do i need a balun with log-periodic?

anarquist · Post by **anarquist** » Mon May 10, 2004 9:22 pm

I just bought RPL 0205 log-periodic antenna from you guys. Theres no instructions but i can figure out how to assemble it. But do i need a balun for it? What is it's impedance at 100mhz? I will be using 50ohm coax as feed line.

Post by **pcs** » Wed May 12, 2004 1:27 pm

Hello!

Check out the support section, there's wiring diagram there.

Its about 50 ohm, you do not need a balun.

Have fun!

anarquist · Post by **anarquist** » Wed May 12, 2004 4:57 pm

Thanks!

Also, can this antenna be mounted vertically for vertical polarization? I assume it can but what does it do to the radiation pattern?

I am getting great performance out of this antenna so far, measured more than 3 miles across the middle of the city with only about 20 feet of elevation, horizontally polarized, at 7 watts. But my car radio is vertically polarized and I think Im only picking up reflections of my signal.

Post by **pcs** » Wed May 12, 2004 5:31 pm

Using vertical polarization will give you about 6db of improvement
in theory at least.

Black_Hawk · Post by **Black_Hawk** » Sat Jul 10, 2004 5:42 am

anarquist wrote:I just bought RPL 0205 log-periodic antenna from you guys. Theres no instructions but i can figure out how to assemble it. But do i need a balun for it? What is it's impedance at 100mhz? I will be using 50ohm coax as feed line.

...Some antenna manufacturers(NOT REFERING TO PCS) have you tape or otherwise attach the coaxial feedline along the length of a boom that is electrically hot, the boom feeding half the elements!! The very fact the boom feeds elements of the antenna requires the boom to have significant VOLTAGE along its length. Any cable parallel to the boom is excited by boom currents and voltages. Cables routed against the hot boom will have whatever the voltage is between the boom and the tower trying to excite current in the feedline shield.

If the beam has an impedance matching balun at the feedpoint, or if you simply want to leave the balun at the feedpoint, you can leave the balun at the feedpoint. The feedline has to be suspended a few feet below the hot Booms.

Just thought that i would include that for general information Purposes..Because if a High Power Transmitter is being used and a Log Periodic is thew Antenna of choice then one has to be aware of the Circulateing Currents in the Mounting Boom element of the Antenna..Those 'stray' currents can cause interference..Hence why i always use RF CHOKES TO CHOKE OFF SUCH CURRENTS

Respects..Storminorm

PCS-Electronics

do i need a balun with log-periodic?

do i need a balun with log-periodic?

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