Tuning your EH Antenna

If you are designing and building an EH antenna from scratch you will need to have a Antenna Analyzer such as an MFJ-269 or an Autek Research RF1.

Mount your antenna somewher so you can tun the coil.

If your analyzer is battery powered you will probably have to gound the shield to get good readings. If your readings are all over the place try grounding the shield side of the coax.

If you haven't downloaded Demonstration #4, then you will need to download it. These steps are from Demo #4.

Step 5 - Connect the top of the coil to the top cylinder. Space the wire 1/2" or more away from the lower cylinder to minimize capacity coupling. We prefer to run this wire down the center of the lower cylinder.

Step 6 - Connect a wire to the lower cylinder. This will be "ground" for the antenna.

Step 7 - Connect a short piece of coax to the lower end of the coil and the lower cylinder wire. Measure the resonant frequency and remove turns to get the frequency just below the desired freequency.

(Note: The resonant frequency is the lowest impedance shown on the antenna analyzer.)

Download Demonstration #4:

Step 8 - Connect the lower cylinder wire (ground) to the bottom of the coil. Connect a short piece of coax to the "ground" of the antenna (you just created" and to a tap on the coil 2 turns above the bottom.

Step 9 - Measure the value of X when R = 50 ohms (you may need to move the tap to get 50 ohms). Calculate the value of a coil with that reactance and install it in series with the center lead of the coax. Alternately, experimentally determine the value of inductance that allow minimum VSWR to occur at the same frequency as maximumum radiation.

Go to the Coil Calculator and it will calculate the number of turns required for the Source Coil.

Step 10 - Adjust the tap on the coil to get perfect VSWR, then again adjust the top turns on the coil to place the antenna resonant frequenc wher desired. The impedance of the antenna can be adjusted by spreading turns on the lower end of the coil. The operating frequency can be adjustedby spreading turns on the top of the coil. Be aware that changing the tap will also change the frequenncy, so start low with too many turns, correct the VSWR, then set it on frequency. Hot glue will keep it from moving and changing frequency.

You will have to experiment around with spreading and compressing the coils to have minimum VSWR and resonance at the same frequency. This will take a little time, but in the end it will pay off.

Now put the coax connector on your antenna and connect to your rig - TRY IT OUT!!!!

Finished Antenna Configuration

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