Our "i" series of feedline isolation baluns provide excellent feedline decoupling and, depending on the model selected, low loss performance from 1.5 to 54 MHz. The model 1115di is a dual core design that will handle 5kW at resonance with a 100% duty cycle and provides high common mode impedance and an extended effective core area for excellent performance. Balun is configured with two SO-239 connectors with additional RF connectors available in the Accessories Category under Alternate Connectors. This balun is comparable to our model 1115du.
When your transceiver and other equipment in your shack acts strangely, it is probably due to stray RF pickup which produces a common mode current problem. This is especially apparent when using end-fed antennas, high-impedance feedlines, or a poor ground counterpoise. Problems can be more evident in SSB mode because the microphone audio line and mic circuitry may be very sensitive to RF. You can even get an RF burn from the mic in worst-case situations, not to mention from the chassis or other equipment used in the system.
If you are using an antenna switch it is important to install an isolation/suppression balun in the main feedline coming into your operating position. The common ground of the switch allows RF/common mode current to come back on the shield of your unused antenna and installing a choke after the switch will suppress any of this before it reaches your equipment.
If you are experiencing what you suspect to be RF interference, such as fuzzy or distorted transmit audio, interference to video or computer equipment in your house or your neighbors', then it is likely that your feedline is acting as part of your antenna system. While common advice may be to improve the station's RF ground, the root of the problem is poor isolation of the feedline from antenna currents.
Unless you get an actual RF burn or a fault warning message from your transceiver or amp, you MAY NOT KNOW that you have a problem with RF feedback. You should monitor your signal with another receiver or get an on-the-air report. Check your SSB signal on every band the first time you set up a new antenna system, especially if using an antenna tuner. If you do have a problem with RF feedback--typically on one or two bands--reducing power may cure it. However, this is not the best solution and a better way to eliminate RF pickup and induced common mode currents is to electrically isolate the rig from the antenna by using a choke balun more commonly know as a Feedline Isolation balun. This unit can be installed at either the rig or the antenna or in severe cases, at both locations.
NOTE: A traditional voltage balun (various turns ratios, usually wound on a large iron-powder core) will NOT perform the same function as a feedline isolation/choke balun. It will be completely ineffective eliminating RF on a feedline or in your operating position.
Tests run using an AIM 4170uhf network analyzer show SWR to be below 1.07 across the entire HF band, transformation is perfectly flat, return loss is typically 60-75 dbmw and choking impedance peaks at over 11k ohms. This unit has the widest operating frequency range, lowest core stress and provides the best overall balance of any balun for given cost, size, and weight. Please click on the graphs shown below to view the complete test results.
|Core Material|| Custom mix low permeability ferrite by Fair Rite Products for maximum bandwidth.
Large 2.4 inch cores are coated and sealed for long term durability.
|Winding Type||Stacked dual core, coaxial wound 1:1 current balun provides larger effective core area.|
|Winding Material|| Mil Spec 50 ohm coax rated 19kW @ 1MHz, 9kW @ 10 Mhz and 4kW @50MHz.
Silver flashed braid and center conductor with solid Teflon dielectric.
|Power Rating|| 1 to 35 MHz - 5kW, 10kW intermittent. 35 to 54 MHz - 5kW.
All ratings at resonance. High SWR will reduce power handling ability.
|Useable Frequency||1 to 54 MHz|
|Insertion Loss||Less than .02db|
|Connectors|| SO-239 connectors are gold center conductor with Teflon insulation.
Alternate connectors and Mounting Options are available in the Accessories section.
|Hardware||All Stainless Steel|
| Enclosure Type
|| NEMA rated 4x marine grade junction box for outdoor installations.
Cover utilizes integral neoprene gasket for weatherproof integrity.
|Dimensions|| 4x4x2 inches for main body of unit
Dimensional Drawing of Standard Enclosure
|Additional Info|| Very high efficiency.
Will not heat up or saturate at like many of the "less expensive" designs.