In a message dated 03/07/2009 20:46:44 GMT Standard Time, [email protected] writes:
Building a prototype that works on Earth for project like this is only a few percent of the effort required. Treating it as a radio club project won't be effective as people need to sign up for a 5-year project.
Hi all.
John is absolutely right in saying the complexity cannot be easily compared to a terrestrial radio project. One other thing that stands an almost zero chance of succeeding is a dish antenna that needs to point towards the earth. If NASA and the ISS have trouble with moving parts on the solar array you can imagine how much more difficult it would be on the moon.
However, how about this. The problem with the higher bands is power generation / path loss / antenna gain. Any higher band like 1.2, 2.4 or 5.8G would need a high gain antenna to offset the increased path loss.
But, instead of a conventional steerable dish....with its unreliable moving joints...How about an electrically steerable array of patches / dipoles / or any other type of antenna element.
But how to 'point' it?
Well. actually I think Tom Clark provided the answer for that with his proposal of a few years ago. The principle is this: If you have 2 arrays. One say on 5.6G uplink and one on 5.8G downlink, then the receiving array can electrically look in different directions for a signal from the Earth. Once the receiver has identified a signal and optimised the RX Antenna, the information on the direction of the Earth i.e. the direction of the strongest incoming signal can be used to configure the transmit array which will then beam a signal back to earth with high ERP.
Directional, high gain, and no moving parts.
Thanks
David G0MRF
Hello David, Principally, the same as the Fyllingsdales BMEWS steerable phased array, yes ??.
We have some info on it on OBSERVATIONS.
73 John. [email protected] .................................................................................................
From: [email protected] Date: Fri, 3 Jul 2009 19:21:08 -0400 To: [email protected]; [email protected] Subject: [amsat-bb] The Moon is our Future / antennas
In a message dated 03/07/2009 20:46:44 GMT Standard Time, [email protected] writes:
Building a prototype that works on Earth for project like this is only a few percent of the effort required. Treating it as a radio club project won't be effective as people need to sign up for a 5-year project.
Hi all.
John is absolutely right in saying the complexity cannot be easily compared to a terrestrial radio project. One other thing that stands an almost zero chance of succeeding is a dish antenna that needs to point towards the earth. If NASA and the ISS have trouble with moving parts on the solar array you can imagine how much more difficult it would be on the moon.
However, how about this. The problem with the higher bands is power generation / path loss / antenna gain. Any higher band like 1.2, 2.4 or 5.8G would need a high gain antenna to offset the increased path loss.
But, instead of a conventional steerable dish....with its unreliable moving joints...How about an electrically steerable array of patches / dipoles / or any other type of antenna element.
But how to 'point' it?
Well. actually I think Tom Clark provided the answer for that with his proposal of a few years ago. The principle is this: If you have 2 arrays. One say on 5.6G uplink and one on 5.8G downlink, then the receiving array can electrically look in different directions for a signal from the Earth. Once the receiver has identified a signal and optimised the RX Antenna, the information on the direction of the Earth i.e. the direction of the strongest incoming signal can be used to configure the transmit array which will then beam a signal back to earth with high ERP.
Directional, high gain, and no moving parts.
Thanks
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----- Original Message ----- From: [email protected] To: [email protected]; [email protected] Sent: Saturday, July 04, 2009 1:21 AM Subject: [amsat-bb] The Moon is our Future / antennas
In a message dated 03/07/2009 20:46:44 GMT Standard Time, [email protected] writes:
Building a prototype that works on Earth for project like this is only a few percent of the effort required. Treating it as a radio club project won't be effective as people need to sign up for a 5-year project.
Hi all.
John is absolutely right in saying the complexity cannot be easily compared to a terrestrial radio project. One other thing that stands an almost zero chance of succeeding is a dish antenna that needs to point towards the earth. If NASA and the ISS have trouble with moving parts on the solar array you can imagine how much more difficult it would be on the moon.
However, how about this. The problem with the higher bands is power generation / path loss / antenna gain. Any higher band like 1.2, 2.4 or 5.8G would need a high gain antenna to offset the increased path loss.
But, instead of a conventional steerable dish....with its unreliable moving joints...How about an electrically steerable array of patches / dipoles / or any other type of antenna element.
But how to 'point' it?
Well. actually I think Tom Clark provided the answer for that with his proposal of a few years ago. The principle is this: If you have 2 arrays. One say on 5.6G uplink and one on 5.8G downlink, then the receiving array can electrically look in different directions for a signal from the Earth. Once the receiver has identified a signal and optimised the RX Antenna, the information on the direction of the Earth i.e. the direction of the strongest incoming signal can be used to configure the transmit array which will then beam a signal back to earth with high ERP.
Directional, high gain, and no moving parts.
Thanks
David G0MRF
Hi David, G0MRF
The following article from G3RUH is a good additional answere to your message.
http://www.amsat.org/amsat/articles/g3ruh/110.html
I have extracted from it the most important following part:
73" de
i8CVS Domenico
Extracted from G3RUH article "THE EARTH MOVES"
Moon Downlink
The maximum total excursion of 9.5° is the same as the beamwidth of a 5 wavelength diameter dish antenna. This has a gain of some 20 dbi, and represents an upper limit for an unsteered Moon-based antenna. However the higher the frequency used, the smaller mechanically is the antenna, which makes 2.4 or 5.6 GHz a good choice. Five wavelengths is 60 cm and 26 cm diameter respectively; quite small.
For a given TX e.i.r.p., signal strength received at Earth depends only on the mechanical size of the RX antenna; frequency is irrelevant [1]. Noise level however is not, and S-band (2.4 GHz) is a sensible downlink choice because very low noise performance is robustly obtainable "off the shelf".
An example, 1 watt transmitted from a 20 dbi gain dish on the Moon, received on a 1.2m dish at Earth with a system noise temperature of 100K results in a signal to noise ratio in 2.4 kHz bandwidth of 10.5 db. (Note that frequency matters not). This would support one rather noisy SSB voice signal. Alternatively it would carry an error-free 2400 bps binary PSK data transmission without coding, 9600 bps with modest coding [2].
Thanks to all contributors for an enjoyable thread, with some very interesting ideas, however, there is a fundamental obstacle to transponders on the Moon. The science packages used and left on the Moon by the Apollo astonauts had radioactive heat sources which prevented the electronics from being destroyed by the extreem cold of the lunar night.
I don't believe there is any likelyhood that we can fly a radioactive source on an amateur radio payload.
73 John G7HIA
You mean no orbiting nuclear power station?
john heath wrote:
I don't believe there is any likelyhood that we can fly a radioactive source on an amateur radio payload.
An interesting question for the short term is what can we do with 1 watt of RF from a LEO satellite. RS-10 and RS-12 were interesting as they required only omnidirectional antennas but they had a lot of power available as they were attached to much larger satellites. AO-16 was a small satellite but was capable of only 1200 bps data using uncoded BPSK and simple vertical antennas.
Given the type of hardware developed for Suitsat-2, we should be able to do a lot more. Using modern error-correcting codes 4800 bps is possible using omnidirectional antenas and with modern codecs that can carry 4 voice channels or 3 voice channels plus 40 PSK31-like channels. With 10 dBi of gain at the ground station the data rate and number of voice channels could be quadrupled. The downlink could also be split between 2 voice channels for use with omnidirectional antennas and 8 voice channels for high-gain antennas.
73,
John KD6OZH
I have extracted from it the most important following part:
73" de
i8CVS Domenico
Extracted from G3RUH article "THE EARTH MOVES"
An example, 1 watt transmitted from a 20 dbi gain dish on the Moon, received on a 1.2m dish at Earth with a system noise temperature of 100K results in a signal to noise ratio in 2.4 kHz bandwidth of 10.5 db. (Note that frequency matters not). This would support one rather noisy SSB voice signal. Alternatively it would carry an error-free 2400 bps binary PSK data transmission without coding, 9600 bps with modest coding [2].
participants (6)
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G0MRF＠aol.com -
i8cvs -
John B. Stephensen -
john hackett -
john heath -
Nigel Gunn G8IFF/W8IFF