I was given four long-boom 432 MHz yagis that I'm planning to mount on an H-frame to make a moonbounce array. A couple of them came with short coax phasing feedlines.

I believe that the yagis are essentially built according to a K1FO design, either similar to or identical to the antenna that was described in the ARRL Handbook for at least several years, including in the 2004 Handbook (where it is described as "A High-Performance 432-MHz Yagi" starting on page 20.63).

The driven element of each yagi uses a coax balun and a T-match, and I have a 4X power divider. So I believe that the phasing feedlines between the power divider and each of the driven elements must each have 50 ohm impedance and they must have equal lengths.

Shown below is a photo of one of those feedlines - I'm wondering whether it is likely to be Heliax. I don't see any markings on the cable jacket, but it sure looks like there's a spiral underneath the jacket. Both ends are terminated in type N connectors, and it looks like the feedlines are about 8 feet long.

I'm wondering if it might be LDF1-50 1/4" Heliax line (http://www.repeater-builder.com/antenna/andrew/andrew-ldf1-50-spec-sheet.pdf) but maybe it's something similar but different. The cable jacket OD looks like it's a bit less than 8 mm, (7 point something mm - it was raining when I took a quick measurement so I didn't stick around to get the most accurate reading - but that would put it at about 1mm greater than a nominal 1/4" diameter).

I'd like to get either the raw material that I can use to make two phasing lines that are identical to the two that I already have, or perhaps get two already assembled ones. But maybe I'm being foolish, and instead I should just make up four identical phasing lines rather than trying to get away with only making two of them and reusing the two existing ones. I don't have much in the way of test gear for 70 cm (I've got a Bird 43 wattmeter with the appropriate slug), although I am working on building an antenna analyzer.

Has anyone assembled type N connectors on such small diameter Heliax? Would I need an expensive tool and/or jig to do it, and is it a difficult thing to do, or is it something that anyone with 'normal' ham skills can do?

Here's what the coax looks like:

Yes, that's Heliax or an other brand equivalent.  (Same thing, different name.)

Heliax always requires special tools for connector installation.

Heliax is available in sizes up to 1-5/8".  At that point connectors are in the 200 dollar each world.

Be aware, just because a cable is SIMILAR to heliax, does not means it uses the same TOOLS.  Eupen and Andrew/Commscope cables may be similar but they can't use tools or connectors made for the other brand.

Unless your cables are small (under an inch) it's probably more cost effective to order pre-terminated cables built to your specs than it is to buy the tools and connectors and make the cables yourself.

That's what I was afraid of - it is only 1/4" or so diameter, so that qualifies as "small" according to your description, but since this project is likely to be only a "one-off", it may not make sense for me to even consider getting the tools for putting on the connectors.

Then again, I have not priced pre-terminated cables - and maybe the sticker shock from that will lead me to reconsider my options.

It does not require special tools to install all connectors on Heliax.  It just makes it much, much easier.  Half inch superflex is frequently available used or NOS.  Connectors frequently show up on QRZ very reasonable.  PM me as I might have some available at a reasonable cost.

Thanks for the offer - since the two phasing lines that I have in hand are 1/4-inch dia, my first goal would be to match those, but if I'm not successful with that, then I could consider 1/2-inch superflex.

I'm only using the heliax for the phasing lines - my goal is to mount the 432 transceiver, amplifier, preamp, and related stuff fairly close to the antennas (which my current planning has them sitting less than 20 feet above ground) - so heliax is probably overkill, and I could get away with something like LMR-400 for the short run from the power divider to the T/R relay etc. - in fact I could get away with using LMR-400 for the phasing lines as well) - but since I may want to do other UHF and above stuff where heliax might make a noticeable difference I'm interested in learning more - so I'll shoot you a PM.

Most phasing lines that I have worked with in the past have been 75ohm. There were a few that were 50ohm. Both had a feedpoint impedance of 50ohm.

Really doubt that would be 75 ohm heliax. It would be common practice for that kind of installation to simply match all the feedline lengths in phase and then use an appropriate power divider.

After doing some more investigation I agree about the equal feedline lengths with 50 ohm cable.

But I'm not sure whether I should get some 1/4-inch heliax and make two more phasing lines, or make up two phasing lines from a different type of coax, or make four new phasing lines (either from heliax or some other type of coax).

If I were to try to come up with the other two required phasing lines by making them out of a different type of coax (such as LMR-400, which I have a spool of), I suppose that I could use the published velocity factor for the heliax and the LMR-400 to come up with an equivalent length of LMR-400, but I've heard that the published VF may not be the real VF at a particular frequency.

So I'm also wondering whether a better method might be to use an antenna analyzer to figure out the 1/4 wavelength frequency of the existing phasing lines, and then try to do the same with the LMR-400 to come up with the equivalent electrical length.

If you're going to make new ones, this is what to do. Test the actual electrical length of the existing lines, then make new ones to match.

It would be easier to use the same type of coax though. 1/4" heliax connectors aren't that hard, and the cable price wouldn't be too unreasonable for the shorter lengths.

If you were going to make new ones, I'd probably make all new rather than trying to match the old and new.

Yes, that makes sense indeed, thanks...

When you get that thing done let me know. I have a similar setup that I am using for EME.

I can give you some help on things that took me a bit to figure out. I have made a handfull of contacts with very limited radio time due to other obligations. I just completed a Fox Delta ST-2 automatic tracker to computer control the rotar so I can concentrate making contacts. Will get some picks in the morning.
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Thanks...

I think that it may have been one of your earlier threads that inspired me to go ahead with this project.

Before I can get the H-frame and antennas in the air I need to get some welding done on a custom base for the mast that I'm planning to use.

I did set up one of the 22-el yagis for a couple of hours during the June VHF contest from the top of a 1700-foot hill about a half hour from my home.

Looking at your photo, it's interesting to see how you've offset the cross-member of the H-frame rather than centering it (no doubt to improve roof clearance for the lower two antennas). I may want to do something similar. With the relatively small size of the 432 yagis the asymmetrical configuration will probably not cause any problems - I will be using a Yaesu G500-A for the elevation rotor and a ground-mounted Ham-IV for the azimuth rotor, and those should have more than enough torque to handle the array. Antenna spacing will probably be about 6 feet.