[amsat-bb] Re: The Moon is our Future
Joe
nss at mwt.net
Fri Jul 3 12:57:33 PDT 2009
Been Thinkin',
John B. Stephensen wrote:
>A more meaningful appoach for an exercise like this is to start with DC
>power input for the entire package. Receivers consume power and transmitters
>(especially linear ones) are inefficient and the efficency goes down with
>increasing frequency. On the moon, you also have to heat the electronics at
>night to prevent failure.
>
>
What difference is there and why if there is any a difference of shadow
cold on the moon, vs shadow in orbit? If anything i would think you
would get some thermal radiation heating from the soil. wjereas in
space you don't get this benefit.
>Linear microwave power amplifiers have 20-35% efficiencies and VHF
>amplifiers might reach 50%. You can make more efficient amplifiers by
>converting the output signal into magnitude and phase or frequency
>components and using class C, D or E amplifiers. However, the added
>circuitry (whether analog or digital) also consumes power. FM makes sense
>for single channel transponers as the amplifiers can be nonlinear and you
>can get 80% efficiency at VHF. SSB amplifiers have a double inefficiency as
>you must design for peak power output which is 4-5 times the average power
>output. Amateur HEO satellites have used SSB for multichannel applications
>as you can count on the voice peaks for different users to occur at
>different times and design for the average power of all users. However, you
>need lots of users to reach this goal.
>
>73,
>
>John
>KD6OZH
>
>----- Original Message -----
>From: "i8cvs" <domenico.i8cvs at tin.it>
>To: "Joe" <nss at mwt.net>
>Cc: "Jack K." <kd1pe.1 at gmail.com>; "AMSAT-BB" <amsat-bb at amsat.org>;
><kg4zlb at gmail.com>
>Sent: Friday, July 03, 2009 14:41 UTC
>Subject: [amsat-bb] Re: The Moon is our Future
>
>
>
>
>>Hi Joe,
>>
>>The specification given by Miles WF1F is for a Lander transmit power of 5
>>to 10 watt in 70 cm from the moon.My calculation shoves that a single SSB
>>station to be received in 70 cm with a S/N ratio of 10 dB on the earth a
>>power of 10 watt in 70 cm is necessary on the moon.
>>
>>If you like an IF window 10 time greater i.e. 250 KHz to accomodate more
>>stations at the same time than the Lander transponder must have the
>>capability to get around 100 watt wich is out the WF1F specifications.
>>
>>73" de
>>
>>i8CVS Domenico
>> ----- Original Message -----
>> From: Joe
>> To: i8cvs
>> Cc: MM ; kg4zlb at gmail.com ; AMSAT-BB ; Jack K.
>> Sent: Friday, July 03, 2009 12:59 PM
>> Subject: Re: [amsat-bb] Re: The Moon is our Future
>>
>>
>> This is all good except for one thing,
>>
>> The IF window is 10 times too small.
>>
>> Look at the mess the FM single channel birds are with their tiny surface
>>foot print. Imagine now a whole hemisphere worth of people trying to use
>>it at once. The thing would be useless
>>
>> i8cvs wrote:
>>----- Original Message -----
>>From: "MM" <ka1rrw at yahoo.com>
>>To: <kg4zlb at gmail.com>; <amsat-bb at amsat.org>; "Jack K."
>><kd1pe.1 at gmail.com>
>>Sent: Thursday, July 02, 2009 1:31 PM
>>Subject: [amsat-bb] The Moon is our Future
>>
>>
>>We need a simple Mode-J transponder (2-meters up, 440 down).
>>Low power consumption.
>>Assume minimal antenna gain from the Lander (3 dBd on each antenna)
>>Assume transmitter power 5-10 watts.
>>
>>Questions:
>>What’s the link budget?
>>How much gain will be needed on earth for such a setup?
>>Can we build a working mockup in 1 year or less.
>>
>>The Moon is within Reach. Let’s Go for IT.
>>
>>Miles WF1F MarexMG.org
>>
>>
>>Hi Miles, WF1F
>>
>>The gain of the 2 meters antenna on the Lander is 3 dBd = 5.14 dBi
>>Assume that the Noise Figure of the 2 meter receiver is 0.5 dB = 35 kelvin
>>and the sky temperature as seen by the 2 meter Lander antenna looking at
>>the earth is conservatively 290 kelvin but (probably more ).
>>The isotropic path loss earth-moon in 2 meters at an average distance of
>>380.000 km is 187 dB
>>You don't specify the IF bandwidth of your transponder so that for
>>simplicity I will assume that only one QSO will be possible in SSB and 3
>>on CW in a total BW = 2.5 KHz
>>With the above data the calculated Noise Floor (KTB) of the above 2 meter
>>Lander receiver is -139 dBm
>>We assume to use an earth 2 meters antenna with a gain of 13 dBi and a
>>power
>>of 100 watt pep in 2 meters.
>>
>>UPLINK BUDGED:
>>
>>Earth TX power 100 watt.............................+ 50 dBm
>>Earth antenna gain............................. .............+ 13 dB
>> ------
>>Earth EIRP.....................................................+ 63 dBm
>>2 m isotropic attenuation earth-moon..............-187 dB
>> ------
>>Isoptropic power received on the moon .........- 124 dBm
>>2 meters Lander antenna gain.........................+ 5 dBi
>> ------
>>Power applied to the 2 m Lander receiver......- 119 dBm
>>Lander receiver 2 m Noise Floor...................- 139 dBm
>> ------
>>S/N ratio available from the Lander receiver.. + 20 dB
>>
>>COMMENT:
>>With a 2 meter signal +20 dB above the noise floor the
>>70 cm TX on the Lander transponder is in condition to
>>supply a noise-less power between 5 to 10 watt pep to
>>the 70 cm TX antenna.
>>
>>DOWNLINK BUDGED:
>>
>>The gain of the 70 cm antenna on the Lander is 3 dBd = 5.14 dBi
>>and the 70 cm power is 10 watt pep
>>Assume that the Noise Figure of the 70 cm earth receiver is
>>0.5 dB = 35 kelvin and the sky temperature as seen by the 70 cm
>>antenna looking at the moon is 75 kelvin
>>Assume that the antenna gain of the 70 cm earth receiver is 18 dBi
>>The isotropic path loss earth-moon in 70 cm at an average distance of
>>380.000 km is 197 dB
>>With the above data the calculated Noise Floor (KTB) of the 70 cm
>>ground receiver is -144 dBm
>>
>>Lander 70 cm TX power 10 watt...................+ 40 dBm
>>Lander antenna gain.......................................+ 5 dBi
>> ------
>>70 cm EIRP from the moon...........................+ 45 dBm
>>70 cm moon-earth isotropic attenuation .........-197 dB
>> ------
>>70 cm power available in to isotropic antenna -152 dBm
>>70 cm earth receiving antenna gain..................+ 18 dBi
>> ------
>>70 cm power on input of the earth receiver.....-134 dBm
>>70 cm Noise Floor of the earth receiver..........-144 dBm
>> ------
>>S/N ratio at the output of 70 cm receiver.......+ 10 dB
>>
>>COMMENT:
>>Using a Lander transponder on the moon with 2 meters and
>>70 cm antenna's gain in the order of 5 dBi will not produce
>>serious problems of pointing at the earth due of libration.
>>If the Lander transponder is capable to develope 10 watt
>>pep and the IF bandwidth is very narrow in the order of
>>2.5 KHz it is possible to accomodate one SSB QSO or 3 CW
>>QSO just using the actually available TX and RX equipments for
>>satellite communications i.e.
>>For the uplink in 2 meters 100 watt pep and a 13 dBi antenna gain
>>For the downlink in 70 cm a receiving system with an overall Noise
>>Figure of 0.5 dB and antenna gain of 18 dBi
>>The rate of change of the frequency due of doppler shift in 2 meters
>>and 70 cm is very slow and easily manually compensated even into
>>only a 2.5 KHz bandwidth
>>The antenna polarization is very important because a linear signal
>>transmitted from the earth or from the moon by stations located in
>>different continents can be reversed from Vertical to Horizontal
>>polarization so that at least on the earth circular RHCP and LHCP
>>switchable polarization is recommended.
>>
>>Best 73" de
>>
>>i8CVS Domenico
>>
>>
>>
>>
>>
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>>
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>
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