However, I was unable to tune all of the bands.

In particular, 20m wasn’t even close to tuning. The match was terrible. That was most likely due to a lack of sufficient bonding between the rack and the body of the car. I tried straps to threaded points in the door jambs (see photos below), but they weren’t enough. I was unwilling to remove paint or make the mechanical modification needed to improve my bonding. I’m a Volkswagen enthusiast first, ham radio ranks further down my list of passions. Therefore, I abandoned roof rack mounting and moved to the hitch.

The hitch is probably the least efficient place to mount an HF antenna. But it seems to be my best option, given my desire to use the antenna as a part-time accessory. The hitch is far more convenient than the roof rack as a “temporary” mounting point. If you have a hitch, then you know that installing a ball mount is super-easy. My ball mounts are hollow and have internal threaded anti-rattle devices. Rather than a pin, I secure my mounts with a 1/2-inch bolt, capped with lock washers and a nut. It’s VERY sturdy and nearly impossible to wiggle loose without me noticing. Given the double-nut and two-inch bolt, I don’t think I can drive long enough between rest stops for the bolt to work its way out of the antenna mount.  😉 The aluminum spacer shown in this photo is a quick-release mount that used to be offered by Breedlove Mounts. It is no longer available. I bought it for ease of mounting/dismounting when the antenna was on the roof. If I’m honest, it isn’t necessary when mounting on the hitch. The 3/4″ bolt will hold fine, so long as you tighten it appropriately.

Bonding the antenna would be a challenge, or so I thought. Bonding straps are best kept short. However, there is no short path from the ball mount to the body of the car. There’s a lot of plastic back there. I decided to use the hitch itself as a bonding point. It’s fastened to the body at nine points, seven of which are at the factory impact bar locations. Electrically, the hitch is certainly grounded… but would it make a good RF ground? The answer turned out to be YES. I concluded this by connecting a bonding strap to the hitch and then comparing SWR readings with and without additional (and longer) bonding straps to body points farther under the car. The additional straps made no difference; so, I removed them. I also bonded the doors, hood, and exhaust system. See photos below.

For my first test, I compared results during a local 10m net that I’ve joined. Net control is ~15 miles away from my usual operating position. Ten meters is “nearly dead” for the time being. So, all tests were via ground waves. Using my ATAS-120A, I could just barely hear net control; he was a weak signal that was buried in the noise. He could barely hear me, as well. I told him via e-mail that I had never used 10m before and was surprised by all of the noise. He said it’s normal. A few weeks later, I went back to the same spot with my Scorpion. The first thing I noticed was a substantially-reduced noise floor. I’m told that’s because of the high “Q-factor” of the antenna. I could hear net control very well, easily a 5×5. He said I sounded much better, too. I think he gave me a 5×5 signal report.

Field Day was the next weekend. I operated for just an hour from a small peninsula in southeast Virginia and managed to make seven HF contacts. Six were on 20m, with the farthest being ~1000 miles away in Texas. I made a contact to North Carolina on 80m, which is a new band for me. [edit: 8/16/2021] So far, my most distant contact was to Slovenia, over 4500 miles (7200 km) away. [/edit] I’m tempted to install a 500-watt amplifier. Perhaps that will give me just a tad more “punch” to be heard in the distance. But pulling an additional 80 amps through my car’s electrical system would possibly introduce a new set of challenges. These are all things I must consider before stuffing more electronics into this small car.

I eventually tried a larger, 35-inch, 12-spoke caphat by W8UZZ. It increases radiation resistance and allows me to operate with even less coil exposed. I cannot claim to notice a significant improvement over the Scorpion caphat, but there’s something to be said for needing less coil to tune a band. The only drawback I’ve noticed is the additional wind loading at highway speeds. As a result, I prefer to keep my speeds at 65 mph or slower. That’s a fine speed on my local highways. However, If I’m traveling farther and on roads with higher speed limits, then I simply mount the 67-inch whip, which will tolerate flying at speeds that will send me to jail! 😉

All said, I think the Scorpion is a great purchase. Sure, I’m probably not maximizing its effectiveness the way I have it mounted. But it is a definite improvement over the ATAS-120A it replaces (I still use the ATAS for 6m). Better yet, the Scorpion will accept full legal power, which is 1500 watts for my non-ham visitors. That kind of power would be nuts in a mobile platform and probably would cause a lot of interference in the car. But adding a 500-watt amp isn’t out of the question. Maybe I’ll do that someday. Regardless, I’m very pleased to have an HF antenna that’s easy to install and remove. It gives me good performance on the HF bands while allowing me to return my car to its pretty-self in just five minutes. See more info and an install demonstration in this video.

Presto Chango,

Scott

Here is my wife’s first view of the Scorpion antenna. She had no idea it was so large. See her reaction at https://youtu.be/w0HUYnjDjsc.

Here is how I had bonded the rack. The paint on the inside of the crossbar is pierced by star washers. The bolt into the door jamb feeds into a threaded hole. This was an excellent DC ground, but apparently inadequate for RF.

I moved everything to the hitch, which turned out to be much easier.

This is the shunt coil box with its lid removed…

With the capacity hat…

With the whip…

Coax and electrical connections…

Bonding strap…

The coax enters through the bottom of the floor pan; I use this cap and tuck the SO-239 connector into the bumper when the antenna is not mounted…

My Field Day setup…

I made HF Field Day contacts from this small park on a peninsula in southeast Virginia…

Pointing eastward before sunrise with hopes of reaching Europe…

W8UZZ’s 12-spoke 35-inch caphat!

My clearance is 8’3″ with the antenna retracted…

The 67-inch whip may be less efficient than a caphat, but it’s better for speeding on the highway!