Sunday, December 13, 2015

Some Antenna Work and Repair

UPDATED: Tue Dec 22 21:38:59 PST 2015

I removed the 9:1 BalBal from my Off-Center-Fed Long Wire Antenna, as described below, it did not work as well as expected. More testing and measurement needed.

There has been a lot of chatter on the local Yahoo pQRP email list about building some 9:1 Ununs as a group project. I already have the Toroids and Wire and had planned to make several of my own - I was just waiting for a Round-TUIT (TUIT).

For the last several (6 or so) years, I have been using a 300 foot Off-Center-Fed (OCF) Long Wire antenna. It is strung up near the top of some nice tall trees with the feed point at about 90 feet AGL. It has worked very well on all bands for WSPR, QRSS, CW, and general Ham use. The antenna is fed with 450 ohm ladder line fed from a Tuner with an internal Balun. I rarely have to provide much L or C adjustment for reasonable performance.

With a crippled antenna (see below), last night I worked Sandy - KG7FFP as she is new General License Ham - Good going Sandy! We were on 80m, 3.885MHz.

There are several things that I have wanted to try, to see if I could improve performance.

The first, is a no-brainer; Ground the Tuner and the Rig, something that has always been waiting for another TUIT.

The second, may be more controversial, I have wanted to put a 9:1 BalBal at the feed point of the OCF Long Wire.  With 450 ohms ladder line in, the output should approximate 4050 ohms, which I think would more closely match typical OCF Long Wire feed impedance. In my case the short end of the Long Wire is about 20 feet. The Feed Line drops straight into my Loft's window, across the celling to the Ham Rig, I think more impedance is desirable, in reality, I thing everything in close proximity becomes the antenna, that is; the long wire, feed line, metal roof, and the moss soaked wet-trees, and I don't think they are typically just 450 ohms  :-)

Another "nit" that I wanted to improve (or remove) is the "egg" insulator at the feed point. I have never really liked this centre point set up, but it is what I had when it was first installed. The new set up is a now a 14 inch long, 3/4 inch PVC (conduit) with three holes in each end. The antenna wire goes through a "Z" bend at each end of the conduit, then "V's" down to my new 9:1 BalBal, which is about 18 inch lower. The antenna wire is standard, solid copper 12 AWG conduit wire.

My antenna tuner is still in my eShop waiting replacement diodes (CDSH270), they are on order and should arrive soon.  The antenna and Tuner took a near hit during one of the last electric storms. I was near the radio and heard a snap or spark across the terminals or somewhere inside, the radio did not suffer any ill effects, the tuner TOOK it ALL.

So, now what?

My newly configured OCF Long Wire Antenna is now up and ready for use, but still waiting tuner repair.

I am expecting some VERY GOOD to EXCELLENT performance from this antenna configuration, because it was installed exactly as per the weather-man specification - that is, it was raining all the time I was outside working with; support lines, antenna wire, BalBal, and feed line. I got soaked ! Everyone knows, that the best antennas always go up during inclement weather.

But, time will tell, I will post my impressions, measurement, and results, when available.

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