- 137MHz "V" Antenna advice needed ...
Re: 137MHz "V" Antenna advice needed ...
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DiskCone is what I see ...
On Tue, Dec 21, 2021, 7:04 PM David Slipper <softfoot@...
It's NOT a Yagi - this picture (see HERE)
is similar to what I am building but for 137MHz (the one in the
pic is for a higher frequency).
The two dipole elements are horizontal and 120 degrees apart.
Do the reflector elements need to be connected together??
Do they need grounding ?? or connecting to the feed in some way
On 21/12/2021 23:30, Kriss Kliegle KA1GJU wrote:
Slightly confused... any images of said 8 element horizontal V
With that said...
A beam (Yagi) with 8 elements will be highly directional, not
something you want when chasing a satellite that is moving across
the sky... unless you plan on using an azimuth/elevation rotator
I know one satellite operator in the club uses the 'egg beater'
type antennas, they're omnidirectional and no there are no moving
parts to fail.
Typically in a beam antenna, the elements are +/- 1/2 wave long
(two +/- 1/4 wave elements connected together to form one +/- 1/2
wavelength long element). Since the center of each parasitic
element (essentially a dipole) is at 0 volts, the element is
usually clamped to a metal boom without being insulated.
Lots of info on the web to get dimensions of each element and the
spacing (google "VHF beam antenna dimensions" or similar)
Yagi beam antennas are great for narrowing the 'field of view' of
RF, but once not aimed within the beam width, the RX'ed signal can
drop off dramatically.
Antenna specs of commercially available antennas will state what
the half-power beam width is. For example a -3dB drop or half
power drop from the main lobe:
The more elements added, the more forward gain (better front to
back ratio)... at a cost of a more narrow beam width. Of course
there are lots of variables that can be tweaked, height above
ground, element spacing, element lengths, etc to change the specs
of a beam.
73 Kriss KA1GJU/AM
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