1:1 Balun 400w

It's a bit of an animal - actually, it's a lot of an animal -  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 using RG142 coax and the ferrite core is an FT240-31 offering resistive performance 3.5MHz up to 30MHz so a perfect companion for your resonant HF aerial or fan-dipole.  At resonance, this balun is good for around 1kW CW/Datamodes.

• 8 turns of RG142 on a FT240-31 core
• 2 side eye-bolts for wire support
• 1 top eye-bolt for use with a halyard
• SO239 connector
• 120x80xx40mm
• Filled with potting-compound for a complete weather-proof solution
• Weight: 585g
• PDF Balun Guide : Dipole

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

Made (and used) by us - Be weary of any supplier who can't (or won't) tell you what's inside the box you buy!

Choosing a Balun
We are often asked "what balun should I use?" by customers - here's our simple guide to choosing the right one:

• Resonant dipole, coax-fed - 1:1 Choke Balun (we have 100w and 400w versions)
• Doublet fed with ladder-line - 1:1 Choke Balun or 4:1 Current Balun (most times, a 1:1 is preferable)
• Random/long-wire down the garden (or up a pole) - UnUn, 9:1 is the common ratio, but our model offers 4, 9 and 16:1
• Choking Coaxial Cable - 1:1 Line Isolator

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.