Depends on the antenna. My article for 440 - each element is 50-ohms. That is due to mast spacing and the different diameters on the element. However, a similar UHF element on a Decibel antenna is 100-ohms and the major determining factor is spacing to the mast. Others (Sinclair, Comprod, Telewave) use a longer spacing from the mast and have a matching transformer section inside of the element to get it to 50-ohms. A folded dipole, out in the open, with no matching, is a bit less than 300-ohms.
I've done very little 2-meter antenna work since I have very little interest there. Chuck WB2EDV ----- Original Message ----- From: "wd4nmq_1" <[email protected]> To: <[email protected]> Sent: Wednesday, August 26, 2009 8:11 PM Subject: [Repeater-Builder] 2 meter folded dipoles for multi bay design information needed >I am looking at building a 2M four bay antenna, But, I have a question > > My question is the design and construction of folded dipole antennas used > as individual elements in bay type antennas. In doing research into their > construction I came upon a catch. All design info I found in books, ARRL > Antenna Book, etc, says a two element folded dipole has a nominal input > impedance of 300 ohms. But, all sources, DB Products, Benelec, etc, I see > say the nominal input impedance for each folded dipole element is 50 ohms, > 300. I reference WB2EDV's article on a 440 antenna he built. > > But, the bottom line is can anybody point me to where I can find the info > on designing each element for 50 ohm impedance? > > Jeff > wd4nmq >
