Saturday, September 5, 2009

45ft Vert

I've written about my diversity setup so I thought it might be interesting to see my setup. This is my 45ft vertical in the front yard. It is a wire up to a eyebolt that I had installed on one of my pine trees. Here is a shot of the waterproofed autotuner at the base of the antenna

The tuner is a MFJ 929 auto tuner in a 50 cal ammo box

The coax connector from the transmitter is connected to a 2 inch barrel connector that feeds through a hole and is bolted to the back of the box that acts to suspend the tuner in the box. The antenna connection is visible in the above picture. I ran the antenna coax out through another hole. It turns out that the input and output coax feeds need to be isolated. My first idea was to use 2 barrel connectors but that failed miserably. By using this method the tuner behaves properly. The toroid was put on the coax in an attempt to get the "RF" out of the circuit when I had both antenna ports connected to the barrel connectors. It probably isn't necessary.

The MFJ-929 has the feature that it can be powered over the coax through a voltage injector so no additional power line is needed.

MFJ sells an injector

or it is simple enough to build if you have the parts laying around.

The feedpoint is thus. The vertical wire goes into a 4 turn 3" loose coil. This has plenty of give so the wire is not taught as the tree sways in the breeze.

For this installation I have only a couple of radials since this was intended to be a RX antenna. However it turns out this antenna is a quite good transmitting antenna especially from 40M to 6M. It is fair on 80 and poor on 160 as a transmitting antenna but it does work as an RX vertical on that band as well.

As you can see the antenna is quite stealthy

And with a more adequate ground plane would be an excellent antenna for people who have to deal with stealth and covenants and home owners associations. This set up is good for 200W transmitted power.

To use this antenna I simply set PowerSDR to ant-3 (the port to which this antenna is connected) and run about 7 watts down the line in a second or less the antenna is matched. I then turn on diversity in powerSDR using my other full size verticals out in back. I have run tests using as my remote receiver and 100W. I have made dozens of DX contacts using this antenna on 40M and 30M, and I have made contacts on 6 as well.

My diversity setup has the 2 antennas separated by about 200ft Here is a shot of my other vertical from my website You can see the tree from which the 45ft wire hangs directly in line through the garage.

I thought it might be interesting to document this little antenna since it works so well. It is not as good as my full size verticals out in the back but if I had to put up one stealth antenna this sucker would fill the bill.