49:1 or 64:1 EFHW matching transformers
for appropriately designed end-fed half-wave antennas. Select the ratio, winding and compensation components for the intended antenna and bands.
Custom ABS enclosure, winder and hardware for antenna builders
Your transformer. Our custom enclosure.
Build your next balun or unun in the box behind the CHA B3D.
Spend your bench time building the transformer, with a compact enclosure and the connection hardware already selected. The CHA ENCLO gives antenna builders Chameleon Antenna’s own custom ABS enclosure, an SO-239 coaxial connector, a gasket and stainless steel mounting hardware—a practical starting point for your next balun or unun.
This is the same enclosure used in the CHA B3D Broadband Base Dipole. Build the matching network that suits your antenna, whether you are experimenting at the bench, preparing a portable wire antenna or assembling several projects for a club workshop.
- Custom ABS bodySame enclosure as the CHA B3D
- FT240-size buildsIntentionally snug fit
- SO-239 includedWith stainless fasteners
- Two field colorsTan and OD Green
Plan the fit before you wind
See how your build will fit
Check the body, opening, cavity depth and extended lid/winder dimensions before planning your connections.
Choose your circuit
One enclosure. Several transformer projects.
You supply the core, winding wire and circuit components. Potential projects include:
9:1 ununs
for suitable nonresonant end-fed wire systems, normally used with a tuner and an appropriate counterpoise or return path.
4:1 impedance transformers
for selected loop, off-center-fed dipole or other matching applications. Choose a balun or unun circuit to suit the load; a 4:1 impedance ratio does not itself provide common-mode isolation.
1:1 current baluns
for suitable coax-to-balanced-antenna feed points. A coax-to-coax line isolator requires a second coaxial connector and any necessary enclosure modification; only one SO-239 is supplied.
These are project ideas, not complete circuit kits or a guarantee that every published design fits. Check winding dimensions, insulation clearance and electrical performance.
Complete product reference
Key specifications
- Body outside
- 3-1/2 × 2-3/4 × 1-3/4 in (89 × 70 × 44 mm)
- Internal opening
- 3-1/4 × 2-1/2 in (83 × 64 mm)
- Cavity depth
- 1-3/8 in (35 mm), rim to floor
- Extended lid / winder
- 8 × 4 in (203 × 102 mm)
- Material
- ABS (acrylonitrile butadiene styrene)
- Colors
- Tan and OD Green
- RF connection
- One SO-239 female connector
- Hardware
- Stainless steel fasteners and eyebolt
- Lid seal
- Gasketed lid
Dimensions are nominal, with rounded metric equivalents. Chamfered corners, wall taper and installed hardware reduce usable clearance.
Know what arrives
Included and customer-supplied equipment
Quantities below are for one enclosure kit. Every kit in your selected pack receives the same listed hardware.
Included with each kit
- 1 ABS enclosure body and extended lid/winder, pack color
- 1 gasket
- 1 SO-239 connector
- 1 × 2-inch eyebolt
- 2 × #10-24 × 5/8-inch socket cap screws
- 4 × #10-24 KL nuts
- 2 × #10 lock washers
- 2 × #10-24 wing nuts
- 2 × #6-32 × 1/2-inch button screws
- 2 × #6-32 KL nuts
- 4 × #4-40 × 1/2-inch Phillips screws
- 4 × #4-40 KL nuts
What you supply
Ferrite core, winding wire, circuit components, antenna wire, feed line, tools, solder and any additional mounting or sealing materials required by your design. No wound transformer or completed antenna is included.
Choose your pack
- Pack of 2 - two colors: one Tan enclosure kit and one OD Green enclosure kit.
- Pack of 5 - Tan: five Tan enclosure kits.
- Pack of 5 - OD Green: five OD Green enclosure kits.
Compact by design
A snug fit for FT240 projects
The enclosure was intentionally designed for a tight fit around an FT240-size transformer, including a transformer built with an FT240-43 core. Plan the winding layout and trial-fit the completed winding before final assembly. Wire diameter, insulation, winding placement and terminal clearance all affect the finished fit. The lid must close without pinching insulation or forcing the core into place.
Other ferrite mixes can be used when the finished transformer fits the same available space. Choose the mix for the electrical design and intended frequency range; a matching core size alone does not establish suitable RF performance. Stacked cores and oversized windings require a separate fit check.
Build with care
Build and test before transmitting
The finished transformer’s frequency range and power capability depend on its circuit, core material, winding, insulation, load and duty cycle. The enclosure does not establish a power rating. Start testing at low power and check matching, heating and insulation clearance before increasing power. Provide strain relief for antenna and feed-line loads. Keep antenna installations clear of power lines.
Seat the gasket evenly and address every connector and hardware penetration when preparing an outdoor installation. A gasket alone does not establish an IP rating or make the completed assembly submersible.
