DIYing a QRO cobwebb

[NH7RO]

After cutting and stringing the new elements I attached very thin Dacron rope to the ends (Mac's Sport Utility Cord) with some terminal block pieces. It was fairly easy to tighten and adjust the elements up thereafter.







After initially using single sections of cut up terminal blocks it dawned on me to use double sections so that one part could be used for the elements (and element extensions if needed) and the the other solely for the Dacron rope. I went back to Radio Shack and bought two more 12-section blocks for the task. Later photos will show this last-minute change.

I have a lot more photos to post and will resume doing so later when I have the time; stay tuned!

73, Jeff

[NH7RO]

Didn't realize it until I looked at my last photo above just now but I had already replaced the single terminals with the double blocks I can wholeheartedly recommend. They really make the adjusting so much easier.

Now that I had the antenna all together it was ready for the tuning and pruning. Since the cobweb was only about 7' off the ground on my stand in the carport I decided to transfer the whole operation over to the shadiest side of our big yard. There I could rebuild the stand so that it would be a few feet higher and not have any other objects (like roofs) close to it.

Before I set the stand back up I layed the cw down on the lawn for a photo:



A few minutes later I had raised my antenna testing stand by putting it on a makeshift table; now it was high enough to tune but low enough to reach via a stepladder:





I love how the fresh copper glinted in the sunlight:

[NH7RO]

Here are a few closeups of the element attachment points and ends. Before anyone points out that the single cable tie arrangement might last all of a couple months in this UV I will mention that this was just the preliminary method used before the final adjustments had been made.







Thereafter, I wrapped each attachment point with a 12" length of Mac's Dacron (triple-knotted) and then wrapped it all around with electrical tape.


I also applied coatings of liquid electrical tape to the terminal blocks as well as the top and sides of the PVC balun box. I sealed the elements where they enter the box with both hot glue and liquid electrical tape. I wrapped the box's lid with electrical tape and spray-painted the box and spreaders with flat green cammo paint (my standard procedure for all antennas involving plastic and or fiberglass) for further protection against the harsh UV.

[NH7RO]

In my enthusiasm and eagerness to get the cobweb in the air I never got around to photographing the finalized version before I hoisted it onto the roof. Also, once I had the cobweb on top of the carport I realized that I needed to get back to work on my 6M antenna as the rotator base for it was now free and ready to be installed.

Switching gears I made some last-minute adjustments to the big Yagi and got busy putting it atop the roof.





Once I had also put a wooden pallet on the spot where the rotator base would sit I mounted the base, layed out the guy ropes and got the mast and Yagi into position. With the help of my xyl I hoisted it up one afternoon and voila, I was QRV on the Magic Band again!

[NH7RO]

The very next day I enjoyed a major sporadic E opening on 6M so I took a break with work on the cobweb. I also needed to revise the telescoping mast a bit so I would feel safe extending it to a height of 25.5 feet above the wooden roof mount I had already built (also used a wooden pallet from Home Depot and some 4x4s like my rotator mount).

A few thunderstorms passing through Albuquerque also slowed my progress somewhat but eventually I affixed the cobweb atop the New Wave Portapole mast and began inching the whole array skyward.

Inching is no exaggeration as the procedure I used was simple:
Because I was doing all of this on my own I took great care in seeing that the mast and antenna would not collapse (either while I was raising it or once in position). After laying out all six guy ropes I would loosen the hose clamp on the topmost section of the mast and raise several inches. Next, re-tighten the hose clamp and proceed to run around the roof to let out a bit of guy rope so I could raise and repeat the process over and over again.

It seemed like forever before the first section snapped into place (the mast has spring clips that pop out into holes on either side of the next telescoping section to lock it into position) but as I often say, "better safe than sorry." This is especially apropos where antennas are concerned.

If I were to let out too much guyline the whole assembly could tilt over and collapse; conversely, if one line became too taught it could be quickly pulled over too far to the same effect. I took my time and only raised it no more than a few inches at a time.

A couple of times I had to stop work and reposition one of the guy lines so the guying force was better distributed. I was using two sets of three lines so all the lines were interdependant to a large degree but my guy attachment options were somewhat limited to begin with. I ended up tying off most of the lines to some protruding vigas (New Mexican style wooden beams) with some thick Dacron rope loops and clothesline tighteners. These also made my life a good deal easier in the days I was up on the roof running around loosening, raising and reloosening them again and again.

After several anxiety-ridden raising sessions (the strong Albuquerque winds didn't help my situation) the cobweb was finally aloft.

Here's a few pix at various stages:

[NH7RO]

So there you have it. As best as I can determine the antenna is around 34 or 35' aloft and the only bad thing I can say is that the resonant frequencies of each band shifted very little from when it was being adjusted on the ground to being aloft. If I had known this beforehand I would have tuned accordingly but at least all bands are easily matched with my built-in tuner.

The only bands where I'll need to use the ATU are 12 and 10 meters and that's when I want to operate on the higher phone portion of ten at that.

I'll post some SWR data next if anyone's curious...

Meanwhile, I'll close with a few more shots of my QRO cobweb slightly swaying in the New Mexico skies:









Aloha from Albuquerque!

Jeff, NH7RO

[G3TXQ]

Jeff,

Nice write-up!

Just hope no-one sees that rotator in the photos and mistakenly thinks it's a beam

73,
Steve G3TXQ

[NH7RO]

Oh, but Steve, it is! 0.05db fwd gain off the best side at least!

Thanks for all of your help along the way, too---I wouldn't have done it in the first place without your super balun tutorial, either.

Vy 73,

Jeff

[G3TXQ]

Oh, but Steve, it is! 0.05db fwd gain off the best side at least!

You're right - I was forgetting

How about sending some of that sunshine our way?

Steve G3TXQ

[NH7RO]

I'd be more than happy to do so, Steve, but I'm afraid that---like all the rain I tried posting from Hawaii---it'd come right back marked "RETURN TO SENDER"

Any rate, the sunshine is not so bad lately as we've finally had a bit of damp weather to cool things off considerably. Only downside is always having to remember to disconnect my antennas and cables coming into the hamshack as the threat of lightning is well about us this time of year.


73, Jeff