Dipole Antenna, 20m-6m

The SteppIR Dipole Antenna, 20m-6m has a small profile, but it offers big performance.  This antenna functions in a manner that would normally be consistent with a three element Yagi, due to its unique 57” (1.45m) boom length.  When placing a parasitic element very close to a driven element, approximately .1 wavelength or less, the antenna will achieve gain performance that is quite high for a 2 element Yagi, more like the performance expected from a 3 element Yagi.  There would normally be a caveat to this, at least with a fixed length aluminum Yagi – the antenna would have greatly limited bandwidth – roughly 120 Khz!  This would be a highly impractical design since traditional fixed length Yagis are single-frequency devices – the bandwidth is very narrow unless you use traps, interlacing or simply add more elements in order to “trick” the radio into thinking it is resonant.  Of course, all of those methods lead to significantly reduced performance when compared to a single frequency Yagi.

In the case of a SteppIR Yagi, our antennas adjust to the exact length required at any given frequency.  In other words, the signal is NOT degrading – the characteristics of the antenna change as you adjust through the bands due to spacing of the elements.  What does this mean?  As it turns out the laws of physics and the allocation of ham bands collide to help us out.  When the Yagi is on 20m, there are two nicely spaced elements and there is gain of 6.6 dBi free space, and front-to-rear ratio of 21dB.  As the antenna is tuned towards 10m, the spacing gets wider so the characteristics of the Yagi change – gain stays steady, and front-to-rear is reduced – on 10m, gain is 6.2 dBi but front-to-rear is reduced to 9 dB.

On 20m the band conditions are busy – the band is crowded, there is a ton of noise and that is where good gain is important, but front-to-rear is REALLY important.  On 10m, the band is large, quiet and generally the goal is to transmit long distances, so great gain is more important than front-to-rear signal rejection.  As an aside, you will find when a 3rd element is added to a Yagi, that the gain actually goes UP when tuning from 20m to 10m but on a 2E Yagi the gain does not change significantly throughout the frequency range.

At SteppIR we measure our gain figures in dBi free space, it is the most realistic and objective performance evaluation for an antenna.  Many of our competitors use dBd over ground for their specifications, which is fine except that the height over ground can be manipulated to make the gain figures look better than they really are.  For the same reason, we use Front-to-Rear measurements for our Yagi instead of front-to-back, because when measuring front-to-back, the “back” ratio of the antenna model can be theoretically anywhere behind the front, meaning the very best performance scenario can be taken even if it is not practical in actual performance.  With front-to-rear, we are taking the worst–case scenario every time – directly 180 degrees behind the front lobe of the antenna.

The two element Yagi functions as a beam antenna on 20m, 17m, 15m, 12m, 10m, 6m and EVERY frequency in between, making this a fantastic antenna for both Amateur Radio and Emergency Communications use.  With the 57” (1.45m) boom and telescoping support poles, this is an extremely portable package.  The telescoping poles when extended are 36 feet (10.97m) overall length, 18 feet (5.48m) per side.  These poles remain extended while the actual antenna – copper strip on the inside of the telescoping poles – adjusts to the exact length required. 

The turning radius is 18.2 feet (5.53m), weight 30 lb (13.6kg) and wind load is 4.0 sq ft (0.37 sq m).  Because of its small size and profile, this antenna can be easily mounted on a medium duty mast and rotated with a light to medium weight rotator product, and for portable operation can be erected in a very short period of time, especially after initial assembly!  

The 2 element Yagi has 3 purchase options:

00202-SDA  

This version of the 2 Element 20m-6m Yagi includes the basic SDA 100 electronic controller in the purchase price.  While there are three options that can be purchased for the basic SDA 100 option, only two of them can be purchased with this particular model:

PN 40-1231-301 Transceiver interface (antenna will automatically tune to the frequency indicated on the radio, cable not included);

PN 40-1240-311 Tuning relay (locks out the amplifier from transmitting when antenna is tuning);

If you wish to purchase the Advanced Lightning Protection module, you will then need to select:

00202-ALP

00202-ALP 2 Element 20m-6m Yagi includes the basic controller as well as PN 40-1220-343 Advanced Lightning Protection (protects the driver board of the controller by having sensitive relays in front of each driver chip, in the event of a lightning or near lightning event or even a dead short, the relays trip to protect the controller.  It also allows you to have advanced troubleshooting support).  Note that on a dead short situation, the antenna must not be in the process of tuning, in order to be protected.

00202-PRO

The third purchasing option would be 00202-PRO 2 element 20m-6m Yagi, the key difference here being that instead of the SDA 100 Controller, the SDA 2000 OptimizIR is included instead.

The OptimizIR controller includes as standard equipment, all three of the options you would normally purchase with the SDA 100 (transceiver interface, tuning relay and advanced lightning protection). Further advantages of the OptimizIR are the color screen, larger screen and better GUI.  The main advantage of the OptimizIR is the ability for the user to create antenna models using EZNEC, Auto-EZ or other antenna modeling software (antennas are not created using the OptimizIR), and then download them to the OptimizIR for use on any and all bands.  In addition, some cool antennas are already placed on the OptimizIR (Max gain, max f/r, and wide-angle antennas), all viewable on a full color “power band” so it is very easy to visually determine the gain/FR weighting on the antenna model.  Lastly, we plan on introducing an option for a Power/SWR meter, and all the OptimizIR’s that are shipping now have the “hooks” in them for purchasing that option, when available.

Other 2 Element Antenna Options:

Lightning Protection

When considering lightning protection – the advanced lightning protection module will provide protection for the SDA 100 or OptimizIR controller, but some people prefer to take care of lightning protection outside of the building.  For that we offer the PN 20-8052-01 12-wire line protector/lightning suppressor.  The lightning suppressor comes in a fully sealed weather-proof housing and protects the controller against lightning hits or near incident lightning events. This unit often is placed just outside of the building where the operating room is located.  For the best lightning protection, use both the ALP board option and the lightning suppressor.

Cabling Options

With either the SDA 100 or the OptimizIR, when using the transceiver interface, a cable is required to connect from the radio to the SteppIR controller.  When ordering the cable, a drop down box will appear so that you can select your radio make/model.   If the comm port in the back of the radio is being utilized  we offer a PN 20-6014-01 Y cable, which allows the user to utilize the comm port for more than one function – our controller is querying the radio at all times, in other words listening to the radio for commands, which makes it possible to use the comm port for more than one activity

The 2 Element Yagi utilizes PN 21-5002-01 12 wire shielded control cable (purchased by the foot) used to remotely tune the antenna, routed from the operating room to the antenna.  Each active element on any SteppIR antenna employs a 4-wire shielded control cable (included) – in the case of the 2 Element Yagi, that would be 8 wires, four wires per EHU. The control cable from the EHU’s connect to one side of a terminal strip header, and the 12-wire control cable is connected to the other side of the terminal strip.  Why does one side have 8 wires and the other has 12?  The answer has a lot to do with supply and cost.  12 wire shielded control cable is a third the cost of 8 wire and is MUCH more readily available.  And, if a user ever decides to upgrade the 2 element Yagi to a 3 Element Yagi, there is no need to replace the cable.  When the connections have been made on both sides of the terminal strip, the bulk wiring is then placed in a plastic cylinder, and the cylinder is then attached to the boom of the Yagi.

Junction Box

The PN 70-2034 Connector Junction Box option is a bit more elegant, and much less complicated to use than the standard plastic cylinder – the necessary components are mounted inside a hinged, weather proof case, for easy access.  The connector junction box has a db25 female connector mounted inside the box for connecting the controller – this way the antenna can easily be tested at the install site-point without requiring someone in the ham shack to operate the controller.  Once installation is completed, the connector junction box is readily accessible for any future testing or troubleshooting.   

Cabling Connection Options

When connecting the control cable to the electronic controller, there are three options – a 25 pin connector with backshell is provided, and then the control cable must be soldered (by the customer) to the dsub connector.  We recommend using the PN 70-6010-01 25 pin DSub splice (most customers purchase this option).  It is inexpensive and easy to install – simply push the bare wire ends from the control cable into the respective terminal header slot and tighten with a small screwdriver.  The last option would be to purchase the “install connector at factory” option, which while convenient, is not inexpensive and can also lengthen lead times since we do not do this very often.  The reason most folks don’t go this route, is because when routing the control cable from the ham-shack to the antenna, usually the routing path won’t allow for a bulky connector being on one end of the control cable.

Passive Element

PN 06002 6m Passive Element; The two element Yagi has a functional 6M antenna on it but since the spacing is a bit wide, the gain is good but the front to rear is poor, making it essentially a high-gain dipole.   By adding the 6M passive element kit option, the Yagi then has three nicely spaced elements on 6m and both the gain and front to rear are solid.   

Driver Board

PN 01324 Remote driver board; The remote driver board allows the user to run control cable from the antenna to the bottom of the tower, and then run cat 5 cable up to 900 feet away.  It is designed specifically for towers that are long distances from the operating location.  In the event this option is purchased, the advanced lightning module is included as part of the module, which is then mounted at or near the base of the tower – the controller inside the shack has no sensitive electronics in it.  Note that when ordering the remote driver board option, the user will be required to purchase a housing for it, if desired.  Many people mount the bare board (it comes with an aluminum mounting plate) inside a building.