The Wolf River Sporty Forty is a single band base loaded coil for 40 meter operation using the Wolf River 213 inch, Chameleon CHA SS-17, or MFJ-1979 whips. Add the coil to your base of the antenna, extend the whip to its fullest length and the antenna will be resonate on the 40m band.

Wolf River Sporty Forty Coil:

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If you are familiar with Wolf River’s products, you will know of the Silver Bullet 1000. This is their flagship coil that is part of an HF base loaded antenna system for the 10 through 80 meter band. To use the coil, you connect a whip of an arbitrary whip and then adjust the coil until resonance. This system works well and lets you use whips of most any length for multi band coverage.

If you have their 213 inch whip, the MFJ-1979 whip, or the Chameleon 17 foot whip, you soon realize that you really don’t need to use the coil for 20 meters and above. Bypassing the coil and adjusting the whip length to resonance lets you use the system as a ¼ wave antenna. Then you can add the coil for the lower bands.

Seeing how users were using their products in this fashion, Wolf River came out with a new coil pretuned for only the 40 meter band. Dubbed the Sporty Forty, this coil allows you to leave the larger Silver Bullet 1000 at home for a streamlined portable antenna kit that covers 40 through 10 meters when you use the long whips.

Wolf River did send me a unit in exchange for a review, a link to the antenna can be found in the video description below.


Looking at the Sporty Forty coil, the unit is small, much smaller than the Silver Bullet 1000 or even the Silver Bullet mini. The Sporty Forty Coil measures 6 ½ by 2 inches and weighs 9 ounces. Construction is similar to the larger coils, a stainless steel wire is wrapped around a plastic form and there are 3×8 x 24 studs on the bottom and top. The bottom will screw into a stand or stake and the whip screws into the top. The coil is wrapped with heavy duty shrink wrap for protection. For power handling, the coil is rated at 75 watts digital, 100 watts CW, and 200 watts sideband.

When the coil is pared with their 213 inch whip, the system will be resonant at the bottom of the 40 meter band, or approximately 7050 khz. To move the resonant point up for phone operation, you will decrease the whip length a bit, usually about 3-6 inches. With the MFJ or Chameleon whips, the resonant point will be at the top of the band and we will talk about that in a bit.


Deployment is pretty straightforward. You screw the coil into your base, either a stand or a stake; my preferred mounting solution is this jaw clamp. Then you connect the whip and raise it up. Lay out the ground radials and connect the coax and you will be on the air. Depending on your frequency choice, you may need to slightly adjust the whip length, but otherwise no additional tuning should be required.

Now I’ve used this coil with both their 213 inch whip and the chameleon 17 foot whip. I’ve found that the chameleon whip is 11 inches shorter than the wolf river whip, so it puts the resonant point at the top of the 40 meter band. If I want to use the antenna at the bottom of the band, I need to add a bit of length. There are a few different methods you can do that, some are using extension rods, like this one, either below or above the coil, or what I’ve done is to take about 11 inches of 12 gauge solid wire and add an alligator clip. This makes my whip electrically longer and moves the resonant point down the band.

Another performance aspect that I’ve found with the coil is that your cable length and ground network can make a difference. With their silver bullet 1000, I’ve been using 8 16 foot ground radials with great results on the 40 meter and higher bands. When I use this setup with the sporty forty, that is, 50 feet of RG-8X coax and 8 16 foot radials, my SWR does not go much below 2:1. Now this may sound like a bad thing, but on investigating the situation with my antenna analyzer, I’m finding that the impedance is dropping down to 25 ohms and that reactance is almost eliminated. While my SWR is high, my antenna is almost entirely resonant. I find this to be a good thing and the SWR issue didn’t affect my ability to make contacts. In fact I’ve gotten excellent signal reports even in mediocre band conditions.

Seeing that my SWR was a bit high in the field, I decided to do a bit of experimenting and set the Sporty Forty in my front yard and ran a couple of tests. I found that with 50 feet of coax, if I used 4 radials, my SWR decreased a bit, down to about 1.8:1. Reducing my coax length to 25 feet and keeping the radials at 8 dropped me down to 1.34:1 and finally reducing radials to 4 and coax to 25 feet gave me the best performance or 1.18:1 at about 7200 khz, my target frequency.

But what about resonance? In all four tests, the reactance stayed fairly consistent, close to zero, but varying slightly. You can see on the chart how the green line, signifying reactance is consistent between all four tests. The impedance changed, though. Shorter coax increased my impedance to 50 ohms and longer coax reduced it closer to 25 ohms.

Long story short, when using the Shorty Forty, your SWR will vary depending on radial network and coax length. But the reactance stays very low and the antenna is close to resonant despite the elevated SWR.

I can see this as causing a bit of frustration with new users, especially if they don’t have an analyzer to check the numbers. You may be expecting the coil to give you perfect results but the interactions between ground and cable length skew the results. With the silver bullet 1000, you can easily fix that issue with it’s infinitely variable adjustment, sometimes giving the coil a ¼ turn fixes those other issues. But with the sporty forty you don’t have that luxury. My recommendation is to practice with it a bit, if you have an analyzer, look at the numbers to see how it is performing on all levels, and make adjustments to the ground network until you are satisfied.

Or you can be like me, don’t sweat the SWR and instead go forward knowing that the antenna is resonant and will work to great effect, even if the SWR is approaching 2:1.

So how well does it work?

I had no problem pulling in contacts with it on the 40 meter band. Even with the slightly elevated SWR, signal reports were on par with what I would expect with the silver bullet 1000 in the same configuration. The radio wasn’t running hot, nor did I notice any physical issues with the coil. My previous video of the parks on the air activation on Wildcat Mountain has more on air contacts if you are interested.

So what’s the good and the bad about the Sporty Forty. First off, the coil is compact, it sets up fast, and it has good power handling capability. If you are like me, and don’t do 80 meter portable operation with a vertical antenna, then the Sporty Forty is a great addition to your portable kit. In fact, I just may start leaving my big coil at home as this really streamlines my portable kit.

Now the bad, I think the big variable with the Sporty Forty is the whip length. The coil is designed for use with Wolf River’s 213 inch whip, so that leaves the MFJ-1979 and Chameleon 17 foot whip users a bit out. Those two whips are shorter and when fully extended will put the resonant point at the top of the band instead of the bottom. Adding extensions helps, but if the coil had a bit more wire wrapped on it, maybe like a half turn more, then those other whip users would have the same amount of versatility that the 213 inch whip users enjoy. Remember, you can always shorten a what that’s too long, but adding length can be troublesome.

Will Wolf River come out with pretuned coils to support other whip lengths or bands? Probably not. The Sporty Forty fits a very specific niche and it does a very good job at it. If you are using a non adjustable antenna like the folding manpack antenna or a 102 inch stainless whip, you are better off with the silver bullet mini which will give you the multiband support.

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00:00 Introduction
00:34 Wolf River Sporty Forty Coil
01:56 Specifications
03:11 Deployment
04:31 Ground network can make a difference
05:32 Sample Contact with Sporty Forty
06:40 Performance
10:02 Good and bad
11:18 Final Thoughts

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