With the help of friends I am again active on all bands from 80 through 10 meters. Until more antennas go up my flexibility is limited, so I cannot call this progress. That explains the title of the article. Over the next month there should be enough progress that I can truly claim that I have taken one step back and then two step forward.
For now it's just one step forward in which the station is different but at similar capability to what it was a month ago. In this article I'll run through the progress so far.
TH7: high tri-band yagi
I will have little to show for 10 meter antennas when this year's work is done. That is acceptable for the next year since signs of life on that band will remain elusive for at least that long. With a large tri-bander up at 43 meters this will give me flexibility during contests to target, say, South America at the same time as Asia on 20 meters. I am assuming my new 20 meter and 15 meter stacks on the new tower will be ready and I am working hard to make it so.
I really like this picture. The Hy-Gain TH7 dangles at the bottom of the tram line fully rigged and ready to be hauled over the hay field to the top of the big tower. Posing with the antenna is my trusty ground crew (left to right) John VE3NJ, Don VE3DQN and new ham Alan VE3KAE.
Notice how the antenna is well balanced so that the boom is level and the elements point straight ahead. This is the correct orientation to clear the guys and not strike the tower or mast. Those element tips are fragile. Two people lifted the boom as the tram line was pulled tight to prevent the elements from catching on the ground. Two people manually operated the haul rope during the lift. Power makes the job easier but increases risk of damage when the the antenna strikes an obstacle.
Many hams attach yagis to tram lines with custom made rigs that guarantee good orientation. I do it old style with ropes. With practice ropes work very well and allow for rapid removal and easy packing at the top of the tower, an important consideration. In this instance it worked beautifully as the close spaced driven elements of the TH7 slid right around the tower and mast.
One mistake I made was to point the antenna backwards. Although this is easy to correct by calibrating the prop pitch rotator controller the direction I dressed the cables and rotation loops is not compatible with a north centred rotation, which is the preferred method in this part of the world. I avoided rotation until it was fixed a few days later.
The TH7 was retuned to resonate lower in the band. SWR is a little higher than ideal at the low ends of 15 and 10 meter. but better than it was before. The boom is attached to the 3" mast using the same modification I used for the TH6. I shortened the DX Engineering saddle clamp on the top side to avoid it contacting the phasing line between the driven elements.
Other tri-band yagis
The reason the TH7 is up there and not the TH6 is because the close spacing of the driven elements does not easily permit tower side mounting. The TH6 is better for this. It was trammed to 75' and pointed roughly south to permit working Caribbean and Central American multipliers and the southern US, all of which are present during opening to Europe on the high bands. It uses the same side mount bracket as used previously for the Explorer 14.
The Explorer 14 is now gone to its new home where it will soon bring home the DX to its new owner. Although a small antenna it did well for me during the past several years.
The TH6 was inspected after removal from the tower. A couple of defects were discovered which I assume these were responsible for problems that began last winter. The worst was the poor design of the driven element clamps that connect wires to the balun and beta match line.
The tabs on the aluminum wraparound clamp bend when the bolt is tightened. There is no provision in the TH6 to prevent this so the wire studs don't sit flush against the tabs: they wobble. My antenna was particularly bad due to its great age.
I added two backing nuts to allow fine adjustment of the clamp pressure and squarely bond stud and tab. The TH7 is better than the TH6 in that it has one backing nut, but still not the two I used. The studs were weatherproofed after taking the picture since the tinning has deteriorated. The hardware is stainless.
I took the opportunity to move the yagi's optimum performance higher on each band. Previously it was set for CW so the SWR was poor at the upper ends of the SSB band segments. Not wanting to lose CW performance I opted to shift it slightly higher, just below the settings for "Lo Phone". Because there is only so much bandwidth possible with a tri-band trap yagi some compromise is necessary. Eventually the TH7 will be converted to a TH6 so the two can be stacked for added performance. The conversion is necessary to achieve a similar impedance and therefore good power division.
I made a mistake with the tram which at least doubled the time to raise it to its new home. The upper tram anchor and haul rope pulley were too close to the mounting position. Manoeuvering a big yagi in a stiff breeze with ropes getting in the way and pulling the antenna out of my hands was too much. We lowered the antenna and redid it properly. Expedience costs rather than saves time.
XM240 40 meter yagi
This small 40 meter 2-element yagi has been returned to its original location on top of the Trylon tower at a height of 21 meters. The lift went pretty well considering the necessity of dropping several above grade cable runs and navigating the long elements around the trees that have grown over the previous two summers.
A few modifications were made to improve the antenna. The previous owner modified the antenna to make it more robust in extreme weather. He did a fine job of it but he should have chosen better hardware when he replaced the Cushcraft element-to-boom clamps. The cheap galvanized muffler clamps do not have enough grip to prevent the elements from rotating.
I inserted galvanized mesh under the clamps to provide mechanical texture to improves the grip. While not ideal I could not simply use better clamps such as the flattened and textured DX Engineering Cycle 24 clamp since there is no reliable sizing of muffler clamps and I'd have to drill more holes in the aluminum channel. Too many holes risks weakening it. Time will tell how this improvisation deals with the wind.
The other improvement was to ground the reflector element to the boom. This is a popular mod to reduce precipitation static by providing a path to ground for the static charge. Performance is not affected. Precipitation static was a serious problem at 150'. We've had one rainfall since the antenna went back up and...there was precipitation static, though not as bad as in the past. I'll continue to monitor.
I adjusted the rigging to ease attachment to the mast. Ideally two on the tower eases installation of this unwieldy yagi but I made do on my own by adjust the rigging and the procedure. The lift was done the same day as the TH7 with the same ground crew. I spent two days beforehand to prepare the antennas and rigging on both towers to best utilize the time of my friends.
In the picture I am in the process of attaching the mast clamps. There are a few interesting features of the rigging that are worth mentioning:
- I attached the boom truss to the lift rope. This kept it out of the way during the lift, made it easy to slip onto the mast and by keeping it in one piece there is no risk of one end slipping out of reach while it is being assembled on the tower.
- Long ropes are looped over each side of the boom. These tag lines allow fine control of antenna orientation in tight spaces. When done pull one end of the rope and it falls to the ground.
- Precise positioning of the mast clamp needed to insert the clamps for an antenna this size is no easy task for one person. I used a couple of cargo straps as a third hand. I previously slipped all 4 clamps onto the mast and raised them one by one, top to bottom, for attachment. The rigging must keep the plate flush to the mast since there is nothing on the boom to grab onto to rotate it.
80 meter inverted vee
The 40/80 meter inverted vee that was on the Trylon is headed to its new (old) home on the 150' tower. However the 40 meter element of the fan dipole has been removed so that it's solely for 80 meters. It is no longer needed on 40 meters and it used to twist and tangle in the wind which would make it unusable on 40.
The tower mount has been improved from an ABS pipe to a steel angle bracket. The new bracket is far stronger and will take more tension. It is also a better mount for the balun (common mode choke). Strain relief for the wire legs keep stress away from the balun studs.
Modelling tells me the best pattern for short paths and low directivity is at a height at or a little above 30 meters. This will also keep it well away from the other antennas on the tower. Unlike its original installation the two legs will go down into the tree line on the north end of the hay field, avoid ground anchors in the hay field. The model shows almost no effect on the pattern by doing this.
It should be a good antenna for the QSO rich northeast, mid-west and south-central US. After sunrise and before sunset a horizontal antenna often works better than a vertical on 80 meters on both short and DX paths. Unfortunately it's resonant frequency is ~3700 kHz, ideal for neither CW nor SSB. If widening the legs of the vee more doesn't help I'll lengthen it to lower the SWR below 2 within the range of 3500 to 3600 kHz. My primary use for the antenna is CW contests and DXing.
|One step forward
With the bulk of the tramming on the 150' tower is done I deployed the radials for the 160 meter antenna and connected the over-ground coax. I kept the field free of trip hazards for the safety of the crew. The match is different each year I deploy this antenna. This year it resonated at 1800 kHz so I adjusted it to resonate at 1825 kHz. I believe the variability is due to the distance from the antenna from guy wires and the directions the radials run, neither of which are identical each year.
Work on the 80 meter vertical yagi is delayed. Since this antenna can be done by myself on the ground in the cold weather it is low priority. It's just a little frustrating that this project is taking two years to reach fruition. However I budget the time and energy I devote to amateur radio so that it doesn't become a burden. On the positive side it really is almost complete.
The last stage of aluminum work on the 20 and 15 meter long boom yagis is done. I have only to cut and insert the element tips, mount them on the boom, build gamma matches and raise them for tuning. October will be a busy month.
The mast bearing plates for the new 140' tower were assembled and declared unfit for use. I made an error in the template that requires modification in my workshop. This is a temporary obstacle. I expect to raise the top sections of the tower along with the mast and prop pitch motor by mid October.
When everything is completed I will be ready for the winter contest and DX season. Next year will be less busy with only a few large projects. More on those in the coming months. Right now I remain focussed on antenna building and becoming reacquainted with the HF bands since I did little over the summer other than 6 meter DXing.