300 to 75 ohm TV balun for dipole / wire loop antenna?

[walterb]

Just wondering if anybody has had any experience (good or bad) with one of these on a wire dipole or wire loop antenna?

http://www.summitsource.com/images/products/CO105T.jpg

[k8mcn]

It will work fine, in fact, the well known "Scantenna" ships with one to go from 300ohm to 75...........if you are feeding a wire antenna, try to run the 300ohm as close to the receiver as possibly-i assume you are using it for receiving only, as you would need a different setup if you are going to transmit----------IE a balanced line tuner, not much power through 300ohm etc..........

[walterb]

Originally Posted by k8mcn

It will work fine, in fact, the well known "Scantenna" ships with one to go from 300ohm to 75...........if you are feeding a wire antenna, try to run the 300ohm as close to the receiver as possibly-i assume you are using it for receiving only, as you would need a different setup if you are going to transmit----------IE a balanced line tuner, not much power through 300ohm etc..........

Hi, yes. I have a scantenna (works great too) and it uses one. I was just wondering if anybody has used one on a wire dipole or wire loop antenna. I am using it just for receiving.

thanks

[Jakemcgraw]

Originally Posted by walterb

Just wondering if anybody has had any experience (good or bad) with one of these on a wire dipole or wire loop antenna?

http://www.summitsource.com/images/products/CO105T.jpg

If memory serves me, The type balun you picture there, is an indoor use only type. The Outdoor use ones are a little more larger in diameter,and with longer leads.

[zz0468]

A resonant dipole is around 70 ohms impedance, so putting a 300 ohm to 75 ohm balun is introducing an unnecessary mismatch. Looking at the picture, I'm not convinced that one is 300 ohms. There are 75 ohm baluns, and 75 ohm ribbon line. I suspect THAT is what the scantenna actually uses.

[walterb]

Originally Posted by zz0468

A resonant dipole is around 70 ohms impedance, so putting a 300 ohm to 75 ohm balun is introducing an unnecessary mismatch. Looking at the picture, I'm not convinced that one is 300 ohms. There are 75 ohm baluns, and 75 ohm ribbon line. I suspect THAT is what the scantenna actually uses.

ok, thanks!

[BKIN]

Originally Posted by zz0468

I'm not convinced that one is 300 ohms. There are 75 ohm baluns, and 75 ohm ribbon line. I suspect THAT is what the scantenna actually uses.

I respectfully disagree

http://www.antennawarehouse.com/Scanner/Scantenna.htm

[k8mcn]

Originally Posted by zz0468

A resonant dipole is around 70 ohms impedance, so putting a 300 ohm to 75 ohm balun is introducing an unnecessary mismatch. Looking at the picture, I'm not convinced that one is 300 ohms. There are 75 ohm baluns, and 75 ohm ribbon line. I suspect THAT is what the scantenna actually uses.

i have to disagree,as soon as you introduce the 300ohm twinline to the equation, you cause a mismatch for the receiver that is looking for a 50ohm input on its connector...........now if it is an old receiver like my Hammarlund 145x, no problem running the twinlead directly to the antenna screws, but in think the OP was talking about twinlead 300ohm connecting to 75ohm coax......

[zz0468]

Originally Posted by BKIN

I respectfully disagree

http://www.antennawarehouse.com/Scanner/Scantenna.htm

Ok! They apparently have a 300 ohm feedpoint for the thing. It's a bit more than the multi-element dipole that I though it was. I sit corrected.

[zz0468]

Originally Posted by k8mcn

i have to disagree,as soon as you introduce the 300ohm twinline to the equation, you cause a mismatch for the receiver that is looking for a 50ohm input on its connector...........now if it is an old receiver like my Hammarlund 145x, no problem running the twinlead directly to the antenna screws, but in think the OP was talking about twinlead 300ohm connecting to 75ohm coax......

I didn't mean to imply that twin lead should be used. What I was TRYING to express was my mistaken belief that the balun was 300 ohms on the balanced side.