Range Optimized Coaxial Line Isolator.
ON7FU coaxial line isolators are compact high power potted Common-Mode Choke type 1/1 UNUNs.
These devices are a variant of the well known ON7FU 1/1 high power current baluns, built using the same high quality materials and proven construction standards.
They are intended to be placed in the coaxial transmission line of radio amateur HF antenna installations, to eliminate common-mode (outer shield surface) currents caused by non-perfect transitions of a-symmetric to symmetric media.
Such conditions are often found in HF antenna installations with non perfect balanced behavior, like Windom antennas, antennas in the vicinity of obstacles, end-fed wire antennas with the coaxial cable acting as counterpoise or verticals with less than perfect ground systems.
ON7FU line isolators are characterized by their high common-mode choke impedance over the specified frequency range, including the largest possible resistive part contribution.
Furthermore, a grounding terminal is provided, allowing for connection of one side of the isolator to a clean RF ground, thus forming an “L” configuration filter for sheath currents, and providing additional (secondary) lightning protection. This configuration results in higher TX common-mode current rejection ratios and higher RX noise rejection characteristics.
The Common-Mode Choke line isolators can be installed at any place in the coaxial feedline.
The most popular, convenient and recommended places however are at the bottom of the tower or at the building entrance.
When installed correctly, the line isolator will effectively avoid RF from entering your shack, possibly causing RF interference in your TRX and other electronic equipment in your house, as well as avoiding RF noise caused by digital electronic devices to reach the antenna and enter your wanted weak signal receive path in conducted emission mode.
Noise floor can effectively be lowered by several dB.
These single core line isolators are effective over the entire HF frequency range.
Using different types of ferrite material and by manipulating the number of windings, the CMC impedance maximum can be optimized over a decade of the frequency range.
(e.g. 1,5 – 15 MHz, 3,0 – 30 MHz, 5,0 – 50 MHz)
As such, LOW band optimized and high HF optimized variants are available.
To achieve the highest possible optimized impedance / bandwidth, a Low HF and a High band version can be cascaded (placed in series)
or a wideband variant (see next page) can be chosen.
From August 1st 2018 on, all Line Isolators are built into UL508A certified polycarbonate enclosures provided with flanges for convenient installation .
- Deployable frequency range: 1.5 – 55 MHz.
- Low HF range optimized variant: 1,5 – 30 MHz (Optimized 1,5 – 15 MHz)
- Mid HF range optimized variant: 3,5 – 55 MHz (Optimized 3 -30 MHz)
- High band optimized variant: 3,5 – 55 MHz (Optimized 5- 50 MHz)
- Nominal system impedance: 50 Ohms.
- Operation principle: Coaxial UNUN Common-Mode Choke.
- Max Power: 3 kW PeP @ VSWR < 2,0/1, (ICAS)
- Insertion loss: < 0.05 dB.
- Intrinsic VSWR: < 1.2 / 1
- SO 239 coaxial connectors. (N-type or 7/16 DIN optional)
- Tamper proof and UV resistant polycarbonate enclosure / Stainless Steel hardware / Teflon isolated connectors.
- Fully waterproofed , mechanically stabilized and increased insulation by coating and potting with synthetic resin.
- IP 68 (Gasket sealed cover and internally coated).
- Mounting option included.
Price: 113 Euro.
- Option: N-connector (N-connector instead of SO239): + 6 Euro / connector.
- Option: Optimized for the low HF bands (Mix 31 ferrite instead of Mix 43): + 6 Euro.