The reference I could not remember -- QEX, July/August 2005, page 28: Ground
System Configurations for Vertical Antennas, by Al Christman, K3LC. It was
done with "EZNEC4" which I assume is EZNEC v4 -- which uses NEC2. The model
results may therefore be suspect given the recent TT comments about using
NEC2 to model ground effects and radials.
73,
Larry
W1DYJ
----- Original Message -----
From: "Larry Banks" <larryb.w1dyj@verizon.net>
To: "Robert Carroll" <w2wg@comcast.net>; "'Towertalk'"
<towertalk@contesting.com>
Sent: Saturday, March 15, 2008 3:33 PM
Subject: Re: [TowerTalk] Radial length
>
> As to the pattern of radials -- and I can't remember the reference but I
> think it was in QEX -- not having a "perfect circle" is OK -- it just
> skews
> the beam pattern. toward the direction with the densest radials.
>
> 73,
> Larry
> W1DYJ
>
>
> ----- Original Message -----
> From: "Robert Carroll" <w2wg@comcast.net>
> To: "'Towertalk'" <towertalk@contesting.com>
> Sent: Saturday, March 15, 2008 2:23 PM
> Subject: Re: [TowerTalk] Radial length
>
>
>> The general sense of the discussions I have read is that the intent of
>> the
>> radials is not to provide a near perfect reflecting surface under the
>> antenna, but to provide a ground return with as little loss as possible.
>> If
>> I were going for something that in the extreme would look like an almost
>> perfectly reflecting copper sheet under the antenna, I would use the same
>> angular spacing between each pair of radials. On the other hand if I
>> were
>> only trying to provide a low loss ground return, I might route the
>> radials
>> for convenience in avoid things like a garden, a pool, or some other
>> object.
>> Which view is the correct one?
>>
>> 73
>> Bob W2WG
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of Larry Banks
>> Sent: Saturday, March 15, 2008 1:42 PM
>> To: donovanf@starpower.net; Towertalk
>> Subject: Re: [TowerTalk] Radial length
>>
>> Just to close the loop an all of this great info, I will paraphrase from
>> the
>>
>> ARRL Antenna Book, (c) 2007, 21st edition, page 3-9 which matches up
>> pretty
>> well with all of these comments:
>> ----------------------------
>> Practical Suggestions For Vertical Ground Systems
>>
>> At least 16 radials should be used if at all possible.
>> Experimental measurements and calculations show that with
>> this number, the loss resistance decreases the antenna effi-
>> ciency by 30% to 50% for a 0.25 wavelength vertical, depending on
>> soil characteristics. In general, a large number of radials (even
>> though some or all of them must be short) is preferable to a
>> few long radials for a vertical antenna mounted on the ground.
>> The conductor size is relatively unimportant as mentioned
>> before: #12 to #22 copper wire is suitable.
>> a.. If you install only 16 radials they
>> need not be very long - 0.1 lambda is sufficient.
>> b.. If you have the wire, the space and the patience to lay
>> down 120 radials (optimal configuration), they should
>> be 0.4 lambda long. This radial system will gain about 3 dB
>> over the 16-radial case.
>> c.. If you install 36 radials that are 0.15 lambda long, you will
>> lose 1.5 dB compared to optimal configuration.
>> ----------------------------
>> 73,
>> Larry
>> W1DYJ
>>
>>
>>
>> ----- Original Message -----
>> From: <donovanf@starpower.net>
>> To: "Towertalk" <towertalk@contesting.com>
>> Sent: Saturday, March 15, 2008 1:22 PM
>> Subject: Re: [TowerTalk] Radial length
>>
>>
>>> W8JI posted a classic reply to this question nearly ten years ago.
>>>
>>> Not coincidentally, sixty 1/4 wavelength radials have since become the
>>> defacto standard among serious 160 meter DXers.
>>>
>>> Here's a brief synopsis, followed by the original text of Tom's original
>>> e-mail.
>>>
>>> All of these measurements are referenced to the performance of sixty 1/4
>>> wavelength radials. Actual results are highly dependent on your local
>>> ground conditions.
>>>
>>> Elevated .03 wl Conventional
>>>
>>> four -4.3 dB -5.5 dB
>>> eight -2.4 -2.7
>>> sixteen -.8 -1.3
>>> thirty two -.7 -.8
>>> sixty -.2 reference 0 dB
>>>
>>> 73
>>> Frank
>>> W3LPL
>>>
>>> Subject: TopBand: Elevated GP vs. Vertical Antennas - long
>>> From: w8ji.tom@MCIONE.com (Tom Rauch)
>>> Date: Tue, 17 Mar 1998 18:30:34 +0000
>>>
>>>
>>>> buck?"... I asked the same question of Tom recently and while I am
>>>> still
>>>> attempting to parse the various dB's quoted it appears that somewhere
>>>> between
>>>> 32 and 64 ground radials is the breakpoint compared to 4 elevated
>>>> radials of
>>>> 1/4wl...
>>>
>>> No, here's how it stacked up in dB. 0 dB is the reference of 60
>>> radials. These are farfield signal levels, accurate to + - .1 dB.
>>>
>>> Elevated .03 wl Conventional
>>>
>>> four -4.3 dB -5.5 dB
>>> eight -2.4 -2.7
>>> sixteen -.8 -1.3
>>> thirty two -.7 -.8
>>> sixty -.2 reference 0 dB
>>>
>>> I selected the 60 radials as the reference antenna, so ALL the
>>> measurements are in reference to the field from that system. In
>>> theory, that system is about 1 dB below perfect.
>>>
>>>> It appears to me that 8 elevated radials are closer to reality for the
>>>> average
>>>> topbander than a ground radial system of more than 64 radials....
>>>
>>> That would be OK if you accept being about 3 dB or so down. Myself, I
>>> want that 3 dB since it only takes a few afternoons work and $120 or
>>> so of material. That's about the cheapest 3 dB I can buy, since I
>>> have a 1500 watt PA.
>>>
>>> Consider this, going from the 3/8 wl vertical to the four square only
>>> gained me 5 dB! I got almost that just by going from four radials to
>>> 60 radials.
>>>
>>> It is often claimed 120 1/4 wl radials are ideal. Not according to
>>> extensive tests. With 1/4 wl radials, more than 60 offer very little
>>> advantage. The results were:
>>>
>>> 30 -1.56 dB
>>> 60 -.93 dB
>>> 113 -.79 dB
>>>
>>> The nearest to ideal measured in the famous L, B, and E RCA report
>>> was 113 .412 wl radials. In that test, the end result was 0.2 dB from
>>> perfect! Going from 113 .412 wl radials to 60 .274 wl radials
>>> will cost you all of .7 dB!
>>>
>>> By the way, these tests showed a nine foot on a side ground screen
>>> was meaningless when a large ground system was used, but did make a 3
>>> dB difference when only 15 radials were used. But this was for
>>> a short radiator (1/16th wl tall). With a taller antenna the ground
>>> screen would mean less, of course.
>>>
>>> Disclaimer:
>>> Other than my own tests, the data above is available in "Ground
>>> Systems as a Factor in Antenna Efficiency" Brown, Lewis and Epstein,
>>> RCA Manufacturing Co. and was printed in Proceedings of the IRE
>>> Volume 25 number six in June 1937. I converted the results into dB
>>> from the published mV/m, so it is easier to follow.
>>>
>>> 73, Tom W8JI
>>>
>>>
>>>
>>>
>>> ---- Original message ----
>>>>Date: Sat, 15 Mar 2008 12:34:21 -0400
>>>>From: "Alex Malyava" <alex.k2bb@gmail.com>
>>>>Subject: Re: [TowerTalk] Radial length
>>>>To: "Bill Turner" <dezrat@copper.net>
>>>>Cc: Towertalk <towertalk@contesting.com>, Tom Osborne
>>>><w7why@verizon.net>
>>>>
>>>>there is an article (in russian - http://dl2kq.de/ant/3-33.htm) on
>>>>DL2KQ website with MMANA/NEC2 computer analysis of vertical of various
>>>>length like 1/8, 1/4 and 5/8 with radials like 1/10, 1/4 and 1/2 above
>>>>different soil.
>>>>Depends on your soil and vertical height there is different number of
>>>>radials of different length you need to put.
>>>>If you have, for example, 1/8 vertical on medium or good soil you need
>>>>more then 16...32 radials of 1/4 to work better than the same number
>>>>of short 1/10 radials.
>>>>
>>>>K2BB
>>>>
>>>>2008/3/14, Bill Turner <dezrat@copper.net>:
>>>>> ORIGINAL MESSAGE:
>>>>>
>>>>> On Fri, 14 Mar 2008 16:20:13 -0700, "Tom Osborne" <w7why@verizon.net>
>>>>> wrote:
>>>>>
>>>>>
>>>>> >Is it true that my radials only need to be around 100 feet long
>>>>> instead of
>>>>> >125 for full sized 160 meter radials or is that an old wives tale?
>>>>> 73
>>>>> >Tom W7WHY
>>>>>
>>>>>
>>>>> ------------ REPLY FOLLOWS ------------
>>>>>
>>>>> Well, yes and no.
>>>>>
>>>>> If the radials are laid directly on the earth, length is much less
>>>>> critical than if they were up in the air, as in a counterpoise. The
>>>>> missing few feet in your case will be made up by the earth itself,
>>>>> but
>>>>> having almost a full 1/4 wavelength of radials, you may not notice
>>>>> much
>>>>> difference. I'd go ahead and try it.
>>>>>
>>>>> 73, Bill W6WRT
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> TowerTalk mailing list
>>>>> TowerTalk@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>
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