Dan,
> Go to the ARRL antenna book and look at a windom. It DOES NOT have
> a break at the feed point for coax center and coax shield. It is a
> straight wire with the coax center at the off center point. The
> shield is not connected, or else it is a single wire feed to the
> horizontal wire.
Amateurs have been calling off-center fed dipoles a "Windom" for
more than 40 years. The oldest ARRL Antenna Book I have owned
includes that same discussion. Whether you insist on calling only
the single wire fed antenna a "Windom" or apply the name broadly
to the whole family of antennas that operate the same way is not
material ... whether you use a single wire attached at its
characteristic impedance, "balanced" feeder attached at its
characteristic impedance, or coax with a balun attached at the
transformed impedance, the antennas all operate identically.
By the way, even the single wire fed version of the off center fed
antenna is not really a Windom. Loren Windom only reported the work
of a group of Electrical Engineering students at The Ohio State
University when he was a law student there. If you want to be
precise in naming the antenna, give credit to the proper persons.
In the meantime, I choose to recognize Windom in the concept of
all off center fed antennas just like any center fed doublet is
a "Hertz" and any end fed antenna against ground is a "Marconi."
73,
... Joe, W4TV
On 4/26/2010 10:29 AM, Dan Schaaf wrote:
> Joe,
>
> Go to the ARRL antenna book and look at a windom. It DOES NOT have a break
> at the feed point for coax center and coax shield. It is a straight wire
> with the coax center at the off center point. The shield is not connected,
> or else it is a single wire feed to the horizontal wire.
>
> The AV-640 has a break at the feed point. The coax center goconnects to the
> main radiator thru a balun or unun. The shield goes to the counterpoise
> radials from the other side of the balun/unun.
>
> It is an off center fed DIPOLE not WINDOM. 3/8 wave from the coax center and
> the difference from the shield to the counterpoise.
>
> Dan Schaaf
> K3ZXL
> "In the Beginning there was Spark Gap"
> www.k3zxl.com
> ----- Original Message -----
> From: "Joe Subich, W4TV"<lists@subich.com>
> To:<towertalk@contesting.com>
> Sent: Monday, April 26, 2010 10:13 AM
> Subject: Re: [TowerTalk] AV-640 (was GapChallenger ComparisonTesting
> Studies)
>
>
>
> > The AV-640 in no way resembles a Windom.
>
> Straighten the "radials" into a single wire and the AV-620/640,
> or R5/R7/R8 certainly resemble an off center fed antenna -
> what it often called a "Windom."
>
> > It is high impedance because it is larger than 1/4 wave.
>
> No, the high impedance is because of the off center feed. The
> total electrical length from the tip of the radials to the top
> of the vertical element is on half wave. The heavy loading on
> the lower bands coupled with the short radials moves the feed
> point progressively farther away from the center of the "short"
> loaded dipole as the operating frequency decreases. This has
> the fortunate effect of keeping the feed impedance higher as
> the natural impedance of the shortened antenna decreases.
>
> No matter what you call it, the W1JR design used in the R5/7/8,
> AV-620/640 is arguably one of the best and most effective for
> elevated multi-band verticals.
>
> 73,
>
> ... Joe, W4TV
>
> On 4/25/2010 10:45 PM, Dan Schaaf wrote:
>> HyGain calls it a Windom, but a Windom is a single wire fed in from the
>> end.
>> The AV-640 in no way resembles a Windom.
>> It is simply a 3/8 wave vertical and the counterpoise is the other side,
>> analagous to radials.
>> It is high impedance because it is larger than 1/4 wave.
>> Another nicety is the static bleeder choke inside the box. I have since
>> bought several chokes from HyGain and installed them on other verticals.
>>
>> Best Regards
>> Dan Schaaf
>> K3ZXL www.k3zxl.com "In the Beginning, there was Spark Gap"
>> ===============================
>> NOBSKA
>> www.nobska.net
>> ===============================
>> Cape Cod Instruments
>> www.oceanbiz.net
>> ===============================
>> ----- Original Message -----
>> From: "Art Trampler"<atrampler@att.net>
>> To: "'Tower and HF antenna construction
>> topics.'"<towertalk@contesting.com>
>> Sent: Sunday, April 25, 2010 10:00 PM
>> Subject: Re: [TowerTalk] AV-640 (was GapChallenger ComparisonTesting
>> Studies)
>>
>>
>> I'm going to beg to differ on the theory of operation of the AV640,
>> specifically its native impedance and the use of the 4:1 unun (yes, it's
>> wired as a unun).
>>
>> The 4:1 is not stepping up from 12.5 to 50 ohms. It is stepping down from
>> roughly 200 ohms to 50 ohms. Yes, the elements are cut at roughly 1/4
>> wave,
>> but they are mounted electrically about 1/10 wl above the feed point
>> yielding a 3/8 wave antenna.
>>
>> It is thus electrically more akin to a vertically mounted OCF dipole or
>> (in
>> Hy-Gain's words) Windom. This is why the native feedpoint impedance is
>> about 200 ohms. The R8 is similar (from what I gather designed by the
>> same
>> person) but feeds at about 220 ohms. The unun in the R8 is actually
>> something like 4.4:1. Yes, there it does wind up electrically a bit longer
>> than the 3/8 wave, hence the series capacitor.
>>
>> It is the 220 ohm impedance which gives any hope of the 72" counterpoises
>> being effective from an efficiency standpoint. If it were really 12.5
>> ohms
>> it would be like running an vertical radiator with no radials at all.
>>
>> I'll also submit that at least according to the manual and my usage, it is
>> not derated on CW, though for SSTV or RTTY I would agree that it is. I
>> had
>> problems with QRO on 40 meters which we traced to an improperly wound
>> current choke; the windings were bunched together at roughly 5 O'Clock, so
>> the choke was getting very hot there. My SWR would climb, so I quickly
>> lowered it and sure enough had a hot core.
>>
>> Hy-Gain saw the pictures and supplied a new unit even though it was out of
>> warranty. I have no problem running 1500 watts out on 40 or 20 into it
>> and
>> haven't had the sunspots on other bands to do more than jumping on a new
>> one.
>>
>> Now if I'm wrong in my presentation of how it works, so be it--but I'll
>> refer people to Hy-Gain as this explanation matches theirs.
>>
>> As for improving it, before Hy-Gain agreed to replace the unit I was going
>> to go with Balun Designs 4:1, 5KW unun and 1:1 current choke (5KW). A bit
>> pricey but I have no doubt they would have worked.
>>
>> 73,
>> Art, KØRO
>>
>> -----Original Message-----
>> From: towertalk-bounces@contesting.com
>> [mailto:towertalk-bounces@contesting.com] On Behalf Of Bill Gillenwater
>> Sent: Sunday, April 25, 2010 7:37 PM
>> To: Tower and HF antenna construction topics.
>> Subject: Re: [TowerTalk] AV-640 (was GapChallenger ComparisonTesting
>> Studies)
>>
>> I had the AV620 on a 40 foot tower for four years, unguyed. Used it as an
>> SO2R second radio antenna, it performed well. It is rated to take 70 mph
>> winds. After 4 years the base of the antenna started to come apart, with
>> the aluminum splitting at the lower bolt pattern. I replace the bottom
>> section of alum. and now it is guyed. Still works well.
>> 73 Bill K3SV
>>
>> ----- Original Message -----
>> From: "Roger (K8RI)"<K8RI-on-TowerTalk@tm.net>
>> To: "Tower and HF antenna construction topics."<towertalk@contesting.com>
>> Sent: Sunday, April 25, 2010 7:39 PM
>> Subject: Re: [TowerTalk] AV-640 (was GapChallenger ComparisonTesting
>> Studies)
>>
>>
>>> The AV640 is electronically simple, although a bit complex mechanically
>>> (lots of parts)
>>> Each band is independent of the others and there is no interaction
>>> between bands when setting the resonant frequencies. The matching
>>> network consists of a current balun wound on two toroid cores. This is
>>> followed by a 4:1 balun which is also wound on two cores and is used to
>>> "step up" the antennas low impedance of 12.5 ohms to 50 ohms. The
>>> elements are a bit longer than a 1/4 wave electrically and that
>>> reactance is tuned out by a fixed value "compensating" capacitor. SWR
>>> "for mine" is virtually 1:1 at resonance on all bands. It will also
>>> cover each band in it's entirety with the exception of 40 with a low
>>> (read useable) SWR. IIRC it'll cover about half of 40 at less than 2:1.
>>>
>>> Although advertised as self supporting, with mine mounted at 40' I have
>>> insulated guys at roughly the mid point.
>>> I cut a disk out of 1/4" Lexan using a hold saw and drilled 3 1/4" holes
>>> around the edge at 120 degree spacing. The center has a hole just large
>>> enough that it's a loose fit over the center radiator, so the guy
>>> connection is more of less floating.
>>>
>>> The system is broad banded compared to trap verticals and should be a
>>> better performer than trap verticals although I'd not expect the
>>> performance between any of the multi band verticals to be "blazingly"
>>> different.
>>>
>>> It is rated for the legal limit on SSB for 40 though 10 and 300 watts on
>>> six meters. The antenna is derated for other modes. I'm assuming the
>>> de-rating is due to heating of the toroid cores. I believe the early
>>> ones were rated for 200 watts on six. I've run 800 watts SSB on six for
>>> up to two hours with no problems
>>>
>>> I'm going to try 4 toroid cores in both the 4:1 and current balun and
>>> see if it will handle more power. It'll be #31 mix for the current
>>> balun, but I'm not sure which mix to use for the 4:1 voltage balun as
>>> it's a true transformer.
>>>
>>> I have no experience with the R7 and R8 but I'd expect them to be
>>> comparable to the AV640 and all to be much better than the trap, multi
>>> band verticals.
>>>
>>> 73
>>>
>>> Roger (K8RI)
>>>
>>> Dan Schaaf wrote:
>>>> I didn't get it to work on 160. !!!
>>>> But, if you notice, the frequency on the 17 meter band is 10 times the
>>>> frequency on 160 meters. A tuner can load it. but it is not wise to do
>>>> so.
>>>> Once I realized that I had the antenna switch in the wrong place, it was
>>>> too
>>>> late.
>>>> Likewise, a 17 meter vertical too close to a 160 meter vertical causes
>>>> SWR
>>>> fluctuations when the wind blows the antennas around.
>>>>
>>>> Dan Schaaf
>>>> K3ZXL
>>>> "In the Beginning there was Spark Gap"
>>>> www.k3zxl.com
>>>> ----- Original Message -----
>>>> From: "RICHARD SOLOMON"<w1ksz@q.com>
>>>> To: "TowerTalk"<towertalk@contesting.com>
>>>> Sent: Sunday, April 25, 2010 6:44 PM
>>>> Subject: Re: [TowerTalk] AV-640 (was Gap Challenger ComparisonTesting
>>>> Studies)
>>>>
>>>>
>>>>
>>>>> How did you get the AV-640 to work on 160 ??
>>>>>
>>>>> 73, Dick, W1KSZ
>>>>>
>>>>>
>>>>>> From: n7xy@clearwire.net
>>>>>> Date: Sun, 25 Apr 2010 15:40:58 -0700
>>>>>> To: towertalk@contesting.com
>>>>>> Subject: Re: [TowerTalk] AV-640 (was Gap Challenger Comparison Testing
>>>>>> Studies)
>>>>>>
>>>>>> I haven't had any insulator issues, but one of the 40 meter capacity
>>>>>> hat wires has a noticeable bend from putting it up single-handed.
>>>>>>
>>>>>> I have had better-than-expected results on 160 at 100 watts (> 150
>>>>>> QSOs at distances up to ~1500 miles). I wouldn't try running higher
>>>>>> power than that.
>>>>>>
>>>>>> Bob N7XY
>>>>>>
>>>>>> On Apr 25, 2010, at 3:13 PM, Roger (K8RI) wrote:
>>>>>>
>>>>>>
>>>>>>> Dan Schaaf wrote:
>>>>>>>
>>>>>>>> Right, My AV-640 has worked the world, literally. I could spend a
>>>>>>>> lot of
>>>>>>>> time telling stories .
>>>>>>>> On 12 meters, ragchewed with N2WB op at VP6DX on 12 meters between
>>>>>>>> band
>>>>>>>> opening. I was running 100 watts SSB
>>>>>>>> Likewise on 30 and 40 I have 266 and 269 countries logged .
>>>>>>>> You just have to keep an eye on the 17 meter stub insulator at the
>>>>>>>> top of
>>>>>>>> the stub. The insulator can burn and short the stub to the main
>>>>>>>> radiator. I
>>>>>>>> think it happened here once due to accidentally loading the
>>>>>>>> antenna on 160
>>>>>>>> meters. That point on the stub became a high voltage point and the
>>>>>>>> insulator
>>>>>>>> was wet from morning dew.
>>>>>>>> Replaced the insulator and all was well again.
>>>>>>>>
>>>>>>>>
>>>>>>> I've had a couple of the insulators break. (hit a tree on the way
>>>>>>> up and
>>>>>>> down - Hired tree trimming crew, Strong wind blew small limb from
>>>>>>> neighbor's lot and hit antenna) I made new ones from scrap 1/4"
>>>>>>> Lexan.
>>>>>>> Just use one of the old ones for a template. I also found that if the
>>>>>>> material from the broken one is sound, they can be "super glued" back
>>>>>>> together and last quite well.
>>>>>>>
>>>>>>> Compared to sloping half wave dipole it does quite surprisingly
>>>>>>> well on 40.
>>>>>>> Not meant for heavy duty QRO.
>>>>>>>
>>>>>>> 73
>>>>>>>
>>>>>>> Roger (K8RI)
>>>>>>>
>>>>>>>
>>>>>>>> Dan Schaaf
>>>>>>>> K3ZXL
>>>>>>>> "In the Beginning there was Spark Gap"
>>>>>>>> www.k3zxl.com
>>>>>>>> ----- Original Message -----
>>>>>>>> From: "Bob Nielsen"<n7xy@clearwire.net>
>>>>>>>> To: "Tower and HF antenna construction topics."
>>>>>>>> <towertalk@contesting.com>
>>>>>>>> Sent: Sunday, April 25, 2010 4:40 PM
>>>>>>>> Subject: Re: [TowerTalk] Gap Challenger Comparison Testing Studies
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> Try<http://www.championradio.com/HF-VERTICAL-PERFORMANCE-TEST-
>>>>>>>>> METHODS-RESULTS.3>.
>>>>>>>>>
>>>>>>>>> The AV-640 was not included in the comparison, however it is quite
>>>>>>>>> similar to the R8. Based on the R8 data I decided to purchase a
>>>>>>>>> AV-640 and have not been disappointed.
>>>>>>>>>
>>>>>>>>> Bob, N7XY
>>>>>>>>>
>>>>>>>>> On Apr 25, 2010, at 12:19 PM, Dan Schaaf wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> This link only takes me to the home page. (http://
>>>>>>>>>> www.championradio.com) I
>>>>>>>>>> want to know where is the related comparison?
>>>>>>>>>> I want to see how my AV-640 stacks up against the others.
>>>>>>>>>>
>>>>>>>>>> Dan Schaaf
>>>>>>>>>> K3ZXL
>>>>>>>>>> "In the Beginning there was Spark Gap"
>>>>>>>>>> www.k3zxl.com
>>>>>>>>>> ----- Original Message -----
>>>>>>>>>> From:<K7LXC@aol.com>
>>>>>>>>>> To:<towertalk@contesting.com>;<ka2qwc@verizon.net>
>>>>>>>>>> Sent: Sunday, April 25, 2010 2:16 PM
>>>>>>>>>> Subject: Re: [TowerTalk] Gap Challenger Comparison Testing Studies
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> In a message dated 4/25/2010 8:38:22 A.M. Pacific Daylight Time,
>>>>>>>>>>> towertalk-request@contesting.com writes:
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>> Has anyone done a study? evaluating? the GAP CHallenger DX,?
>>>>>>>>>>>> against
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>> other verticals?
>>>>>>>>>>> Butternuts, Hygain, CrushCraft, Steppir rtc..
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>> If so I would like to see the results as the peratin to
>>>>>>>>>>>> performance. I
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>> am not intersted in anecdotal evidence just fact. If any one has
>>>>>>>>>>> performed
>>>>>>>>>>> testing I would like to hear from you. If there is enough?
>>>>>>>>>>> response I
>>>>>>>>>>> will
>>>>>>>>>>> summarize and post the results.
>>>>>>>>>>>
>>>>>>>>>>> Yessireebob. To quote from _www.championradio.com_
>>>>>>>>>>> (http://www.championradio.com) , "Now you can read an unbiased
>>>>>>>>>>> report on
>>>>>>>>>>> how they really
>>>>>>>>>>> performed. Antennas tested include the Cushcraft R8, Butternut
>>>>>>>>>>> HF6V, MFJ
>>>>>>>>>>> 1798,
>>>>>>>>>>> Force 12 ZR-3 and V-3, Diamond CP-6, Hustler 6BTV and Gap Titan.
>>>>>>>>>>> It's 64
>>>>>>>>>>> pages of protocol, data sets and summaries. Presented at the
>>>>>>>>>>> Dayton
>>>>>>>>>>> Hamvention."
>>>>>>>>>>>
>>>>>>>>>>> Not exactly the Challenger but full of lots of actual data
>>>>>>>>>>> and
>>>>>>>>>>> observations. It's the only on-the-air HF vertical comparison
>>>>>>>>>>> report in
>>>>>>>>>>> the world.
>>>>>>>>>>>
>>>>>>>>>>> Cheers,
>>>>>>>>>>> Steve K7LXC
>>>>>>>>>>> Champion Radio Products
>>>>>>>>>>> Cell: 206-890-4188
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> _______________________________________________
>>>>>>>>>>> TowerTalk mailing list
>>>>>>>>>>> TowerTalk@contesting.com
>>>>>>>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>> _______________________________________________
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> _______________________________________________
>>>>>>>>>> TowerTalk mailing list
>>>>>>>>>> TowerTalk@contesting.com
>>>>>>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> _______________________________________________
>>>>>>>>> TowerTalk mailing list
>>>>>>>>> TowerTalk@contesting.com
>>>>>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>>>>>
>>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> TowerTalk mailing list
>>>>>>>> TowerTalk@contesting.com
>>>>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> _______________________________________________
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> TowerTalk mailing list
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>>>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> TowerTalk mailing list
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>>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
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>>>>> _______________________________________________
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> TowerTalk mailing list
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>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
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>>>>
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
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