Vertical vs Horizontal shootout part one
On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo
wrote: .... My setup is: Icom IC-761 Antenna 1 - Homebrew OCF dipole at ~ 50 feet. Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground. Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Mike, I understand that feedline radiation is an un-escapable characteristic of an OCF dipole, caused by the asymmetric feed. Some even claim it as a major advantage (eg Caroline Windom). Whilst no dipole is perfect in that respect, the OCF dipole is less perfect, and it may be worth modelling the thing to comment in your findings on the probably magnitude of the contribution by the feedline. Great project, look forward to follow-ups. Owen -- |
Vertical vs Horizontal shootout part one
On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo
wrote: Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Hi Mike, Not all 4:1 BalUns exhibit enough (or sometimes any) common mode Z. 73's Richard Clark, KB7QHC |
Vertical vs Horizontal shootout part one
Hmmm... Gee, I could connect a spectrum analyzer channel to each of
two different antennas and get a continuous real-time comparison of the signals and noise them. Cheers, Tom |
Vertical vs Horizontal shootout part one
Richard Clark wrote:
On Tue, 07 Mar 2006 14:18:47 -0500, Michael Coslo wrote: Question, does the magnitude of feedline radiation from the OCF (presumably predominantly vertical) significantly affect qualification of it as a horizontal antenna? There shouldn't be any feedline radiationn, this is oan antenna running coax to a 4:1 balun at the feedpoint. Hi Mike, Not all 4:1 BalUns exhibit enough (or sometimes any) common mode Z. Okay. Perhaps I might better characterize my experiment as a comparison of a vertical and an OCF dipole of indeterminate vertical vs horizontal performance. I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". In that case you would feed the antenna with balanced line. Certainly the antenna doesn't seem to be radiating RF from anywhere but the antenna bits. p.s. forgive the spelling, I am using a beta of Thunderbird for my newsgroups, and it seems to have a few quirks that make it hard to see what I have written!! - 73 de Mike KB3EIA - |
Vertical vs Horizontal shootout part one
On Wed, 08 Mar 2006 09:47:18 -0500, Michael Coslo
wrote: I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". It is pretty well known that an OCFD is a bear when it comes to common mode current on the feedline. Usally requiring more than one common mode choke to tame the sucker. Danny, K6MHE |
Vertical vs Horizontal shootout part one
On Wed, 08 Mar 2006 09:47:18 -0500, Michael Coslo
wrote: I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". Hi Mike, This is not outside the realm of possibility. Whose antenna is it? 73's Richard Clark, KB7QHC |
Vertical vs Horizontal shootout part one
Michael Coslo wrote:
Okay. Perhaps I might better characterize my experiment as a comparison of a vertical and an OCF dipole of indeterminate vertical vs horizontal performance. I was under the impression from the designers of this flavor of dipole that they were not radiating from the feedline unless you wanted that "feature". Unfortunately, even if the designers don't intend the feedline to radiate, it's very difficult to avoid. A single balun at the feedpoint is very likely not enough to prevent it. In that case you would feed the antenna with balanced line. That would make no difference at all in determining whether or not the line would radiate. Certainly the antenna doesn't seem to be radiating RF from anywhere but the antenna bits. The amount of feedline common mode current and therefore radiation will vary from band to band, probably a great deal. It's easy enough to make up a simple current probe with a clamp-on core and make quantitative measurements if you're interested. They've been described on this newsgroup several times. Roy Lewallen, W7EL |
Vertical vs Horizontal shootout part one
Radiation from feedlines is grossly exaggerated.
For many purposes, practically it does not occur. When discussing the importance of such radiation one should always crudely estimate its level relative to transmitter or radiated power. If you don't know what its level is then you don't know what you are waffling about. ---- Reg. |
Vertical vs Horizontal shootout part one
On Wed, 8 Mar 2006 21:55:42 +0000 (UTC), "Reg Edwards"
wrote: If you don't know what its level is then you don't know what you are waffling about. Hi Reggie, Seeing you lack any quantifiables, are you offering belgian waffles? 73's Richard Clark, KB7QHC |
Vertical vs Horizontal shootout part one
On Wed, 08 Mar 2006 13:58:19 -0800, Richard Clark
wrote: On Wed, 8 Mar 2006 21:55:42 +0000 (UTC), "Reg Edwards" wrote: If you don't know what its level is then you don't know what you are waffling about. Hi Reggie, Seeing you lack any quantifiables, are you offering belgian waffles? 73's Richard Clark, KB7QHC Richard, Just anouther one of Reg's factoids (e pluribus unum). Danny |
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