The following scan is for a 1:1 current balun with 14 turns of #14 covered
wire. The band width is shown below and is narrower than wanted.
The
picture below shows the coil wound on a 3/4" PVC pipe. The coils
were covered with electrical tape (not sure what the dialectic is).
One 53.6 Ω resistor on the output. The bifilar, air
core, winding diagram is shown below (trying to get a better picture) with the resistor across the
balanced output to allow a balanced current on the input to the 50 coax.
Balun picture
- - -
Coil data
| Description |
Dimension |
|
Form Diameter |
0.75" |
|
Wire |
14 awg
THHN (covered) |
|
Wire diameter |
0.0641" |
|
Coil diameter(OD) |
1.0" |
|
Turns |
14 bifilar |
|
Coil Length |
3.25" |
| |
|
- - -
Inductance
Calculated (based on 4:1 or 205/4=51.25) and Measured
Frequency
(MHz) |
Rs
(calculated) |
Rs
(measured) |
SWR |
| 3.5 |
51.25
Ω |
52.165 Ω |
1.017 |
| 7.1 |
51.25
Ω |
53.552 Ω |
1.025 |
| 14.2 |
51.25
Ω |
58.139 Ω |
1.134 |
| 21.0 |
51.25
Ω |
64.577
Ω |
1.260 |
| 28.0 |
51.25
Ω |
70.282 Ω |
1.371 |
As you can see, the SWR begins to rise approaching 30
MHz. Will try winding the balun with magnet wire instead of
covered.
- - -
Scan - HF
- - -
Scan - Full
- - -
If you have any graphs that could be added to
this site please send them along. I'll post and credit your
information.
