Elecraft BL1 (1:1) - Manual

E
L E C R A F T
BL1-1
W I D E B A N D 1 : 1 B A L U N
R e v B , N o v e m b e r 1 0 , 2 0 0 6
The Elecraft BL1-1 is a general-purpose wideband balun with a 1:1 impedance ratio. It is intended to match
balanced feedlines to the unbalanced antenna connection of an Elecraft or other manufact
ur er ’ s t r a ns c e i ve r
or antenna tuner. It is very similar to the BL1 4:1 balun except in this case the secondary windings are
connected in parallel rather than in series.
Specifications
Power Rating 150 watts maximum.
Bandwidth Input VSWR less than 1.2 when connected to a 50-ohm resistive load, 500 kHz to 55
MHz.
Assembly

Perform an inventory of all parts in the kit.
Parts List
1 Balun Printed Circuit Board
20 inches of Balun Wire, brown or white sheath
3 Right-Angle Output Terminals
6 #6 Flat Washers 1 Right-Angle PC –mount BNC Connector
3 Thumb Screws
4 Self-Adhesive Mounting Feet

Install J1, the BNC connector, in the position indicated on the PC board silkscreen

Cut the sheathed twisted pair cable into two 10-inch (25.4 cm.) lengths.

Wind 3 turns of the cable through each of the balun core holes. The wire will completely fill the
holes in the balun core. Leave about 1 1/2 inches (3.81 cm.) of cable exposed. Wind the turns
tightly. The wire should be flat against the core. You will have to use a small screwdriver to
press each turn against the inside of the core opening to get the third turn through. A few drops of
rubbing alcohol as a lubricant can help get the last turn through. Be patient, it can be done. Use
the photo as a guide

Trim the cable (4 places) to about 1 1/4 inches (3.18 cm.).

Remove the outer sheath from the trimmed ends of the cable and then strip the conductors so only
about ¼ inch (6.3 mm.) of the RED and WHITE colored insulation is exposed on one end of the
core. Trim the wires on this end of the core so that the exposed conductors are about ¼ inch
(6.3mm) long. See the photo.

The insulation on the wires on the other end of the core will be cut to different lengths. First
remove the insulation from the WHITE wire on one side so that ¼ inch (6.3mm) of insulation
remains and then on the other side remove the insulation from the WHITE wire so that ½ inch
(12.6mm) of insulation remains. Perform the same operation on the RED wires except the longer
length of insulation on the RED wire must be on the same cable as the short length of insulation
on the WHITE wire. Trim the wires at this end of the core so that the exposed conductors are
about ¼ inch (6.3mm) long. See the photo.

Lightly tin the exposed end of each wire.