Survivalism & Self Sufficiency Topics > Amateur Radio Gear Reviews

MFJ-17754 40/20 Meter Dual-Band Dipole

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Alan Georges:
Last year I reviewed this thing's big brother, a similarly constructed 80/40m dipole (http://thesurvivalpodcast.com/forum/index.php?topic=44578.0).  It's still working great, even after a year out in the weather.  So I picked up the smaller 40/20m for go-gear, and it works great too.

Beyond saying "same thing, just 2x smaller," here are a few more particulars:

- I rigged it as a 90deg inverted V, from a 20' PVC mast.  Tuned up pretty easily.

 - It covers both the 20 & 40m bands completely, though admittedly the SWR was pushing 3 at the edges of 40m.  An internal tuner like some HF rigs come with can handle it fine.  So it will let you do CW, PSK, etc. on its longer band and still let you talk on that band too, without going outside to lengthen or shorten any wires.  This is in contrast to the 80/40, which will do all of 40m, but can only handle about the bandwidth of the phone portion on 80m– or the code portion if you choose to lengthen things out, take your pick.  Anyway, this smaller one will handle all of 20 & 40m bands while keeping the SWR < 3.

- Works great!  Talked to Carl last Sunday on 40m with the bigger 80/40 and on this smaller 40/20, and got a better signal report (maybe an S-unit or so) on the smaller antenna.  Of course, band conditions were bad-to-variable at the time and it was only one QSO, so this wasn't exactly a thorough test.  But I'd say, compared to a full-sized 40 similarly deployed, this trap dipole doesn't compromise the signal in any significant way.

- Maybe my usual 20m double bazooka is a tad quieter, it's hard to tell without having the two up at the same time.  Anyway, this thing works about as well on 20m, and I made a few phone and PSK contacts on it in these tests.

- Its yard footprint is much, much smaller than that of the 80/40.  As an inverted V from a 20' pole, it's only about 40' long.  Lots of yards can manage that.  (Your HOA may be another matter...)

- The copperweld wire is thinner and easier to handle than on the 80/40m.  It doesn't tangle so much, and if it does, it's much easier to sort out.

- With those last two items, this antenna much more go-bagable than its 80/40 big brother.  The whole thing spools up fairly neatly around a plastic coffee can, and my 2m slim Jim rolls up inside the same can.

Looking at the results from a poll on which HF ham bands people use (http://thesurvivalpodcast.com/forum/index.php?topic=50705.0), it's pretty clear that 40 & 20m are the two most popular ones.  It makes sense to focus on these for a go-kit, and the trap coils give this antenna 40m capability for not much more length than a 20m-only.  I won't say that it's the perfect HF antenna, or even my favorite HF antenna, but if I could only have one antenna this would probably be it.

Here's a link to the mfg's web site: http://www.mfjenterprises.com/Product.php?productid=MFJ-17754  The list price is about $60.

Carl:
And I must add that Alan and I are only 200 or so miles apart and that represents NVIS ,a near vertical bounce of the signals to come back to earth that close. It in no way indicates a weakness of the antenna or installation of the antenna. NVIS makes HF HAM a viable medium range communications mode.

 The gear ,at my end,is a 20/40 meter inverted "V" with wires for each band tied to a 1 to 1 balun as a common feed point...with these two wires 25 feet at highest point,I work 40 and 80 meter NVIS,and all bands 80 through 6 meters with my radio's 3 to one internal taking up the slack from not having a set of wires stretched for each band.

My radio,powered by solar charged battery, runs at about 20 watts (though I could turn it up to 100 plus ,if needed) as power is really not so much a component of capability as are propagation and antenna...and LUCK.

My antenna is loosely modeled after a military command HF antenna the AS-2259 , below is a link to some modifications and original plans to set up your own,with a auto or manual tuner it covers all HF bands.These file are FREE,just as I found them,and if you claim ownership...I will gladly remove them on request. Hosted on my Google Drive for safe downloading.

https://drive.google.com/folderview?id=0B5ZIZLZV4AwIY3NoMkthTEVQRE0&usp=sharing

Saint-TyR:

--- Quote from: Carl on July 25, 2014, 07:20:03 AM ---My antenna is loosely modeled after a military command HF antenna the AS-2259 , below is a link to some modifications and original plans to set up your own,with a auto or manual tuner it covers all HF bands.These file are FREE,just as I found them,and if you claim ownership...I will gladly remove them on request. Hosted on my Google Drive for safe downloading.

https://drive.google.com/folderview?id=0B5ZIZLZV4AwIY3NoMkthTEVQRE0&usp=sharing

--- End quote ---


Awesome! Thank you for sharing! I am just getting into the HF set-up and I am always looking for another antenna system that can be set up  and taken down quickly.

Stay Safe!

Carl:

--- Quote from: Saint-TyR on July 25, 2014, 08:11:24 AM ---
Awesome! Thank you for sharing! I am just getting into the HF set-up and I am always looking for another antenna system that can be set up  and taken down quickly.

Stay Safe!

--- End quote ---

With the files I hosted,many versions ,or variations,of the AS 2259 can be tried. all with the same 'basic' configuration and modifications for various additional bands etc. With an auto tuner (LDG is a favorite) at the antenna feed point  you have a very frequency agile,LOW LOSS ,due to tuner at antenna end of feed line, antenna system that uses a single support and ground anchors to support it...I have tossed a parachute over the antenna ,with me and vehicle under the shade/camo to take advantage of a system that takes minutes to errect and has so much potential for NVIS and long distance communications...PLUS is a usable shelter..the mind wobbles with possibilities.

  My home antenna is the slightly modified version with a proper 20 meter and 40 Meter wire (40 just 2 feet over true cut length) to provide full coverage of 80 thru 6 meter bands ..3.4 to 54 MHZ with the auto tuner! it is cut for 20 and 40 meters as they are my most used bands and I do gain just a little TX and RX improvement with wires cut for those bands. But the AS 2259 offers many possibles in a small package , my backpack version uses a 20 foot carbon fiber fish pole that weighs near nothing,collapses to 18 inches ,and the whole antenna(with auto tuner) weighs just a few pounds and fits in a day pack with the radio , battery (lithium ion) and 10 watt solar -folding panel. I know ,I am a little light on the solar, but these days I don't stray far from the vehicle as age,diabetes,and cancer ...have a way of slowing one down a bit.

Canadian Prepper:
Thanks fellows!

That's lots of info to digest about both the MFJ and NVIS antennas. I'm hoping to augment my MFJ portable vertical with another reasonably portable setup. Just my luck the local ham outlet only carries the 40/80m version of the dipole discussed by Alan, which might be just small enough to fit in my yard. I might just have to ask them if they can order it for me.

I was looking at the MFJ 33' telescoping pole several weeks back, but decided that since it could only really be used for an end fed at my location that it wasn't really that much of an improvement over what I've got for over $200 once everything is ordered and shipped. OTOH, I could get a 20' crappie pole around here for about $20, and if there's an antenna setup that would work with it, that would be perfect. The provincial emergency net up here uses 40m, and an NVIS setup would be perfect for covering the region.

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