I second this idea.
Wes N7WS
On 12/19/2021 9:11 AM, Wes Attaway wrote:
Without going into all the feedline details, why not just add the extra wire
to the far end of the horizontal portion? If you don't have enough space
for all of the extra horizontal wire then I would suggest letting any excess
drop down at the far end. I would leave everything else the same other than
possibly pruning the far end to regain whatever you lost on the original SWR
curve.
-----------------------------------
Wes Attaway (N5WA)
Shreveport, LA
-----------------------------------
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Pete
Smith N4ZR
Sent: Sunday, December 19, 2021 9:59 AM
To: TowerTalk
Subject: [TowerTalk] 160M Antenna puzzlement
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).
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|