[amsat-bb] re: Lunar repeater?

["William Leijenaar" <pe1rah@xxxxxxxxxxx>]

Hi AMSATs,

I'm happy that the lunar repeater topic is started again :-)
But I see that most of the amateurs still don't understand that a moon 
station is not that difficult to work !!!!! A moon transponder IS NOT LIKE 
EME !!!!!!

EME uses the moon surface to REFLECT your own power, and has lot of losses.
A transponder has not these losses !!!

Then amateurs are talking about tracking antennas, extreem warm/cold, 
batteries that will die etc etc... these are only DETAILS.

My answers to this:
-------------------
Tracking antenna's
==> In my opinion, not specially needed. Just fixed antenna is okay. This 
will be the same problem like AO40 with its Squint problem.

extreem warm/cold
==> There are many technical solutions for it. E.g sun shield, like 
sun-glasses that only pass through little sun-light.
==> I just read that there are some placed on the moon with average constant 
temp. of -64C. Thats also a solution, and a station can technically be made 
to work in this enviorment.

Batteries:
==> When they can not survive we only use solar-cells. Yes, the station will 
only work during sun-light, but Ao-7 is also working only in sun-light but 
nobody complains !!!


Then about the difficulty to work a station on the moon. I showed in a 
message before that it is not that difficult as many hams think. Many hams 
think it is like EME, but its not. A MOON STATION IS NOT LIKE AN EME 
CONTACT.

I will re-write the calculations I have showed before:
------------------------------------------------------
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 :-)

PS: Some amateurs are serious interresting in making some lunar transponder 
station ???? (not complaining but just showing that it can be done :-)

73 de PE1RAH, William
---

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