Yagi Dipole
Vertical
(Patented)
80m Coil Kit for the BigIR
nstruction Manual
I
SteppIR BigIR MK III Test Installation W/80m Coil
S
teppIR Antennas
2
112 -116th Ave NE, Suite 2-5 , Bellevue, WA 98004
Tel: 425-453-1910 Fax: 425-462-4415
Tech Support: 425-891-6134
www.steppir.com
Revision 2/22/08
SteppIR Antennas - 80m Loading Coil Kit
Table of Contents
2
opic
T
Table of Contents 2
Parts List 3
The SteppIR 80m Loading Coil 4
Things to Know when Using Your 80m Loading Coil 4
BigIR MK III Procedure to add 80m Coil 6
Modifications Needed to Operate the BigIR MK II at 1500 watts 7
Disassembling the Antenna 7
Bypassing the SO-239 on the Element Control Unit 8
BigIR MK I (original model) & MK II Modification Procedure 8
Mounting the Coil Housing 10
Removing the Small Screw in the CPVC Liner Coupler 10
Page
Reassembling the Antenna 11
Installing the New Firmware Chip (retrofit kit only) 12
Powering up and Enabling the Coil 15
Wiring Diagram 16
SteppIR Warranty 17
SteppIR Antennas - 80m Loading Coil Kit
3
80m Coil Kit
PARTS LIST
ITEM QTY PART #
BOX 1
4 60-1004-01
4 60-0072-01
10 60-0061
14
1
1
1
1
60-0019
10-1029-01
20-6020-01
1 Firmware Chip
1 Chip Extractor
10-1029-01
Hardware Kit for Shipping Coil With BigIR MK III
Hardware Kit for Shipping Coil Alone
DESCRIPTION
80M Loading Coil
1/2” Nylon Spacer
10-32x1-1/2 SS Screws
10-32x7/8” SS Screws
Connector Protector
Single Terminal Block
Connector Protector
10-32 Nylok Nuts
SteppIR Antennas - 80m Loading Coil Kit
4
The SteppIR 80m Loading Coil:
Th
e SteppIR 80m coil is designed to mount on the base of the SteppIR BigIR vertical an-
tenna. It will give the BigIR the capability to continuously tune from 3.4 MHz to 60 MHz.
It does this by adding a multi-tapped, high Q, base loading coil and a rotary selector switch
that is controlled by the SteppIR controller.
The SteppIR coil has 4 taps on the 80m band and one tap on the 60m band plus one position
that switches the coil out of the circuit. The SteppIR controller automatically selects the
proper tap and antenna length for the selected frequency to give the best performance. When
the frequency is greater than 6.9 MHz the coil is switched out and the BigIR operates as before.
Things to Know when Using Your 80m Loading Coil:
• Always
from the control box before doing any work on the electrical system of the antenna. Any
short or crossed wires may permanently damage the controller circuit board
here are high RF voltages present at the coil output
• T
you.
• There are modifications required on the original BigIR and the BigIR MK II to operate
the coil at its full power limit.
• The original BigIR (and the BigIR MK II) are limited to 500 watts (key down) when they
are set to a frequency below 6.9 MHz. The BigIR MK II modifications are listed in these
instructions. The original BigIR can be modified for the higher power limit at the factory. Call the factory for more information. The BigIR MK III operates with the coil at
1500 watts (key down) with no modifications.
• The power for the coil (below 6.9 MHz) is limited to
• The loading coil, by design, adds extra length to the antenna electrically. As a result you
- A
lways
nplug the control box and / or disconnect the 25 pin control cable
- u
, they can burn you but not shock
1500 watts (key down) .
may find that the BigIR and the BigIR MK II will not tune to the high end of the 10m
band. This is not a problem on the MK III because the copper beryllium tape retracts
completely into the element housing unit (motor box). For this reason and the following
two, we recommend using the 3/4 wave mode on 15m and 6m.
1. The SWR is higher on these bands when using the 80m coil because of the added
electrical length that the coil introduces. The match is affected because this added
length is not a straight vertical path.
SteppIR Antennas - 80m Loading Coil Kit
2. Modeling shows that 3/4 wave can provide greater gain than a 1/4 wave vertical at all
a
ngles above about 27 deg. The increase is 3 db to 4 db from about 27 deg to 45 deg
elevation. Above 45 deg elevation take-off angle the gain is even greater, up to 8 db
which can be good for closer in contacts. The only downside is you could potentially
hear more close-in man made noise from high angles, but reports from the field indicate this hasn't been a problem.
The 3/4 wave vertical will also show gains at angles below 27 deg down to 8 deg of between 1 db to 3 db when ground quality is less than average and fewer than 25 radials are
used. The length of the radials also affects this phenomenon. Twenty five one wavelength radials (which is what a 1/8 wave radial is on 80m) when used on 10m, makes the
3/4 wave and 1/4 wave vertical very close to equal at the low elevation angles and the 3/4
wave always has the advantage above 27 deg. With shorter and fewer radials the 3/4
wave vertical begins to have gain over the 1/4 wave vertical at low angles.
• The operating frequency ranges and power limits befor
• 3.4 - 6.8 MHz @ 500 watts
• 6.9 - 27 MHz @ 3000 watts
e modification are:
5
Gain of 3/4 over 1/4 Vertical
4 wave
3/
40
1/4 wave
35
30
25
20
15
10
5
Over real, average ground with 12 one wavelength radials
SteppIR Antennas - 80m Loading Coil Kit
BigIR MK III Procedure to add 80m Coil:
• I
*
f you have purchased the MK III and the coil togethe
skip the * steps.
• * Mount coil housing to the element unit using 4 (10-32x1-3/4) screws
(Figure 9 & Figure 11).
• * Disconnect the coax feed line from the MK III element housing unit
(Figure 33).
• * Disconnect the radials from the MK III element housing unit (Figure
33).
• Connect the output lead of the coil to the coax conne
element housing unit.
• Connect the coax line from the transmitter to the coax connector on the
80m coil housing (Figure 33).
• Connect the radial system to the ground lug on the 80m coil housing
(Figure 33).
r at the same time,
ctor on the MK III
6
::: Note :::
• Use ONLY the ground lug on the coil
housing for ground and radial connections.
• Connect NOTHING to the ground lug
on the element housing. The coax connector and the ground lug on the element housing are now “RF HOT”
• It’s a good idea to cover them with
tape or RTV silicone or something
similar to protect pets and children.
onnect the four terminal lugs from the control cable to the appropriate
• C
four terminals on the coil housing (Figure 33). Apply tape or silicone to
weatherproof the connections.
• * The coil is now ready for use after you install the
ware.
new controller firm-
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