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Reviews Categories | Antennas: HF Verticals and Wire | 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: http://force12inc.com/sigma40XKinfo-001.htm
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KY6R Rating: 5/5 Apr 10, 2003 08:32 Send this review to a friend
Try This  Time owned: 3 to 6 months
I was very skeptical about a vertical dipole at first - before I bought one I built a full sized 30M vertical dipole and it stunk. And other shortened antennas that I've used also stunk - especially trapped verticals.

I then downloaded a copy of EZ-Nec and started comparing full sized horizontal (up 1/2 wl) and full sized vertical dipoles (up 2 feet). I actually thought the vertical dipole looked worse until I reduced the size (in EZ-Nec) to the Sigma's size.

That's when I realized that the Force-12 hype on their web site was true. Its all in the low take off angle - because the gain and the pattern sure don't explain why these work so well.

Of course, nothing beats on the air success.
 
KG6AMW Rating: 5/5 Feb 9, 2003 21:23 Send this review to a friend
Excellent Product  Time owned: 0 to 3 months
Assembly
This is a quality package. Everything was present when I opened the box. The hardware, coils, cross members, balun and main vertical sections are separated and completely sealed or taped for easy identification. Assembly was quite easy. Everything is marked with letters with line crossing over between to the pieces that connect so you can line it up.

Putting it up
Putting up the antenna was not difficult.Just make sure your support is solid.While this antenna isnít heavy, with the coax coming out of the center and the fact you will be tipping it up and down, this antenna needs solid support.

Performance
Performance for this vertical was measured against an Alpha Delta dipole at 35 feet.

(10 Meters) SWR ranges from 1 to 1 at 28MHz up to 1.5 to 1 at 29.6 MHZ.
New Zealand (4/3 Vertical 5/5 Dipole)
New Zealand (5/7 Vertical 5/7 Dipole)

(12 Meters) SWR 1.3 to 1 through the entire 12 meter band.
Johnston Island (5/9 on first call with vertical. No answer on Alpha Delta)

(15 Meters) SWR 1.5 to 1 through the entire 15 meter band.
Japan (receive only, 5/8 on vertical, 5/7 on dipole)
Johnston Island (5/9 on third call with vertical)

(20 Meters no adjustment) SWR 1.3 to 1 up to 1.7 to 1 for entire band.
Several USA stations, 5/8 vertical, 5/9 dipole)

This is a good performing antenna. Most of the time it matched the dipole in performance and at times exceeded it. Keep in mind however, its the ionosphere that determines the difference. What you should be looking for is having several antennas to meet all the different conditions your going to run up against. There will be times a vertical will perform better and times the dipole will perform better. It does seem the dipole performs better during day light hours and the vertical performed better in the evening.

Recommendation
The one issue I have with the antenna has to be with the fold over base. It has two bolts with nuts separated 2.5 inches. Remove one, and the base hinges on the remaining bolt. For the life of me, getting the one bolt removed was a major pain. Once I removed it, it would not go in with the weight of the antenna present. When I looked through the hole, it seemed lined up, but must have been just off enough to be a problem. I ended leaving the one bolt in and put in a screw driver (just slightly narrower) which was a better fit and with the handle present it was easy to remove and put in.

Given the fact that this antenna will be up and down quite a bit,lose the nut and bolt system and replace it with a smooth hardened metal shaft that has a handle for gripping and cotter pin at the other end to hold it in place.

Other than this one recommendation, I highly recommend it.
 
WA2BHJ Rating: 5/5 Feb 2, 2003 13:59 Send this review to a friend
great for size  Time owned: 0 to 3 months
I have a tough situation. Small lot. (Too small for 80m dipole and only 40 feet wide, hence no room for radials on 80.) No trees bigger than about 20 feet. Lots of houses around and man-made QRN on low bands. Living on the side of a hill that faces SW (into the Pacific ocean void). Cranky neighbors behind me who are obsessed with their "view". I needed a decent 40m antenna to get 40 m dxcc, work contests, etc.

This antenna works far better than the CW40 (too low), the half sloper I had (too low), etc. by 2 s units or more. Have worked nearly all the European LP that has been on in the mornings (I live in California.) The evening, shooting East, are harder, but it works adequately then too.

I'm not always able to break pile ups. Some of those who beat me have high dipoles. Still, I'm very happy with the performance, given the size of the thing. I'm looking foward to trying it on 30m later in the year.

Painting this antenna green and positioning it behind a tree (the antenna is only 16feet) is very stealth. I dug a hole, put a 1 1/2 foot pvc pipe in the ground, and put a bit of concrete around it. I can easily lift the antenna in and out by myself, e.g. to adjust the coils. I use two ropes to "guy" the lower "T" element to keep it from turning in the wind.

Now, if I could just solve my 80 m problem, I'd have 5bdxcc. (Can't go with the 80m sigma--too high for the neighbor situation.)
 
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