Re: Topband: Elevated Radials
Good Day Again All, Well, I've done my best to summarize all the respondents' comments in the matter of elevated vs. ground-mounted radials---and I'll try now to summarize these in a single-page format for benefit of all to see... The results are certainly interesting, and some are as different from one another as we might be physically! In any event---and FWIW---here goes: (A) Is it true that a couple of elevated radials are just as effective as the "optimum" amount of buried ones...? -It depends. -Don't know. -Don't know. -If 2 or more are used, maybe. -It depends. (B) What is the "ideal" number of elevated radials that one should use...? -It depends upon their height. -2. -2 to 4. -7 to 8. -1 to 5. -2. -8. -1 to 2. -16 to 32. -16 to 32. -The more the better. -Any amount, but use pairs (ex. 2 to 4, 6 to 8, etc.). (C) How many elevated radials are "just enough"...? -Enough to overcome ground losses & establish resonance. -2. -2 -2. -2. -4. -4 (8 is overkill). -1. -32. -8. -Depends upon soil quality (D) How high should these radials be...? -The higher the better to clear pedestrians, animals, etc. -10'. -6' to 8'.-6' to 8'. -12' to 14'. -7' to 8'. -6' to 15'. -20'. -6' to 10'. -8'. -10' to 12'. -20'. -1' to 10' (but the higher the better). (E) Would it be a requirement that I raise the feedpoints of my "L's" to the same height as the elevated radials, or can I simply leave the bases where they are now (at ground level) & simply slant the radials upward with no effect upon performance...? -"Gull wing" arrangement OK. -Feed point should be 8' high. -Not sure. -Makes no difference. -"Gull wing" OK. -"Gull wing" OK. -Not sure. -Same height as radials (to minimize ground loss). -Makes no difference. -Optional. (F) Is it OK to bend the elevated radials to fit property allotments...? -Slight bends OK. -Yes. -Yes. -Yes. -Not sure. -Not sure. -OK, but gradual bends only. -No. -Yes. -Best kept straight. (G) What is the desirable length of an elevated radial...? -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Quarter wave. -Use short radials with a common coil. -Quarter wave + height above ground. (H) Should any existing connections to real earth at the base of the "L's" (i.e. a ground pipe) be completed severed with a system of elevated radials...? -If radials one quarter wave long, makes no difference. -No ground. -No ground. -With a ground, there'll be noise on receive. -NEVER ground. -No ground. -No ground. -No ground. -No ground. -No ground. Additionally, four respondents recommended using a choke balun at the feedpoint...one person avowed that a single elevated radial was the equivalent of 30 ground radials...another stated that 8 elevated radials were "super good", but that even 1 to 2 would be good...another affirms that one simply can not beat the optimal number of buried radials... Several recommended this site as an excellent reference as well: http://www.antennasbyn6lf.com/2012/02/elevated-radial-ground-systems-some-cautions.html I personally haven't taken a look at it myself here, but it is most certainly on my "to do" list! I hope my effort here might help dissipate some of the "fog" surrounding elevated radials, vs. ground-mounted ones---certainly there's stuff here that I wanna digest still...and again, I thank one & all for their feedback, & trust that I've done justice here to your many responses... ~73~ de Eddy VE3CUI - VE3XZ _ Topband Reflector
Re: Topband: Elevated Radials
This white paper, written by Clarence Beverage may be of interest to the discussion: http://www.commtechrf.com/documents/nab1995.pdf Paul, W9AC - Original Message - From: "ZR" To: "Guy Olinger K2AV" ; "Eddy Swynar" Cc: Sent: Friday, March 01, 2013 9:53 PM Subject: Re: Topband: Elevated Radials > Elevated radials avoid a collection of lossy mistakes that one finds in less than optimal buried/on ground radials. If a full size radial system is done properly, dense, uniform all around, you will not be able to tell the difference. If there were huge efficiency issues with buried radials never seen with elevated, you would be seeing elevated radials at AM BC stations all over the place. 24 radials on the ground is not optimal unless you are over midwest USA flat-land black super-dirt. 73, Guy. Ahh, but the BCB folks have been using elevated radials mostly in rebuilds of failed buried systems as new station construction is at a minimumthere aint no more room unless they get rid of one sideband or run real QRP at night high up the band. One of the locals here runs 2.5W at night but being in a salt water marsh they do cover their assigned in town area well. Carl KM1H _ Topband Reflector _ Topband Reflector
Re: Topband: Elevated Radials
Forgive me, please, if I'm re-hashing a bit of the "...same-old, same-old" here, but I am really curious as to any "real world" experiences that might be out there in the matter of elevated radials, vs. those that are simply laid atop the ground... (A) Is it true that a couple of elevated radials are just as effective as the "optimum" amount of buried ones...? Probably not a "couple", but almost certainly in small systems a few elevated radials are better than the same number of buried radials. Everyone would like this to be a "cookie cutter" answer, but the actual results depend heavily on the soil and installation. Even N6LF warns over and over that his data only applies for conditions like his. (B) What is the "ideal" number of elevated radials that one should use...? As many as you can. More never hurts the signal, it just is more work. (C) How many elevated radials are "just enough"...? It depends on the soil, the height, the antenna, and what you want. (D) How high should these radials be...? It depends on the antenna, soil, and installation. Radial height takes away from the effective antenna height. Certainly the safest thing is about .05 WL , unless the antenna is really short and that takes away significant radiator height. (E) Would it be a requirement that I raise the feedpoints of my "L's" to the same height as the elevated radials, or can I simply leave the bases where they are now (at ground level) & simply slant the radials upward with no effect upon performance...? It probably doesn't make much difference. (F) Is it OK to bend the elevated radials to fit property allotments...? It depends on where they are bent. The best practice is straight and symmetrical. (G) What is the desirable length of an elevated radial...? 1/4 wave resonant length. (H) Should any existing connections to real earth at the base of the "L's" (i.e. a ground pipe) be completed severed with a system of elevated radials...? If the resonant radials are grounded to an earth ground, the system will lose efficiency. This much is always the case. Pick the particular story you like Eddy, that's what most people do. :) Read the fine print though. N6LF, whose study is one of the most comprehensive is a good source for that particular test condition. Most people seem to miss this: http://www.antennasbyn6lf.com/2012/02/elevated-radial-ground-systems-some-cautions.html What he writes isn't often what people actually paraphrase. 73 Tom _ Topband Reflector
Re: Topband: Elevated Radials
Good Day All, Wow...! I received well over TWENTY responses from the Topband crowd in the matter of elevated radials vs. those simply laid atop the ground---many thanks to all for sharing your insight & personal experiences with me. For benefit of the curious who asked, as well as for my own benefit here, I shall attempt later to summarize everyones' answers, and condense them in a presentable way that may (or may not!) be a good source of reference material for possible future use... Stay tuned---and many thanks again to all who took the time to write... ~73!~ de Eddy VE3CUI - VE3XZ _ Topband Reflector
Re: Topband: Elevated Radials
(C) How many elevated radials are "just enough"...? Depends on how many dB you want to throw away. If you can, do 12 to 16. 32 is the kill-the-loss, never-look-back number. The link below leads to a detailed post on this topic by William Culpepper, a broadcast consulting engineer. Here is a relevant quote from W. Culppeper's post: "The result was an RMS value of the eight radials of 302.7 mV/m/kW at one kilometer. This compares with the FCC Figure 8 value of 307.8 mV/m/kW for a 93 degree tower with 120 ninety degree buried radials, however, a tower 87.2 degrees (the height of the WPCI tower above the four horizontal radials) has an FCC rated efficiency of 303.7 mV/m/kW, one mV/m more than our measured value." The system using four elevated radials produced an accurately measured field that was 0.029 dB below the FCC theoretical field for the height of the monopole above the elevated radials. Not much performance thrown away, there! http://lists.contesting.com/archives//html/Topband/2007-11/msg00248.html RF _ Topband Reflector
