Have been using a AI1H Coaxial Resonator Match dipole for years. It does
exhibit the double bump in SWR and covers nearly the whole band with <2:1 VSWR.
A little more difficult to build than a standard dipole but has been working
well.
http://www.arrl.org/files/file/Antenna%20Book%20Supplemental%20Files/23rd%20Edition/A%20Simple%20Broadband%20Dipole%20for%2080%20Meters%20-%20AI1H%20-%20QST%20Sep%201993.pdf
Earl
N8SS
------------------------------
Message: 3
Date: Mon, 25 Apr 2016 20:00:41 -0700
From: Bob K6UJ <k6uj@pacbell.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] [Bulk] Rehash of 80 CW/SSB Switchable
Dipole/Vee
Message-ID: <571ED9D9.1030105@pacbell.net>
Content-Type: text/plain; charset=windows-1252; format=flowed
Grant,
Great solution to broadband our 80M dipoles, thanks for sharing !
I am going to try it on my 80M inverted V.
73,
Bob
K6UJ
On 4/25/16 2:49 PM, Grant Saviers wrote:
> I think the simplest broadband 80m dipole is the one W6RNL/W6NL
> proposed. Resonate at 3675, then 1/2wl of 50 ohm coax to the
> feedpoint, then 1/4wl of 75 ohm coax, then any length of 50 ohm you
> like. My EZNEC/autoez otimized design came out 129.2' dipole, 107.3'
> RG8X-LL, 44.2' Belden 8281. Less than 1.6:1 3.5 to 3.9 then rising to
> 2.1 at 4.0. I cut the coax to length with an antenna analyzer, since
> the velocity factor can vary quite a bit from nominal spec. This is
> being built as a Field Day antenna so the swr voltages on the matching
> sections aren't a concern, but for QRO RG11 and RG8 sizes may be
> needed, lower loss is better. (although w/o the swr the small coax is
> fine for QRO at 80m, so they might be worth a try given the weight &
> cost savings)
>
> Modeled better than 2.1:1 swr for the full band, w/o any complications
> of jumpers, raising/lowering, switches, caps, inductors, etc. For
> pluggable cw vs ssb stubs near the dipole ends, there can be some
> mighty voltages and opportunities for corona or arcing with jumpers at
> QRO.
>
> http://www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qst/1993/09/page27/
>
>
>
> Fans, bowties, staggered designs, etc. can all be a PITA with the
> multiple wires, strings, spacers, etc. but will have lower loss than
> the coax resonator match. Some of these are also very sensitive to
> height and shape.
>
> EZNEC with AutoEZ driving it are an amazing tools for finding an
> optimal design, running hundreds of design trials automatically.
> ac6la.com
>
> For a pluggable cw stub addition to a ssb dipole , the suggested
> banana plug on the stub is the way to go and a jack on the dipole.
> Then there is no high voltage wire waving around in the air. I
> drilled Budwig HYE-QUE HQ-2 insulators (small, light & deep ribs) to
> fit a 10-32 screw for the wires to the plug and stub and slightly
> larger for a cheap Chinese banana jack w/o an insulator on the ssb
> end. That worked fine for multi-band tuned radials for an "on the
> beach vertical" at 500w.
>
> Grant KZ1W
>
> On 4/25/2016 9:57 AM, CJ Johnson wrote:
>> Howdy-
>>
>> I have been working on rebuilding my 80M dipole setup for camping and
>> the
>> fall/winter contest season.. My one main question is I know that I
>> can make
>> the ends for SSB, tune it where i want (most likely 3800).. then on the
>> other side of the insulator, add the extra length for CW and tune that
>> portion (~3550).
>>
>> I *don't* have a pressing need to have this remotely switchable or other
>> things as discussed in the archives -- a semi fancy matching setup, etc.
>> Given that the dipole is temporary in nature, it doesn't pain me to walk
>> outside and clip on the CW section when I want to.
>>
>> That brings me to a couple questions maybe someone can help:
>>
>> 1) The dipole is being constructed with materials to handle 1500W
>> (balun,
>> wires, etc.) -- Will this extra length of wire for CW arc where I
>> "clip" it
>> on to add the extra length at the end of the SSB wire running 1500W?
>>
>> 2) Given that it's "temporary", how would one suggest constructing the
>> point where I switch from SSB to CW.. Alligator clips? There may be a
>> potential for exposure to the elements (mostly rain and some snow).
>>
>> Thanks,
>> WT2P
>> _______________________________________________
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