Model 1151 - 1:1 ATU Current Balun, 1 - 54 MHz, 2kW
- Calculated at Checkout
This new release provides excellent choking and feedline isolation across the full HF spectrum, but is a departure from the normal 1:1 isolation/choke balun. Rather than a 50 ohm characteristic impedance, this balun utilizes a bifilar pair designed to maximize inter winding breakdown voltage. This balun and utilizes a bifilar pair designed to maximize inter winding breakdown voltage found on multiband antennas such as doublets and multiband loops. The 1151 is ideal for moderate power operations, is lower in overall weight and provides outstanding performance. This balun is also excellent when installed between a remote auto tuner and multiband antenna to suppress common mode allowing a cleaner more accurate match. The 1151 is NOT recommended for use with antennas resonant at or near 50 ohms such as monoband dipoles, fan dipole, yagi/beam antenna etc.
Power ratings for all baluns degrade as SWR increases. Typically a balun loses 40% of its power rating at 2:1 SWR and 60-70% at 3:1. The SWR for most bands on the antennas mentioned above will typically be at or above 2:1 when using a 1:1 balun. Consequently the power rating of this unit should be used as a baseline for calculations using your actual SWR as measured where the balun is installed.
N connectors and mounting options are available in "Accessories & Connectors" section of our website
IMPORTANT: This balun is NOT wound with the normal 50 ohm pair, rather the design criteria is maximizing inter-conductor breakdown voltage which results in a 97 ohm pair. Consequently, this balun is intended primarily for use with ladder line/open wire fed multiband antennas such as doublets and loops where there will be a wide range of impedance values generated across multiple bands and with a tuner required for the final match. Use with coaxial fed monoband wire or beam antennas is NOT recommended.
For a good graphical explanation of why this design works well, read through Steve's (G3TXQ) website page
- T match antenna tuners perform quite poorly if the resistive component of load impedance is very low, even worse if there is also a high capacitive reactive component. This is a common load found in shortened dipoles fed with open wire line.
- The traditional approach is to use a 4:1 balun on such antennas, but antenna tuner loss is worse with low resistive loads.
- The need to tolerate high voltages occurs when the balun happens to be located near a differential voltage maximum.
- Ability to generate high choking impedance for effective reduction of common mode current.
- Balun is intended for use with an antenna tuner which will manage SWR and transformation mismatches.
- Differential insertion loss is not significant in this application, the dissipation in a current balun is primarily from the common mode current which is installation dependent and not easily predicted.
| Custom mix ferrite from Fair Rite Products.
Large 2.4 inch core is coated and sealed for long term durability.
|Bifilar pair 1:1 current balun at 97 ohms wound on single core.
| Heavy gauge Essex polyamideimide Allex 240 Winding Wire wire inserted in teflon tubes.
Breakdown voltage in excess of 10kv
|1 to 31 MHz - 2kW in to resonant load 32 to 54 MHz - 1.5kW, 2kW intermittnet.
|1 to 54 MHz
| Less than 0.1db
| SO-239 connectors are gold center conductor with Teflon insulation.
Studs and eyebolts are 1/4 inch.
Alternate connectors and Mounting Options are available in the Accessories section.
|All Stainless Steel
| Enclosure Type
| NEMA rated 4x marine grade junction box for outdoor installations.
Cover utilizes integral neoprene gasket for weatherproof integrity.
| 4x4x2 inches for main body of unit
Dimensional Drawing of Standard Enclosure
| Very high efficiency. Light weight 1lb 2oz total.