In addition to matching the feed-line cable to the antenna for maximum transfer of RF energy, the BUXCOMM MasterMatch BALUNS improve the radiation pattern for more predictable coverage.
Antenna BALUNS, UNUNS, and Line Isolators
When you connect center fed antennas, like dipoles, Inverted Vee s, Loops, Yagis, Rhombics, etc, to coaxial cable, care must be taken to insure that you don't end up with feed line radiation.
Not only can the loss in power be quite significant, but the radiation
characteristics of the antenna system will also be seriously compromised. In
lay terms, it won't be what you are expecting from the pattern of your antenna.
The feed-line, coax or twin lead is to be considered part of the antenna. RF currents can flow from the feed-line shield or wire feed-line into the utility power mains and into nearby t elevision and other communications cables. Support masts and metal poles can cause a variety of TVI and EMI problems that can be very difficult to trace. Frequently these problems are due to the lack of antenna line-isolation or no BALUN to prevent this condition. The solution is to use a BALUN at the feed-point of your antenna, or a Line-Isolator (B2KLISO) at the output of your transceiver or linear. In other words, at the input to your coax feed-line to the antenna.
High impedance BALUNs exhibit a poor bandwidth because of increased reactance caused by parasitic's within its core. With BALUNs having ratios of 12:1, and 16:1 we begin to see some self resonant activity due to the added inductance(s) that are employed in these BALUNs.
As we move higher in frequency this added inductance begins to "ring" or display parasitic's which causes the BALUN efficiency (and band-width) to degrade rapidly, in effect, causing the maximum usable frequency to suffer. When this happens several troubles arise; Core saturation (regardless of the core size), VSWR begins to rise, VSWR creates heat (RF power loss/dissipation) within the transmission line, and self-resonance at the higher HF frequencies above 14 MHz. All can cause unnecessary losses.
So when you consider using an antenna with 600 (12:1), or 800 (16:1), ohms (Z impedance) at the feed-point, think again about the consequences that lurk as you move up in frequency.
For most antennas with feed-points that exhibit impedances near 200 ohms, Windom's, Sky-wire/Loops, etc, use the 4 to 1 BALUN. When the 4:1 BALUN (50 to 200 ohms) is constructed in the correct manner, it has a band-width that is wider than any other BALUN made. Our BUXCOMM 4:1 BALUNs exhibit an operating range that reaches above the VHF region.
Rule of Thumb:
1 to 1 BALUNs are used mostly with center-fed dipoles.
2 to 1 BALUNs are employed with high-frequency Quads and loop antennas (above 40 meters).
4 to 1 BALUNs are commonly used with Windom's, Off-Center fed, and Sky-wire loops cut for 75/80 and 160 meters.
6 to 1 BALUNs are sometimes used with Off-center fed antennas that are installed above 70 feet.
9 to 1 BALUNs are the BALUN of choice when feeding end-fed, long-wire antennas.
The 9:1 is also preferred when feeding a T2FD antenna that has a 450 ohm balanced terminating load at its center.
Here's the got'cha; When feeding mobile antennas that are end-fed, use coax cable, HOWEVER, the feed-point impedance of most (bottom) end-fed mobile antennas is somewhere between 12 and 32 ohms. To remedy this requirement, we have developed the B1K5022 UNUN.
a VHF or UHF yagi is in use, improved transfer of energy is realized when using
the B1VBALUN. For practical purposes,
the 12 to 1 and 16 to 1 BALUNs should be avoided where possible. In rare
cases. the 12 to 1 BALUN will be necessary when feeding an antenna with 600
ohm open-wire, transmission line. A 16 to 1 BALUN is often used with Rhombic antennas that employ 800 ohm termination balancing network resistors.
BUXCOMM BALUNS are in the Commonwealth of Virginia
We highly recommend using CoaxSeal, CS104 on all BALUN and UnUn
terminals and attachments. Any BALUN installed out-of-doors is subject to harsh
weather, hard driving rain, and heavy winds. These conditions can allow
moisture to develop inside a BALUN when the connections are not sealed.