Jerry Martes, Los Angeles, Ca, U.S.A captured some NOAA pictures with his “selfmade simple APT antenna for 137 MHz” and get some fairly good results from the antenna that he designed I'd like to get some 'recognition' for this design. It is made of 3/4 inch diameter PVC and TV (300 ohm) twin lead so the cost is somewhere around $1.00.
See a picture of the "Double Cross" that indicates that the cross concept can be applied to APT antennas. The image is recorded with this antenna mounted on the roof of his house. Jerry has alot of data on this antenna and some drawings (actually rough sketch) and the pictures shows how this Double Cross can be built by others. For more info, mail to firstname.lastname@example.org
For more info, mail to email@example.com
The Cross is two ½ wave dipoles, crossed, and spaced ¼ wave and fed in phase.
Fig 1 is a picture of the Cross .The Red and Green is intended to show how the dipoles need to be phased for RHCP along an axis in line with the horizontal white boom. This fig 1 shows the cross as viewed from the North West, looking toward the South East as the Cross is pointing North.
With the dipoles mounted as shown in figure 1, there will be a null in the radiation pattern at zenith. To minimize that zenith null, the ends of the dipoles can be bent to point to the North thereby providing some sensitivity to a satellite at/near zenith.
Figure 2 shows how I bent the ends of the dipoles. Figure 2 shows the bent Cross as viewed from the South West looking toward the North East.
a collapsible version that works very well. And it can be carried in a laptop carrying case. It assembles in about a minute, maybe two if you don't hurry.
Here is a picture of the bent Cross on Jerry Martes roof.
Simple APT 137 MHz Antenna
See a example, captured from a NOAA pass, when the satellite is over about Regina Canada till it was about 800 miles south of Cabo San Lucas Mexico, decoded with WXSat
.NOAA Capture received with a Hamtronics APT receiver, and this simple Antenna