ND2E's Blog

Hexbeam

Well, it has happened again. The winter winds came and the HexBeam went. During the summer I performed some repairs to the antenna because it had come loose from the rotator … the center shaft had been eaten by the teeth of the rotator clamp. I repaired the problem area by epoxiying a bit of aluminum to the affected areas hoping that that would reduce the wear until a proper fix could be made next summer.

The fix evidently worked well, The antenna stayed in place and rotated properly for several months. It even survived several high wind events. But last week, the high winter winds took their toll and the center shaft failed.

When I did the repair, I forgot about the loss of strength that the fiberglass center shaft tubing suffered when the teeth notched the shaft. The wind bit hard and the shaft sheared where the teeth had been. The epoxy paste I used did not provide sufficient strength to prevent the catastrophic failure of the center shaft even though it was strong enough to prevent rotation.

The antenna is now on the ground with yet another broken limb and a broken center shaft.

I will rebuild come Spring, but until then I will be using my 35 foot vertical as well as my NVIS 40M hamstick dipole.

Although this is yet another chapter in the ongoing saga of how not to build a fiberglass-based antenna, there are many lessons to be learned. And I am sure that there will be many more. The most important one that I have learned so far is: DON’T USE A FIBERGLASS MAST WITHOUT USING SOME SORT OF ARMOR! The next center shaft I build for the antenna will be aluminum tube over the fiberglass tube. Not only will this save wear and tear on the rotator clamping area but will also be a good clamp base where the limb baseplate mates with the center shaft.

I intend to do a full rebuild on the antenna and possibly add a 6M section. I also want to revisit the mast and its erection/mounting method. As currently configured, the antenna must be lifted vertically over 10 feet and placed in the rotator clamp. I had used a very primitive ginpole to handle this as well as the extension of the pushup mast. I is exceedingly difficult for me and the XYL to handle this task. I originally had the help of a local Ham but I really hate to keep bumming help when there should be an engineering solution to the problem.

So, during the rebuild, I will try to build some sort of tilt-over mechanism for the mast so I can mount the antenna with everything on the ground. I also want to find a way to mechanize the extension of the pushup pole once the antenna is mounted. If I am successful with the mast revisions, I will be able to bring the antenna down when High winds are expected and possibly not have to rebuild the antenna again.

It has been a long dry summer, I design and build Joomla-based web sites for several organizations. I am really quite new at web site design and operation so it should not be a shock when one of the sites was hacked. It has taken me a long time to understand how it was done and what was needed to slow down the attacks. The version of Joomla that I was using was really easy to hack, as was this blog. So to cut down on things I was forced to turn off comments and do several things that made several sites less useful. I am slowly returning things to normal after rebuilding, modifying, and adding security to the sites. The web security activities have not left me with much time to do Ham radio things.

I was able to work Field Day from home. I think I did better this year than the last two years. Hopefully I have learned a bit and become a better operator.

Just before Field Day I noticed that my hexbeam was not looking right. It was slouching off at a strange angle and the beam was not facing the same direction as the rotator. I managed to get through Field Day without everything falling down but my main antenna definitely needed a lot of work.

So this month I have made it a priority to get the radio things in order for the winter season.

I lowered the antenna and found that the fiberglass mast I was using had been eaten by the mast clamps on the rotator. I had expected a bit of wear but the clamps had removed enough material that the antenna was almost falling out of the rotator.

I modified the clamps and mast by epoxying an aluminum protective skin to the clamping surface. I also shimmed the spider to the mast and epoxied it in place.

So far the modifications seem to work. We have gone through one major wind storm and the antenna stayed facing the proper direction and there was no apparent wind forced movement of the various parts. Hopefully, that will solve the problem for a couple of years. I expect that the antenna will need to be rebuilt in a couple of years but until then I think it will survive.

There has been some recent solar activity and there is a chance that the higher bands will come back this coming year. Thinking that 6meters might be a useful band again, I built a 6meter dipole to be added to the short mast that carries my NVIS 40meter hamstick dipole.

I also want to finally get my 40ish foot vertical working in time for this winter. I had been using that aluminum mast as the 2m/70cm mast for the J-pole. I was having doubts that the vertical and the J-pole could co-exist without putting a lot of RF back on one or the other of the feed lines, so the J-pole had to come down.

The solution was to get my four-band mobile vertical out of storage and mount it on top of the short mast. I knew that the 2m/70cm sections would work as they were complete antennas but suspected that the 6 and 10meter sections would not be really effective since they were 1/4-wave sections. I was hoping that the 20ish foot mast would be enough of a ground for the 6- and 10meter sections to be somewhat useful but knowing that I had 10-meters available on the Hexbeam and a new 6-meter dipole gave be a chance to play with the verticals. I am running out of feed lines to the antenna farm so I put the 6meter and 40meter dipoles on the same feed with no attempt to phase them. So far both tune up well using the autotuner in the K3.

The aluminum vertical is now up but has no feed lines and the SGC coupler has not been mounted nor have the radials been run. If we have a couple of sunny days, I will get that done before the winter rains start.

Hopefully, all the antennas will survive the winter and I will have time to play with the radio.

ND2E is back on the air. For a few details about what was done see the article on the web site. So now it is time to get back into a daily operating routine and try to finish the WAS on 20M PSK before we are overtaken by good propagation.

There are still a couple of antenna experiments that need to be finished plus the build of some sort of 6 M antenna for use when we finally get some sun spot activity.

I also need to check out 10 M since my first tests on ten meters didn’t show that I was putting any power into the antenna. I don’t know what was wrong but I do know that the FT-857 is really finicky about the loads it will feed. So it is possible that the AT-897 auto tune unit just isn’t capable of tuning to the 10 M portion of the HexBeam. I need to break out the antenna analyzer and see what kind of impedance  I am actually running. I need to characterize the antenna now that I have it in place and have good coax to it.

I will publish the impedance run when I have it finished.

Finally getting back to Ham Radio things. I have the 2 meter J-pole up and the cabling is running across the lawn. The next chore is to run the final Heliax from the shack area to the garage wall, install the ground bus and the, install the arrestors, dig the trench, and install the final section of permanent transmission line. Not much-should get that done before Christmas.

All kidding aside, it looks like I should have that done before the end of August as I need to bring the HexBeam down to fix a couple of things I have noticed…it is facing SE when the rotator is pointing north, the last segment of line isn’t working well and is not properly coiled between the mast and the antenna. THe biggie however is the upper guys are not set properly and in a high wind will force the mast to rotate and the new slack will probably bring the mast down.

So in the next few days I will need to work on those problems. At the same time this  happpening, I need to play with the SGC coupler and see if that part of the experiment is going to work…that needs to be done before I close the trench. It starts to get complicated

73 de ND2E

I finally got a chance to raise the aluminum mast with the 2 meter j-pole on it. Again I am short good transmission line. I used a piece of RG-213 so I have around a 2 dB loss going to the antenna. That coupled with the short secction of LMR-240 and the piece of LMR-400 going up inside the mast I should have a bunch of loss.

So sometime in the near future I need to locate two pieces of Heliax and run them to the mast…underground this time because I don’t want to mow over them.