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Reviews Categories | Antennas: VHF/UHF+ Directional (Yagi, quad, etc.) | M2 440-18 70cm Yagi Help


Reviews Summary for M2 440-18 70cm Yagi
M2 440-18 70cm Yagi Reviews: 7 Average rating: 3.9/5 MSRP: $125.00
Description: 18 element yagi for 70cm
Product is in production.
More info: http://www.m2inc.com/
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AB0RE Rating: 1/5 Mar 29, 2015 13:55 Send this review to a friend
Not as advertised for FM use  Time owned: 0 to 3 months
I purchased the M2 440-18 new from AES a while back and just got around to assembling it a couple weeks ago. This was my 7th M2 antenna I’ve built so I was pretty comfortable with the keeper system they use to keep their elements in place. I took my time assembling the antenna, measuring everything multiple times as I went, and ensured the element lengths were equalized on either side of the boom to within a fraction of a millimeter. Total assembly time took me about 4 hours.

When the antenna was finished with the antenna, I mounted it to a fiberglass mast system, approximately 12’ off the ground, and fed the antenna with LMR-400 to a RigExpert AA-600 to check the VSWR. To my astonishment, SWR at the top of the band (445-450 was 2:1, quite some distance from the 1.2:1 VSWR M2 advertises the antenna as having across its 420-453MHz operating range. I called M2 and spoke at great length with Robert about the objectionably high VSWR as most solid state radios like to see 1.5:1 or less. Robert explained that on UHF even 1/16” variance is critical. He went on to say M2 has sold thousands of these antennas and never had an issue like mine. He implied I must’ve done something wrong.

Robert had me measure the element spacing on the antenna. The reflector hole was a whopping 3/16” off. When I brought this to Robert’s attention he said that was within tolerance. Robert suggested I do some additional testing. He asked that I use a different cable to rule out a cabling issue, and test with the antenna pointed straight up to rule out the possibility of objects in the near-field affecting VSWR.

I took the time and expense to assemble another cable to go from the M2 440-18 to the antenna analyzer. This time I used quality Belden RG-58 cable with RF Industries ends – the crimp-on ends ensure that I don’t melt the inner portion of the coax and cause an impedance bump or other issue. I even went so far as to trim the cable down so that it was a half wave integer at 448MHz, taking the velocity factor of the coax and the ends into consideration, so that the cable itself would be “invisible” in the overall antenna system. Total coax length was around 19’ when this task was completed. Upon retesting, this time with the antenna pointed straight up, the SWR curve looked about the same graphically, but the SWR values were less. This would be due to the increase of coax loss in the new line (~3dB) vs the coax loss in the initial line tested (<.5dB), as confirmed by looking at a chart in the ARRL Handbook.

Again, I contacted Robert for additional assistance. Robert asked me to measure each element again to rule out a possibility of the elements being mis-cut at the factory, saying the elements are cut by hand when they are made. I went out and bought a 16” combination square and used that in conjunction with the “slider” from a second combination square to make a “poor man’s caliper” so that I didn’t have to cut off all the element keepers to get a precision measurement. I also had to download an inch/fraction/decimal conversion chart to translate all of M2’s decimal readings (i.e. 10.633”) to their fractional equivalents. When measured, one element was shown to be 1/32” of an inch off. Additionally, the rod on the T-match was 1/8” off. I reported these findings to Robert and he emailed back saying the t-match rod being too long wouldn’t matter and that he’d report my findings to the Engineering Department to determine what we should do next.

That was last week and I never heard back from Robert by end of day Friday. I brought the antenna to a hamfest this past weekend and sold it “as is” for pennies on the dollar of what I paid for it. I feel I’ve spent way too much of my time trying to track down an issue that does not pertain to my assembly of the antenna. I’ve given up on the 440-18, and I’ve given up on the idea of M2 providing an acceptable solution.

What I find most troubling is the mixed messages from M2 during this frustrating experience. First, all of M2’s literature says the antenna ha a 1.2:1VSWR from 420-453MHz. That seems like a bit of a stretch, expecting 30MHz under 1.2:1, but that’s what M2 has promised their customers. In conversation with Robert, he mentioned he was showing a chart on his end that had SWR at the top of the band at 1.8:1. How could that be if we’re told VSWR is under 1.2:1?

Another mixed message was in regards to the tolerances of the antenna. When Robert was discussing my assembly of the antenna he mentioned 1/16” of an inch was critical. When I indicated there was a hole that was 3/16” off, and that the t-match was 1/8” too long, he said it didn’t matter. Apparently M2 doesn’t hold themselves to the same standard they have for their customers when the antenna assembly is done. All the measurements taken confirmed the elements were placed in the correct position and properly equalized on either side of the boom – any variances from the cad drawing in the manual were the result of manufacturing issues, not assembly error.

Finally, Robert mentioned there was an “FM Mod” for the antenna in which the T-match can be trimmed down and 2 parasitic elements also trimmed. This would lower the SWR towards the top of the band but, of course, this modification would be permanent, greatly reducing the re-sale value of the antenna should one wish to sell it for SSB use towards the lower portion of the band. Additionally, I can’t help but wonder why there would even be this “FM Mod” if the antenna does, in fact, have a 1.2:1 VSWR as M2 indicates. Also troubling is that Robert said M2 does not have any modeling data on the antenna with the FM Mod performed… in other words, VSWR may be better towards the top of the band, but one may have adversely affected the gain or radiation pattern of the antenna.

It goes without saying that this antenna is not as advertised and it has clearly earned a “1 / “Poor” rating for the FM user. I’ve lost a lot of faith in M2 after my experience with the 440-18. I think M2 owes it to their customers to modify the technical specifications printed on their website and through their vendor network (AES, DX-Engineering, HRO, etc) to show the antenna is incapable or providing an adequate SWR above 445MHz.
 
N0TTW Rating: 5/5 Jan 26, 2009 16:54 Send this review to a friend
This is a great antenna  Time owned: more than 12 months
I read the reviews and question some of the comments.

It went together easy and the instructions are no different now then they were then (IE: 2000 and beyond).

This antenna is rugged as it took a nose dive off a tower during an Ice storm (the mast broke). I was able to straighten the elements and it is working flawlessly.

Take the time to assembling this antenna and you'll be glad you did.

Works great during contesting.
 
W4TXS Rating: 4/5 Jun 3, 2004 19:44 Send this review to a friend
Not that tough to assemble  Time owned: 0 to 3 months
I recently purchased this antenna for use as a rover in the upcoming June VHF Contest. I agree that the keeper washers for the elements can be a pain, but once you give it a try it's not that bad. You CAN remove the keeper if you slide it on too far by simply pulling the element out of the boom and sliding the keeper off the opposite end of the element you inserted it from. You can then reuse it. I found it helpful to mark the elements on both sides of the boom with a Sharpie after centering it. That isn't all that difficult either....just measure and adjust. I'm sure we can find fault with any antenna. I bought a 10 element Cushcraft for 432. Sure the elements don't need to be measured, but the saddles that the elements sit in do not line up as well as "through-the-boom" types like the M2. And, how about an SO-239 connector for 432....that's what the Cushcraft comes with. Give me a break. M2 even uses "N" connectors on their 2 Meter models. I'll rate this antenna again after I see what it does in the contest.
 
WB5VNX Rating: 2/5 Aug 26, 2002 19:08 Send this review to a friend
Emphasis questionable  Time owned: 3 to 6 months
Upon unpacking the M2 I reviewed the instructions (yes, not a manly thing to do -- read the instructions) and thought the instructions were very skimpy. But what the heck, I’ll give it a try, I’ve built many antennas in 25 years and not all store bought. The first thing I noticed is that they didn’t ship the coax balun. Being a Sunday I proceeded on and decided to call them later.

The keeper system for the elements is one of the shoddiest and hardest systems I’ve ever encountered on an antenna. One of the rods was substandard sized and wouldn’t stay in the plastic keepers. I assembled the antenna on sawhorses and rolled it from side to side to keep it at a comfortable distance. Every time I would roll it the small diameter element would fall out. The push tube in my estimation is a somewhat dangerous procedure in that it would be all too easy to run a rod through your hand using this system. To start the keepers you must use considerable force – usually you end up cupping your hand to get enough grip on the push tube. A L or T shape would prevent this or even installing a grip onto it. The keeper system makes accurate element placement difficult and woe unto the individual who puts one too far on, backing out is almost impossible. Without a center mark you must measure the elements for centering, a poor system for such an expensive antenna. Why they put insulators to insulate from the boom I’ll never know, it isn’t necessary. Having just assembled a Cushcraft the day before I may have been somewhat spoiled however as the Cushcraft 26B2 had pre positioned element mounting points and didn’t use a keeper.

The drawing for the M2 was in decimal equivalents. Most users in the US are still using fractional rulers. Why bother with decimals and use inches? Makes no sense to me. Looks like someone at M2 was too lazy to calculate the fractions and put them on the drawing. Lucky for me I have a decimal to fraction calculator handy in my woodshop, I feel sorry for those who don’t.

The instructions gave no indication that the 3rd boom section fits inside rather than over the 2nd one. Looking at the ONLY full drawing it looks like it is swaged and the boom is constant diameter. Seems to me that a few bucks spent on a qualified CAD engineer would be helpful here. Either that or they made a design change and didn’t bother to update the drawing.

No silicone grease was included as was the Cushcraft I had assembled the day before. Also no boom end caps. While not necessary for operation boom caps serve several purposes (hint, hint M2): They prevent insects from making nests (ever had to fight off an angry yellow jacket at 50’ hanging off the side of a tower?) and they prevent ice buildup inside the boom. While not a problem at my QTH for some hams this could be an issue.

While the elements are supposedly stainless steel and the nuts and bolts on the boom are SS the U-bolt hardware to mount the boom to the mast is cadmium plated. It will rust. Seems like the mast mounting was an afterthought.

A boom joining hole had to be redrilled as it did not line up. Glad I have a full shop. In general the holes need deburring and most of the parts appear to have been made at Bubba’s beam-n-BBQ barn.

On Monday I called and they happily sent me the missing balun. It installed as specified. After plugging it in I saw a flat SWR on the entire band, a good indication. It looks like they spend all their time and money in the machined matching block and the whole rest of the antenna was an afterthought. And to second the motion their quality control in the factory sucks. There is much room for improvement in the execution of what otherwise could be an outstanding antenna. The customer service is EXCELLENT.
 
K9KJM Rating: 5/5 Mar 27, 2002 05:23 Send this review to a friend
BIG SIGNALS  Time owned: more than 12 months
I have had an M2 440-18 up at about 68 feet for several years now, vertical, and can work stations over 150 miles on 446 FM simplex on a regular basis..... I hope to get one more to stack them for a little more gain..... The one I have up is mounted on a horizontal cross pipe all set for one more..... A great antenna for UHF FM simplex and repeaters.
 
NX7U Rating: 5/5 Nov 30, 2000 00:14 Send this review to a friend
Great UHF yagi  Time owned: 0 to 3 months
Well...basically I second AD6H's comments.
 
AD6W Rating: 5/5 Jun 28, 2000 18:53 Send this review to a friend
Well made, rugged  Time owned: more than 12 months
I've had arrays of two and four of these antennas stacked and phased using M2 power dividers and have been very pleased with them. The typical M2 machined, gel-filled feed block on the driven element is rugged and head and shoulders above anything else I have seen. The antenna goes together quickly and also looks good in the air.
 


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