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THE COAX FED 6 METER EXTENDED "These plans for this version of the EDZ for 6 Meters came from the previous Webmaster of the NRRL, the counterpart of the ARRL in Norway, LA2PJ, for all to enjoy and our many thanks and best wishes go out to him. This is a very inexpensive and easy antenna to build and has been used for many years in Europe by 6 Meter operators with great success!"......N4UJW
Feeder Length
(matching section) Calculations 936 / 52mhz = 18 feet = one full wave length = 360 degrees 18 feet = 360 degrees or one full wave length. 18 / 360 degrees = .05 feet per degree. .05 times (x) 48 degrees = 2.4 feet = 2.4 x 12 = 28.8 inches for the feeder length. Now take the suggestion of adding
10 to 15 percent to that for tuning and we get, 28.4 X .15 =
4.26 inches added to 28.4 inches = 32.66 inches for the feeder before trimming for best SWR! They can be controversal as to which works
the best in all
installations.
From W2OZ, Skip: Hello all, I think that the constants used in the
formula are 'walking away' with sort of imbedded correction factors.
Here is what I mean. I believe that the zip cord
design works, because it has been done for so long, so there is
experimental merit in the final numbers. 2 5/4 = 1.25 WL, ain't no getting
around this.
So it looks to me like there is a fudge factor also built into the '1.28' "constant" to correct my suspicion of a long time error in the ARRL constant 468[234 for 1/4 W], such that 1.28/1.25 = 1.024 representing about a +2.4% correction on the long standing constant. It is better to separate these in one's mind to avoid correcting other constants that others are already using, otherwise everytime someone goes to design an EDZ the numbers keep moving. This can be seen by 234 x 1.024= 239.616. The 239.616 is very close to numbers found in independent experiments by many hams, and leads to an EDZ constant that agrees with other sources like Keith WB2VUO, http://home.frognet.net/~mcfadden/wd8rif/text/zepp.txt . He uses a constant of 600 per element/freq and for the entire flat top this would be 1200, amazingly close to the Norsk 1198 ! Looking at the error factor, if there is truly a +2.4% error correction on the 468[234] in the ARRL constant then it should not be applied and reapplied, so those using 'correct constants' should only be using 1.25 for the 5/4 Wave numbers, not the 1.28. Also there is a nagging hint of misunderstanding about percentages that makes me think someone might have wanted a 3% correction and instead of multiplying 1.25 by 1.03 to get 1.2875 instead they just added .03 to 1.25 and got the 1.28. Why do I bring this up ? Because of 2 reasons, one if you multiply the ARRL 234 by 1.03 you get 241.++ which is even closer to many of the recent experimental constants, and when you multiply by 1.25 and 4 to get the EDZ constant, you get the mysterious 1205 ! So are we correcting a 2.4% or a 3% error ? Other higher numbers appear likewise to be coming from the
application of 1.28 on already corrected constants, like 239 and 241. The
new ARRL number, looks like an 'in air' value not an 'in wire' value ie
based on the 246 in air [no velocity factor applied] and then erroneously
applying the 1.28 instead of 1.25 [note that .64= 1.28/2] .
I can't prove any of this, other than to restate the
merits of the original experimenters correctly recording their results and
trying to arrive at a synthesizing factor [1.28] based on the published
standard 468 [234]. And this results in a constant of 1198 within 2 of
what is quoted by Keith WB2VUO.
I hope you can follow my thinking here. Hamuniverse.com is a perfect platform to get everyone on the same page, and help us all to have the precision in our hobby. Next....
The WL for the length / degrees calculation should
be based on the corrected constant ie, 468[234] times 1.024 =
239.61, this will adjust the 18 FT length of the calculation
above in the article. So using 52Mhz as an example, we have 239.61
as a constant (for 1/4 wave length) x 4 (for full wave length) =
239.61 x 4 = 958.44/52Mhz = 18.43 feet rather than the 18 feet
mentioned!
Next..... The use of the word 'error'..... from other sources, 'Antenna Engineering Handbook' by Jassik, the ARRL's numbers are more inclined toward 'Fat' cylindrical elements, tubing not wire, and must be corrected if used for wire, this avoids finger pointing. 'Error' can be a harsh word leading to time wasted in petty arguements while the hobby stops going forward ! Next.... The match....I won't know until I construct and measure on
the AIM4170 what the results will be, but suspect that when the WL is
corrected, the match will be around 45 +/- degrees with possibly an
inductive stub for single band [no tuner] applications as is mentioned in
the WB2VUO article briefly. There is a very excellent treatment of this
type of match [BETA match] by Gary O'Neal N3GO, it is out there on the web, and moves around , on
matching [correctly], the Jpole or original [single]Zepp, and the concept
is very similar.
In the 2 step adjustment [coax tap + inductive stub] the coax stub is located such that the Parallel Equivalent Resistance is = 50 ohms with -J [capacitive reactance, this is NOT an SWR minimum! The AIM4170 C reports the Rp as you adjust the tap point, when the resistive component is near 50 ohms, then the inductive stub is introduced and adjusted for SWR Minimum, the AIM4170C both annonces and gives a varying pitch tone.... low tone = low SWR. Without the inductive stub the antenna will not be optimum, but very usable. By adjusting just the coax tap point, one can arrive at the less efficient setting of Z=50 ohms, meaning that some part of the feedpoint will remain reactive preventing 100% loading on the elements. Next....A bit about the 6 meter band plan. A couple of words on design frequencies; The 6m U.S. ham
band true center is 52Mhz, (used as an example in the article above), but
this antenna will not cover more than 700KHz, and the band is further
subdivided lessening that need. 52 to 53 MHz is FM [vertically polarized]
repeater inputs where most repeater users need to center their SWR so pick 52.5 MHz for vertically
polarized FM if you want to use that part of the band.
The part from 53 to 54 is repeater outputs. Most repeater users never transmitt here, good SWR therefore optional. Most Horizontally polarized emissions are from 50 to 50.5 MHz and are USB or CW. This is where I am intending this application in a future 2 meter antenna project. European DX comes in around 50.105 to 50.115. US calling frequencies are 50.125 , 50.2 MHz. I will design for 50.15 or so. The freqs above 50.5 to 52 are for special uses like ATV, FM simplex ,and AM. Most of the high power contesting is done in the USB portion of the band. This is where the individual hams SWR must be optimum. Hitting repeaters only takes a few watts and does not require the gain of an EDZ type antenna, however a 2 or 3 element Vertically polarized EDZ 'H' might be an excellent repeater transmitter array! Like wise for 2m, I'm after the USB contesting portion of the band, not being 20db over into the local repeater, so I'm trying to get the SWR optimized for 144.2, and build a stacked horizontal array. Hopefully in the future, you will see it here on Hamunivere.com....stay tuned! 73 Skip
- W2OZ
Editors note...as with any antenna, there are always variables, sometimes very small, that are involved in how it will perform on the air. Many of these variables can not be accounted for in your installation by using only one single "standard formula". Remember there is NO PERFECT antenna or formula that can be duplicated EXACTLY (at least we know of none), every time, in every case using different locations, installation variables, varying material specs, space variables, height above ground and Murphey's Law.
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