A favorite ham activ­i­ty is mak­ing con­tacts via satel­lites.  There is the idea of send­ing mes­sages into space, but you also have to fol­low the orbit of the satel­lite with your anten­na while tun­ing the radio, to adjust for the Doppler effect.

The satel­lites orbit the Earth act­ing as repeaters. Repeaters are  relay sta­tions that allow hams to send sig­nals over a greater dis­tance using low-pow­er hand held trans­ceivers. The satel­lites allow hams to send mes­sages from Earth to space and back to oth­er hams on earth. The Inter­na­tion­al Space Sta­tion (ISS) also has a repeater, the astro­nauts turn on their radio to make con­tact direct­ly with hams on the ground.

All you need is a  VHF/UHF trans­ceiv­er and an anten­na, to get you start­ed lis­ten­ing to the satel­lites.   For bet­ter results, you can use a Yagi anten­na con­nect­ed to a mut­li-mode radio and a license (if you want to trans­mit). A Yagi anten­na can also be used to improve the received sig­nal of your hand held radio.

Start by vis­it­ing Heavens-Above.com to check the orbit of the satel­lite you want to lis­ten to and indi­cate your loca­tion.  Check the pass­es of your spe­cif­ic satel­lite or the ISS. Make sure that the pass­es are shown for your cor­rect loca­tion

The Start of a pass(when/where the satel­lite enters on the hori­zon), the Max. Alti­tude (when/where the satel­lite is at its high­est point in the sky), and the End (when/where the satel­lite fin­ish­es it’s pass).  The alti­tude is the angle of the satel­lite from the observer’s hori­zon. 0 degrees is exact­ly on the hori­zon, and 90 degrees is direct­ly above the observ­er. The Azimuth is the car­di­nal direc­tion of the satel­lite from the observer’s point of view.

Satel­lite repeaters work with two dif­fer­ent fre­quen­cies, an uplink and a down­link. You will lis­ten to sig­nals received on the down­link. If you wish to trans­mit, you’ll need to pro­gram in the uplink fre­quen­cy as well.

When using a Yagi anten­na, you do not aim the anten­na direct­ly at the satel­lite. Instead, you’ll keep it per­pen­dic­u­lar to the satel­lite. You can rotate the anten­na by rotat­ing your hand to try and get a bet­ter sig­nal.

You will trace the path of the satel­lite orbit with the anten­na using the Heav­ens-Above pass chart as a guide. At the Start Time, start with the anten­na per­pen­dic­u­lar to the Azimuth. direc­tion at the giv­en Altitude.It can be very dif­fi­cult try­ing to catch the satel­lites and you may spend a lot of time not hear­ing any­thing.

The Doppler effect makes the fre­quen­cy vary by 10 MHz. As you trace the path of the satel­lite with the anten­na, you will also need to tune the radio plus or minus 10 MHz until you hear a good sig­nal.




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