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.

160m/80m : If you intend to use this Choke mostly below 15MHz, we can supply it with 12 turns instead of the usual 8. This gives improved choking performance on the lower bands but it can still be used across the whole of HF.  Please note that this is a custom option and will add 24 hours to the delivery time.

• 8 (or 12) 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 wary 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.