找回密碼
 立即註冊
搜索
樓主: VR2GY

業餘衛星 AO 51 通聯......繼續追擊

[複製鏈接]
 樓主| 發表於 10-5-2010 10:15:44 | 顯示全部樓層
下鏈 AO 51
0016 VBU.jpg
 樓主| 發表於 11-5-2010 00:40:24 | 顯示全部樓層
下鏈 AO 51
0018 VBU.jpg
 樓主| 發表於 24-5-2010 18:07:50 | 顯示全部樓層
通聯 泰國 E21EJC
MAY 24    AO51.jpg
 樓主| 發表於 24-5-2010 18:09:58 | 顯示全部樓層
通聯 泰國 E21EJC 錄音

0010 E21EJC MAY24.mp3

155.23 KB, 下載次數: 310

 樓主| 發表於 30-5-2010 08:09:14 | 顯示全部樓層
Operating AO-51
Howard Long, G6LVB
g6lvb@amsat.org
AMSAT-UK
Uplink        FM        145.920, 67Hz PL
Downlink        FM        435.300
Table 1: AO-51 frequencies
AO-51 is a satellite in the Amateur Satellite Service, and one of its functions operates very similar to a traditional terrestrial FM repeater. It’s available for general amateur use, and described below are the operating techniques and equipment used to access it. As with many areas of technology, satellite operation includes its fair share of jargon. Although not exhaustive, a number of these terms are used in this introduction, with corresponding explanations. Good luck & welcome to the world of amateur satellites!

•         A Repeater in Space?
Figure 1: AO-51 orbits 500 miles above the Earth
Well, nearly. The uplink (equivalent to a repeater input, or where you transmit) and downlink (equivalent to a repeater output, or where you receive) are on different bands. The point of having the uplink and downlink on different bands is that it allows you to monitor the downlink (normally using headphones to stop feedback), and check that you are making it in. If the uplink and downlink were on the same band, we’d need some expensive filters so that we could listen to the downlink without our uplink de-sensing the receiver. It’s possible to operate without listening to the downlink, but it’s not recommended unless you’re pretty experienced. Being able to hear your signals coming back from the satellite will save you a lot of frustration!
•         How far can I get?
Figure 2: AO-51 footprint
The coverage area, or footprint, (see figure 1) is huge compared to a terrestrial repeater, and is typically 3,000 miles in diameter. Depending on the pass (how the satellite travels relative to the groundstation), most if not all of Europe is usually available, together with Northern Africa. It’s often possible to operate across the Atlantic. This means that there are potentially hundreds of thousands of amateur stations who could simultaneously operate the satellite. With only one channel, this satellite is inevitably very busy! QSOs are generally contest style, with an exchange of callsigns, QRA locators, signal reports, and occasionally names are exchanged.
•         Prediction
The satellite is continually orbiting the Earth. This means that it is not always visible to an observer. So how do you know when it will be visible? The answer is to use prediction software. There are a number of software packages available, including freeware. Check out http://www.amsat.org and http://www.amsat-uk.org. Predictions are also online, at http://www.amsat.org/amsat-new/tools/predict/ and http://www.heavens-above.com/.
Having a prediction listing together with a magnetic compass will allow you to plan the pass in advance by knowing where to point the antennas. If you’re not completely confident about the software you’re using yet, having a listing printed out in advance will save a lot of ‘computer panic’ during the satellite pass.
•         Doppler
Because the satellite is moving relative to the ground station, it’s necessary to be aware of a phenomenon known as Doppler shift. This is similar to the apparent drop in frequency you hear when a police car screams past with its siren on. When the satellite is hurtling towards you, the frequency appears higher than when it is going away from you.
o         As a rule of thumb, at the beginning of each satellite pass (known as AOS, or acquisition of signal) on the 435.300MHz downlink, the frequency on the downlink will appear at the observer to be about 10kHz above the published frequency. At the end of each satellite pass (known as LOS, or loss of signal) the downlink will appear to be about 10kHz below the published frequency. The frequency on the satellite in fact remains constant.
o         On the other side of the coin, on the uplink on 145.920MHz, in order for this frequency to be correct at the satellite, you can uplink at about 3kHz below the published frequency at AOS, and 3kHz above at LOS. In practice, it’s generally not necessary to adjust the uplink on a 2m FM uplink, but you will benefit from being able to tune the downlink. On some radios it’s possible to set the uplink frequency together with the 67Hz PL tone into a memory, which will help.
o         It’s possible to automatically correct for Doppler using a suitable computer program and transceiver.
•         Equipment
A commonly held misconception is that you need large Yagi arrays and expensive rotators to operate satellites, not to mention expensive radios in the £1k bracket. This is not true! To operate AO-51, you need a radio that can receive FM on 70cm and transmit 5W FM on 2m with a 67Hz PL tone, i.e., a typical handheld radio these days. You can also use two separate radios, one on each band, equally well. If you use a single dual band radio, it’s extremely worthwhile using one
Figure 3: The Arrow Antenna
which allows you to transmit on one band while simultaneously receiving on another. Ideally the radio should be able to tune to within 5kHz so that you can correct for Doppler. Pre-programming the radio’s memories will help here if you’re using an FM only radio. Be aware that some ‘satellite-ready’ radios have a problem setting PL tones in satellite mode.
The old adage, “if you can’t hear them, you can’t work them” is especially true in satellite operation. So before considering increasing your ERP, concentrate on your downlink! This can either be with antenna mounted low noise preamps, better quality coax and/or better antennas, depending on the configuration.
Date (Z)        AOS (Z )        LOS (Z )        Duration        AOS Az        Max El        LOS Az
02/10/2004        00:10:49        00:17:19        00:06:29        263°        3°        315°
02/10/2004        10:27:01        10:42:26        00:15:24         16°        66°        188°
02/10/2004        12:06:08        12:20:12        00:14:04          9°        27°        236°
02/10/2004        13:45:40        13:55:01        00:09:20          2°        6°        286°
02/10/2004        18:33:13        18:42:53        00:09:40         79°        7°        358°
02/10/2004        20:08:27        20:22:31        00:14:04        128°        29°        351°
02/10/2004        21:46:35        22:01:36        00:15:01        176°        57°        343°
02/10/2004        23:28:29        23:39:40        00:11:11        231°        10°        329°
03/10/2004        09:48:00        10:02:49        00:14:48         20°        34°        168°
03/10/2004        11:26:53        11:41:52        00:15:00         11°        47°        217°
03/10/2004        13:06:16        13:17:52        00:11:36          5°        12°        266°
03/10/2004        14:46:13        14:50:47        00:04:33        357°        1°        321°
03/10/2004        17:56:29        18:03:27        00:06:58         57°        3°          1°
03/10/2004        19:30:28        19:43:13        00:12:45        109°        17°        354°
03/10/2004        21:07:22        21:22:30        00:15:07        157°        75°        347°
03/10/2004        22:47:35        23:01:07        00:13:32        208°        21°        336°
Table 2: AO-51 pass predictions for Donington, UK, 2 & 3 October 2004
Because the signals on the downlink are not always very strong, and because the downlink will have fading due to polarisation changes, it’s recommended that the receiver’s squelch is opened permanently during the pass.
It can be tricky to receive AO-51 using just the rubber duck antenna supplied with most hand held radios. Using a small hand-held directional antenna will help enormously. Even an HB9CV, or alternatively a three element yagi will make quite a difference on the downlink. For AO-51, you shouldn’t need more than about 10W ERP to make contacts, but this is assuming there’s no other stations running QRO and have insensitive receivers. There’s nothing more frustrating than knowing that you’re making it in (by listening to yourself on the downlink), only to be trampled on by a station who clearly cannot hear the satellite at all. These operators are known as alligators – all mouth and no ears.
Satellite        Uplink        Downlink        Comments
ISS        437.800        145.800        Alternates between voice mode and packet mode. Uplink for 1200bps packet is 145.990
AO-27        145.850        436.795        Sometimes switched off due to power budget restrictions
SO-50        145.850        436.795        Short 74.4Hz PL activates transponder’s 10 minute timer, then 67Hz PL to hold QSO
Table 3: Other amateur satellites you can work with simple FM only VHF/UHF equipment

One antenna, now available in the UK from AMSAT-UK is the Arrow Antenna (Fig. 3) (http://www.arrowantennas.com/146-437.html) which is infamous in the amateur satellite community. Alternatives include homebrewing your own antenna. Two WA5VJB antennas (http://www.clarc.org/Articles/uhf.htm), one for 70cm and the other for 2m mounted orthogonally on the same boom (http://www.g6lvb.com/HomebrewArrow.htm), or commercially, the Cushcraft A270-6S.
The real benefit of these hand held Yagis over a combined azimuth and elevation rotator system is that the operator has feedback and can very rapidly correct for polarisation mismatch by turning the boom along its axis.
•         Operator conveniences
AO-51 passes are short (normally only 15 minutes or less), so preparation will pay off. Also keep in mind that Wednesdays are Experimenters’ days when the voice transponder may be switched off – check http://www.amsat.org/amsat-new/echo for the schedule.
Consider all the tasks you’ll be doing:
o         Retune due to Doppler: on FM-only radios, pre-program five memories in 5kHz steps into the memories for the downlink: 435.310, 435.305, 435.300, 435.295, 435.290. The start of the pass will be at 435.310 and will decrease in frequency.
o         Key the PTT: you might want to consider a foot switch. Beware of VOX: the VOX tail delay can hamper the rapid QSO style on FM satellites. There is a short delay for the uplink PL tone to be recognised.
o         Hold the microphone: a headset/microphone combination is a good idea, giving you a free hand. Use headphones to avoid feedback in full duplex operation!
o         Point and orient the antenna: although the antennas are light, your arm will start to ache during the pass!
o         Check the predicted heading and elevation with the prediction listing and a compass: it’s worth preparing for the pass by tracking the predicted pass of the satellite, ensuring that there are no obstructions.
o         Log the QSOs: a cassette recorder or dictation device helps a lot here.
o         Have a QSO in a very busy channel: patience is a virtue  here. It is likely that you won’t succeed on your first attempt, and this is where preparation and the learning experience come in.
•         Good luck!
Satellite operation is a challenge, both technically and from an operating perspective. But you don’t need large or expensive equipment to operate them. Remember to support AMSAT-UK who represent amateur satellite operators in the United Kingdom. Finally, welcome to the space age and the world of amateur satellites!                               73, Howard G6LVB
 樓主| 發表於 30-5-2010 11:24:34 | 顯示全部樓層
5月30日 是近期測試 AO-51 的好時機
0 AO 51-0010.jpg
 樓主| 發表於 30-5-2010 22:05:28 | 顯示全部樓層
因為距離比  希望一號的1200公里更近
=1 HO68-12U YAGI.jpg
 樓主| 發表於 31-5-2010 12:46:55 | 顯示全部樓層
九龍中-東涌 通聯
0010.jpg
發表於 1-6-2010 00:15:34 | 顯示全部樓層
本帖最後由 VR2VBU 於 1-6-2010 12:21 AM 編輯

.
ao51a.JPG
 樓主| 發表於 2-6-2010 17:59:34 | 顯示全部樓層
用 HB9CV  天線 上鏈 AO51
0028 VBU.jpg
您需要登錄後才可以回帖 登錄 | 立即註冊

本版積分規則

中華業餘無線電研究會 - 業餘無線電考試(筆試)班

手機版|小黑屋|存檔|VR2GY 網站

GMT+8, 29-3-2024 20:52 , Processed in 0.040897 second(s), 18 queries , Gzip On.

本討論區基於 Discuz! X3.5

版權所有 © 2005-2024 VR2GY.com,保留一切權利


重要聲明:本討論區是以即時上載留言的方式運作,VR2GY.com 對所有留言的真實性、完整性及立場等,不負任何法律責任。而一切留言之言論只代表留言者個人意見,並非本網站之立場,讀者及用戶不應信賴內容,並應自行判斷內容之真實性。於有關情形下,讀者及用戶應尋求專業意見(如涉及醫療、法律或投資等問題)。 由於本討論區受到「即時上載留言」運作方式所規限,故不能完全監察所有留言,若讀者及用戶發現有留言出現問題,請聯絡我們。VR2GY.com 有權刪除任何留言及拒絕任何人士上載留言(刪除前或不會作事先警告及通知),同時亦有不刪除留言的權利,如有任何爭議,管理員擁有最終的詮釋權。用戶切勿撰寫粗言穢語、誹謗、渲染色情暴力或人身攻擊的言論,敬請自律。本網站保留一切法律權利。

快速回復 返回頂部 返回列表