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Reviews Categories | Antennas: HF: Verticals; Wire; Loop | MFJ-1788 Super Hi-Q Loop Help

Reviews Summary for MFJ-1788 Super Hi-Q Loop
MFJ-1788 Super Hi-Q Loop Reviews: 53 Average rating: 4.0/5 MSRP: $429.95
Description: High Efficiency 7-21.5 MHz Continuous Coverage Magnetic Loop
Product is in production.
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WB5AGF Rating: 2/5 Feb 22, 2018 15:40 Send this review to a friend
Very Poor Quality Control  Time owned: 0 to 3 months
I've wanted to try a small transmitting loop for several years and so a few weeks ago I ordered the MFJ-1788 (40M - 15M) transmitting loop through my local Ham Radio Outlet (HRO) store (they're only about 5 miles from me).

The loop arrived (via UPS) on my front porch this morning but it has already been sent back (and here's why).

Having heard stories about poor quality control on the part of MFJ the first thing I did after getting the antenna out of the box this morning was to take out all the self-tapping screws, remove the cover, and look inside.

There really isn't much ... the pickup loop at one end of the housing ... and the (fairly good sized) tuning capacitor (coupled to its tuning motor) on the other end.

I'd been quite curious about MFJ's claims that the tuning capacitor has its plates 'welded' (for extremely low RF resistance) and so I gave it a close inspection ... that part seemed to be OK. There is a thick bead of a silvery material (some kind of brazing material I suspect) run along two sides of the capacitor plates to bond them together and then metal 'ears' on either side of the capacitor body are welded/brazed to the two open ends of the aluminum tubing (bent into a 3 ft diameter circle) that is the radiating element.

The reason that the antenna is on its way back to MFJ (with HRO having generated a replacement order) is that 3 of the plates of the tuning capacitor were significantly melted on their edges (at first it looked like a HV arc accident) right next to the place where one side of the capacitor is welded/brazed to the aluminum tubing. I'm thinking that whomever did the welding/brazing (bonding the two ends of the circularized aluminum tubing to the tuning capacitor) was sloppy with their gas torch and they melted the edges of the capacitor plates. (I'd have thought that if MFJ has any kind of QC inspection that they would have at least filed-down and sanded the burned edges of the capacitor plates ... that might have been sufficient - but instead nothing was done to try and repair the damage.)

I still have hopes for this antenna design but when the replacement arrives (in probably several weeks) I'm going to go through the same 'incoming inspection' as performed this morning.

In my opinion this is a classic case of 'Caveat Emptor' ... let the buyer beware (and check it out).

- Paul, WB5AGF (22 Feb 2018)
KM6NFF Rating: 0/5 Feb 3, 2018 13:30 Send this review to a friend
Bad Luck I Guess  Time owned: 0 to 3 months
Well let me start off by saying I'm sure this antenna works great for some but for me It didn't work at all times 2. I'm new to Ham and ordered my first 1788 in November and received it several weeks later.The control box didn't work at all. No movement whats so ever.I called MFJ and they had me do a couple of things then determined it was broke. I sent it back then received a second 1788 brand new as well and that control box didn't work as well. The folks at MFJ are nice people but quality control is another story. I Decided to buy a Comet 250B vertical and it works great.
KB3BF Rating: 2/5 Oct 27, 2017 19:39 Send this review to a friend
Solid Loop, excellent welds, but that is it  Time owned: more than 12 months
I got the loop second hand and it still was mounted on a 20ft mast. It had not been used for a while, maybe at least a year. Luckily is was mounted horizontally because it is not water resistant in the vertical position. When i removed the loop covers i found the inside full, and i really mean full of old wasps nests, so all gaps need to be sealed. There were bad solder joints, as a few component leads were loose and the motor shaft had play, but somehow it still worked as long as I kept retuning it from time to time.
While the loop is well built with excellent welds to the capacitor to minimize losses, everything else is so-so quality, which does not reflect its cost. A stepper motor with a suitable controller would be a better choice for a magnetic loop. Luckily there are many controller designs available on the net that calibrate capacitance value with frequency of operation, so you don't need to transmit just to change frequency, and some use the excellent Arduino platform with digital display. It is time for MFJ to improve their QC and upgrade this loop design. There is real potential for a great compact antenna for portable use and for locating HF RFI sources.
EA2EKH Rating: 4/5 Mar 21, 2017 07:29 Send this review to a friend
Excellent compromise antenna  Time owned: more than 12 months
Currently I am using it indoors and I am really impressed. Retuning even for small frequency changes is a hassle, but the extremely high Q also means that it's efficient. Other more convenient loops have more losses. So no complaint there. The performance is amazing for its size.

The only problem with this antenna, however, is that many units seem to need some final touch to work.

Mine really benefitted from realigning the coupling loop properly. Trying to reshape it, as some suggest, didn't help much. But making sure that the planes of the coupling and main loop are properly aligned really made a big difference.

Beware when doing these adjustments, though. It's better to use a VNA as voltage in the loop is really high. I did it with my miniVNA Tiny.

I would certainly recommend it to someone who wants a discreet antenna. Its extremely short bandwidth also helps to mitigate interference from nearby transmitters, which is a bug plus.

I would give it 5 stars if not because of the "final touch" needed.

VA2DV Rating: 2/5 Mar 13, 2017 11:22 Send this review to a friend
Not for winter !  Time owned: 0 to 3 months
I am sorry but I must downgrade my rating after using the antenna for a couple of weeks. The tuning is inconsistent at best. I found myself retuning the loop several time during a session on the same frequency. Seems like there is some play in the capacitor movement. Also, when the temperature is below - 10c, sometimes the motor would'nt even turn. That's pretty bad for a 750$ antenna. Great idea in a poor application.
Returned for a refund. Not for cold places.
AB1XG Rating: 4/5 Jan 14, 2017 14:48 Send this review to a friend
Great When I Finished Putting It Together!  Time owned: 3 to 6 months
Received my MFJ-1788 from my ham radio dealer, it was VERY, VERY well packed, kudos in that respect to MFJ!

Got is all setup, then found out it didn't work at all. When tuning nothing happened. Though MFJ tried to be helpful during several calls, I finally figured it all out myself.

When the meter light doesn't light, you may have a problem with your antenna system. Mine did not light, but I knew everything else was OK despite this.

Yet the antenna would not tune. After disassembling it, I discovered the Allen screw that connected the capacitor to the motor armature was loose.

After tightening it, suddenly the antenna would tune like a champ!

I still have not fixed the meter lamp light, I use a more accurate LP-100A Vector Watt Meter.

Antenna is currently mounted about 12 - 15 feet up, oriented horizontally pointed east-west, it works amazingly well on JT-65 or JT-9.

I get and give good sig reports, very happy with it!

If MFJ had not made me finish assembling it, I would have given it a 5.
MI0HPE Rating: 4/5 Dec 20, 2016 20:17 Send this review to a friend
Looking good so far  Time owned: 0 to 3 months
Because I live in a very antenna unfriendly environment I have had to experiment with all sorts of ideas, especially for getting on 40 m. I Live in a three storey terraced house in the middle of the Belfast post industrial conurbation. I have found that 20 or so meters of wire in a delta loop configuration around the back yard usually works remarkably well as it can to be quite harmonic, (depending on baluns etc.)I have come up with some other weird and wonderful solutions which also do the job but the main problem is that every winter around December and January a serious Gale or two hits us and the fiber-glass poles get broken or at best knocked over, sometimes they can be repaired but it's usually 30 each to replace them. So, I decided to try the magnetic loop solution, it arrived about about 3 weeks ago and I can tell you without prejudice that I am pleasantly surprised. It's an expensive investment and a bit of a leap into the dark as magnetic loops are a bit of an unknown quantity in the scheme of things, however the results so far are very impressive. It's up in the highest room in the house surrounded by a lot of metal objects... and it actually works, even on 40m! It's a lot better on 20m but considering it works from inside the house I'm wondering how good it could be when the weather gets better and I can experiment with it on a 10 m telescopic pole outside. I have made more 40m qso's with it inside the house than all my other attempts. I have yet to discover what the efficiency is on these antennas but I think if they are properly set up outside it could be surprising. Getting qso's on 40 from inside the house is something I didn't expect.It's all been ssb so far but I suspect cw will be an experience when I get round to it. Digimodes could be very promising on these antennas as well because you won't need to tune them as much. I'm looking forward to trying that as well soon .The bad propagation conditions at the moment is a good time to work on your experimental skills and make things work for you. If the propagation was good you might get lazy 73 de Paul
AB1XG Rating: 3/5 Nov 10, 2016 09:25 Send this review to a friend
Works Well Now  Time owned: 0 to 3 months
The good:

I've only managed to get this antenna up temporarily about 5.5 feet.

Easy to tune after you get the hang of it (short learning curve).

Even at this temporary low height (horizontal) it's really works well. MFJ says it will work about on par with a dipole at the same height.

Now for the bad:

When I received the antenna, it didn't work. I called MFJ tech support, we finally determined it was due to the Allen screw that locks the capacitor in the antenna itself was not tightened to the motor armature. Fairly easy fix except for during reassembly the screw holes on the antenna body were not aligned.

Only other problem I had was the light in the meter didn't work. When I took the cover off the controller I discovered only one wire was connected to anything.

Once I got everything straightened out, as I said earlier, I really like this antenna!

MFJ should test every one of these before they go out the door. The QC tech should then place a slip in with the antenna identifying him/her as the person why tested it.

One last note and a kudo to MFJ, this thing was REALLY packed well!
VE4FX Rating: 3/5 Jul 13, 2016 06:00 Send this review to a friend
MFJ-1788 high SWR  Time owned: 0 to 3 months

I live in an apartment and decided to get the MFJ-1788 Loop after having very good experience with a homebrew loop. The homebrew loop was limited due to the cap i had but it worked well on 20 meters. The MFJ-1788 works on multiple bands but the swr is high and I can't seem to bring it down. I opened up the loop to check everything and all hardware was tight, the only thing I found was the lever on the "up limit switch" was too low and was being missed by the part on the shaft of the cap. But that didn't have anything to do with swr. I'm not sure what to adjust to get a better match. There is the driven loop or the coil at the input. I also got the wrong power supply, I got the one for 240 Volts so right now I'm on batteries
KB6LA Rating: 5/5 Apr 3, 2016 11:53 Send this review to a friend
Unparalleled performance for size  Time owned: more than 12 months
This little antenna is a brilliant piece of hardware for those who can't put up yagis, string up wires, etc. I have this antenna on a small cinder block roof mount about 6 feet up in the air, and I can work North America on digital, and often into Japan, Australia, NZ, and - if I'm lucky - Europe as well, all from Los Angeles.

The antenna design, to shrink down a multiband HF antenna into a 36" loop, is amazing. But there are drawbacks. Tuning is very narrow, and the loop requires retuning frequently. This is bad if you are an SWLer or a guy who likes to tune around the band. For me, I am usually on fixed frequency digital modes (PSK), so this is not the end of the world.

Also, I have the sense that with this design, someone could put some real muscle behind it and bang out a loop that has some better controls. Despite it being "auto-tunable", it still requires a lot of fussing to get the SWR where you want it. Look, I'm sure MFJ has done it this way for as long as they've made the loop, and I have to be grateful that they make this piece of hardware, since I think they are the only ones these days. (There used to be an AEA version, but I think that company is long gone).

Nevertheless, I give this 5 stars, because this loop - in my opinion - is really the "future" of those of who want to preserve amateur radio on HF. HOA boards are getting more and more restrictive, younger people are living in apartments and with parents longer, etc., and if you want people to be on HF and preserve it for amateur radio, we need some antenna designs that fit people's situations. This loop is about as good as it gets for size and performance wise. And I give it a 5 because MFJ is making it, supporting it (I just ordered some replacement mounting parts), and it works exactly as advertised.

If you are in a limited space, I highly recommend picking this up. It's expensive, but it's worth the price. I also would recommend the 1788 version over the 1786. Reason: if you want to be on 10 meters, it's easier to do a second antenna for that band and use it along side the 1788, than it is to buy the 1786 and try and do a second antenna for 40 meters. Plus, with the 1788 you pick up a lot of the SWL bands down near 40 meters.

Cheers and happy hunting!
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