Sunday, April 22, 2007


The weather has finally improved here in New England bringing clear skies and temperatures into the 70's. This, after a week of cold and rain, was very welcome indeed. Time to go outside, soak up some sunshine, and play with antennas!
I had blogged earlier about making a 10m beam from Buddipole parts and had promised myself that I would give it a try on the first really nice day. So, Saturday afternoon Sandy and I pulled my big buddipole along with the new parts that had arrived recently out to the front steps. It only took a few minutes to build the yagi as I had designed it and hook up the AntennaSmith analyzer. The SWR curve was as predicted. The antenna appeared to be mechanically sound. This last point wasn't surprising as these Buddipole parts are robust, one of the reasons I like this stuff so much. The thing was so solid Sandy suggested we build another version with six arms on the boom instead of four giving it a total length of 11 feet.
The new version of the antenna also seemed solid. The long telescopic whips extend to 9.5 feet but are lightweight so even with three lengths of arms between the VersaTee and the IT adapter holding the whips, there was very little sag along this lengthened boom.
I've not had time to model this new version (3-element beam with 11-foot boom) but I'm pretty sure it would be a good performer. The only exigent problem was matching the antenna to 50 ohms. The analyzer showed a real resistance of about 120 ohms at resonance for a large chunk of the band. A balun stepping this down by 2:1 would be just about right. I'll see what the computer model says before I do any more work on this.
With the Mosley Mini-32-A on order, you might be wondering why I'd be fooling with this antenna. Imagine a trip specifically for the ARRL 10 meter contest. A three element yagi with an 11 foot boom will likely outperform a two element yagi with a 6 foot boom like the Mosley. Gee, I wonder if I could put any more arms in this thing without breaking something?
Content with my progress on the 10m investigation, we then moved to 6m. Carl Gosselin KG6WTF has a page describing a 6m 3 element yagi that uses four arms, six whips, and 3 IT adapters. We built that antenna as per those directions, then built another version with six arms instead of four again giving the antenna an 11 foot boom.
We had built something similar on Montserrat but had no 6m openings. I'm pretty sure I'll get some business during the CQ WW VHF Contest this Summer. So, I'll give this thing a try first at Field Day then again during that contest.
Finally, one of the cool things in my shipment from Chris was a new antenna mast bag. The original bag that was used to carry my big Buddipole system was just a little too small. The newly designed bag is big and roomy. I love it! Recommended.


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