| WY3O |
Rating:  |
2022-02-06 | |
| Getting this antenna to work will be a project |
Time Owned: 6 to 12 months. |
I do not recommend that you buy the MFJ-1768 antenna owing to poor quality control, lack of technical support, and a weak warranty. I was eventually able to get it to work, so here are the key steps that worked for me in case they are useful to others. After this summary, I will give more details about my experience.
(1) To get the snap-bushings to fit into the holes, drill out the holes with a 5/16” diameter bit.
(2) Remove the circuit board from the mast.
(3) With a large pencil eraser or very fine sandpaper, lightly burnish or sand the back of the circuit board and the mast where it comes in contact with the circuit board. I discovered a light oxide layer that was preventing good electrical contact.
(4) Solder short pieces of copper wire through the vias on the circuit board to ensure good contact. (This step may not be required; see discussion below.)
(5) Remount the circuit board.
(6) Shorten the driven elements for the 70 cm array to 5 in each, using a pipe cutter to ensure a smooth and even cut.
(7) When inserting the push-washers on the elements, grooves are provided to assist getting the washers in the correct place. However, the placement of the grooves was not accurate on mine, and using the grooves for placement resulted in the elements being noticeably off-center. Consequently, you should ignore the grooves, and measure/mark the proper placement on each element. The distance in inches of the first washer from the nearest end should be (L – 1.125)/2, where L is the length of the element in inches. The second washer should be pushed on from the other end all the way to the mast, to fix the element and minimize movement with respect to the mast.
(8) In other respects, complete the assembly of the antenna according to the directions.
Here are more specifics about my experience: I discovered that the snap-bushings wouldn’t go in (the directions indicate you should just push them in with your thumb—this was impossible). Being hesitant to drill out the holes, I was able to tap them in with a hammer (a bit more than a tap, actually). However, since the holes were too small, the insides of the bushings were compressed so that the parasitic elements wouldn’t fit through them. I tried to tap one in with a hammer, but this shattered the bushing. I then reached out to MFJ technical support for help. Customer service responded the next day, and forwarded the question to the “antenna shop personnel.” Two and a half-weeks and multiple emails later, I have not received any other response from MFJ.
Having not received a response, I took a closer look at the warranty, which states simply that if you mail it back to them at your expense, they will repair it. Curiously, unlike most warranties, the warranty is not voided by attempts to repair it yourself. (This seems to indicate that having to repair things is pretty common!) Since mailing an oversized antenna back would cost a significant fraction of the cost of the antenna, disassembling it would require destruction of the push-washers that hold the elements in place, and having no response from technical support raised questions about whether or not they could actually help, I decided that trying to return it was not a promising option.
Realizing I was on my own, I drilled out the inside of the bushings so that the elements could be inserted.
However, being curious about why the bushings didn’t fit, I examined the bushings and discovered they are Heyco SB-312-3, which is intended for a hole diameter of 0.312” (https://www.heyco.com/Hole_Plugs/product.cfm?product=Snap-Bushings-1§ion=Hole_Plugs ). However, my measurement of the holes with a caliper gave 0.285”. Consequently, the more appropriate way to fix this would have been to drill out the holes in the mast with a 5/16” bit before trying to insert the snap-bushings, as mentioned above. (Apparently the factory drilled the mast with a 9/32” bit by mistake.)
Next, I discovered that using the grooves to locate the push washers as instructed resulted in the elements being noticeably off-center, so these grooves were not located correctly. I was able to properly center them by measuring as described above, but not before having to clip and replace a number of the washers (fortunately, MFJ did include several extras).
After finally getting the antenna assembled, I checked the SWR using both an MFJ-269 antenna analyzer as well as a tinyVNA, and received similar results with both. The match on the 2m band was very nice—well below 2:1 SWR across the entire band. However, the results on the 70cm band were not acceptable. The SWR was below 2:1 at the low end of the band near 420 MHz, but it was well above 2:1 in the 442-444 MHz section of the band used for repeaters. In fact, it looked like the band that was matched the best was below 420 MHz. To see if shortening the driven elements would help, I replaced the 70cm driven elements with ¼”-wide brass strips, and gradually trimmed them to see if I could move the match higher in frequency. Trimming it down to 5” on each side did not seem to help. I googled to see if anyone else had this problem, and found a report of someone who soldered wires through the vias to ensure good contact, and this solved their problem. I did the same, but it didn’t make any difference for me. However, while the circuit board was off, I noticed that there was some oxidation along the circuit board where it came in contact with the mast. I used a large pencil eraser to burnish the circuit board along this area and re-attached the circuit board. This time the 5” brass driven elements gave a better than 2:1 match over the entire band from 420-450 MHz! Being hesitant to destroy the original driven elements, I ordered another short piece of aluminum tubing (K&S Precision Metals, https://www.amazon.com/gp/product/B00G6J6C7E/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1 , and made a set of new elements 5” in length. The good match over the entire band remained with the brass strip replaced by the aluminum tubing. Knowing that this worked, the easiest thing to have done was to simply shorten the original elements. (Precisely drilling the mounting holes in the new tubing was actually a bit tricky with the tools I had available—basically a drill press and vice to hold the tube).
The reason for calling attention to the vias given by the other customer was that it appeared that the through connections were made simply by soldering through the holes. Certainly if this were the case, then adding wires would increase the reliability of the connection. However, PC boards with vias are normally plated through when fabricated. If this was how the boards were made, then there is no need to add the wires through the vias. Perhaps the reason why this made a difference for the other customer was that when the board was remounted, it made a better connection between the ground plane and the boom, and actually had nothing to do with the wires through the vias. Adding the wires will not hurt, but it may make sense to go to this trouble only if burnishing the back of the board and the mast where they contact does not result in a good match at 70 cm.
The fact that the oxidation was apparently an issue does not bode well for external use of the antenna, but since I am interested in an attic installation, I’m hoping this will not be a problem for me. I have since successfully installed the antenna, and it has been working well of almost 1 year. |
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| KX7H |
Rating:   |
2020-09-18 | |
| MFJ needs help |
Time Owned: 0 to 3 months. |
| Order this from HRO in Portland. Speedy delivery! Great Service! The antenna assembly is unnecessarily time consuming. Element centering marks on several elements were incorrect. Inserting the plastic insulators was easy but should have happened at the factory. The capture washer installation was a pain... Once assembled it was noted that the circuit board the driven elements mount to was drilled incorrectly and resulted in the driven elements not being in the same plane as the rest of the elements10 degrees or so. I contacted MFJ and HRO... No response from MFJ with 2 emails. Almost instant response from HRO with a replacement being shipped same day. Replacement antenna assembly experience was the same except all the holes were drilled correctly. Initial antenna analyzer data shows the SWR to be acceptable across both VHF and UHF bands. |
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| KN6SU |
Rating:   |
2019-03-24 | |
| Problematic |
Time Owned: 0 to 3 months. |
It was hard to assemble because the holes in the boom were too small for the plastic insulator washers to be inserted, so I had to drill them out. Fortunately I have a good drill selection and found one that did the job. It was also fortunate the element holes lined up so I didn't have to re-position them, as I've had to for another MFJ antenna... The "push nuts" MFJ uses to hold the elements in position are a huge pain to slide on. The "push nut tool" included for this task (just an aluminum bar with a hole drilled in it) might have worked OK if MFJ sized the hole right...they didn't and it didn't...I drilled a smaller hole and it was still a bear to use but at least it worked better. And if the push nuts were sized to better match the element diameter they would have slid on more easily and this system would be more acceptable.
Attaching the 2m driven element was impossible without removing a lot of the silicone sealant MFJ globbed over the match feedpoint.
After a couple of unecessarily tedious hours assembling this thing and putting it on the roof, it resonated at somewhere above 155 MHz and the SWR was >5:1 in the 2m band...
I called MFJ and was told to try lengthening the driven elements, which sort of made sense except it didn't when I considered that the driven elements couldn't possibly be 10 Mhz undersized. Nonetheless I tried MFJ's fix by incrementally splicing length onto the elements. Didn't help...Checking every bit of the antenna that I could see, I couldn't imagine what the problem was. I figured it must be something I couldn't see, namely the feed point, so I cut away all of that black silicone goop and sure enough the coax braid connection was loose. After tightening it down the SWR was <1.2:1 across the whole 2m band.
70cm was resonant down around 430-440 MHz, but didn't match well in the 444-448MHz range I use for FM repeaters. That did look like a problem that could be fixed by shortening the 440 driven elements a bit. I used 1/4" copper tubing cut about an inch shorter than the MFJ 1/4" aluminum tubing and this gave an acceptable match in the 440-449 MHz range. If you want to work towards the lower end of the band, you could leave it as MFJ made it.
Now I'm very pleased with the antenna. It has good directivity and gain, about what you'd expect from a 4-element/7-element 2m/70cm Yagi.
The electrical design is actually quite good, at least on paper. IF it were easier to assemble and IF it worked as well as it works now without hours of tedious tinkering, I would have given it a solid 5 out of 5.
The 1768 illustrates the usual MFJ problems, i.e.: 1) Poor quality control, as evident by the loose feed point connection buried under a mound of silicone goop; and 2) Poor mechanical execution, evidenced by off spec drilled holes in the boom, a poorly made "push nut tool" along with improperly sized push nuts.
MFJ would do well to emulate Ikea and have staff whose job it is to check how easy or difficult it is for customers to assemble their products. Had they done so with this antenna (and with a host of their other products) they would undoubtedly be improving customer satisfaction. |
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| KM3F |
Rating:  |
2016-10-09 | |
| Quality control, and caution not user friendly.. |
Time Owned: 0 to 3 months. |
This is one of those items that doesn't need much user time to access it's design.
Yes the assembly is a bit difficult and assembly instructions can be much improved.
Boom holes had to be over sized so insulators would set in without excessive force.
The strip line Diplexer board needed some work on the feed through points.
2 meters match was very good according to my Commet CAA 500 MK II analyzer. 440 side resonated down in the 390 mhz. range.
What was to do? Take a chance and try moving the match up in band without upsetting the 2m match.
It was accomplished to a satisfactory degree by altering the 440 driven element lengths even though they were correct according to conventional formula 476/f X 12 divided by 2 for length each side in inches.
Also offsetting the first 440 director to help improve the match.
These changes indicate the strip line Diplexer physical design needs to be revisited for design dimensions.
Overall this antenna can now be used on both bands with very flat SWR on 2m and good low to mid band SWR rising to about 2.5 toward the upper end where it is of lesser importance for FM repeater use.
Attempting modification without using an analyzer can result in a waist of time and unusable parts, in the end.
I have reservation as to the effects of water and Snow accumulation on the Diplexer board without a cover.
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It seems the MFJ company needs to assign an evaluation tech or engineer to assess every product line that needs to be assembled for Instructions, assembly and performance to find out what's going on with their product complaints.
Do not expect a telephone call to answer these kinds of issues if the person has no knowledge of what's going on when they have not assembled and tested the product.
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| W8AB |
Rating:   |
2014-11-13 | |
| Not soldered Properly |
Time Owned: 0 to 3 months. |
I put the antenna together with considerable difficulty due to the "snap-rings" used to hold the elements in place. What a headache.
Once assembled, the antenna had a terrible match across all of 2 meters and a somewhat better match on 440. Contacted MFG, and they were very little help. They looked at my photo and said it looked like I put the antenna together correctly.
They had no suggestions on how to fix it and did not respond to requests to return the antenna. So I was on my own. It looked like a reasonable design, other than the snap-rings, so it should be working. I tried different coax and mounting without any change.
Next I carefully inspected the printed circuit board that is used to feed the antenna. I noticed that a number of the thru-holes where soldered but the solder did not flow all the way through to connect to both sides of the board on all the holes. Some were soldered correctly so a DC connection was being made, but most were not soldered all the way through to both sides and did not make contact to both sides.
So I added a short piece of wire (thru-holds without wires are prone to failure, even when soldered correctly) to each thru-hole by re-soldering them all so each hole connects the top and bottom circuit board traces with the short wire.
What a huge difference it made, the antenna started to work.
If you have one of these antennas and it does not work properly, check these solder points.
Since the MFJ design does not include a wire in each of these thru-holes, they are much more likely to fail after a few years in the sun, and cold.
It's an easy fix if you have the problem, once you get the antenna on the ground.
The customer should not have had to fix this on their own. MFJ was totally unresponsive after my first message.
I have to wonder. MFJ does not seem to understand this antenna well enough to build it correctly or support it.
So I gave it a two (2) because it is working, now that I fixed it, but what an ordeal.
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| KN4MC |
Rating:     |
2008-02-09 | |
| Good LITTLE antenna |
Time Owned: more than 12 months. |
I put this antenna up a little over a year ago. I have made 2 meter (SSB) contacts well over 500 miles away with only 50 watts. I made one contact on (SSB) 70cm to Canada from Western Kentucky with only 20 watts, (VE3TMG has a great station).
If you just want an antenna to get on 2m & 70cm SSB (or set it vertical for FM) and do not have a lot of room for larger antennas, this is a good antenna. I am thinking about stacking 2 of them just to see if it can be done. |
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| KB9WSL |
Rating:     |
2006-07-08 | |
| Works for me |
Time Owned: more than 12 months. |
When I opened the box I was not sure about the antenna when I saw the feedpoint connection on a circuit board type setup. But being a new ham
in 2000 I assembled the antenna and mounted it at 66 feet on my tower. The antenna is mounted horizontally for SSB work. The antenna has performed well for me and has been exposed to Northern Indiana summers and winters for 6 years now without any problems. SWR on both bands is nearly flat in my experience. While not a contesting antenna by any means..I would recommend it to a new ham who does not have a big budget.I will eventually take this antenna down and use it for rover and portable use due to its size..(5 foot boom) |
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| WB5MHA |
Rating:   |
2005-11-27 | |
| poor quality |
Time Owned: more than 12 months. |
"cheap" is a word that comes to mind regarding the price as well as the quality of this antenna.
Instructions are not clear. Holes and parts do not line up. Workmanship is poor. It is made just well enough to work.
In all fairness it does load up. It is directional but I doubt it's gain figures.
For a little more money you can buy a higher quality beam. Expect what you get from a product that is made in China by slave workers who really don't care.
Mine sits in the yard while my coax is put to better use. |
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| W5RHR |
Rating:   |
2005-04-11 | |
| poor quality |
Time Owned: 0 to 3 months. |
very poor manufacturing and design. the parasitic elements are not in line with the driven element assembly, which is a copperclad circuit board.
the mounting holes for the matching assembly were not at a 90 degree angle to the parasitic elements, resulting in the driven elements being cocked. I had to remove the assembly and drill out the holes till I could line up the assembly.
Also MFJs method for securing the parasitic elements were to use a type of speed nut to hold the element in the boom. lines were scribed in the elements to capture the speed nuts, but the lines were scribed for a larger diameter boom.I had to manually center the elements on the boom.
In fairness, the antenna does have a low VSWR for the band it is cut for, but I have yet to make a contact with it.Purchase a Cushcraft instead, the few dollars you save on the MFJ are not worth it. |
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