Tom,
What kind of A/B FS comparison could be done by disconnecting radials that
already lay on the ground under the vertical, for example with a large
relay??
Say you have 50 radials spread out, and for the A/B test you disconnect 40
of them connected to a bus wire via a relay, will this be equivalent to
just having 10 radials under the vertical?
If this is possible it would be a nice way to evaluate the performance of a
full radial system vs a light one, however I have a feeling it is not that
easy..
Any thoughts, has anyone tried this?
73/Peter SM2CEW
At 04:14 2004-10-23 , you wrote:
>> I do not agree on the elevated radials as being overrated,
>for Arizona
>> desert anyway. I had my 40m 4sq installed with 8 buried
>radials under each
>> element. The tuning method for the array was to erect all
>elements
>> identical, observe the frequency where the least amount of
>power went into
>> the 5th port (the dummy load) in each direction, apply a
>little Kentucky
>> windage and adjust the vertical elements lengths (all
>equal) to the desired
>> operating frequency. I never could observe a frequency
>where the wasted
>> power was minimum in any direction, and I was never happy
>with the array's
>> performance.
>
>Everyone pretty much knows eight buried radials can be
>somewhat lossy. Dump power, however, has NOTHING to do with
>element efficiency. Element efficiency was the concern. If
>you are only going to use four or eight radials and can
>stand them hanging in the air, then elevated is definately
>the way to go. Just don't pretend it competes with a good
>system using an adequate number of radials on the ground. It
>doesn't.
>
>> When I moved to the present location I decided to try
>again but with
>> elevated radials. I put up 4 tuned radials at 9 feet
>elevation under each
>> element and the array tuned sharply and works very well.
>Good enough that I
>> decided to build an 80m 4sq also. And I am very happy
>with it's
>> performance.
>
>Being happy is very important, it's really all that matters
>for any of us.
>But "happy" isn't a unit of field strength and it certainly
>is not an efficiency measurement.
>
>In order to measure loss change, we have to measure FS
>change. In order to tell if the radial system made a loss
>change, we have to ONLY change the radial system and measure
>the change in FS with proper protocol. Dump power, SWR, F/B,
>and tuning don't tell us a thing about system efficiency. To
>do a comparison the systems have to be at the same location.
>We have to only change the radial system. We have to measure
>F/S, nothing else will work.
>
>> And my RG-213 feed line and RG-11 foam impedance matching
>> transformer/phasing lines do not get hot, even running
>full power cw during
>> a contest (I only run 800 watts on RTTY).
>
>Line heating has nothing to do with ground loss. A feedline
>doesn't get any hotter feeding an antenna with 100%
>efficiency as it does a dummy load with 0% efficiency.
>
>> I think the important thing here is he wants an effective
>antenna and in my
>> opinion he will be very, very happy with 4 or even 8
>elevated radials under
>> each element, provided they are at least 9 feet above
>ground.
>
>On the other hand I know people who swore 4 elevated radials
>were perfect, until they installed 40-50 radials with no
>other changes.
>
>In at least three systems I compared FS of 2, 4, 8, 16, 32,
>and 64 radials and compared elevated to ground radials and
>while the elevated radials were better than ground radials
>when the system was sparse, 3 to 6dB was gained by using
>50-60 radials on the ground. WVNJ radio gained 2.5-5.5 dB
>when they went from six elevated radials to a conventional
>ground system. No other changes, only the radials were
>changed.
>
>If anyone wants to give up 3-6dB, lose lightning protection,
>have radiating radials, and have the maintanence and
>physical clutter problems associated with supporting 4 or 8
>wires per vertical in the air, that's OK with me.
>
>I wouldn't be happy with that, but then that's me. Someone
>else might not want to bury 25-50 radials, and would prefer
>the other system. That's great too.
>
>Let's just not imply the efficiency of four radials 1/25th
>of a wavelength above ground is near 90%, like it is with
>25-50 wires laying on or in the dirt.
>
>> Further, I will caution him to electrically measure the
>1/4 wavelength lines
>> rather than use the formulas. The lines on my 40m 4sq are
>stretched taught
>> between the phasing box and the element feed points and
>according to the
>> formula they should have enough slack in them to touch the
>ground.
>
>Which is another problem when the system is floated above
>ground. We not only have the radials to contend with, we
>have to have the feedlines hanging above ground. Some people
>certainly don't mind that, but I would.
>
>Since there is no advantage other than perhaps a 50% savings
>in labor and wire for the same efficiency, a person just has
>to decide what effort he wants to put where. I prefer to
>have the system buried, so nothing happens to it. I prefer
>to have the lightning protection that buried feedlines and
>buried radials provide. I like to have other antennas around
>without threading rope through a ceiling of wire, to drive
>my truck or tractor through pastures, and to have high
>system efficiency. I don't like radiating things with
>voltage on them in arm's reach, or near other conductors.
>
>Others might have different priorities. The effort of
>burying wire or pinning it to the ground is too great or it
>is just mechanically not workable. That's OK too. You do
>what you got to do to get on the air.
>
>73 Tom
>
>
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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