Topband: VSWR changes with ground precipitation changes

Dennis Peterson dennisissure at comporium.net
Mon Mar 16 06:33:17 PDT 2009





GM morning all;  I have noticed an unusual change in the VSWR in my inv-L over the past week or 10 days due to an increased amount of rain and water absorption in the soil around the ground radial field.  

Prior to the much needed rain her in York, SC my inv-L showed a VSWR range of a resonance that began at 1.785.000 of 1.5:1 and again at 1.855.000.

With approximately 2 inches of rainfall and snow over the past 10 day period, the VSWR has changed to 1.765.00 and a 1.5:1 VSWR and again at 1.865.000.

When I go further down in frequency to check for the 2.0:1 points it shows up at 1.745.000 and again at 1.875.000 where the IC-735 shuts the transmitter down by way of a XMIT shut down.  IT DOES NOT do this when going the other direction, in fact it shows a 2.6 at 1.700.000 but does not shut down.

1:1 VSWR range is 1.800.000 to 1.820.000 which I consider EXCELLENT WITH NO TUNER .  The tuner is in line ONLY when operating above 1.845.000 SSB.

The radial field is predominately located around the base of the L and the lengths are approximately 36 feet long in a 235 degree plain.  There are two (2) FULL QUARTER WAVE radials that extend out from this field in a Western direct but fold back from the property line back towards the base.

Will a ground rod out at the end of the quarter wave radial/s make any significant difference?  The ends of all radials are currently unterminated they just go out to their ends and are left to float.  

Does anyone have comments or information pertinent to these conditions and prevailing issues?  I would really be interested in knowing what is going on if anything.

By the way, I have noticed one other intersting phenominum; that is the NOISE LEVEL on the L has gone from S7/S8 down to S0/S1n and doesn't get any higher than maybe S3 to S5 on 160 meters. Does anyone have an answer or rhyme and reasoning for this?

Thanks and 73s 
de K0CKDennis











Dennis G. Peterson
326 East Jefferson Street
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York, SC  29745
803-389-9366

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