Saturday, September 1, 2012

G5RV in a Sloping-V Configuration

I built a G5RV for portable work about a year ago and have used it on occasion as a flat top and as an inverted-v with good reports.

My back yard is small so I have difficulty installing even the G5RV as a flat top so I decided to give a sloping-v a try so I could get on 80 meters with better results.  The antenna was installed about a month ago.

I have been reading on N.V.I.S. and plan to make a N.V.I.S. antenna over the winter.   This is some of my reasoning on using the G5RV in different configurations including N.V.I.S. 

My sloping-v is not the traditional as the ends are about 7-1/2 feet off the ground.  The apex is about 25 feet from the ground. 

So far I have worked most of the South Eastern states with this antenna on 80.  Not DX by a long shot, but much better than I have been able to work on any other antenna.

Plans are to try this at more of a slope to bring the ends closer to the ground as a true sloper would require and to try it with terminating resistors.  The G5RV is not resonant on any single ham band especially using this configuration.  I do not have the ends terminated nor am I using a counter poise.  I have radials on the vertical and they provide the ground plane for the sloper.

Checking the antenna with my handy-dandy but how accurate MFJ antenna analyzer the antenna has a 1.2:1 VSWR @ 50 ohms @13.848 MHz and 1.5:1 @ 50 ohms @14.000MHz.  The analyzer shows a 1:1 VSWR @ 50 ohms @35.565MHz and again at 75.6935 MHz.  I do not fully trust the MFJ analyzers, but they get close.  I question their accuracy because they will indicate 1:1 at anywhere from 35 to about 60 or 70 ohms.  I have used several and find the same results.  I plan to check this antenna with a GR bridge when the weather gets cool enough. 

This is the G5RV.  A bit difficult to see the V.

Feed point is the white in the lower right corner.

End supported by 2 LCSS aluminum poles

Each end pole is held by a section of PVC pipe attached to angle iron driven into the ground.

This is the apex about 25 feet high.   Guy plate is between the 5th and 6th section of a mast made from MS-44 aluminum sections from an AB-155/A/U
How important is a 1:1 VSWR?  Not important really. I have worked at enough radio stations and done commercial communications to know that the best match is not generally at 1:1.  There are many references that will support this. To me it's just nice to know if something can be 1:1.

1 comment:

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