[TenTec] A Low VSWR Will Kill You

[Bob & Linda McGraw K4TAX]

Keep in mind that a center fed wire antenna, of equal lengths each side
of the center feed point, fed with a twin lead, open wire or otherwise,
does not make a balanced antenna.

Ask yourself these questions:  
Is each side of the antenna see the same inductive or capacitive loading
from nearby objects? Most likely not.
Does the ground resistance under the entire antenna remain constant?
Most likely not.

Here's what I've found by inserting an RF amp meter (thermocouple type)
in each side of the feed line.  The curents were not equal.  Measured
the length of the wires again.  They were within 1/2" of 128 ft.  The
feed line was of equal length on each side.  RF currents were about .25
amps different.  Swapped meters.  Still the one feed current indicated
about .25A more than the other.  Swapped meters again.  Still the same
feed indicated .25A more than the other.  Grounded one side of the feed,
measured the current.  Grounded the other side of the feed.  The
currents were not the same.  Conclusion:  The antenna, in spite of being
physically identical was not electrically identical.  Solution: Move one
end of the antenna so it didn't go over the trees and the house (even at
65 ft).  Problem solved.  Feed currents are now the same.  

So from now own I'm gonna be careful about using the term "balanced
feeders" or balanced antenna.  Not necessarly so.

I'm a long time and firm user of a balanced feed on an HF wire antenna,
even having to use a unbalanced tuner and a balun to get it to work
right.  

As to antennas on 6M and higher, very low loss coax is the only way to
go.  Dealing with keeping a balanced line balanced at VHF will make you
have grey hair before your time.  Ever tried G line with launchers on
VHF?  I have.

73
Bob K4TAX


--
FAQ on WWW:               http://www.contesting.com/FAQ/tentec
Submissions:              tentec@contesting.com
Administrative requests:  tentec-REQUEST@contesting.com
Problems:                 owner-tentec@contesting.com