I think your statement that radials only apply to verticals is up for debate!
<G> I have friends that have dipoles at 70 feet and they have a lawn full of
radials.
Paul Gates kd3jf
> Date: Sat, 3 Aug 2013 18:01:31 -0400
> From: jh.graves@verizon.net
> To: tentec@contesting.com
> Subject: Re: [TenTec] OT: Openwire/Window Line and Bad Wx
>
> I hope this does not add to the confusion too much. However...
>
> Radials really only apply to quarter-wave verticals. The reason is
> that the radials allow the field to act as though is is a half wave
> antenna, although the bottom half is virtual. A half-wave vertical only
> requires a ground. There is no question that at 40 meters and below, it
> is not easy to put up a a half-wave vertical and so, depending on how
> the vertical is constructed, and which bands are covered, radials may be
> needed to create or maintain the desired pattern. Although I have not
> seem this, it would seem to me that for multi-band verticals, there
> should be some isolation of the radials in order to maintain the desired
> pattern for the upper bands.
>
> John / WA1JG
>
>
>
> On 8/3/2013 12:18 PM, Darrell Bellerive wrote:
> > It is not just the quality of the ground, but rather the proximity to
> > the ground. Ground losses are present for a low horizontal antenna
> > regardless of the quality of the ground.
> >
> > For a vertical antenna, the ground quality is what matters, hence the
> > need for radials.
> >
> > Model a dipole in free space and note the maximum and average gain of
> > the antenna, then model the same antenna at 0.05 wavelength above
> > perfect ground and compare the gain. Changing the ground quality from
> > perfect to normal to poor will also influence the loss.
> >
> > At low heights the radiation pattern will totally change from free
> > space, with most of the radiation going straight up. Not necessarily a
> > bad thing on 160 and 80 metres.
> >
> > One of the tricks for tropical shortwave broadcasters is to bury a
> > radial under a dipole and then optimize the height of the dipole to
> > get the desired radiation pattern. Usually these stations are looking
> > for a coverage area within a few hundred miles of the station, and a
> > radiation pattern directly up is what is desired.
> >
> > Darrell Bellerive
> >
> > On 08/03/2013 08:17 AM, k6jek wrote:
> >> How big are the ground losses? Are they the difference between an
> >> EZNEC prediction over perfect ground and what it says over average
> >> ground assuming average is what you have? Is it the difference
> >> between the model's prediction of impedance over perfect ground and
> >> what you actually measure as Bob Orr said in his book years ago, for
> >> example, the model says the impedance should be 35 +jx over perfect
> >> ground and you measure 50 +jx, at the feed point, that's 15 ohms of
> >> loss?
> >>
> >> Jon
> >>
> >> On Aug 3, 2013, at 7:46 AM, Darrell Bellerive wrote:
> >>
> >>> The other factor that I don't think has been mentioned is ground
> >>> loss of the transmitted signal. For horizontal antennas, antenna
> >>> height is the major factor, and for vertical antennas, radials.
> >>>
> >>> The impact of ground loss on a low horizontal antenna on the 160
> >>> and 80 metre bands will be significant compared to feedline
> >>> losses. A dipole at 25 to 30 feet above ground for 160 metres is
> >>> only 0.05 of a wavelength high. As a horizontal antenna is lowered
> >>> below 1/4 wavelength above ground, ground losses increase
> >>> significantly.
> >>>
> >>> Remember though that lots of hams make lots of contacts with low
> >>> dipoles, and any antenna is better than no antenna. So like Bob
> >>> has stated, striving to eliminate that last dB of feedline, tuner,
> >>> or balun loss may be insignificant compared to other factors. We
> >>> need to be mindful of our complete system of transmitter power,
> >>> losses, propagation, etc. and the impact each has on our
> >>> transmitted signal.
> >>>
> >>> 73, Darrell VA7TO
> >>>
> >>> Darrell Bellerive
> >>>
> >>> On 08/03/2013 06:37 AM, Bob McGraw - K4TAX wrote:
> >>>> Steve et al:
> >>>>
> >>>> I'm not saying that loss does or does not change with the vinyl
> >>>> type window line between wet and dry. I do agree with your
> >>>> results in that loss does increase with a wet line as opposed to
> >>>> a dry line. I also agree that loss is greater per unit at 28
> >>>> MHz vs. the same length of line at 1.8 MHz or 3.8 MHz regardless
> >>>> if the line is wet or dry.
> >>>>
> >>>> My point, with today's receivers, in most all cases the
> >>>> atmospheric noise and man made noise will mask any receiver
> >>>> internal noise and will easily overtake any loss in the
> >>>> transmission line. However, the loss in the transmission line
> >>>> will affect the NF of the receiver, which on HF is of little
> >>>> significance. In many cases, we worry about 2 or 3 dB loss in
> >>>> the transmission line but run the attenuator of 10 dB to 20 dB
> >>>> at the input of the receiver. Now on transmit, that point makes
> >>>> a different in the power arriving at the antenna. Again,
> >>>> typically less than 1 S unit on the other end. To that point,
> >>>> most of the time I run the Argonaut VI at 10 watts and can work
> >>>> about any station I hear, regardless of line loss.
> >>>>
> >>>> True open wire line, by definition, is two conductors supported
> >>>> only at the source end and the termination end, drawn taught,
> >>>> and without any spacers. This of course is a real challenge to
> >>>> make work reliably in practice unless one uses large conductors
> >>>> and spaced at 6" to 18" and used at lower frequencies and
> >>>> typically with very high power in the near megawatt range. We
> >>>> used this feed line approach in some of the commercial SW
> >>>> stations to which I attended. Some of these feed lines were each
> >>>> several thousand feet in length. All of this is far beyond the
> >>>> scope of most ham installations.
> >>>>
> >>>> I would like to see more data on dry line vs. wet line from
> >>>> natural cause as opposed to "wetted" line. I use the vinyl
> >>>> covered line with 66% of the web spacers removed. {Remove 2,
> >>>> leave 1, remove 2, leave 1.} I see little change from wet to dry
> >>>> on HF.
> >>>>
> >>>>
> >>>> 73 Bob, K4TAX
> >>>>
> >>>>
> >>>> ----- Original Message ----- From: "Steve Hunt"
> >>>> <steve@karinya.net> To: "Discussion of Ten-Tec Equipment"
> >>>> <tentec@contesting.com> Cc: "Phil Sussman"
> >>>> <psussman@pactor.com>; "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
> >>>> Sent: Saturday, August 03, 2013 8:01 AM Subject: Re: [TenTec] OT:
> >>>> Openwire/Window Line and Bad Wx
> >>>>
> >>>>
> >>>>> We're talking here about reported changes in loss that - if
> >>>>> true - would be equivalent to a 5dB change between dry and wet
> >>>>> on a 100ft of ladderline feeding a doublet on 10m.
> >>>>>
> >>>>> Are you folks trying to tell me that 5dB makes "little to no
> >>>>> difference"?
> >>>>>
> >>>>> Steve G3TXQ
> >>>>>
> >>>>>
> >>>>>
> >>>>>
> >>>>> On 03/08/2013 13:27, Phil Sussman wrote:
> >>>>>> Bob is right! In the end, propagation will dictate. External
> >>>>>> conditions have more of an effect than the subtle
> >>>>>> differences over which we have control.
> >>>>>>
> >>>>>> Sure we can increase efficiency, yet the results are subtle.
> >>>>>> It all depends upon whether the band is open, eh?
> >>>>>>
> >>>>>> Well said, Bob!
> >>>>>>
> >>>>>> 73 de Phil - N8PS
> >>>>>>
> >>>>>> ------
> >>>>>>
> >>>>>> Quoting Bob McGraw - K4TAX <RMcGraw@Blomand.net>:
> >>>>>>
> >>>>>>> As I said in my closing remark in an earlier post:
> >>>>>>>
> >>>>>>> "I realize that we'd like to eak out every dB we can, but
> >>>>>>> in the end, it makes little to no difference on HF."
> >>>>>>>
> >>>>>>> If one can match the load, using what ever means and
> >>>>>>> equipment, then energy will be transferred. On receiving,
> >>>>>>> atomospheric and man made noise will overtake any losses
> >>>>>>> in the antenna system and will over ride most all receiver
> >>>>>>> noise.
> >>>>>>>
> >>>>>>> 73 Bob, K4TAX
> >>>>>>>
> >>>>>>
> >>>>>> _______________________________________________ TenTec
> >>>>>> mailing list TenTec@contesting.com
> >>>>>> http://lists.contesting.com/mailman/listinfo/tentec
> >>>>>>
> >>>>>>
> >>>>>
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> >>>>>
> >>>>
> >>>>
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