1:1 Balun QRO

It's a bit of an animal - actually, it's a lot of an animal -  Featuring a revised design as part of our new "Elite" range, it's a 1:1 Balun for use on HF (1.8-30MHz) that easily handles 400w RF power (full-duty cycle). Ideal for Dipoles at the home QTH.  We don't cut corners: This balun is wound on an FT240 ferrite core which you can specify to match your needs.

The standard offering is 9-turns on an FT240-31 which is ideal as a general (400-watt) HF solution - But, if you have a specific frequency range for it, you may wish to tweak the spec:

160m-40m : If you intend to use this Balun on a "long Dipole/Doublet" up to 7MHz, the 75-mix is the best choice. This gives improved choking performance on the lower bands but performance drops off once you get above 10MHz.

160m-20m : If you intend to use this Balun mostly below 15MHz, we can supply it with 12 turns instead of the usual 9. This gives improved choking performance on the lower bands but it can still be used across the whole of HF.

QRO option : For extra power handling, this offers 2x FT240 ferrites with RG142 making the balun capable of 1000-watts continuous.  The 3rd picture shows an example Choke/Isolator before the box is water-proofed: 2 cores, RG142 carefully wrapped and secured.

A top-mounted eye-bolt allows for hanging/tying from a pulley, pole or suitable wall-fixing, side eye-bolts provide strain-relief for the wires and there are 2x M5 bolts on the rear of the box for mounting to our optional pole hardware.

Optional Hardware : A more elegant/secure solution comprises an aluminium plate with a V-bolt.  This lets you mount the Balun on any pole (up to 2-inches diameter).The rear of all our "Elite" boxes have 2x M5 bolts fixed from the inside which screw onto the plate.  These fittings are compatible with the outdoor "Elite" series boxes sold by us.

USE WITH : Resonant Dipole

• 9 (or 12) turns on a FT240 core
• 9-turns: >2k-ohm choking across 1.8-30MHz , 12-turns: >4k-ohm below 10MHz
• 2 side eye-bolts for wire strain-relief
• 1 top eye-bolt for use with a halyard
• SO239 connector
• 125x85x55mm
• Filled with potting-compound for a complete weather-proof solution
• All fixings are stainless-steel (M4 wire terminals, M5 rear pole-mount)
• Weight: 585g

We also have a Doublet/G5RV Choke, using the same internal configuration, but with the terminals at the top of the box.

Baluns - What/Why?
It's good practice to put a Bal(anced)Un(balanced) where coax meets aerial or balanced-feeder.  A Balun will help prevent "common-mode current" on the outer of the coaxial braid - This is vital to ensure that RF does not flow down the coax, turn it into part of the antenna system and give you "RF in the Shack".  Using a 1:1 Current Balun at the junction of balanced-feeder+coax is also recommended.

We do not advise the use of "ugly chokes" (air-cored coils of coax) for use at HF - these do not offer a consistent choking impedance and, in some cases, can actually increase common-mode current!  Simply put - Use a 43 or 31 mix ferrite toroid and a coax of a suitable power rating.  At VHF, a few turns of coax is perfectly adequate - for 50MHz/70MHz, Aerial Parts of Colchester offer a ready-made choke for a yagi.