N5PUV’s 4 Band Fan
Dipole Experiment
Using the New SRI (Stanford Research
Institute) Method
Goals of Experiment
• Develop a Multi-band Antenna that does NOT
require a tuner
• Build using the new, easier tuning method “SRI”
• Use least expensive methods to build using leftover
materials and few new hardware pieces
• Be easy to build and hang in less than a day or two
• Be easy to install by one or two people using
existing structures (1 in this case)
• Be a good performer on chosen bands
Materials List • PVC pipe 3 to 6 inches in diameter (left over)
• Caps to fit either end of that pipe
• Copper strip (left over)
• Brass Screws, washers and nuts (left over)
• Eye Bolts with nuts
• THNN House Wiring 220 feet (had this left over)
• 18 to 21 feet RG8X Coax (left over)
• SO-239 Connectors
• 2 – 10 foot ½” PVC pipe for spreaders
• Oh, and whatever tools you have to use on this.
Step 1:
Prepare 2 buss bars
Needed: 2 Strips of Copper
at least 18 inches long.
Drill 3 holes in each for brass
screws every 5.5 Inches
Here I used some brass
Channel for Stained Glass I
had lying around.
You could use copper pipe
strap or any stiff piece of
copper strips
Step 2:
Solder Brass Screws
Here I soldered the Brass
Screws to the copper strip
This makes installation easier
in a future step, but is not
mandatory at all. If you are
patient or have better tools
you could omit this step
2 Identical Finished Copper Strips with Brass Screws Attached
Here I made 4 screws
spaced at 5.5 Inches Apart
for a 4 element Fan Dipole.
You can use 2 or 3 if you
want
Step 3: Create Ugly Balun on bottom end of
PVC pipe
This is using 18 to 21 feet of
RG8x, but any malleable coax
will do for low power.
Simply wind the coax around
the 3-8” PVC tube as shown,
drilling holes in the PVC for the
start and ending ends.
PVC size is not critical nor is
number of turns, just the
length.
Step 4: Drill Holes for
the Copper Strips
Here I carefully lined up the
holes with the finished strips
on opposite sides of the
pipe above the balun.
Drill holes on opposite sides
of PVC pipe for brass screws
to poke through from the
inside.
Step 5: Insert the copper buss bars inside
the PVC Pipe
With the screws soldered to
this single strip, it was easy to
get the screws lined up with
the holes if they were
carefully spaced the same
distance (5.5 inches) apart
on each side of the pipe
Not doing this would require
a way to hold the screws in
place from the inside.
Step 6: Bolts on outside of Copper Strips
All screws get capped with
Wing nut or other type of nut
as long as it is metal to
metal.
On the finished project I put
a nut on first, then a SS star
washer, then a SS Wing Nut
on every dipole connector
here that is connected to
the copper strip inside.
Step 7: Install Dipole Stress
Relief Eyelets
90 degrees from each brass
dipole electrical
connection, install two
eyelets directly opposite
from each other for stress
relief on the dipole.
The 2 dipole ends of each
band will loop around these
and then become
electrically connected to
each brass screw
Step 8: Prepare Balun Coax
end for Attaching to Copper buss bars
This is the end going to the
balun inside the PVC pipe.
Here I removed 3 inches of
insulation then
Carefully unbraided the
coax shield 2 inches back
then
Soldered each end
Step 8: Solder the Balun
Coax to the Copper Buss Bars
Here solder one of the ends
to once buss bar going
down the pipe, and the
other to the other side.
I did not allow the buss bars
to protrude inside the balun
“Air coil” further down the
pipe. Nothing exists in that
part of the pipe but “Air”.
Step 9: Insert the caps
and Final Holding Loop
Drill a hole in the bottom
cap and put the coax
coming from the bottom of
the balun through it and
seal.
Put another eyelet or loop
on top cap and seal, careful
to not short out antenna
wires inside pipe
Step 10: Prepare Dipole
Wires
Top wire longest Band 4%
shorter than normal:
(468/Frequency) x 0.96
Middle Frequency Normal
(468/Frequency)
Lower Band 1% longer
(468/Frequency) X 1.01
I cut a lot longer just in case.
But you should mark these
locations with marker
anyway.
Step 11: Attach Each Dipole leg to
Antenna Lugs
Each Dipole Leg goes on
opposite connectors 180
degrees on pipe.
I used ring connectors after
looping dipole wire through
stress relief several times.
Longest Dipole on top
Then second longest
Then Shortest on bottom sets
of brass lugs
I used 14 gauge THNN
stranded house wire
Step 12: Space out the
Dipoles so they Fan Below
Here I used two 80 inch
sections of PVC pipe ($1.75
each) with holes drilled at
center and both ends to
attach the dipoles to.
You can use halyards or any
other method you can think
of to keep the ends 38
inches apart to (up to 18
Mhz.)
Step 13: Tune it up
According to the method,
little if any tuning is needed.
We found this to be true as I
had left each side a foot
longer and we ended up
taking much of that off of
the higher bands. The lower
80 meter band not so much,
so it is preferable to mark
the calculated locations,
then leave some wire longer
to trip back if needed.
Tune it up
Remember to tune with the
antenna up close to actual
height and away from you or
anyone else. You can use
your radio set to 5W and read
your SWR meter. If you started
long, you know you only need
to take off inches at a time to
lower the SWR on each band.
Tune from the lowest band
down (Top down on antenna)
We used a pulley for easy
retrieval.
Step 14:
Enjoy!
This antenna proved itself on
3 bands without the need
for an antenna tuner.
80 Meters: 1.4 SWR
40 Meters: 1.1 SWR
20 Meters: 1.7 SWR
Contacts made on all three
bands with 59 RST.
How Much Time and Cost? Very little..
If we can do it, so can YOU!
To build Balun and Center Insulator = 3 hours and $20.50 for stuff I did not have lying around, guy rope, eyelets, etc. Just me. To Hang the Antenna, 2 well “Experienced” guys ~ 4 hours with a long lunch in-between rain storms last Friday. Summary: 599 REPORTS on every band without the need for a tuner!!! I will add a 10 meter to it after field day.