The Pocket Vertical

2010/07/08                    日本語は下にあります   ve3cgc@hotmail.com

 

 

“ The Pocket Vertical “     「ポケット バーチカル 」

 

 

The antenna was designed and experimented by VE3CGC including the computer simulation using the MMANA and here is called as “the pocket vertical”.  It can be easily and cheaply homebrewed.  It is a mono-bander using wires so as to be packed small when folded in.  Once the final tuning has been made, it can be deployed without adjustments for the most of time ready to go on air depending on the set up.  It is good for the portable use as well as for the limited space use.

 

I uploaded some pictures including a figure of the sketch under  “ The Pocket Vertical “  on July 08, 2010.  Please click it to enlarge the image. 

 

The loading coil:

The loading coil can be homebrewed with a coil form using a plastic cap or a bottle with a diameter of 2 1/2 inched or larger and with the A.W.G. 18 or heavier.   I recommend use the formula shown in the ARRL radio handbooks for making coils.  The easiest way for the loading coil is to pick up the air inductor by the Barker & Williamsom (B & W) in a hamfest.  It is 46 µH for 40m, 16 µH for 30m, 5 µH for 20m and 8 µH for 15m band.

 

The elements:

The antenna has the upper element, the lower main element and the counterpoise.  The materials can be practically any wires and in my case I used the left over wires for the Christmas lights. 

 

Calculating the elements:

L= 1/4 of one wave = 75/F   (meters)

F= Frequency in Mhz

V.F. = velocity Factor of wires = 95% =0.95

L’ = L x V.F. = (75/F) x 0.95   (meters)

 

The upper element = L’ x 0.25   (meters)

The lower main element = L’ x 0.4   (meters)

The counterpoise = L’ x 0.6    (meters)

 

The example calculations are shown below:

 

Pocket Vertical Antenna

 

40m

30m

20m

15m

remarks

F=design freq. Mhz

7.05

10.11

14.05

21.05

 

L=1/4 one wave

10.64

7.42

5.34

3.56

0.25×300/F

V.F.=velocity factor 95%

0.95

0.95

0.95

0.95

 

 

 

 

 

 

 

L’=LxV.F.

10.11

7.05

5.07

3.38

 

 

 

 

 

 

 

upper element, m

2.53

1.76

1.27

0.85

L’ x 0.25

lower main element, m

4.04

2.82

2.03

1.35

L’ x 0.4

counterpoise, m

6.06

4.23

3.04

2.03

L’ x 0.6

 

 

 

 

 

 

loading coil, micro H

46

16

5

8

 

 

The tuning:

Set up the antenna outside to carry out the tuning.

The tuning can be made by adjusting the length of the upper element to get the best SWR.  I used my MFJ -259B antenna analyzer.  The length required by the formula for the upper element is not definite by calculation and it is approximate.  

Once the final tuning is made, no additional adjustment is required when deployed for the most of the cases.   When it is set up close to a building, poles etc. then you may need relocating the counterpoise or away from trees and buildings on the antenna if you do not have a reasonable SWR.  From my experience, I have had no additional adjustment required for QRL.

 

Good luck and 73.

VE3CGC  Hiro Hayashi   ve3cgc@hotmail.com

P.S.  A figure (sketch) could not be successfully uploaded.  If you need it please e-mail me.   I will attach the figure with-mail to you.

This entry was posted in ham radio, amateur radio,ハム ラジオ、アマチュア無線. Bookmark the permalink.

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