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Homer,
For your 4:1 Guanella or current balun you need to have 100 ohm balanced line. The 4:1 is wound in series on the load or antenna side (100 ohms + 100 Ohms = 200 ohms), and in parallel (100 ohms /2 = 50 ohms) for the radio side. Use the formula for balanced line 276 Log b/a, where b = Center-to-Center spacing of your wire in inches, and a = radius of the wire in inches. If there is insulation on the wire (in the case of close spacing like you have) then the formula is modified to (276/SQRT(K)) x LOG b/a, where K is the velocity Factor of the insulation (typically .97 to .95), and a and b are as defined before. Just remember to include the thickness of the insulation in your Center-to-Center spacing. It is best to use some form of tape (can be electrical for low power application) to hold the wire spacing consistent. Using this model, your wire spacing for a 1:1 choke balun should be 50 ohms. For higher power applications you could use a 2.4" diameter ferrite toroid. This will help provide a wider VSWR bandwidth. For the lower bands such as 160 and 80 meters I would use a #43 ferrite, however a #61 is used by most for a wider range up to 6 meters. Another choice would be a K ferrite from Ambidon or a #52 from Fairite. Another wire choice for the 1:1 is RG-142/U coax for high power applications or RG-58/U with a solid dielectric. Don't use coax with a foam dielectric since the center conductor will eventually migrate from center to the outer radius of the cable, and may eventually slice through the foam and short out to the shield after a number of years. But before that happens your calculated impedance will change since the Center-to-Center spacing is modified due to the center wire moving out of center with the tight radius bend around the toroid.

73,
Mike, KC9Q

<blockquote data-quote="KC9Q" data-source="post: 585707" data-attributes="member: 23691">Homer,For your 4:1 Guanella or current balun you need to have 100 ohm balanced line.&nbsp; The 4:1 is wound in series on the load or antenna side (100 ohms + 100 Ohms = 200 ohms), and in parallel (100 ohms /2 = 50 ohms) for the radio side. Use the formula for balanced line 276 Log b/a, where b = Center-to-Center spacing of your wire in inches, and a = radius of the wire in inches.&nbsp; If there is insulation on the wire (in the case of close spacing like you have) then the formula is modified to (276/SQRT(K)) x LOG b/a, where K is the velocity Factor of the insulation (typically .97 to .95), and a and b are as defined before.&nbsp; Just remember to include the thickness of the insulation in your Center-to-Center spacing.&nbsp; It is best to use some form of tape (can be electrical for low power application) to hold the wire spacing consistent.&nbsp; Using this model, your wire spacing for a 1:1 choke balun should be 50 ohms.&nbsp; For higher power applications you could use a 2.4&quot; diameter ferrite toroid.&nbsp; This will help provide a wider VSWR bandwidth.&nbsp; For the lower bands such as 160 and 80 meters I would use a #43 ferrite, however a #61 is used by most for a wider range up to 6 meters.&nbsp; Another choice would be a K ferrite from Ambidon or a #52 from Fairite.&nbsp; Another wire choice for the 1:1 is RG-142/U coax for high power applications or RG-58/U with a solid dielectric.&nbsp; Don&#039;t use coax with a foam dielectric since the center conductor will eventually migrate from center to the outer radius of the cable, and may eventually slice through the foam and short out to the shield after a number of years. But before that happens your calculated impedance will change since the Center-to-Center spacing is modified due to the center wire moving out of center with the tight radius bend around the toroid.73,Mike, KC9Q</blockquote>

[QUOTE="KC9Q, post: 585707, member: 23691"] Homer, For your 4:1 Guanella or current balun you need to have 100 ohm balanced line. The 4:1 is wound in series on the load or antenna side (100 ohms + 100 Ohms = 200 ohms), and in parallel (100 ohms /2 = 50 ohms) for the radio side. Use the formula for balanced line 276 Log [B]b[/B]/[B]a[/B], where [B]b[/B] = Center-to-Center spacing of your wire in inches, and [B]a[/B] = radius of the wire in inches. If there is insulation on the wire (in the case of close spacing like you have) then the formula is modified to (276/SQRT([B]K[/B])) x LOG [B]b[/B]/[B]a[/B], where [B]K[/B] is the velocity Factor of the insulation (typically .97 to .95), and[B] a[/B] and [B]b[/B] are as defined before. [U]Just remember to include the thickness of the insulation in your Center-to-Center spacing.[/U] It is best to use some form of tape (can be electrical for low power application) to hold the wire spacing consistent. Using this model, your wire spacing for a 1:1 choke balun should be 50 ohms. For higher power applications you could use a 2.4" diameter ferrite toroid. This will help provide a wider VSWR bandwidth. For the lower bands such as 160 and 80 meters I would use a #43 ferrite, however a #61 is used by most for a wider range up to 6 meters. Another choice would be a K ferrite from Ambidon or a #52 from Fairite. Another wire choice for the 1:1 is RG-142/U coax for high power applications or RG-58/U with a solid dielectric. Don't use coax with a foam dielectric since the center conductor will eventually migrate from center to the outer radius of the cable, and may eventually slice through the foam and short out to the shield after a number of years. But before that happens your calculated impedance will change since the Center-to-Center spacing is modified due to the center wire moving out of center with the tight radius bend around the toroid. 73, Mike, KC9Q [/QUOTE]

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