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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: 58 Average rating: 3.9/5 MSRP: $429.95
Description: High Efficiency 7-21.5 MHz Continuous Coverage Magnetic Loop
Product is in production.
More info: http://www.mfjenterprises.com/products.php?prodid=MFJ-1788
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You can write your own review of the MFJ-1788 Super Hi-Q Loop.

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K0INN Rating: 4/5 Oct 19, 2018 22:01 Send this review to a friend
Review after 3-4 years of ownership  Time owned: more than 12 months
I've had the loop installed outside on my roof horizontally for about 3-4 years. I've gotten very familiar with it during that time.

As far as the performance goes, 20m on up - very good, 30m - good, 40m - OK. I'm almost 100% a cw op. For 20m on up - I've had many international contacts, 30m - some, and 40m - pretty much just north american.

Recently, the tuning stopped working. I took the antenna down and apart and I determined that the motor gears were jamming. The motor is sealed so the only option is to replace the motor. The motor is a HanksCraft 12v 1RPM motor - the "black" motor. I contacted MFJ and they asked whether I had the black or the silver motor. Apparently a silver motor was used in older loops. There was some confusion as to exactly what part I needed by the person I was talking to and he was supposed to contact me via email to let me know the price and availability of the replacement part. I never heard back from him. In the meantime I checked ebay and there were 2 used HanksCraft 12v 1.5RPM motors listed there for 13 dollars apiece so I bought those.

I examined my antenna more and the movement of the variable capacitor was somewhat tight. I'm guessing that this led to the gears wearing and then failing. I tried to determined where the capacitor shaft was binding. There is a nylon "lash" nut installed on the end of the capacitor shaft (opposite the motor). The lash nut was causing the binding by squeezing the shaft. I removed the lash nut. I found (in my junk box) a nut the same size as the capacitor shaft thread. I used this nut as a standoff before installing the nylon lash nut against the standoff nut. After doing this the capacitor moved freely.

I've read MFJ1788 owners comments that the antenna wont tune in cold weather. I suspect that if a standoff nut were installed on the end of the capacitor shaft before the nylon nut they likely would tune correctly.

After replacing the motor and reinstalling the antenna, all is working correctly.

Since I replaced a 1 RPM motor with a 1.5 RPM motor, I adjusted the slow tune to move at a slower rate. You can do that by using a non-ferrous tool to turn a capacitor through a hole on the top of the control box.

All in all I'm happy with my MFJ1788. It's been a great stealth antenna. I painted the covers of my antenna the same battleship grey that satellite dishes are painted so it blends in quite well in the neighborhood.

I'm grateful that MFJ makes this antenna. If they put a little bit more engineering and attention to detail in the manufacturing process, it would be a fantastic antenna. I think that is where many people get frustrated - when the antenna does not work correctly out of the box.
 
GM4WCE Rating: 5/5 Sep 16, 2018 07:27 Send this review to a friend
Works well  Time owned: 6 to 12 months
I bought mine from Martin Lynch who give these a thorough checking before despatch. As a result the loop and controller worked perfectly once installed. I have mounted mine in the attic and am delighted with the performance, particularly on 40m. I use CW and digimodes and have worked the USA on both CW and digimodes on a number of occasions using 30 watts only. Around Europe is no problem during the day. Also works well on 20m and the receive noise is far lower than on an attic mounted dipole. I was planning to relocate the loop outside in the garden but the performance in the attic is so good it almost does not seem worth the effort. For the size of the antenna the performance is very impressive, although retuning is needed if moving frequency even by a small amount. It is well worth the money if you want an easy to use small multiband antenna that works well. I wish MFJ made one covering 80m, I will have to build my own loop for 80m.
 
SP9HZX Rating: 5/5 Jul 20, 2018 13:16 Send this review to a friend
Good job  Time owned: more than 12 months
Cheers for MFJ!
I am very pleased with this magloop.
Works fine in horizontal and vertical position.
Mounted on balcony about 23m AGL.Easy and fast tuning.No problem to work with any DX station
 
K6PBL Rating: 0/5 Jun 28, 2018 22:32 Send this review to a friend
Wish it worked  Time owned: 0 to 3 months
I tried one of these antennas during Field Day and it was fantastic. Good enough that I bought one the next day. The guy I bought it from said ďI hope you get a good one.Ē Well, I didnít. When it arrived, it didnít work at all. I opened the cover and found the set screw for the motor shaft lying in the case. I put the set screw in and tightened it. The capacitor rotated and stopped exactly as it should. I then sent a signal to the antenna per the instructions. The shaft rotated between the stops and the meters never moved. I called MFJ and they told me to send it back, but not to wait longer than 10 days from when I received it. The antenna is supposed to be warranted 12 months. Whatís with the 10 days?
I talked to one guy and he said it took an electrical engineer four hours to repair the antenna to work.

Itís manual tune, but I think Iím going to buy a Bushcomm instead.
 
WB9OTX Rating: 2/5 Apr 27, 2018 18:10 Send this review to a friend
Prepare to fix   Time owned: 0 to 3 months
Owned this unit for one week. It did not work right out of the box. I emailed MFJ to get clearance to fix it and I received several hints on how to fix it. I removed the 20 screws (some were not seated because there was no holes on the inside of the cover) I found the allen screw on the motor to the capacitor shaft was loose. The screw was covered by the circuit board. I had to loosen the capacitor side allen screw and 2 nuts holding the motor to get to the screw that was loose. I tightened the screw that was loose, reassembled it all like it should be with the capacitor 1/2 way closed. I put the cover back on and drilled the missing holes. It worked but the fine tune buttons had no effect. There is a hole in the top of the tuning box, I adjusted this pot back and forth several times. Now the fine tune began to work as it should. Now with the antenna only 5 foot up I made several contacts on 40 and 30 meters. With 25 watts I worked 2 stations in Europe and 1 west coast on FT8. I received as good or better than I sent. To sum it up the antenna performs very well and I am impressed with it. It is too bad that MFJ has such poor quality control.
 
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.
 
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