Adding the top hat wires will increase the radiation resistance. If the VSWR
was 1:1 before it will be higher after the wires are added. The wires should
just about triple the radiation resistance. Given a high ground resistance the
radiation efficiency will triple.
Running the top hat wires horizontal is the best. Angling them downward cancels
some of the current-area of the antenna and results in a lower radiation
resistance.
Recommendation: Run the top hat wires as horizontal as you can. Tune the
antenna to resonance. Adjust the VSWR at the shack using a good tuner.
Dave WX7G
-----Original Message-----
From: tyron@globalnet.co.uk
To: mryan001@tampabay.rr.com
Cc: towertalk@contesting.com
Sent: Mon, 22 Jan 2007 1:44 PM
Subject: Re: [TowerTalk] Butternut HF2V 'Top Hat Wires' Question
Hi Mike,
Have you tried adjusting the shorting straps on the coils to reduce
inductance? I have no experience of this myself but have read the
instructions having recently bought the remains of a wrecked one - it is
missing the sections above the coils (parts G to M according to
instructions). I hope to find the length these sections make up to
source replacement parts, or perhaps an accurate overall length if
anyone can help please? The instructions don't unfortunately give
accurate assembled length - guess I could experiment but it'd be nice to
get it right from the off! Also I intend mounting it above ground with
raised radials so will be tricky to keep taking it up and down.
Interested in your experiences Mike, are you using the 160M add-on I
wonder? That would further complicate setting up I suppose.
If anyone needs instructions I think I got them from Butternut website
or I'm happy to email to whomever needs.
Regards to all,
Tyron, M1AQV
mryan001 wrote:
>Has anyone put top hat wires on an HF2V? Having done so has adversely
>effected the swr curve and efficiency of the antenna to some extent. Before
>adding the wires the standing wave was near flat in the dx window. After
>adding the wires the standing wave is just below 2:1 at the resonant point
>but I would like to drop it below 1:5 if possible. Will changing the angle
>of the top hat wires from the radiator do this in the way that changing the
>angle of or trimming a sloper wire does? Should the recommended length of
>25ft for the top hat wires be shortened or lengthened per wire to adjust the
>swr in some way? Would attaching the top hat wires to the VERY TOP instead
>of about 5ft below the top as indicated by Butternut effect this? Any
>suggestions? - Mike
>
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