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Reviews Categories | Antennas: HF: Vertical, 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: 35 Average rating: 4.3/5 MSRP: $429.95
Description: High Efficiency 7-21.5 MHz Continuous Coverage Magnetic Loop
Product is in production.
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WA6MJE Rating: 2/5 Jan 12, 2013 20:00 Send this review to a friend
Variable Capacitor Mis-Aligned  Time owned: 0 to 3 months
I just purchased the MFJ 1788. And of course I had to drill out the mounting holes like everyone else. After ten years of manufacturing this same product, MFJ has yet to address this minor but annoying issue.

Here is the real problem. The loop will tune 15 meters and the bands below until it gets to 40M. At that point it will tune down to about 7.125mhz as shown on my antenna analyzer, but no lower. I need to go all the way down to 7.0 mhz to work CW and JT65.

So then I moved the loop all over my yard, and put it higher, and lower to see if this problem was specific to my location, and nothing made it tune lower. Then I took off the lower covers, and played with the inner loop configuration from round to oval and back again as the manual suggests, which changed the SWR at 7.125 but did not allow it to tune lower than 7.125 mhz.

I then took off the upper covers, and noticed that the variable capacitor plates are not aligned properly. The variable plates are closer to one side of the fixed plates than the other. In other words, on a scale of 1 to 100 with 50 being the center line between the plates on the fixed bank, the variable bank is about at the 80 position, very close to one set of plates on the fixed side, and very far from the other set. It should be half way (50 on a scale of 100) or equidistant if it were within design specifications.

At the low end of the tuning range, the plates are fully meshed, but the misalignment would likely produce less capacitance than when properly aligned, and this likely explains why it will not tune below 7.125.

I see no way to adjust the alignment of the capacitor variable and fixed plates to that it will tune the bottom of the 40 meter band as advertised.

I was hoping that this would be the exception to the lack of MFJ quality control rule, but sadly here I am again in MFJ hell. It will be awhile until this is worked out with them.
KB8BO Rating: 5/5 Sep 7, 2012 11:54 Send this review to a friend
Exceeded Expectations  Time owned: 0 to 3 months
I received my MFJ 1788 two and half weeks ago. Everything worked fine out-of-the-box. I have been pleasantly surprised how well it works. I have had other mag loops made from 1/4" copper tubing that are far less efficient than the 1788. I have made a/b comparisons with my inverted L antenna. On 20 m and above, the 1788 is usually better than the inverted L. On 30 m, it is almost an S unit down from the inverted L. And on 40 m it is about an S unit and a half down from the inverted L. For its size, I am pleasantly surprised at its performance. By the way, I haven't yet put it outside. It is standing vertical in a spare bedroom on the second floor.

The only downside is that it is more noisy than the inverted L. This is consistent with the other mag loops that I have owned. The literature says that mag loops are quieter than most other antennas, but my experience has been just the opposite.

Overall, I would highly recommend the 1788 to anyone who has antenna restrictions. Be careful of where you place it, because metallic objects do have an effect and moving it or turning it can make a drastic difference in the SWR. Here again, this is consistent with other mag loops that I have owned.
STAYVERTICAL Rating: 5/5 Aug 7, 2012 03:07 Send this review to a friend
Antenna restricted no more  Time owned: 3 to 6 months
The lure of a small yet effective H.F. antenna is the holy grail of many hams.
The MFJ1788 I have is a nice piece of MFJ engineering, and works like advertised.

The ABS cover does not seem waterproof but I think it is thick enough to do its job of protecting the insides from most of the weather.
In fact I simply put a plastic cover over it, have not found it affects performance, and solves the weather problem.

When I first received the loop I had to do the usual final finishing which others have described.
Widening the holes on the mounting brackets to avoid putting in the bolts at an angle and cross threading the nuts inside.
I would suggest first putting in the bolts with the brackets gently by hand and if there is any binding - stop and widen the bracket holes.

The control box was in good condition except that the reflected power needle was off zero.
After opening the box and gaining access to the meter, a simple adjustment set this right.

Apart from those two things the unit was ready to go and has performed very well on 40m to 15m.
It is annoying to have to do some final finishing, but being used to building Heathkits and fixing old radio's it was not too onerous.

It is expensive, but it is not simply a loop but also a cross needle power/swr meter and controller.
Overall, not a bad package - and if you are a ham without space for a big beam or have HOA restrictions this little giant can save your H.F. operation.

Well done MFJ.
KF4FM Rating: 5/5 Jun 8, 2012 07:50 Send this review to a friend
Great antenna  Time owned: more than 12 months
My MFJ-1788 loop is a fantastic antenna and works flawlessly when properly tuned. Tuning can be a bit tricky at first, but becomes easy with use. I find that tuning to the strongest receive signal first, makes it quicker and easier to fine tune to the lowest SWR. That practice also eliminates fine tuning to a frequency you decide not to use because it's busy.

My 1788 is horizontal at 22 feet and I've worked South Africa from east central Florida with very good signal reports both ways. I was very careful to install it away from too much metal as instructed in the manual.
N3OV Rating: 3/5 May 15, 2012 11:25 Send this review to a friend
OK- But a chore to use.  Time owned: 0 to 3 months
OK- After waiting two months the 1788 finally arrived. Being antenna restricted I mounted it vertically seven feet off the ground. 65 ft of Davis BuryFlex good quality coax. Pain to tune. But you do get use to it after some trial and error. High SWR on 40m 2.5 to 3. Better SWR on 20M 1.5 to 2.0 I will attempt to remove the outer covering and adjust the internal tuning loop as stated in the manual. Worked Spain with 100 watts on SSB 20m....Fl, IL, GA, NC all signal reports. Works but a chore to use.
N1LS Rating: 2/5 Mar 28, 2012 13:25 Send this review to a friend
No MFJ support  Time owned: 0 to 3 months
As with other reviews mounting hardware must be modified to make it work. Remote Control box was received with Freq Controls pushbuttons all pushed in and nonfunctional. With HRO help got a replacement from MFJ. Sent back the broken one. Second unit meter light does not work. Fine Tune up/down led's don't work. "Beeper" does not work. You can at least tune the antenna now. Called MFJ and talked with two techs who said I should return it. Would send me return info. Two weeks later...still waiting. Did open unit and found two wires to meter lamp shorted together making lamp inoperable. It does tune but I stll lack all the functionality of the remote box. Poor workmanship- great idea!
VK2LC Rating: 4/5 Nov 20, 2011 21:26 Send this review to a friend
Good antenna when you fix it  Time owned: 0 to 3 months
Ok its MFJ, so that means it has been put together by a first year apprentice and needs finishing off. First of all the brackets dont fit so as in previous posts you need to file out the slots to make it line up with the threaded holes in the main support.

My controll box was bent and needed panel beating must have been that way when packed as no damage to control as it was wrapt in bubble wrap and boxed in tight.

Ok once you finish the quality control and ensure nothing else will fall off it works extremely well. It is about 1/2 to 1 "s" point down compared to an inverted V on 40 meters which is my band of choice and very quiet. Tuning is tricky the first couple of times but a snap once you get the hang of it.

The tuning changes with temperature so sometimes you need to tweak it mid qso.

In summary, quality control is zero, design is 5 out of 5 and ease of use is 4 out of 5. I'd buy another one, but would be nice not to have to fix it before use
KC2RMO Rating: 5/5 Nov 9, 2011 09:40 Send this review to a friend
I'm Amazed!  Time owned: 0 to 3 months
I've only been using it for a couple of weeks, but have been making contacts that far exceeded my expectations. It only takes a little time to get used to tuning it. Pricey? Yes! Does it work? YES!
W4AFK Rating: 3/5 Oct 2, 2011 13:16 Send this review to a friend
How I fixed my MFJ-1788  Time owned: 0 to 3 months
OK... I repaired the antenna (see previous post) as follows:

1. Removed the bottom back cover from the antenna.

2. I cut the bolt with the captive heli-coil.
BTW, I know it's not a real "heli-coil", but you understand what I mean.

3. Bought replacement SS bolts @ Lowe's.

4. Bought matching SS Hex w/Nylon Insert, Lock Nuts.

5. Expanded the slots in the saddles so that the bolts can be straight. This was the most important step! If the bolts are not straight, it's very easy to cross-thread them and as press-fit nuts are not that solid, they pop out.

6. Mounted the antenna to the mast (1x uses the lock nut the others use the stock mounting holes/nuts) <-- It's truly amazing how >> easy << it is to install once the bolts are aligned properly!

7. Reassembled the back cover.

8. Installed the antenna on a ground mounted tripod.


a. Match your mounting holes to the COTS saddles you provide! On my antenna, it was >> impossible << to keep the bolts straight without expanding the slots in the saddles.

b. Add a paragraph in the assembly manual about proper alignment of the bolts. They should be easy to screw. If not, there is a problem. The results are the cross-threaded bolt and the "Imagineered" solution I had to come up with. It wasn't fun for a brand new antenna but hey, I did not want to go though the RMA & exchange process especially since it took almost 3 months to get mine.

BTW, I searched the web and noticed that I was not the only person who has experienced this problem. Could it be a tolerance issue?
N0AH Rating: 5/5 Sep 18, 2011 11:28 Send this review to a friend
Cool Beans! Thx ARRL School Grant!  Time owned: 0 to 3 months
Love this antenna. We went with the MFJ-1788 15M-40M model over the 10-30M model-

1. Working DL's on 17M from Denver with the antenna 4 feet off the ground in test mode was awesome- KH6 was also worked-

2. Now we have the antenna mounted for the Acres Green Elementary School (KD0NIV) Rabbit Ears Radio Club-

3.Tuning is a bit tricky, but using an antenna analyzer, we can find our exact resonant points quickly, then fine tune- Kids will learn a lot with this antenna-

4. It really does have a low profile, and out of the box, everything was there-

5.Mounted horizontally at 25 feet now with Diamond 2M/70cm antenna 2 feet above it. The loop antenna was slightly affected, raising it's resonant point 100KHz, but no problem in performance.

6. Excellent instructions- manual is very informative too of how this antenna works- very surprised by the details, fb!

7. Thx to the ARRL for the school equipment grant! And to MFJ for working directly with us, and HRO for their excellent service-

8. Antenna took only 4 weeks from order date to arrive-

We would take this antenna anywhere to work DX or a contest- It is just fun- Would make a great Field Day antenna too- but keep in mind that EVERYTHING near this antenna can mess with it- Would suggest an ideal installation is to mount it in the clear- even if 4 feet off the ground (-; Kids are loving it- lots of magic in this antenna......

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