[TowerTalk] 160M Antenna puzzlement

[Pete Smith N4ZR]

I may be suffering from a case of too much information, but I'm puzzled 
by my new 160-meter inverted L, about 60 feet vertical with 8 on the 
ground radials each about 65 feet long

My old inverted L broke, so I put up a new one recently.  To my 
surprise, it resonated well above the band, indicating it was about 12 
feet short.  Because of uncertainty about the availability of additional 
height at the top corner,  I temporarily added the additional length at 
the bottom and loosely coiled it.

Measuring the SWR and R/X at the base of the antenna with my Rig Experts 
AA-55 Zoom, I now see a nice textbook SWR curve centering on 1820 KHz. 
Measuring the R and X at the same place, I see R of about 30 ohms and X 
crossing zero near the same frequency.  That seems a little low for only 
8 radials on the ground but...

So now I come into the house.  The feedline is about 75 feet of RG-8X to 
my tower-mounted antenna switch, and then about 170 feet of Buryflex to 
the shack.  I'm well aware (in general arm-waving terms) of the 
impedance transformation effect of feedlines, and even at 160 this one 
is fairly long, but:

In the shack, I see the same nice SWR curve, centered about 10 KHz 
lower. The confusion arises with the R and X curves - the R at resonance 
is a little lower - about 26 ohms - but rises on the upside to about 140 
ohms at the high end (around 1920 KHz and then drops steeply to around 
12 ohms by 2150 KHz.  The X value, on the other hand, crosses zero at 
around 1780 KHz, and rises to around 70 ohms at 1870 KHz and then dips 
sharply, crossing zero again at 1915 KHz.

So, two questions:

1.  Is what I am seeing simply the result of the feedline transformation 
of R and X, and

2.  If it proves impossible to raise the knee of the inverted L further, 
can I just leave that small coil of wire in place at the bottom of the 
inverted L?  It seems to work pretty well  - I worked a number of 
Europeans last night in the Stew, although it was tough to hear them (I 
have not yet reinstalled my K9AY loop).

-- 
73, Pete N4ZR
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