Thursday, 1 October 2015

Antenna Plot

I ran a return loss sweep with the sna and exported the data into Excel. The resulting graph below.  There is no vswr data in the exported data file so I can't display it here.  It is displayed on the sna screen though.

It's an interesting plot, that seems to work very well. I did a sweep from 7 mhz to 29mhz. It was a little chilly this morning and I didn't want to mess around with several runs focusing on the individual bands.  Maybe this afternoon. What I don't know unfortunately, is how much effect the tree has on the results with the antenna leaning up against it? I hope a lot. hihi. 

I do remember years ago trying to tune up a ground mounted vertical I had then. I recall very well the dramatic effect I had when I stood near the antenna.  I can't recall how far away I had to stand to minimize the effect, but I think I was limited by the amount of coax I had and was forced to make due. I seem to remember trying to look at a very small screen from a distance so I reduced the effect my presence was having. Don't have an issue in that regard any longer.

I don't really have time to set up a temp. structure to mount the antenna for further testing so I'll have to hope for the best once its up in the air and re-run the sweep for a comparison.  That alone should be interesting regardless of the results.  If its really out of wack, then I'll make due for the winter and haul it down next spring and set up something.  I have a 10' section of tower that I could use and just guy it off, but that maybe easier said than done.  Anyway I have a 5 band antenna and I see 5 peaks in the plot.  Good enough for now.

73, Peter





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