Our "i" series of feedline isolation baluns provide excellent feedline decoupling and, depending on the model selected, low loss performance from 1 to 31 MHz. The model 1116di is a dual core design that will handle 5kW at resonance with a 100% duty cycle, provides high common mode impedance and an extended effective core area for excellent performance. The core mix used to construct this balun is optimized for the lower frequencies producing a level of choking impedance not available from other designs. Even with the optimization, the core mix is still effective to 54 MHz. Balun is configured with two SO-239 connectors with additional RF connectors available in the Accessories Category under Alternate Connectors.
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.
A few E Ham Reviews:
"After years of having major rfi on 80 meters QRO which set off alarm system, etc., I installed an 1116d at the shack end of the coax of my 80 meter OCF dipole. Now I can run full output from my amplifier with no rfi whatsoever. This product is absolutely a miracle to me. The current balun at the feed point of the antenna could not protect me from the rfi, so a second balun in the shack did the trick for me. Wish I got the 1116d much sooner "
"If I wasn't a believer in magic before I am one now. On the advice of friends I bought a model 1116d and placed it at the feedline in the shack. I never thought that I had RFI issues but reasoned that a balun would do no harm. Well, my wife no longer complains that she can't get on the internet when I'm on the air and, the CO detector no longer chirps!! I'm thinking of getting another to install at the dipole feedpoint -- who knows what'll happen next. Oh, and I see a slight reduction in ambient noise on 80 and 40".
"I installed a Balun Designs 1116d between my Palstar HF AUTO antenna tuner and coax transmission line in the shack and every trace of RFI in the house has suddenly disappeared. Previously, when running at legal power limit I had been getting interference on the house telephones, tripping of the smoke detectors, and an occasional complaint from a next door neighbor. The 1116d stopped all that. To my surprise the 1116d also improved (lowered) my SWR a bit on most bands and broadened out the SWR curves. Your mileage may vary but I for one am a happy camper now. Thanks Bob at Balun Designs".
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 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 falult 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 the feedline or in your shack.
Please review our Accessories Category for additional RF connector types and mounting options.
Tests run using an AIM 4170uhf network analyzer show SWR to be below 1.05 across the entire HF band, transformation is perfectly flat, return loss is typically 60-80 dbmw and choking impedance peaks at over 6k ohms on the lower HF bands. It 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.
Click to Enlarge
Tests run utilizing AIM-4170uhf Network Analyzer and a precision non-inductive 50 ohm load
|Core Material|| Custom mix ferrite by Fair Rite Products optimized for low frequencies.
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 & 4kW @ 50 MHz.
Silver flashed braid and center conductor with solid Teflon dielectric.
|Power Rating|| 1 to 31 MHz - 5kW, 10kW intermittent, 31 to 54MHz - 3kW
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 like many of the "less expensive" designs.