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1-7 of 7 messages
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Lightweight VHF Handheld Yagi?
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by RADIOHEAD on December 18, 2004
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I need a handheld 3 element yagi that's collapsable and can be carried in a backpack. I'm going to use it for 2 meter work. Have you seen or owned any lightweight or titanium antennas with these features?
Is there a place that can custom make one?
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RE: Lightweight VHF Handheld Yagi?
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by K6PDU on December 18, 2004
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Arrow Antennas makes a handheld for 2m and it is 3 element. I am not sure about it being collapsable but here is the site; http://www.arrowantennas.com/
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RE: Lightweight VHF Handheld Yagi?
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by KG4RUL on December 19, 2004
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The Arrow Antenna, 4 Element, Portable Yagi
http://www.arrowantennas.com/146-4ii.html
has a boom that breaks into three sections the longest of which is about 20" in length. Good gain and portability.
Dennis / KG4RUL
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RE: Lightweight VHF Handheld Yagi?
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by WB6BYU on December 20, 2004
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I've built several of them, originally for backpacking
and more recently for radio direction-finding. My
current ones easily break down onto a small attache case
and travel in my hand luggage on a plane.
If you have room for half-wave elements, the simple
method is to use #8 aluminum ground wire (from Radio
Shack) for the elements and slip them through a length
of thin-wall PVC pipe for the boom. The elements can
be pulled out of their holes and slipped inside the boom
for transport, with the ends capped. The resulting
package is about 42" long and 3/4" in diameter. If you
want to sew a bag to carry the elements you can use
fiberglass tubing or rod for the boom - I'd recommend
the designs for J-folded driven elements from this site
as a simple construction method:
http://www.clarc.org/Articles/uhf.htm
I find that a bit long for my backpack (especially when
there are lots of overhead branches), so I have also
made versions where the elements were hinged in the
middle, and the boom was in two sections, but this was
more bother. A better approach is to have the element
half-sections be removable from the boom. One approach
is to use brass brazing rod for the elements and solder
a threaded brass stand-off on the end. These then
screw onto threaded rods passed through the boom. (Make
sure you mark which piece belongs on which element.)
You can do the same thing using aluminum tubing for the
elements and threading the ends to go over bolts sticking
through the boom, as shown in the construction notes here:
http://www.cebik.com/cap.html
(I think this is how the Arrow antennas are assembled.)
My current antennas are designed to be used while running
through the woods, and can really take a beating. The
element material of choice is the metal blade from a
tape measure - this will fold when it hits a branch,
then pop back into place to take a bearing. The 5/8"
blades are usable, though I double the material over
for about half of the element length to help it pop back
into shape faster. For backpacking (unless you are in
windy places) a single thickness should work. The 1"
wide blades are stiffer, but somewhat heavier. The best
thing about these antennas is that they fold up into
very small packages: you literally can roll up each end
of each element, then take the boom apart (slip-fit PVC
fittings) and no piece is more than 12" long. Although
there are many possible variations, the original source
for the antenna is here:
http://home.att.net/~jleggio/projects/rdf/tape_bm.htm
Now, depending on your specific requirements, there may
be other solutions that work also. If light weight is
most important, you can make a yagi by hanging a series
of wires from a tent pole or fishing rod. Long wire
arrays such as vee beams and rhombics can provide good
gain if you can make use of existing supports. For
high gain you can connect rigid elements with two pieces
of string for a boom: with one end tied to a support
you can walk around in a circle holding the other end
taut with more elements than would otherwise be practical
for hand-held use. (I've seen photos of a 60-element
yagi built this way!)
So ask yourself a few questions to start:
1) will I use this while fixed or while walking?
2) do I expect to have other supports available?
3) What is the maximum length that is practical for me?
4) What is my tradeoff for weight vs. performance?
5) How much gain do I need to accomplish my communications?
6) In what conditions do I expect to use this antenna?
The answers will help you choose an appropriate antenna.
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RE: Lightweight VHF Handheld Yagi?
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by WB2WIK on December 20, 2004
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Considering a heavy-duty, commercially-built 3L 2m aluminum beam weighs two pounds, how much would be saved by going to titanium?
I just use an old Cushcraft gamma-match 2m beam, replacing the regular lockwashers and nuts used to hold the elements to the boom with wingnuts instead. When the wingnuts are loosened and the elements folded against the boom (which takes about 15 seconds to do), the "package" for transportation is a little 2-lb bundle that's 41" long and 2" in diameter and can tuck into a slot in my backpack, along with 20' of preattached RG8X coax.
WB2WIK/6
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RE: Lightweight VHF Handheld Yagi?
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by WB6BYU on December 25, 2004
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Since Steve 'WIK mentioned weight, and I know how important
that is for backpacking, I did some measurements on some
of the yagis I have out in the barn.
The tape measure antennas weighed in around 12 ounces
(about 330 grams or so). These are using PVC fittings
to attach the elements, and that contributes much of the
weight, though they do come apart nicely to pack in a small
space.
Elements cut from #8 aluminum ground wire (Radio Shack)
weigh something under 1 ounce (30g) each, and a suitable
length of thin-wall PVC water pipe adds about 5 oz (150g).
The lightest yagi in my collection was 7 oz (200g) and
used a wooden lathe for the boom with copper wire elements
stuck through it. It doesn't come apart, but the copper
wire is soft enough that the elements can be bent down
against the boom for transport and straightened out again
as needed.
Looking at materials I happened to have on hand, the
thinnest brass brazing rods are about 1/2 oz (15g) each,
and a bamboo garden cane is 1 oz, so I suspect a 3-element
yagi could be built weighing less than 3 oz (90g).
Fiberglass tubing or fishing rod would be a good choice
for a boom.
Do consider the durability of the antenna considering the
intended use. Aluminum tubing is light weight, but may
break when the aluminum wire would only bend.
Last summer UA0LS demonstrated some yagis made from pieces
of fold-up umbrellas, using the handle for the boom and
the ribs for the elements. This made a very small package,
since the handle telescopes and each half-element folds
in half.
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RE: Lightweight VHF Handheld Yagi?
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by DAVIDLOCATORSYSTEMS on July 29, 2005
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Check out AF Antronics, out of IL.
They make 3 and 5 element yagis of of aircraft quality aluminium. Best part is that the elements fold and use a wing nut to screw into place. AF also has a neat gun grip that connects to the Yagi boom.
I use the AF 3 element Yagi with a HABIT Research HR2600 Osprey Receiver.
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