A general-purpose 1:1 Current Balun for use on HF with your 100w transceiver. This design uses sturdy screw-eyes for strain-relief on your Dipole wires plus top-mounted terminals catering for balanced-feeder on a Doublet or G5RV. You could also position it at the base of a resonant vertical - to act as a choke/isolator. An effective Balun should be resistive across the frequency range being used - and our choice of an FT140-43 (31-mix is not available in this smaller size) toroid is suited from 5MHz up to 30MHz.
If you're bringing balanced feeder into the Shack, you can also use this in place of the internal Balun found in most ATUs which are usually 4:1 Voltage Baluns and not always ideal. In this instance, the coax to the ATU should be as short as possible.
USE WITH : Doublet, G5RV or resonant Dipole
Running more power and/or want better performance on 160/80/60m? We also offer a 400-watt version... - we also suggest using this model if you are trying to "squeeze" more from a *small* Dipole/Doublet on a low band such as 160m or 80m. If you're using a Doublet or G5RV, a balun with a 1:1: ratio is advised unless you know the impedance of your aerial will benefit from a 4:1 ratio at the frequencies of interest. We offer a 4:1 QRO Balun here.
Using Balun on a G5RV - Really?
Some articles say you should, others say you shouldn't. G3TXQ's website explained why you should and included some pretty diagrams to prove his point. Our own experience (and the lack of units sent back to us!) tells us that using a Choke/Balun on a G5RV is indeed a wise move. In his original description of the G5RV, the inventor suggested use of a Balun but had changed his mind by the early 1980s. Modelling software now allows us to delve deeper into the science without climbing a ladder or walking down the garden in the pouring rain. It doesn't stop the disagreements on the QRZ Forums, unfortunately :)
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 preferable, in most cases, to a 4:1 Balun - and certainly better than the internal 4:1 (voltage) balun found in many tuners!
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. A small clip-on ferrite is perfectly OK for a 4m/2m/70cm Slim-Jim.