Showing posts with label loop. Show all posts
Showing posts with label loop. Show all posts

Thursday, May 3, 2012

In Search of a Telephone Pole

I think these might more appropriately be called utility poles but around here we call them telephone poles, regardless of what they have strung on them.

A couple of years ago, I put up a loop antenna comprised of 536' of wire suspended about 20-25 feet off the ground.  See my blog of December 3, 2011, if you are really interested in the details.  At the time, I suspended the loop, or "skywire" antenna, with four poles made of chain link fencing top rail and my tower, making a total of five supports.

The skywire antenna has worked better than I ever could have imagined and I've decided that I want to elevate it some to allow it to function even better.  I've tentatively settled on 45' as a goal.  The top rails are "maxxed out" at 25' so there is no way to use them at increased heights (without a bunch of guy wires).  Another alternative would be four additional towers; this would be totally cost prohibitive!  At any rate, I have settled on utility poles as the most viable option here.

I'm now finding out that you can't just go down to the utility pole store and buy four poles!  For one thing, they are very difficult to haul (you have to have a very long trailer) and install (a digger derrick truck is a must for this task).  My first try was our local electrical co-op; they weren't too interested since this project isn't going to help them sell more electricity.  The next try was a couple of electrical contractors who build transmission lines for the co-ops.  They are used to big jobs and didn't want to mess with a ham radio operator who only wants four poles!

My last chance to get these poles and have them set is a local electrician who does quite a bit of commercial construction.  If he won't do it, I may have to find a new plan!  I'll let you know.

Saturday, December 3, 2011

160 Meter (Skywire) Antenna


After listening to several people who had loops, I decided that I had to have one. I got it up about a year ago and it has been a wonderful antenna, so good that I took down my modified G5RV.

A short description: it is 536 feet long and is about 25 feet high.It has five sides and one of the corners is attached to my tower. The feedline from it to the house is 450 ohm ladderline, which is very similar to the old television flat wire we used when I was a kid. It runs through a 4:1 balun which is mounted just outside the window and then uses coax to connect to the tuner.

There is only one problem with this antenna: it is very difficult to tune on 160 meters. It works great on 80, 40, and 20 but the band it is designed to work best on is a flop! I'm not smart enough to figure out what is going on but I'm gonna start changing parts till it gets better. This is also the way I work on cars, by the way.

Here is a copy of the antenna performance from 0.5 to 8.0 mHz. You can see that there are "lobes" at about 3.8, 5.5, and 7.2mHz, but none in the 1.8 to 2.0mHz range (160 meters). I gotta learn more about antenna design and performance.