-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
There's a First Time For Everything
- Thread starter HomerBB
- Start date
I looked at the K1JJ tuner. A 40 turns at 5" diameter inductor requires 52' of tubing. Might have to take out a second mortgage for that one. Gonna have to work on homebrew for every ppssible part!
I found a 50 foot roll of 1/4" on eBay for under 30 bucks. It was more expensive at home depot. You probably wont need to use all the turns unless you get on 160. My vac variable is only 350pf but it's plenty for 80 meters.
I didn't use the variable cap on the input link so the center conductor is at DC ground. I made some inductors (basically plate chokes) to ground each leg of the ladder line.
Been browsing eBay, and other places for better prices. Hpme Depot is about $1 per foot for antthing usefull.
All is ready; 4:1 balun, 22' of 50 Ohm coax, and 1:1 balun. Now I need 3/4 hr of time and clear weather to transform my fan dipole into a windom and see how this works out.
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
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
Thanks, Mike.
I would need to order some more toroids to do more than with what I have on hand. The details you're sharing are very helpful.
It's going to rain all weekend so I can rework what I've done.
I would need to order some more toroids to do more than with what I have on hand. The details you're sharing are very helpful.
It's going to rain all weekend so I can rework what I've done.
Are you talking about within the box (balun network), or from the balun to the antenna? My intention is to feed the antenna wires directly from the box.
I follow this in terms of the 4:1, 200:50 Ohms balanced to unbalanced transformation.
Haven't made a K1JJ tuner, yet, but i have removed the fan dipole in favor of an 80 meters doublet. I used what I have on hand to feed it, the two baluns in this thread, and some new 300 Ohm twin lead i had in the attic. I haven't had time to work it the way I want, and I want to raise the ends up higher so it is less an inverted wire, but initially it seems to be preferred to the fan dipole - 2 wires instead of 8, and anyone I've called hears me with < 100 watts.
Time will tell...
Time will tell...
With an 80 meter doublet and a true balanced tuner youll be talking. A lot of the guys on the lower frequencies have crummy antennas and use power to compensate. Your 100 watts will do fine. You've already ditched the fanny dipole so you're making fast progress.
I'm sure there are many folks who get along well with fan dipoles. There's something to be said for resonant antennas. However,
1. Mine was ugly. I am not above an ugly antenna, as anyone who has seen many of the antennas I've built knows, but for a first time out of the chute project it wasn't anything I wanted anyone to see.
2. It had gotten old already being asked numerous times what my call is, and to repeat my name, and getting at best 44 signal reports, or worse. I made a 1/4 wave gp of chicken wire that did that well.
3. Tuning up all the bands worked ok, ears were pretty good, but I couldn't break up any pileups. If I had 100 watts in the wire on 11 meters I would hold my own. I know the wavelengths are different, and losses and radiation pattern are affected by earth proximity, yet, I want to minimize losses where I can. Some kind of twin lead/ladder line feed line seems to be a step "in the right direction", as said.
I know the entire system from the back of the transciever thru the aerial is my antenna system, so I seek to maximize my systems compatibility in its parts given my height, space, and pocketbook limitations.
I will make a K1JJ tuner - soon.
Oh, why are all the internet drawings of the fan dipole so neat and pretty? When the wind blew mine resembled the scattering of blackbirds by a shotgun blast... that's imbarasking.
1. Mine was ugly. I am not above an ugly antenna, as anyone who has seen many of the antennas I've built knows, but for a first time out of the chute project it wasn't anything I wanted anyone to see.
2. It had gotten old already being asked numerous times what my call is, and to repeat my name, and getting at best 44 signal reports, or worse. I made a 1/4 wave gp of chicken wire that did that well.
3. Tuning up all the bands worked ok, ears were pretty good, but I couldn't break up any pileups. If I had 100 watts in the wire on 11 meters I would hold my own. I know the wavelengths are different, and losses and radiation pattern are affected by earth proximity, yet, I want to minimize losses where I can. Some kind of twin lead/ladder line feed line seems to be a step "in the right direction", as said.
I know the entire system from the back of the transciever thru the aerial is my antenna system, so I seek to maximize my systems compatibility in its parts given my height, space, and pocketbook limitations.
I will make a K1JJ tuner - soon.
Oh, why are all the internet drawings of the fan dipole so neat and pretty? When the wind blew mine resembled the scattering of blackbirds by a shotgun blast... that's imbarasking.
Last edited: