Fun With Folded Dipoles (
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- čas přidán 13. 07. 2024
- Sean, KA3UFV, was wondering if I would talk on folded dipole. Watch to learn more about folded dipoles and why it is confusing.
#antennas #dipole #folded dipole
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Many thanks for answering my question, Dave! My dad had a two-conductor folded dipole that he got a lot of use out of and I never had the opportunity to ask him why he chose that design, but this cleared things up a lot.
A flat top dipole has a characteristic impedance of around 75+j43 ohm.
A folded dipole presents 4×75=300 ohm.
And a three wire folded dipole has 9×75=675 ohm.
A homebrew 600 ohm open wire would be needed to feed the antenna.
You may try to argue that a folded dipole in the inverted V configuration has the feed point impedances as you discussed in the video; but I am not for it.
The main advantage of the folded dipole is it's broad banded and the main disadvantage is it's for a single band only especially if it's fed by a 50 ohm coaxial cable with a voltage BalUn interfaced at the feed point as you suggested.
De VU2RZA
Yeah I don't know where 200 ohms comes from? Everything I have read says a dipole is 75 ohms (approx). Assuming D1 and D2 in the folded dipole are are the same, the impedance transformer effect is 4, so 300 ohms not 200 ohms. (75 x 4).
Great video as always!
I'm a big fan of sky loops.. anybody ever do a folded loop? Where would they be shorted? How about a two turn sky loop?
By the way..maybe a stupid question... how do we tune/match a folded dipole made of wire?
hello dave is the feedpoint literally at the center of the ladderline as represented in the drawing or could i feed it from the end of the ladderline with the oposite end shorted. in this example for a two wire folded dipole. thanks for the video
Great video, what is the time clock for at the end of your videos Dave?
He’s tracking his self promotion time. The time that he’s advertising his Patreon
Can you make a 1/2 wave folded Fan dipole?
What spacer length will give 450Ohm with a three wire?
📻🎧
Hi Dave,
Another interesting topic.
However, I have 2 or 3 more important questions that you didn't cover here.
1) you didn't cover how a folded dipole radiation pattern is affected by the extra conductors. As you repeatedly state correctly... When it comes to antennas... Everything affects everything! Couldn't be more true!
2) You didn't state anything about gain by adding conductors! This is important as if you just create your simple folded dipole; how does the of that compare a 3 element, or say a 7 element folded dipole. Is there a formula for that?
2a) related to that on gain & pattern, would the folded dipole work the same as a std. Dipole with 3/2 wavelength, etc. Which do provide gain.
2b) have you or can you run these thru an antenna modeling program?
3) how well, if at all do these cope with noise; i.e. do they reduce local RFI or atmospheric noise like a fullwave loop? Though probably not to the same degree.
Thank you again Dave, for your presentations and elmering activities
I thought the standard impedance of a center fed single wire dipole was 73.
I thought the same... hmm..