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金星反射通信EVE [复制链接]

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离线BA4TB
 
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3431
只看楼主 倒序阅读 0楼 发表于: 2009-03-29
德国ham最近实现了首次eve(earth-venus-earth)金星反射通信,这是迄今为止业余无线电信号到达的最远的距离,100倍eme通信的距离.

http://www.amsat-dl.org//index.php?option=com_content&task=view&id=166&itemid=97
离线BA4II
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27814
只看该作者 1楼 发表于: 2009-03-29
'
德国ham最近实现了首次eve(earth-venus-earth)金星反射通信,这是迄今为止业余无线电信号到达的最远的距离,100倍eme通信的距离.
http://www.amsat-dl.org//index.php?option=com_content&task=view&id=166&itemid=97
'

不可思议!!!
离线BG4XCR
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33381
只看该作者 2楼 发表于: 2009-03-29
eme是不是earth-mars-earth????
离线阿兰
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275
只看该作者 3楼 发表于: 2009-03-29
earth-moon-earth
离线阿兰
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275
只看该作者 4楼 发表于: 2009-03-29
20米的大锅呀,据说成功接收到158亿公里(好像是)的旅行者空间探测器的信号。
离线BA6QH/QRP
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11559
只看该作者 5楼 发表于: 2009-03-29
越玩越嗨了。。。。。。。。。。。。。
离线bg4vkr
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263
只看该作者 6楼 发表于: 2009-03-29
志同道合 就可以解决
离线soom
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24924
只看该作者 7楼 发表于: 2009-03-30
哎,,,,没钱没闲没技术咋混哦
离线bv2ac
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14169
只看该作者 8楼 发表于: 2009-03-30
德國要不是電力電信設施不發達,要不就是電磁干擾控制得很好....
离线BH1FMC
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只看该作者 9楼 发表于: 2009-03-30
'
德国ham最近实现了首次eve(earth-venus-earth)金星反射通信,这是迄今为止业余无线电信号到达的最远的距离,100倍eme通信的距离.
http://www.amsat-dl.org//index.php?option=com_content&task=view&id=166&itemid=97
'

好木,一般人可玩儿不起,感叹ham的进步啊!
离线BD6AHP
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3611
只看该作者 10楼 发表于: 2009-03-30
不可思议,简直太强了。20m dish,就是那个著名的“球”吧?
离线BA4RF
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4101
只看该作者 11楼 发表于: 2009-03-30
多普勒频移了500hz?
离线bd5rv
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2410
只看该作者 12楼 发表于: 2009-03-30
fyi:

hi james, rik, alberto and the group,

yes an impressive distance.. even though the erp was a bit above the usual value for amateur radio on 13 cm. amsat-dl has applied for, and been granted, a special permission for this experiment which expires at the end of this year.
the *principle* was simple:
- send a 5 minute carrier on 2.45x ghz, then
- receive for 5 minutes, remove impulse noise (wlan), run the signal through an fft with ~11 hz equivalent receiver bandwidth
- add all received power spectra to calculate an average (*)
- repeat the above until the sigma (standard deviation) in the frequency bins gets low enough to see the weak reflection in one of those bins.
- while transmitting, keep the frequency constant to one or two hz (not as easy as it sounds)
- while receiving, permanently compensate the doppler shift (which a marvellous piece of software by g3ruh did)
- during the experiment, keep the dish pointed to venus with an accuracy better than 0.1° (which another piece of software by g3ruh did)
- hope that the 5-kw magnetron, and the cooling system (including a vaccum cleaner and a water cooler from a vw polo) holds..

(*) a single fft is not sufficient to lift the signal out of the noise. it was between 8 and 11 db below the noise in a 10 hz bandwidth; the ratio of <signal plus noise> to <noise> was between 0.3 and 0.4 db; the latter measured today when it wasn't raining. this was sufficient to "see" the signal after 2 minutes, so we didn't have to average over consecutive 5-minute-receive intervals.

each dot of the "hi"-message lasted 5 minutes, because that's the approximate travelling time... in other words, "qrss300" dictated by venus ;-)

details, including the "magnetron taming" circuit by dj4zc will appear in english language on www.amsat-dl.org hopefully soon. this vital part of the system includes 3 pll circuits, a servo motor controller for the coarse frequency control (slow mechanical tuning, 6 mhz, on the output waveguide), and a fast controlling loop with about 1.5 mhz (iirc) loop bandwidth which involves 2 * 4cx1000 for the 'faster' frequency control, which also provides the ssb modulation. in fact, the energy not "used" for the ssb signal at a given instance is 'moved away' (spread out) by 15 khz to both sides of the center frequency. maybe some of these principles can be used in class-d amplifiers for other frequencies, which finally takes us back to lf / mf-related topics <g> .


cheers,
wolf dl4yhf .
离线bd5rv
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2410
只看该作者 13楼 发表于: 2009-03-30
on march 25th, 2009 a team from the german space organisation amsat-dl
reached another milestone on its way to an own interplanetary probe
towards planet mars. the ground station at the bochum observatory
transmitted radio signals to venus. after traveling almost 100 million
kilometers and a round trip delay of about 5 minutes, they were clearly
received as echoes from the surface of venus. receiving planetary echoes
is a première in germany and europe. in addition, this is the farthest
distance crossed by radio amateurs, over 100 times further than echoes
from the moon (eme reflexions).

for receiving the eve (earth-venus-earth) reflections, an fft analysis
with an integration time of 5 minutes was used. after integrating for 2
minutes only, the reflected signals were clearly visible in the display.
despite the bad weather, signals from venus could be detected from
1038ut on until the planet reached the local horizon.

the high power amplifier which is described in the current amsat-dl
journal has therefore passed this crucial test as a final key component
for the planned p5-a mars mission. by receiving generated echoes from
venus, the ground and command station for the mars probe has been
cleared for operational use and the amsat-team is now gearing up for
building the p5-a space probe.
for financing the actual construction and launch, amsat-dl is currently
in negotiation with the dlr (deutsches zentrum für luft- und raumfahrt)
among others, to obtain financial support for the remaining budget of 20
mill eur.

amsat-dl wants to show that low-budget interplanetary exploration is
possible with its approach.

more information and the link to the official press release:

http://www.amsat-dl.org//index.php?option=com_content&task=view&id=166&itemid=97


the eve experiment was repeated on thursday, march 26th for several
hours with good echoes from venus. morse code was used to transmit the
well known &#8222;hi“ signature known from the amsat oscar satellites.


73s de db2os
离线bd5rv
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2410
只看该作者 14楼 发表于: 2009-03-30
congratulations to all at amsat-dl.

i see there is a video showing karl meinzer dj4zc and freddy on6ug with the 2.4 ghz amplifier used for eve which can be seen at:

http://tinyurl.com/eve13cmamp

go-mars with amsat-dl's p5a mission
http://www.ticket-to-mars.org/

a video of the amateur radio mars orbiter p5-a presentation given at the 2008 amsat-uk colloquium by achim vollhardt dh2va can be seen via

http://tinyurl.com/p5apresentation

this 2009 amsat-uk colloquium is being held at the university of manchester from friday july 24th to sunday 26th july. further details at

http://www.uk.amsat.org/colloquium

73 trevor m5aka
daily amateur radio rss news: http://www.southgatearc.org/
get daily amateur radio news by email
http://www.feedburner.com/fb/a/emailverifysubmit?feedid=2783644&loc=en_us
离线bd5rv
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只看该作者 15楼 发表于: 2009-03-30
离线bd5rv
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只看该作者 16楼 发表于: 2009-03-30
领头的叫freddy,是个比利时人,on6ug
离线bd5rv
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只看该作者 17楼 发表于: 2009-03-30
amsat-dl international team successfully transmitted and received
signals via venus on 25-03-2009 at 10:38 utc.

the signal received was about 0.3 db under bad interference from wlan
and bad weather in bochum.

the transmitter was about 6 kw cw on 2.4 ghz .
the transmitter used a magnetron that has been locked to rubidium and
for the first time ssb quality was achieved making it possible to use
this transmitter for p5a amsat-dl mission to mars.
the use of a magnetron for this purpose was possible thanks to a new
amsat-dl developed modulator that enables a magnetron to be used for
narrow band operation.

with this transmitter amsat-dl is ready to start the next step in the
mars mission and prepare the spacecraft.
离线BD1LKK
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只看该作者 18楼 发表于: 2009-03-30
看来中国也快有玩的了
离线bg1iwk
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3636
只看该作者 19楼 发表于: 2009-03-30
新知识。。。。。。。。