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
>>>>> TowerTalk@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/towertalk
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>>>> _______________________________________________
>>>>
>>>>
>>>>
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>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
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>>
> _______________________________________________
>
>
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