Choke Balun with T-Switch

A 1:1 Choke Balun that features a switch to turn a Doublet or G5RV into a Marconi "T" Antenna.  This gives you the opportunity to get the lower bands such as 160m, 80m or 60m from an aerial that may, under normal feeding, be too short to operate effectively.

It functions as a normal Doublet/G5RV Choke until switched inline, which makes the feeder+aerial wires radiate and enables the ground-radials.  The unswitched version can be found here.

If you are using this box with a Dipole/Doublet that is always used below 10MHz, the 75-mix ferrite is best.  If you're converting an "all round HF" Doublet, then select 31-mix.

This box should be connected to a short length of coax to your ATU.

• FT240 type 31 or 75 Ferrite Toroid option
• Rated at 400-watt continuous
• M4 (4mm) terminals with washers+wing-nuts
• SO239 connector
• 125x85x55mm
• Weight: 450g
• Unit is NOT weather-proof - but can be placed outside in a dry/covered area

The 3rd image shows a conventional feeding arrangement for a Dipole/Doublet.
The 4th image shows how the switch affects the wiring when "inline".

It should be obvious that, when switched inline, RF is now "in the Shack" so care must be taken to avoid long lengths of radiating feeder!