- Amateur Radio (Ham Radio) Community

Call Search

New to Ham Radio?
My Profile

Friends Remembered
Survey Question

DX Cluster Spots

Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement

Reviews Categories | Antennas: HF: Verticals; Wire; Loop | Force-12 Sigma 40XK Vertical Dipole Help

Reviews Summary for Force-12 Sigma 40XK Vertical Dipole
Force-12 Sigma 40XK Vertical Dipole Reviews: 13 Average rating: 4.8/5 MSRP: $289
Description: 40 - 10M "Manual Band Change" antenna
Product is in production.
More info:
Email Subscription
You are not subscribed to this review.

My Subscriptions
Subscriptions Help

You can write your own review of the Force-12 Sigma 40XK Vertical Dipole.

Page 1 of 2 —>

W7RIP Rating: 5/5 May 19, 2012 07:46 Send this review to a friend
Working well after 4+ yrs  Time owned: more than 12 months
I have been spending some time research hex beams and other antenna options, and it gave me pause to reflect on my current antenna. I have had the Force 12 40XK in continuous operation for going on 5 years and it has endured four Montana winters and is still 100% original. The past week it has been effective for working DX stations from Yemen and Senegal (also thanks to good propagation!!) and has been a good investment for my situation. There seems to be good support from the new owners at Texas Antennas, so there is no reaon to think that it could not last for a very long time. Of ccurse, I would like to put up an antenna with some directional gain and that is what led to this update. 73s W7RIP
W7RIP Rating: 5/5 May 2, 2010 05:01 Send this review to a friend
Two + years & still outstanding  Time owned: more than 12 months
This is an update to my evaluation in 2008. I use this antenna almost daily and it stays up in all kinds of Montana weather with four dacron line guys. I am still very pleased with this antenna. Since I do not change bands very frequently, I do not have issues with taking it down to add coils for other bands. Construction is first class and performance is very acceptable for a vertical dipole. I have been a fan of vertical dipoles for a long time since I used wire vertical dipoles while a maritime mobile with excellent results. I will check back in another two plus years! 73s W7RIP
K0MD Rating: 5/5 Aug 26, 2008 14:24 Send this review to a friend
Excellent Antenna  Time owned: 0 to 3 months
I bought this antenna for portable and Dxexpedition use. I took it to Chile and operated from the South and from Vina del Mar, by the ocean. It was a phenomenal performer!! I received 599 reports from across Europe, Japan and the USA. I could work anyone I could hear.

It is easy to assemble and easy to tune. It is a solid, well built and well designed antenna. It disassembles into short sections which make transport on an airplane quite easy. Assembly takes 10 to 15 minutes and disassembly takes a similar amount of time. I used an outboard tuner with it and had it resonate on 80 meters also.

The factory ships it with all of the parts clearly labeled so that a non-ham could easily assemble it. I had two physician colleagues help me with the assembly and they could do it without the instruction manual.

Force 12 has high standards for design and construction. You will not be disappointed with the quality or the performance.

This antenna is a Real Winner!
KA6LAF Rating: 5/5 Feb 20, 2007 14:49 Send this review to a friend
Not bad  Time owned: 0 to 3 months
I recently got this antenna to use temporarily until I can get some larger aluminum in the air.

I currently have it mounted in my back yard, about 3 feet off the ground, about 20 feet from the rear of my two story house.

I used it in the ARRL DX contest this past weekend, and am actually reasonably surprised how well it worked. With 100W, I was able to work mostly everything I could hear. The exception to that was that there were fairly strong long path EU signals on 40M that while strong on receive, I couldn't work them. On 10-20M though, I could work everything, except I couldn't crack bigger pileups.

Bandwidth is not great, and the 30/40M coils/hairpin arrangement is pretty hokey, and as others have said, the coils are very tempermental. Just a very slight deformity of the coils will through the resonance point 200kHz off. I found the resonant point I was interested (finally) and found that I can get the SWR to a perfect flat 1:1 on 40M usually. Separating the coils moves the resonance point up the band, squeezing them lowers it.

I think a good RF choke would be a good idea with these also.

Once you know the 30/40M coil setup, you can quickly change bands in a matter of a minute or two. If you're using it for a contest or not using it on the WARC bands, then it's even easier. The T-bars used for 20 and 40M are the same, then there's a smaller set for 15M and no T-bars for 10M. Easy! So band changes between 10, 15 and 20 are simple, and going from 20M to 40M requires addition of the loading coils and hairpin. Again, not bad once you have figured out the position and size of the coils for resonance.

All in all, I'm happy with it. The price is high though for what it is, but at the same time, it works reasonably well. I would like to use a set of the full(er) sized Sigma 80's for an 80M parasitic array, which I will likely do when I get my tower and 10-40M yagis in the air.

Incidentally, delivery for me was immediate. I called, ordered, and had the antenna in 2 days.
N6TZV Rating: 2/5 Oct 16, 2006 18:21 Send this review to a friend
Sloppy Execution  Time owned: 0 to 3 months
I ordered the Sigma 40XK in June of 2006. I was there when they called in the order to Force 12. They quoted six weeks. It arrived in late Sept. 12 weeks, not six.

That would be fine if they had used the extra time to build it with care. Instead, holes were all hand drilled, off center, some were not deburred, and all required some touch up. There were many obvious efforts to cut costs including a cheapened unenclosed balun unlike the pictures on their web site. Instead of swaged ends on the tubing as shown in the manual, crude crooked slots were cut so that hose clamps could compress to hold the elements in place. Screws are too long and, as noted by another reviewer, WILL snag your hand and cut you when raising and lowering.

Finally, the coils are wound out of common insulated wire and do not hold their shape. If you change bands between 20-10M all is well. The materials are very high quality, and the settings are repeatable. But when you reinstall the coils for 30/40M be prepared for six or more trips outside to get it back in resonance. The resonance point also changes in the rain on 40M.

Once you get it tuned, it works quite well, but on 40/30M this is a pain. A small compression of the coil moves resonance 100KHz.

Bottom line: They did their engineering homework. It works when adjusted. But the build quality is sloppy, and the mechanical arrangement of the coils will make you pull your hair out. Either set it and forget it on 40/30M or only use it for 20-10. That's my opinion.
NI0C Rating: 5/5 Jul 21, 2005 14:27 Send this review to a friend
Sturdy & Effective Antenna  Time owned: 0 to 3 months
I purchased the antenna during Force 12's April sale and received it about 7 weeks later. I installed it four weeks ago today, and have spent one week each using it on 17m, 20m, 30m, and 40m.

When I unpacked the antenna, I thought at first that the four 0.500" x 48" T bar tubes were missing. They were hiding inside the 0.625" tubes of the same length! I was impressed by the beefy vertical portion of the antenna with welded T bar supports. This antenna is built to last. Band changes from 10m thru 20m are accomplished by adjusting the lengths of the top and bottom T bars. Because of general band conditions this Summer, I started out on 17m.

For 20m, 30m, and 40m, the T bar lengths stay the same (approx. 86" per side, top and bottom). The 30m and 40m bands require installation of loading coils (one for each side of the vertical dipole), plus a hairpin match coil. With the antena installed at the factory recommended height of four feet above ground, the antenna is 20 feet tall, with a maximum wingspan of about 15 feet.

I was able to get a good match on 17m and 20m using the factory recommended T bar lengths. As might be expected using a short antenna with loading coils, tuning the antenna on the lower bands was more involved. I had to take down the antenna three times to adjust the 30m coils, and five times to adjust the 40m coils. The factory recommended 0.25" spacing on the hairpin match coil gave me a low SWR on both bands. On 40m, loading coil lengths of approx. 2.5" gave me resonance in the CW portion, and 2:1 SWR bandwidth is at least 150 KHz.

Although I purchased the optional tilt-base, the wingspan of the antenna does not allow me to lower the antenna by tilting (too many shrubs and trees surrounding the antenna). Instead, I lift the antenna and mounting base out of the pipe I have buried in concrete to hold this (and other vertical antennas). Since the balun assembly is perpendicular to the T bars, a saw horse or lawn chair is needed to support the fully assembled antenna when it is taken down.

On the air performance has been very good. I worked an A6 for a new one on 17m, a YI for a new one on 20m, plus a UA2 for a new one on 30m. Not bad for summertime DX'ing.

The instruction manual was complete and accurate.
8P6SH Rating: 5/5 Aug 27, 2004 23:19 Send this review to a friend
Great first impressions  Time owned: 0 to 3 months
This is a short review after just a few days with the antenna. I'll review again after I've had it running for maybe 12 months and a complete contest season.

When I first saw this antenna advertised, I decided thiw would become my main 40m antenna rather than it's other two more expensive family members for 40m.

It arrived well boxed and clearly marked and assembly was very very easy. I'm still not fully settled on the fianl mounting arrangement but for the moment it's mounted with the bottom bars about 5ft. above ground.

In my anxiety to set up the antenna quickly, I think I must have attached the balun incorrectly, because it wouldn't tune up on any band.

Finally, I disassembled the entire thing and reconstructed using an ohmeter to check everything. It's SWR is now perfect on all bands up to 20m. I will try it on 40m again soon.

The performance on 17m really surprised me, and it really keeps the bands open longer. I worked a few stations on the first call barefoot, and if the performance is anything like this on 40m, then it'll be a killer 40m vertical.

I've found the manual band changes work quite nicely.

I just think there should be a couple more pieces of hardware for the 10-24 bolts used at the feedpoint.

It's also very very strongly constructed. It's not as they say "your daddy's vertical".

F0EGG Rating: 5/5 Jan 3, 2004 13:41 Send this review to a friend
Fun and Extreme Performance  Time owned: 0 to 3 months
Got antenna from good friend in USA- Long for the antenna:

Tried many multiband verticals. Designs with and without radials. Many had their positives and negatives. Those compared to include Gap Titan (deaf), MA5V (great ears but limited to 250W), Hustler 6BTV(solid leaning tower Pisa but needs ground radials) and Butternut HF6V(took forever to build but worked best outside Sigma-40XK) and a home made 20 meter vertical (did ok). Also, a couple of wire dipoles (bad for DX, too low at my QTH).

Nothing hears better so far than this antenna and my signal reports from the Sigma 40XK are very satisfactory comparing to those using home made beams and small yagi's. I like to play with antennas, so manually changing element lengths is part of fun and discovery for me. Best band is 20 meters.

Many assembly concerns. First, bolts used are too long and present a danger when raising and lowering antenna. They can stick right through your hand. Also, hose clamps (pressure clamps) are all over sized creating excess that can also rip a gash in your hands. Strongly suggest using gloves when raising/lowering antenna.

LOve idea of this antenna on a DX'pedition. Rated at 3KW, the only concern I would have is to bring two baluns in case one fails and to check for proper alignment of assembly holes fixed easily by a drill. One of mine was off centered and was easy to fix at home. But would be a big problem on an island.

Two unique problems I encountered when first installing antenna. My SWR resonant point would not go below 2:1 until I raise the base of the antenna's lower bars to at-least 3 feet. At first, the lower bars barely were off the ground as my concrete PVC mount was deep into the ground.

When raised up, then the SWR flatened out to 1:1 accross entire band as manual said it would. I drilled a hole through PVC and antenna to hold it up in place and still have about 10 inches of the antenna in the concrete below ground. So it's not going anywhere-

Only on page 5 of manual does it comment on effects of lower bar elevation effecting antenna and thats only pertaining to take off angle. I think the manual should give a recommended height for lower bars off ground to help newbies get started.

Next issue were my elements were 5 inches shorter on each side for 20 meters vs manual's suggestions. I can see an inch or two but not sure how a total of 10 inches impacted antenna. I had to from 86 inches to 76 inches. But to go from 20M to 17M, you are suppose to shorten elements from 86 inches each side to 48 inches. So it takes more element adjustment than I am use to compared to other types of antennas and maybe this is within expectations?

I just need more time to experience setting up antenna on all bands but once I have the element lenghts figured out, I can pull antenna off supporting PVC and switch bands 10-20M in less than 5 minutes-

Going from 30-40M takes more time as you then have to incorporate coils but you are only adding another 5 minutes for this. Not something I would want to do in storm or at night but easy none the less.

This antenna hears band openings early compared to other verticals and hears band closures later, just like a beam. It is built like a tank and very stealth. Only my MA5V is maybe less noticable but rated at 250 watts, it does not keep up and recent reviews have QC issues.

My Alpha 99 runs full legal with no problems-

Strongly suggest for field day or DXpedition. Not surprised Team Vertical has set so many records with this antenna class.

Manual suggested K6AJ used this antenna on 80M using larger coils.......this is a much needed market niche for those of us wanting on 80M but wanting smaller antennas. Gap Titan gets close but is rated at only 500 watts for this band and is stone deaf here vs long wire. Hoping Force 12 puts coils out with future accessory items-

Antenna was well boxed, manual EASY to follow if you understand radio, and quality materials. I feel lucky to own this antenna- And finally, have found my answer to a very decent backyard antenna vertical for hamming. TU Force 12
VK6AV Rating: 5/5 Aug 25, 2003 11:04 Send this review to a friend
Great DX antenna  Time owned: 0 to 3 months
I use the 40XK in less than ideal circumstances. It sits about 4 metres (12 feet) from a brick wall that is about 1.8 metres (6 feet) tall and 4 metres from a two-story house. It is mounted on the tilt base. Assembly is simple. While the 40XK is described as free standing, the tilt base is lightweight so one set of guys should be used. I didnít do this at the beginning and the first wind storm (it really blows in Perth) put a slight bend in the tilt base. I purchased a hard-sided golf case to transport the antenna from the USA to Australia.

On 40 metres, I make contacts on the U.S. east coast with good signals running just 400 watts. It is also an excellent performer on 30 metres. Of course it is slightly noisier than a horizontal dipole but if you donít have room to put up a dipole that is not a real issue. I have not yet used it on 20 through 10 metres because I use a Sigma GT5.

When conditions are good this is a great DX antenna.
KC0OTU Rating: 5/5 Jul 7, 2003 00:36 Send this review to a friend
Outstanding Product  Time owned: 0 to 3 months
First QSO was RZ4 on 20m barefoot using < 100 Watts! This was also my FIRST DX QSO - Talk about exceeding expecations!

This antenna is easy to assemble, but do keep in mind that this manual band change antenna. With that said, I would recommend taking time to make this as painless a process as possible. Give some thought to various mounting possibilities - especially if you want to move this around. You will need something sturdy at the base. I also advise using a couple of ropes to 'guy' the antenna, taking some strain of the feed point and for safety. As suggested, I use a cotter pin, instead of a bolt at the folder-over base.

When operating, the SWR was near or at the specs. Thus far, I have not needed an antenna tuner. The included manual needs improvement. Despite this, it's obvious that Force12 designed a GREAT antenna.
Page 1 of 2 —>

If you have any questions, problems, or suggestions about Reviews, please email your Reviews Manager.