4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI...

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N5PUV’s 4 Band Fan Dipole Experiment Using the New SRI (Stanford Research Institute) Method

Transcript of 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI...

Page 1: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

N5PUV’s 4 Band Fan

Dipole Experiment

Using the New SRI (Stanford Research

Institute) Method

Page 2: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 3: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 4: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 5: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 6: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 7: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 8: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 9: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 10: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 11: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 12: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 13: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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”.

Page 14: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 15: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 16: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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

Page 17: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.)

Page 18: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 19: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 20: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.

Page 21: 4 Band Fan Dipole Experiment - bcro. · PDF file4 Band Fan Dipole Experiment Using the New SRI ... Create Ugly Balun on bottom end of ... 80 meter band not so much,

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.