[TowerTalk] [Bulk] Rehash of 80 CW/SSB Switchable Dipole/Vee

[Bob K6UJ]

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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>>
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