Since I got my license in 1993, I always dream up of a decent HF antenna that enables me to "chase" DX signals. But being a city dweller in the heart of the Silicon Valley make things extremely difficult for me to put up any decent antenna. In a way, I am luckier than most of my friends, I live in an "old" neighborhood where there is no CC&R. But my property location has the overhead high voltage power lines in the backyard at around 35ft, not much space on either side of the house and a large front yard so it is kinda awkward to install a "serious" antenna for HF work (unless I can convince my wife to let me put it up in the front yard!).
Being a CW person, I keep "falsely" telling myself that I don't really need a good antenna to work DX in CW since CW can get through even during extremely bad condition. So instead of improving my antenna situation, I keep augmenting my city lot property with more low dipole and vertical antennas. As a result, the roof of my house looks very much like a giant spider web with copper wires and nylon ropes every where! The pictures below show what my house looks like with all the wire and vertical antennas. The "antenna web" consists of a Butternut HF9V vertical, a centerfed antenna (80M dipole fed with balance feed line, bent in a Z pattern to fit the property), a homemade 3 band fan dipole, and a Cushcraft AR270B 2M/440 vertical sitting on top of a 40 foot telescopic mast. The 40 ft telescopic mast serves triple purpose to mount the AR270B, anchoring point for the centerfed antenna and the fan dipole.
Here is a 20m/15m/10m fan dipole attached to the top of a 144/440Mhz vertical antenna mast at one end and the RadioShack antenna mast at the other end. The dipole is facing NE / SW direction. I was able to work a lot of South Pacific stations with this antenna but not much in the NE direction except state side stations.
Here is the Butternut HF9VX vertical antenna attached to the side of the house (right at the front door! The XYL doesn't care as long as the antenna does not interfere with her flowers on the ground...)
These antennas seemed to work ok most of the time, I was able to make plenty of contacts with many US and DX stations as long as the condition is good. But I must admit that there were times when I just wished I can hear the DX station a 'lil better so that I could tell that he was indeed talking to me...
About four years ago, a local HAM upgraded his antenna to a Force 12 C4 and offered to sell his old Hygain TH3Mk3 and the Alliance HD 73-1 rotator system for about $100. I couldn't pass up such an opportunity so I drove to his house to pick up the TH3 and the rotator that weekend. He really did a superb job in dismantling the old antenna. He labeled every component of the TH3 with permanent marker and included a manual of the TH3 and the HD-73 in the package - Boy, what a good deal I'd got!
After taking the TH3 package home, I quickly scanned all the components of the TH3 and its manual, I quickly put everything back into the carton, then moved the box into a corner of the garage because this antenna is MUCH MORE complicated (as far as assembling and erecting) than either a parallel dipole or a Butternut HF9V vertical which I am pretty much comfortable with at the time.
The TH3 and the HD 73-1 rotator had been pretty much forgotten for the last 4 years! In the back of my mind, I knew that I would play with it one day, but wasn't really sure how I could put it up...
In early Winter of 2001, after quite a few fail attempts work the DXpeditions in Africa with my dipole and vertical antennas, I decided to survey my property one more time trying to find a place for the TH3. The only place I may be able to put it up is right on the peak of the garage. The TH3 has to be mounted either on a heavy duty telescopic mast or on a roof tower configuration such as the one marketed by Glen Martin Engineering. My garage is not covered so it is quite easy to get up to the bottom of the roof and shore up the structure under the antenna mast and at the guy anchoring points.
After talking to a few friends on a local repeater, I was pretty much made up my mind to go with a mast support structure since it would look esthetically nicer than a roof tower. The mast would sit right at the peak of the garage roof and would be guyed at the four corner of the garage at the 10 ft level. I would use 2 sets of guy wires (2 x 4) to secure the the mast in place. The idea is that one set of guy wires would serve a back up for the other set. This would allow me to work/repair the guys while the other set hold the antenna in place.
But I still could not figure out how to mount a 37 lbs fully assembled HF Yagi antenna onto the 15 foot plus mast. The idea of tying a ladder (or 2) to the first 10 ft section of the mast so that two us can climb up there to attach the antenna doesn't entertain me very much since it is very dangerous. My buddy, Ori, AC6AN, suggested a mast which can be tilted down (like most roof towers) for antenna attachment, then a few of us can walk it up into the upright position while another person working on tightening the guy wires. As soon as Ori said the magic word, I knew exactly how I can build the mast and install it on the roof of my garage! This mast can be tilted down to the driveway to enable us attaching the Yagi antenna to it from a step ladder.
The first step was strengthening the portion of the garage roof under the antenna mast base and the four corners of the roof where guy anchors were to be mounted. A short trip to the local Home Depot to pickup 2 x 6, 2 x 4 woods, guy hooks and couple hours later, the garage roof was ready!
A visit to the my workplace machine shop for scrap metal to build the mast base, I found this block of stainless steel. Wow, this thing looks like it was built for my antenna project! It got all the correct holes and extremely heavy duty. I asked the shop owner if I could have it for my antenna project? He nodded, the mast base is completed! Note that the 2" mast is sawed off at one side to allow it to come to a horizontal position (as shown in picture above), but once it stands up, it wouldn't tip over the other side.
The first section of the mast is built using the 2" EMC conduit tubing at Home Depot. I drilled a couple of 5/16 holes to the bottom of the mast to attach it to the mast base using a 5/16 x 4" screw. Lots of washers were use to keep the mast center since this metal block can accommodate up to 2 3/8 inch diameter tubing.
The homemade guy plate is made of high current electrical box face plate (which I accidentally found at Home Depot during one excursion) The plate has a circular hole about 2" in diameter (It not quite 2", but it almost fit the 2" tubing which I had in mind for the base mast) I drilled four 1/4" holes at the 4 corners of this plate, then with a little bit of filing work, I was able to make one half of the guy plate (there were 2 of these plates bolted back to back to each other) slide through the 2" tubing. To keep the the plate from sliding further down the mast, I drilled a small hole across the mast. Once the holes were drilled, I inserted a metal pin through these holes, then bent the pin to keep it from falling out from the mast. I then tightened a 2" U bolt clamp to the mast just above the metal pin (The U bolt clamp was cut at both ends so that it would fit nicely inside the the guy plate housing) The other plate was "prepared" the same way, then slid into the 2" mast. The 4 1/4" eye pins were then bolted to the guys plates. The guy wires would be attached to these eyes...
Since this is an old antenna, I cleaned up all the aluminum components at the the connection points using Scotchbrite. A thin coat of Ox-Guard anti-oxidant was also applied to the connections before tightening the compression clamps. Since CW is my primary mode of operation, I used the dimension suggested for CW operation. The whole antenna is then assembled in the front yard so that I can get a feel of the dimension and weight of this thing. I also wanted to check out to make sure that all the traps were working properly.
The TH3 is then put on top of plastic sawhorses about 2 ft off the ground. I then hook up the MFJ 259 to the feed point to check out the antenna resonance frequencies. Even with the wire fence around it, the TH3 show very good SWR in the 20m, 15m, and 10m bands. All the traps were working properly...
Another shot of the TH3 before the elements were marked and disassembled for storage in my garage. I decided to mark and removed the elements leaving the last element section attached to the boom. That way I can put them back buy tightening just 6 compression screws.
After the mast was built and antenna assembled, I kept waiting for a weekend with clear weather so that I could organize an "antenna installation party" with the help of my buddies from a local repeater club. But for some reason, the weather in northern California was very unpredictable this year. The rain were still pouring down even in late April, especially on weekends! I had to cancel the "party" more than once just because things looked so good during the week, but turned into rainy weather on weekend. I kept watching the weather patiently and hoped for a break in the storm pattern.
The break came on Saturday, 4/21/01 (after I had called my buddies up to cancel the party the night before because of heavy rain on Friday!) Seeing that the sun came up really early and dried up all the rain water from the day before. There was also no wind! I decided to call up my friends to get the "party" started. Unfortunately, everyone already made alternate plan after I canceled the "party" the night before. Only Bob, W6KO and my brother in-law were available. Figuring out that I could erect the antenna with 3 people, I decided to go ahead with the installation.
The TH3 was re-assembled based on the previous markings. Noted that the right reflector element was not attached to the boom yet since it would interfere with the 4 ft wire fence on the right of the antenna. This section would be attached after we attached the antenna to the top mast, then raised the mast plus the antenna to at least 4 ft above the ground to clear the fence. Also note that the mast (and rotor) is already bolted to the peak of the garage roof. We decided to walk the mast and the rotor (minus the antenna) first to the vertical position. I then tighten up (with just a little bit of slack) the 2 front guy wires. Doing this step will allow the antenna and mast to from tipping over the side when we walk the mast up to vertical position.
I was lucked out, the antenna, once attached to the mast somehow fits through the opening of the fence gate! There is no need to raise the mast up just a little bit so that the reflector just clear the fence. So the reflector is attached through the fence gate at this point.
Things I've learned:
Unlike dipole or vertical antenna projects, erecting an HF beam required a lot of planning. The more time one spends planning the installation procedure on the ground, the less time to think and work out a problem when the antenna is raised (believe me, the last thing you want to do is when the antenna is raised, then a problem comes up and you don't have an answer for it!) Due to certain physical restriction at my property, i.e., 4 ft wire fence in the front yard, power line in the back, tall tree on the side, I did spend quite a bit time thinking about solving these problems. That really paid off since I knew exactly what to do when it was time to assemble the mast, mast base anchor, guy wires and antenna. I was very happy how well things went together that day. Believe it or not, I am already working on my next installation which will raise the beam another 8 ft higher, exerting less load onto the rotator, and mechanically sturdier.
So if the thought of improving the HF signal is in the back of your mind, may I suggest a small tri-band HF beam supported by a mast on the roof of your house. This antenna doesn't have to be very high. A rotatable antenna at a height of 30ft (~1/2 wavelength on 20M) will do wondrous job to your signal. You will be very much surprised to to find out how much better you can receive (and transmit) on this small beam vs. the old dipole or vertical... I worked J5X the other evening with just a couple calls...
Needless to say, I am a very happy camper at this moment...
73 es Gud DX,
This page was last updated on 05/15/01 at 1554 PDT