17 METER 3 ELEMENT MONO BAND
It all started with an
entry into the eHam.net
Tom, K6TC, was looking for help converting an old friend, the Mosley TA33 Junior, into a single band yagi for 17 Meters by eliminating the traps. It was just laying around collecting moss and "Green Slime" (which has collected on the background of this page).
Now I don't consider myself an antenna Elmer, but I decided to jump in with both feet and my foot in my mouth while trying to stay away from the slime. So, armed with the QuickYagi program, I offered what little assistance I could to a fellow Ham!
I had access to WA7RAI'S QuickYagi program on the harddrive and given the fixed length of a 12 foot boom on the original TA33 and the design frequency of 18.130mhz, I started to play with the figures omitting the Green Slime as a parameter.
I emailed Tom the measurements and that's how this re-encarnation started.
The end result, a few emails later and some input by K1WW and lots of fun had by Tom, is this project based on those figures taken from the QuickYagi program and a bit of experimentation, ELBOW GREASE and determination, by Tom!
"Atta Boy Tom"
The Resurrection and re-birth of an antenna.
Some 5 years ago a good friend and fellow Ham passed into the SK column of our W6LI newsletter and while helping his lady sort out his equipment, I happened upon an old very beat up Mosley TA-33-A junior tri-band Yagi that he had discarded to his recycle pile, destined for the aluminum junk pile during the next Boy Scout drive.
Only a 12 foot boom and most of the aluminum was there, even a couple of the u-bolts and one of the blocks that mount the elements on the boom. I asked permission to keep it from the pile and after this nice lady gave her permission along with free access to go through his junk pile in the garage, I looked to see if any other parts might be found that would be useful.
Taking the little beam home, I got out the good old Brillo pads and a bucket of water and started to see if I could bring back some of the shine Mosley is so proud of having on all of their products...not much luck there I'm afraid, but a start was accomplished until other projects got in the way and it was set aside.
After meeting my XYL, "Rocky", K6RGC and the final move to Lakeside, the little beam did make the trip up I-5 and sat for the next 4 years gathering Oregon's famous "green slime", buckets full of it!!!...seems that stuff really loves to find motor homes, antennas, anything made out of aluminum and locks itself on big time, just like super glue.
I have had an interest in the WARC bands, 10-12-17-30 meters, for a long time, if for no other reason, than the contesters haven't really started to congest the bands with their DX contests every waking moment on the weekends. A decent QSO can be had just about to any point of the globe should you have the antenna that can hear the signals that are out there AND be able to answer their call when they hear you.
My Sommers multi-band beam has been doing a great job of working the dx for me but I have had a problem for sometime with the mast I had installed under it when I bought it up north. Frankly it was a piece of junk and after many many dollars with Mike at his repair shop, it still wasn't what I wanted to depend on for reliable communications.
The search was on for a new tower! While the rebuilding of the tower situation was going on, I dug out the little antenna and got in touch with a Ham pal online, N4UJW Hamuniverse.com, who hooked me up with a really super antenna program called "Quikyagi". I couldn't download the program so I told Don what I had to work with it in parts and he got into the program running all of the figures so that we could convert this small trapped triband antenna into a killer 17 meter monoband yagi that would give me that extra punch to get through those pileups when the conditions were running on 17.
I used all of the element parts that I already had and purchased 4' lengths of 5/8 tubing from a flea market in Eugene to give me the length I needed to eliminate the traps. I was fortunate enough to be able to recruit AC7IR, Bruce to help out.
We cut the original elements in half and used them inside of the new tubing and sure enough there was more than enough length to bring each of the three elements into exactly where they needed to be and a resurrection took place right before our eyes!
Now I had a 17 meter yagi that looks so good I could almost swear it came from the factory built exactly as it is right now!
I thank Bruce, AC7IR and Don, N4UJW for their help, without which it would not of happened at all. Tom. K6TC
The program "Quickyagi" by WA7RAI, arrived at these lengths for the elements based on .625 inch diameter elements from end to end and NOT TAPERED. The center design frequency was 18.130 mhz. Antenna is driven as a dipole (direct connection to driven element) thru an "Ugly Balun" 1 to 1 ratio placed close to boom..
The figures below are total length for each element. This is what the program shows:
Reflector length 27.41 feet
Reflector space to driven 4.12 feet
Driven element 26.35 feet (remember this is a dipole type element open in the center)
Director space 7.39 feet
Director length 24.79 feet
You can round the numbers to the next higher digit and not make much difference and make construction much easier....can you read .79 inches on a tape measure?......not me .80 would be easier....hi!
These numbers should yield (in free space) about 7.5dbi gain and 23.8 f/b according to "QuickYagi".
Of course this is the ideal situation.....bet you don't have that! HI!
After running the program several times with different values for element sizes, lengths, optimizing, etc.....it appears that there is not enough difference in each to make any difference on the receive end.
I think this is because of the restriction to the 12 foot boom length which we had to work with.
Click here for ASSORTED PICTURES TAKEN DURING CONSTRUCTION
MODIFICATION OF THE TA33 JR