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[TowerTalk] 1.8 MHz half sloper using tower VSWR question

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Subject: [TowerTalk] 1.8 MHz half sloper using tower VSWR question
From: (Ken Kinyon - W7TS)
Date: Tue Feb 18 17:39:36 2003
I think there may be some math errors in computing your SWR.  Unless I am
mistaken, The lowest possible SWR is 1:1, so if you are getting 0.2 to one
something is wrong with the formula you are using.
Ken W7TS

Kenneth E.  Kinyon
34 Princeton Circle
Longmont, CO 80503-2106
Voice: (303) 684-0037
Fax:  (303) 776-5088

ALPCA #8339

-----Original Message-----
[]On Behalf Of Jose M. Valdes R.
Sent: Tuesday, February 18, 2003 10:05
Subject: [TowerTalk] 1.8 MHz half sloper using tower VSWR question

Hi all.

I'm new to this list but I have being reading your posts at the archives
in and I must say that I enjoy them very much.

Now, I have a question.

After 9 years I'm getting back on the low band, so I built an antenna
for it. This antenna is half-sloper using a tower with the following

The tower is guyed aluminum with a height of 15 meters (+- 49.2 feet)
including the top mast which is 6 meters (+- 19.7 feet) in length, this
mast is the support for 3 monoband Yagis that provides the capacitance
hat and installed in the following order from bottom to top, a 4
elementes for 20 meters on a 11 meters (+- 36 feet) boom, a 5 elements
for 6 meters on a 6 meters (+- 19.7 feet) boom, and a 2 elements for 40
meters on a 5 meters (+- 16.4 feet) boom.

I attached 8 radial to the base of the tower of random length as was
allowed by the available space.

Also I ran a ground wire from the base of the tower to my grounding
system, which consist of a 280 square meters (+- 3014.9 square feet) of
a grid of squares of 2 x 2 meters (+- 6.6 x 6.6 feet) constructed with 2
inches galvanized pipe and buried 3.3 feet below the ground.

The half sloper consist of 39 meters of number 14 wire in a sloping
horizontal "L" shape and attached at the 35 feet point with a very short
insulator (2 inches) and very short (2 inches) wire from the braid of
the RG-8 to the tower, you can see a diagram at the URL below.

This antenna is showing a very unusual bandwidth that spans from 1.800
MHz to 1.950 MHz with a VSWR of 2.0 to 1 or below and a minimum of 0.2
to one on 1.870 MHz and 1.880 MHz, this seems to be unusual for these
band, since I don't recall having any previous 160 meters antenna  with
such a large bandwidth, below is the VSWR table.

1.800 2.0 to 1
1.810 1.7 to 1
1.820 1.6 to 1
1.830 1.4 to 1
1.840 1.3 to 1
1.850 1.3 to 1
1.860 1.1 to 1
1.870 0.2 to 1
1.880 0.2 to 1
1.890 1.1 to 1
1.900 1.2 to 1
1.910 1.4 to 1
1.920 1.5 to 1
1.930 1.7 to 1
1.940 1.8 to 1
1.950 2.0 to 1

At 1.870 MHz and 1.880 MHz the impedance if of 47 ohms.

Now to my questions.

Is this bandwidth possible for a half sloper?

And of not, what may I have done that is wrong?

2 nights ago I talked to YV4GD, in Valencia, about 200 KM form my QTH
and we both running 100 watts and the signals at both ends were 59 + 10

73/DX Jose M. Valdes R. (Joe), YV5LIX.


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