[amsat-bb] Moon station or L1 satellite is not like EME !!

["William Leijenaar" <pe1rah@xxxxxxxxxxx>]

Hello,

The view of most amateurs on the path losses for a moon station or L1 orbit 
are not really true. For such large distances you don't need
bigger stations than for EME ! An EME contact is completely different with a 
direct contact between the ground station and the satellite.

To give you some examples:

Path losses
        EME:       Direct (Earth -> moon-station)    Difference
----------------------------------------------------------------
70cm    261dB              197dB                     64dB !!
3cm     289dB              225dB                     64dB !!

Communication with a station on the moon can be done with common HAM 
equipment, like shown below:

On 70cm when both stations use 20W power and 13dB antennas:
---------------------------------------------------------
          Uplink 20W       =  +43dBm
          Uplink ant. gain =  +13db (medium yagi)
                -------------------
          Uplink ERP       =  +56dBm
          path losses      = -197dB
               ---------------------
          ERP on the moon  =  -141dB
          Ant gain moon    =  +13dB (medium yagi)
               ---------------------
       Moon reciever input = -128dBm

On 10GHz when both station use 10W power and 80cm dish ant. (36dB):
-------------------------------------------------------------------
	  Uplink 1W        =  +40dBm
          Uplink 80cm dish =  +36dB
               -----------------------
          Uplink ERP       =  +76dBm
          path losses      = -225dB
               -----------------------
          ERP on the moon  = -149dBm
          80cm dish moon   =  +36dB
               -----------------------
       Moon reciever input = -113dBm

These stations are not like EME station :-)

When looking at L1 satellites with lets say 4x more distance the situation 
gets some more path losses but still possible for amateurs.

Path losses:
        to Moon         to L1 sat       difference
70cm    197dB           199dB           12dB
10GHz   225dB           237dB           12dB

When both station increase their antenna gain by 6dB the same path 
conditions will stay. On 70cm the satellite can also use 6dB more power 
(80W), and the ground station can use an 16dB yagi instead of the 10dB yagi. 
This is still within the common ham possibility.

On 10GHz the ground station can use a 1,5m dish instead of the 80cm, and the 
satellites power and antenna could be increased to overcome its 6dB. :-)

This is all well within the normal amateur equipment, and still far below 
the needed EME equipment :-) What most people think "More away from the moon 
is more difficult than EME..." is not always true :-)

So, when we start to build the first Moon station ? :-)

73 de PE1RAH, William
---



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