I have an old Cushcraft long-boom, 18-element 2-meter yagi, model 4218XL. There's a copy of the original assembly instructions at http://www.popular-hifi.com/shack/ant_cc18/cushcraft_2m18.pdf

Several years ago, while the antenna was on the ground, some kids twisted and broke most of the elements. I held on to it, thinking that someday I'd rebuild it, and 'someday' is now.

I'm wondering what aluminum alloy to use for the replacement elements. As far as I can see, the original alloy is not specified in the manual.

Cushcraft currently sells a 17-element yagi, model A17B2. I haven't yet compared the boom lengths, element lengths, or element spacings between the two (the A17B2 manual can be downloaded from the Cushcraft download page at http://www.cushcraftamateur.com/support.php?productid=A17B2), but upon looking at the parts list at http://www.cushcraftamateur.com/Product.php?productid=A17B2 it appears that the antenna may be using aluminum alloy 2011 for the elements, well, for the directors anyway.

I'm not sure which treatment, but 3/16" diameter (0.1875) 2011-T3 round rod is available from onlinemetals.com - https://www.onlinemetals.com/merchant.cfm?pid=21565&step=4&showunits=inches&id=288&top_cat=0). I've never worked with it, but apparently 2011 alloy is considered to be the 'easiest-machining' alloy of aluminum, but it is not as strong as some other commonly-used alloys.

The longest director is about 40", and so maybe mechanical strength is not the most important parameter.

Anyone have experience using 2011 alloy for yagi elements?

BTW, there are lots of references to an article about improving the 4218XL by ditching the strange reflector assembly and replacing it with something more usual (written by K1FO, unfortunately now a SK), but I haven't yet located the actual article - I'm a sometimes member of a Northeast VHF group, and so I can probably find it through some of those members, but in case anyone else has experience with that mod I'd be interested in hearing about it.

Not sure on the alloy there, but my 2m rover yagi is a K1FO design. I am not sure if the allow really matters. I would imagine being easy to machine means its soft, it would at least allow some flex in the element, and in my mind make it less brittle. Hopefully someone else here has more info.

If you get up and running let me know, work up into CT all the time on 2m in the mornings and evenings.

I recently moved to a terrible rf location, with nearby tall hills all around. So while I could have had QSOs with VA on 2 meters from my old QTH, I'm not sure that it's going to happen from the new one.

But I can see the sky and the moon, and so I'm thinking that I may be able to do some digital-mode EME with that antenna.

DX Engineering sells " 6063-T832 drawn aluminum " here.



<-- Not affiliated with DX Engineering.

RIF. OP looking for solid aluminum rod.

I dont have any specific info on Al, but my Arrow jpole uses aluminum arrow shafts.

Why not call Cushcraft and ask this question? Their tech. support is pretty good. I had some issues while installing their R8 vertical and they sent me a replacement section free of charge. The guy I talked to, was very knowledgeable.

I suppose that I could try that, but Cushcraft was bought by MFJ in 2009 - the antenna in question predates that by maybe 15 years or more - so it's not clear that they would have parts (or answers) at hand.

but I'm going to compare the A17B2 element lengths and spacing with those of the 4218XL - it is possible that they are using identical parts - but I need to go the 'cheap' route here, so I'll probably be sourcing raw aluminum rod and cutting it to length rather than buying elements from them.

They do have sort of a 'sleeve' around the mid-section of each rod element which apparently is part of the element assembly (it is not something that the person assembling the antenna puts together) - I'll have to take a closer look and measure it with calipers, and figure out whether it is a standard tubing OD and wall thickness that I can duplicate, or whether it will require some machining to get a good fit - I believe that I still have all of those, but it's not clear whether they can be removed and reused or whether they're somehow bonded to the old elements, either when manufactured or simply due to corrosion over the years.

(But I actually know a ham who used to work for Cushcraft, and might contact him first.)

And I thought the slightly broken 2m yagi in my barn was excessive.... that's a big antenna.

I can't help you with the aluminum question, but if I ever get my ducks in a row someday I may join you in an attempt at digimooning.

I don't think it really matters electrically if it's a solid rod or tubing, especially for the small diameter elements. Diameter is somewhat important but it's not very critical as long as the new material is close in diameter to the original part. It does not have to be exactly the same. In the worst case, just adjust the length slightly for best performance. Just find a similar aluminum material that is strong enough structurally for the antenna.

BTW, you'd be surprised about what can be found in metal recycling yards. Find your local recycling facility and ask if they will allow you to wonder around to find the material you need. They charge by weight. I've heard stories about guys finding complete antennas.

Do not rule out meteor scatter also. Very fun and rewarding mode. With the FEC on MSK144 vs the older FSK441, it is better then ever. I worked K1JT this weekend on 6m, and I run a Moxon with 100w on 6.

Wonderful mode to get into, and will kind of lead you into ENE with JT65. Since most of the big stations are also EME stations.

Spec-wise, it looks about the same as 6061, a bit better on yield strength.

I would think it would be fine for elements.

Electrically I doubt there is any difference in the various alloys of Al.

I have wanted to try meteor scatter for ages.

I was not familiar with the Moxon so I looked it up - interesting concept.

I do have a 3-el 6m beam that's currently in pieces that I could quickly get into the air. Not very far into the air, though.

That is more then enough. I guess I will have to do a metor scatter write up. 6m is easy, 2m is more challenging.