Topband: Looking for user experience: DXEngineering Thunderbolt 160m vertical

[Dave Cuthbert]

I refined the DX Engineering Thunderbolt EZNEC model to be exactly like the
actual antennat by changing the capacity hat wire size.

It is resonant at 1930kHz. 2.15uH of series inductance tunes it to 1820kHz
where the input impedance is 4.8 ohms. GND + coil loss of 3.2 ohms gives
the claimed DX Engineering typical 2:1 SWR bandwidth of 40kHz. Radiation
efficiency -- if you can get a 3 ohm GND, is 60%.

    Dave KH6AQ

On Sat, Dec 5, 2020 at 7:49 AM Dave Cuthbert <telegrapher9 at gmail.com> wrote:

> The DX Engineering Thunderbolt antenna includes a means to resonate and
> match the antenna using a series inductor and a  shunt inductor. *It does
> not require a balun*.
> See the manual:
> https://static.dxengineering.com/global/images/instructions/dxe-160va-1_jj.pdf
>
> An EZNEC model shows it to be resonant at 1825 kHz with an input impedance
> of *4.0 ohms*. Adding 2.5 ohms of GND + coil loss it shows a 2:1 VSWR
> bandwidth of 40 kHz. This agrees with the DX Engineering SWR graph on page
> 43. If your installation has 2.5 ohm base referred GND/coil loss the
> radiation efficiency will be ~60%.
>
>     Dave KH6AQ
>
>
>
> On Sat, Dec 5, 2020 at 5:39 AM Wes <wes_n7ws at triconet.org> wrote:
>
>> Or reduce the loading to present a capacitive reactance at the feedpoint
>> and
>> shunt it with an inductor.  Functions as a step up L-network and presents
>> a
>> ground at DC.  That's what I do here.
>>
>> Wes  N7WS
>>
>>
>> On 12/5/2020 7:35 AM, Rudy Bakalov via Topband wrote:
>> > 
>> > P.S. If your vertical has a good set of radials, you will see about 35
>> Ohm feedpoint impedance. You may want to wind your own unun using Jerry
>> Sevick’s cookbook
>> >
>> >
>> http://www.introni.it/pdf/Amidon%20-%20Transmission%20Line%20Transformers%20Handbook.pdf
>> >
>> > or buy a readymade 35 to 50 Ohm unun from balundesigns.com
>> >
>> > The third option is to build a coax transformer per PA0FRI.
>> >
>> >
>> >
>> > Rudy N2WQ
>> >
>> > Sent using a tiny keyboard.  Please excuse brevity, typos, or
>> inappropriate autocorrect.
>> >
>> >
>> >> On Dec 5, 2020, at 8:37 AM, David Aslin G3WGN <david at aslinvc.com>
>> wrote:
>> >> I'm building a contest station and the time has come to make a choice
>> of 160m TX antenna. Looking at DXE Thunderbolt I note that the capacity hat
>> extends to a significant distance down the vertical section. It's my
>> understanding that will shield some of the radiation from the upper part of
>> the vertical. Alternatives like a vertical tee would not have this issue.
>> >> Is my understanding correct?
>> >>
>> >> I'm considering a commercial antenna as high strength telescoping
>> antenna tubing is unobtanium in UK.  My QTH is an exposed windy location so
>> strength matters!
>> >> 73, David G3WGN M6O
>> >>
>> >>
>> >>
>> >> Sent from my Galaxy
>> >>
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