Sunday, July 26, 2015

Building a new antenna at N6QW ~ Part I

A New Antenna Installation at N6QW

When I moved back to California in Mid-2013, it was with great trepidation and sense of loss of my beloved extended Lazy H antenna. Moving to a postage stamp sized lot with no trees surely was a step back from my former QTH that was a 1/2 acre lot with 150 foot tall pine trees, located about 500 feet from Puget Sound with a clear shot to Europe. But life can be cruel and we should always think of the glass as half full!
My  antenna at the new Southern California QTH was a compromise given the time available, my desire to get back on the air and working with what I had. Subsequently I ended up with a 20 Meter Extended Double Zepp that was arranged in an inverted Vee configuration with the apex at 26 feet and the ends at 10 feet. For the center support I purchased a 4 section telescoping fiberglass pole and bracketed the lower section to one of the eaves on the back side of my home.
The antenna is fed with a 35 foot section of 450 Ohm line from a 9:1 Balun which then connects to 52 Ohm coax to the shack. I work all bands and use a homebrew 3 KW "T" type tuner. It was like night and day as compared to my Extended Lazy H. But it was certainly better than being completely off of the air and/or some sort of random wire in the attic.
Below are a couple of photos of that antenna. I must have properly engineered the install as it has held up very well but now is the time for something better.

Using the experience gained with this install I am replacing the 26 foot fiberglass pole with a Rohn H950 push up steel mast that will top out at about 34 feet which gives me 1/2 wavelength on 20 Meters. I will keep the 20M EDZ and that will be at about the same height as today. At the top of the mast will be a Moseley 2 element beam. This beam which is a custom product uses the driven element from the TA-32 and the director from the TA-32 Jr. The idea here is that you can run legal limit into the beam but it weighs less than the TA-32. Turning this monster will be a Yaesu G450 rotator which has been identified as problematic -- but it is what fit in the budget. The known problems involve the control box and not the rotator --so maybe a chance to design an Arduino based rotator control as a retrofit to the Yaesu Controller
In Part II I will document the engineering of the H950 Mast assembly which I have modified so that it will fit in a ground mounted clevis assembly. This was done  so that it can be easily raised into the vertical position. From there a similar house bracket will keep the bottom section "vertical". Guying will be used for the upper section to keep things safe and sturdy. There will be a poured concrete base to capture the clevis assembly and keep the base of the antenna solidly anchored to the ground. The clevis assembly was made from standard metal parts manufactured by Simpson products and sold by Home Depot.
Stay tuned for Part II