KMA 4113 Log Periodic Antenna for 49 Mhz to 1.3 Ghz

Joe PerryWb6dco

March 2010 Testing

What a standard Log Antenna should look like

Description: Frequency Coverage: 40.6 MHZ TO 1300 MHZ Number of Elements: 30 Longest Element: 12 FT Boom Length: 12 FT Turning Radius: 8.5 FT Weight: 12 LBS Wind Area: 3 SQ FT Antenna Gain: 8 dBi (Free Space) F:B Ratio: 26 dB SWR: 1.8 : 1.0 OR LESS Materials: T6061 ALUMINUM AND STAINLESS Connection: DIRECT Options: Ferrite Bead Balun Vertical Mount

EZNEC on the KMA 4113

Assembly if you Dare!

Read the Instructions:

We’ll you have to start somewhere. The 4 pages of information you get for assembly are adequate if you read the instructions closely.

However, I though I would go the instructions one better and assemble the elements on the booms all in a strait line. So, I sorted the short to long elements. I then proceeded to just push one element into the boom. All the elements in a row on one side of the boom. I then made the other boom the same way.

The ill-fated AntennaHere we see I just put the elements into the holes and screwed them to the booms.

I made an SO-239 connector to accept the LM400 at the feed end.

The other end has a shorting bar.

My plan was to use the antenna in the Vertical Position. The elements up and down.

Joes Crank up Test 20 foot pole

The Crank up Test Stand

• I used some 2x6” wood and made a “U” channel that has a 12 foot 2x6” going up high and some shorter ones on the left and right to keep it stiff and strong.

• I attached a pulley at the top. I ran the hand crank wire through the pulley and down to the 20 foot pole. The pole is made of two sections of 10 foot 1.25” EMT with a piece of 1” pipe bolted into each end.

Vertical KMA 4113 ill-fated

Here we go, test the log periodic with the booms INLINE and the ELEMENTS INLINE.

I ran the MJF antenna meter on the antenna looking into 50 feet of LM400.

The SWR was 3+ from 50 Mhz to 176 Mhz and worse in the 440 band.

It will not work in this configuration. So, I took it back down.

Re-Align the elements per the installation instructions

It did not take too long to undo every other element and flip the tube to the other side of the boom. After doing both booms and reassembly in the over and under configuration that the instructions wanted, the beam is ready to test again.

The re-configured Log Periodic

Crank it back upThe 4113 Log Periodic is not back up about 26 feet. I aimed it at Mount Wilson, sort of!

The reason for trying this log antenna was HD over the air TV. I want to get KFLA which is located on Mount Wilson.

Unfortunately the power level off the back side of the KFLA antenna is very weak. Even with 7 dBi gain I see no energy of any TV over the air channels from Mount Wilson.

I do see 64.1 KHIZ in Victorville and Barstow. I have not tried Tehachipe yet to see if I can get Bakersfield links.

Ham Band use of the log

• Now I can try using it to cover 50 Mhz 6M band and the 144 Mhz 2M band and the 440 Mhz band.

• I don’t have any gear to transmit above 440 Mhz.

• The SWR for the antenna properly assembled is between 1.1 and 2 from 49 Mhz to 176 Mhz. The SWR is between 2 and 3 in the 440 Mhz band.

How about DUAL KMA Logs crossed