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Antenna Queston  

post #1 of 6
Thread Starter 
This question is mostly for Glenn L but anyone can answer

I just bought a slightly used Blake antenna. I was directly to atechfabrication.com where they sell bauns for antennas. Why would I want to buy one and wouldnt the bought antenna come with one.

If the purpose is to replace it, what benefits do you get.


Thanks in advance
post #2 of 6
Outdoor antennas typically have a characteristic impedance of 300 ohms. Coaxial cable has an impedance of 75 ohms. A balun transformer converts the 300 ohms to 75 ohms for maximum power transfer from the antenna to the cable. Most antennas will come with a balun transformer if they are 300 ohm type. If not, you will need to get one for impedance matching. Radio Shack will have them.
post #3 of 6
The Blake antennas come with a balun ckt attached to the dipole elements. My impression from the literature is it is more than just a balun, and effects the BW of the antenna also.

Glenn may have more to say about how it compares to his own design balun that he has experimented with.

In any case you do not want to use a standard 300-75 ohm balun with a Blake JBX series (at least the B group ones), since it uses a x shape dipole rather than a folded dipole, so would not have 300 ohms impedance to start with. It looks like a folded dipole but the fold part is just plastic supports.
post #4 of 6
Thread Starter 
I was just told that the Blake comes standard at 75ohm so need to convert.

If I am misinformed, let me know
post #5 of 6
Quote:
Originally posted by Humey
I was just told that the Blake comes standard at 75ohm so need to convert.

If I am misinformed, let me know
I assume you mean "no need to convert".

Re: the Blakes, the balun is built into the dipole connector box, so is rated for 75 ohms as you heard.

Most antennas physically match 150, 300, or some other impedance. Many are rated as 75 ohms by building in the balun right on the antenna. The Blakes do this, and some models of Winegard do it too. Others are designed for 300 ohms and usually give you the standard 300-75 ohm matching transformer in the antenna box.
post #6 of 6
Thread Starter 
jhe,

In my excitement I wrote it incorrectly and you are correct in fixing my error
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