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Reviews Categories | Antennas: HF: Vertical, Wire, Loop | MFJ-17758 80/40 Meter Dipole Antenna Help


Reviews Summary for MFJ-17758 80/40 Meter Dipole Antenna
MFJ-17758 80/40 Meter Dipole Antenna Reviews: 7 Average rating: 4.6/5 MSRP: $79.95
Description: The MFJ-17758 is a two band, 80- and 40-Meter center-fed dipole antenna capable of handling 1500 watts. Its total length is 85 feet. Each side of the dipole is broken up by a coil that presents a high impedance at 40 meters and acts as a loading coil on 80 meters, allowing the antenna to resonate on 80 meters even though it is physically shorter than a half-wavelength (approximately 130 feet at 3.7 MHz).

Because this antenna acts as a dipole on both bands its impedance is around 50 to 70 ohms, permitting it to be fed with coaxial cable. The use of a current balun between the coaxial feedline and the antenna is highly recommended, to help prevent stray RF from traveling down the coaxial cable’s outer shield. This is easily accomplished with an MFJ-915 RF Isolator and a “double male” coaxial connector (MFJ-7702).
Product is in production.
More info: http://www.mfjenterprises.com/products.php?prodid=MFJ-17758
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You can write your own review of the MFJ-17758 80/40 Meter Dipole Antenna.

WA0RXR Rating: 4/5 Dec 19, 2016 14:19 Send this review to a friend
Good antenna  Time owned: 0 to 3 months
I bought this antenna to solve a space problem for an 80/40 dipole. When I put it up, it was much too long on 75, as I expected. I was able to shorten it up quite a bit, but I found it was resonating well below 40 meters, too. I had to remove the clamp before the coils and shorten up the 40 meter portion of the antenna. Once I had that within the 40 meter band, I was able to finish up adjustment of the 75 meter portion.
The antenna performs very well on both bands. Be prepared to do some work on it and you will be well satisfied with the result.
 
K6SDW Rating: 5/5 May 13, 2014 22:08 Send this review to a friend
MFJ winner!  Time owned: 6 to 12 months
Like all us city dwellers a full size 80-10 dipole is hard to find room for and besides I have up a tri-bander and 20-6 mtr vertical so I bought this antenna to cover just 80 and 40 and I wasn't expecting much, I mean its MFJ ya know!!

Well, at 85-ft for 75meters and 1/2 wave on 40 this dipole way exceeds my expectations!!

On 40 it's just a 1/2 dipole, no big deal here and using the K2 auto-tuner I easily cover the band. But on 75/80 meters, I'm impressed and amaze how well my signal gets out -- and it fits my city lot which is cool because I'm able to use neighbor's trees at either end of my lot and get the dipole up higher and still fit!!

Of course on 75, band coverage is very tight, only a few Kc's either way from the center of the band. Thankfully, my K2 tuner handles the SWR fairly well and I can work the entire band. Now, with an amp running 1,000watts this might be another story.

The ARRL Doctor is in, W1ZR, ran an analysis of this trapped dipole and found there would be about a 1/2 db drop in my signal from a standard 1/2 dipole on 75mtrs. Well, a 1/2 db on this band won't be missed.

My opinion is the construction is excellent. I haven't run more than 100 watts into the antenna, so I can't speak to running 1,000 watts into it, but I'm thinking all should be good once I get my amp going again.

Cheers All!

ed
 
AK6ZZ Rating: 5/5 Apr 19, 2013 03:05 Send this review to a friend
Great antenna for small lots  Time owned: 3 to 6 months
I bought the MFJ 17758 loaded 80/40 dipole not expecting a lot. I bought it when my SteppIR three element antenna trombone for 40m broke and I wanted to also try 80m which my lot couldn't support a fan or full sized dipole easily. I hung the antenna at 30' in an inverted v position with each of the legs at about eight feet. Since I put it up in November 2012 I have worked probably 20 new dxcc entities on it for 40m (total now 94 worked) and 18 new dxcc entities on it for 80m (total now 24 worked) all from the west coast. My 80m experience with the dipole is way beyond expectations. It is about to go back up because I had it down for a Super 33 Mosley install but for 80m I doubt I could do better on this small lot. I have had many surprising reports from Europe that they couldn't believe I was working them on a loaded dipole from California. Best MFJ product I own.
 
K4FMH Rating: 5/5 Apr 9, 2013 11:59 Send this review to a friend
Really, really effective.  Time owned: 0 to 3 months
In an HOA community, I have an 80 meter loop put an inch underneath the edge of my shingles, entering the attic space in a soffit to a 4:1 balun. It was built by Maple Leaf Studios just for me. It works very well.

However, I picked up this dipole while visiting MFJ during their 40th Anniversary just to see how it would compare. I had already built and installed a G7FEK multiband dipole but it didn't perform nearly as well as the loop. My roof has the radiator-backed roofing material inside the attic, which is great on energy savings, but open to testing with an actual antenna. (Note: the foil-backed plywood sheets are not bonded together.)

My installation was underneath the ridge vent cap, angling downward at each end where the respective coils are located. I don't understand the ratings of this product having poor construction quality. It is first-rate and I especially liked the metal trough-and-screw devices used to shorten or lengthen the copper stranded wire at the 40-meter and 80-meter ends! No cutting! I added a few zip ties to keep the final fold-back sections of wire tight against the main wires. Couldn't be an easier tune-up for a dipole when using my antenna analyzer.

This dipole gives me a directional gain to the NE/SW which I do not have with the 80M loop. And, it has low noise even in proximity to my HVAC and tankless water heaters. This dipole is well worth the cost, especially since I don't quite have the attic space for a straight running 80M dipole.
 
W8MLD Rating: 5/5 Dec 13, 2012 19:32 Send this review to a friend
Great for a small lot  Time owned: 3 to 6 months
I did have to mod it with a 1:1 current Balun, but at less than $30 for one that can handle 1.5KW it wasn't a bank breaker. So far the antenna is performing superbly on 40 and 75/80 meters. At 85 total feet long it fit nicely between the front and backyard trees. I have nothing to complain about it. It is made better than some $125+ antennas out there. Thankfully they replaced the ceramic insulators with high strength PVC/plastic ones. For someone with limited space that wants to get on 75/80 meters you can't go wrong with this antenna
 
W7MRR Rating: 4/5 May 11, 2008 08:07 Send this review to a friend
Good idea, poor construction and components.  Time owned: 0 to 3 months
This antenna works as advertised, but uses cheapy components and is poorly constructed. I had to replace the center connector (I used a 1:1 balun for better matching), re-solder all the connections and replace the ceramic insulators with the non-breakable kind. Just seems like a lot of money for some wire and coils. After putting it up, I got 350 kcs of <1.5:1 SWR on 40 meters and 50 kcs <1.5 kcs on 75 meters. The addendum to the installation instructions for setting up for the center frequency is right on.
 
WB8ICU Rating: 4/5 Mar 11, 2007 20:04 Send this review to a friend
works for me  Time owned: 0 to 3 months
I have always hated trap dipoles, because most are set up to favor the phone bands. This one is totally adjustable and actually comes adjusted BELOW the bands it works. It takes a while to adjust, but once done, it works good across 40 and about 50khz of 80. Since I only work cw, no problem. I tried it out on 40 and 80. On 40, its as good as the dipole I replaced, and on 80 I can now work without a tuner. The swr goes right down to 1:1 on 80. On 40, minimum was 1.5, but it covers the whole band. I used an mfj analyzer to set up, which makes it a lot easier. Its still a trap dipole, but its more adjustable and more cw friendly than most.
 


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