[ARDF] HB9CV dimensions? in PVC?

[Matthew Robbins]

Dale,

    Thanks for the ideas.  I found the Cebik article about 10 minutes
after I hit "send". It's here: http://www.cebik.com/phase/hb.html

    The question I came up with is:  "How do you know it's tuned right?"

    I noticed on the Compact 144 link, 
the phasing wires in the X part aren't dimensioned enough --- The
bends in the X area aren't dimensioned.  I was thinking some sort of
sliding or threaded adjustment for the length of those elements might
let you peak on a forward signal, and check the null by flipping the
antenna around.  I'm not knowledgeable enough to know if an antenna
analyzer might be useful.  Cebik says, "...the rear element shows an
impedance of R - jX, while the forward element shows an impedance of R
+ jX...".  Does that mean the tuned impedance is pure R, with no
imaginary component?  Maybe I could tune the antenna analyzer to the
frequency I want, then adjust the harness length to get pure
resistance.

    I've looked a little at Moxons, but the tape measure elements are
so good and are easy enough to pack that I haven't felt the need to try a Moxon.

    What are the dimensions for your CAP antenna?  Is the boom length
touchy?  Cebik says, "More efficient at producing raw gain are
2-element Yagis using a director closely spaced to the driven element.
... However, such beams have very narrow
operating bandwidths."  How did you tune yours?

Matthew

On 5/11/05, Dale Hunt, WB6BYU <wb6byu at arrl.net> wrote:
> Matt -
>
>    Check W4RNL's web page (www.cebik.com).  In among all the
> other antenna articles he has a number on the HB9CV and other
> 2-element phased arrays.  There is one version in particular
> that I am thinking of trying for 2m (though he gives only 10m
> dimensions, I can scale the element lengths.)
>
>    I have two of the VK4BRG designs and the F/B is not as
> good as I would like.  I've tried a couple mods, but not a
> significant improvement so far.  (They are usable, but it
> isn't always immediately apparent which is front and back.)
>
>    While you are on the page, check the articles on the Moxon
> rectangle.  I have two of them for 2m now, and they are quite
> nice for DF.  Kuon used one last summer in Russia.  They are
> about 30" wide and 11" long.  I used 3/4" flat aluminum stock
> from the hardware store, which is probably more forgiving than
> tubing or rod.  Not necessarily the best thing for running
> through heavy brush because the closed ends can catch on
> branches, but much easier to use for smaller folks.  The
> biggest problem I have with these antennas is that they are
> so short and light it is hard to find a place to mount the
> receiver with good ergonomics, since the center of gravity
> is always in the middle of the receiver.
>
>     Meanwhile, I recently designed a 2-element yagi for some
> CAP cadets, and got an email this evening that it (along with a
> VK3YNG sniffer) took them right to an EPIRB in a marina
> where others were having fits due to reflections.  A 2m version
> of this would have a 40" driven element, 36.6" director, and
> 6" spacing if built using 1" tape measure elements.  (Though for
> beginners you might consider using #8 aluminum ground wire or
> other simple material if they won't be busting brush as much.
> (The wires can be straightened by hand when they get bent.)
>
>     I also have a Mizuho with a built-in HB9CV using inductive
> loading with link coils wound around them to which the phasing
> line is attached.  I hope I never have to readjust it!
>
>    Hope this gives you some good ideas.
>
>        - Dale WB6BYU
>
>
> Matthew Robbins wrote:
> >
> > Does anyone have the dimensions (or a link) for a 2m HB9CV antenna?
> > I've been looking, but most of the links are for HF antennas.  I've
> > also found a link with the phasing section of the Czech Compact 144,
> > but it doesn't have the complete element lengths:
> > http://www.xs4all.nl/~pa0nhc/ardf/rx2/compact2/compact2.html
> >
> > I'm thinking of making one with an H-shaped frame of PVC pipe holding
> > the phasing lines, with tape measure material extending past the
> > phasing line attachment points.  (Does that description make sense?)
> >
> > Are there any trimmer components in these antennas?  I've seen some
> > references that mention them, but no information past that.  Are there
> > any technical descriptions of this antenna?  (Maybe I should check the
> > ARRL antenna handbook...hmmmm.)
> >
> > I'm trying to make a small, light antenna for kids.  (And if it works,
> > maybe for me, too.)
> >
> > Matthew
> > AA9YH
> > Cincinnati, Ohio USA
> > _______________________________________________
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> > ARDF at kkn.net
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t-to-back ratio of over 22 dB and a feed
point impedance of about 18 ohm