Instructions for making a Linked Dipole of 3-8 frequencies
By Justin Giles-Clark VK7TW
Bill of Materials:
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1 x Insulated Centre Ring
2 x Insulator tabs for each band (ie. 8 bands = 16 insulator tabs)
2 x Winders
2 x Insulated wire for bands of choice
10m x RG-174 Coax
1 x crimp BNC connector for RG-174
4 x number bands less 4 alligator clips
2 x 3m segments of cord
2 x steel pegs
4 x Cable ties
4 x heatshrink (2 x 20mm length of 5mm and 2 x 20mm length of 10mm)
Solder
Planning your Dipole
1a). For a 3-5 frequency dipole go to SOTABeams website and use the calculator:
http://www.sotamaps.org/extras.php
1b). For a 5-8 frequency dipole go to VK7TW’s blog and grab the spreadsheet:
https://vk7tw.wordpress.com/2015/01/26/vk7tw-linked-dipole-experiments/ (bottom of the page)
2). Enter the centre frequencies for each band starting with the highest frequency. The spreadsheet
will provide the length of each segment in feet and metres. I have found that you need to add
approximately 80mm to the length to give you enough to tie off the segment.
Building your Dipole
3). Carefully cut two of each wire segment and mark segment number with a permanent marker –
highest frequency is No.1.
4). Half hitch the two No.1 segments onto the centre insulated ring leaving 40mm of end to connect
to the Coax.
5). At the other end of each segment tie to and insulator tab leaving
40mm of end, then repeat with segment 2, 3, 4, etc. On the insulator on
the squid pole side of the segment - write in permanent marker the
band and frequency you are tuning for (see picture). This will help when
tuning.
6). Solder an alligator clip onto the stake side (not squid pole side) of
each segment at each insulator tab and clean 5mm of insulation of the squid pole side segment.
7). Tie the last segment onto an insulator table and the 3m of cord on the other side.
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8). Wind each completed side onto the winder.
9). Cut 10m of RG-174 coax and weave through the centre strain relief holes as shown in the picture
leaving 50-80mm tail. Place a 20mm
length of 10mm heatshrink on coax.
Carefully strip back 30mm of the coax
braid from around the centre
conductor. Cut two 20mm lengths of
5mm heatshrink and place on the
dipole segments. Strip the insulation
from 5mm from each end of the
dipole segments and tin with solder.
Tin the ends of the coax braid and
centre conductor – solder together
one dipole segment to the coax centre
conductor and the other dipole
segments to the braid. Slide the heatshrink down the dipole segment to
cover the soldered connection and heat to shrink the insulation. HINT: This picture shows an earlier
model with cable ties – the ones we will build just have a half hitch.
Tuning your dipole
10). Start with the highest frequency (shortest segment) unclip the rest of the segments. Raise it up
to the maximum height on squid pole.
11). With the antenna analyser go to the frequency you want the segment tuned for and see where
the lowest SWR is. If it is at a lower frequency then you need to shorten the segment – done by retying the end of the segment without the alligator clip and winding the excess up the segment. Raise
the squid pole and check where the SWR trough has moved to. If the SWR is higher in frequency
then you will need to add some wire and this is easily done by jumper clips. Repeat the exercise until
you have reached less than 1.5:1 SWR – HINT - don’t be too finicky!!
12). Lower the Squid pole and clip the next segment together and repeat the exercise for each
segment. HINT: if the segment is already below SWR 1.5:1 then move on to the next segment.
13). Repeat until you have checked all
segments.
Finishing off
14). Solder the other alligator clip onto the
remaining segments once tuned.
15). Loop the four cables ties through the
winder holes and around the steel peg and
lightly tighten to hold the peg to the winder
(see picture).
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16). You have completed your linked dipole!
Erecting and Using your Linked Dipole
17). Extend the highest segments of the squid pole and place the centre insulator over the pole.
18). Unroll each side of the dipole (do not tie to anything yet) and make sure you clip the alligator
clips together up to the frequency you want to use.
19). Raise the squid pole to maximum height and wedge the squid pole in rocks or a tree, etc
20). Tie off each end of the dipole to a tree, rock or use the steel peg in to the ground.
21). Plug in the BNC connector to the transceiver, set the band and mode and start operating.
22). To change bands lower the squid pole to a level where you can reach the relevant alligator clips
for the band you wish to move to. Raise the Squid pole back to full height. Change bands and mode
and continue operating.
SAFETY FIRST – LOOK UP AND LOOK OUT
Squid poles enable 9m of height and in suburbia this means the ability to touch powerlines and your
antenna is made from conducting wire!!!
LOOK UP AND LOOK OUT
Enjoy
73, Justin, VK7TW
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