[amsat-bb] Re: Path to HEO
schrieb Ken Ernandes on 2013-04-30 09:49: > I note the disclaimer at the bottom, so I'll help with the incorrect > assumptions. > > 1. g = 9.81 m/sec only applies to one Earth radius (i.e., the Earth's > surface). Gravitational acceleration drops of as an inverse square of the > radius. > 2. GEO altitude is close to 36000 km, but GEO radius is approximately 42164 > km (you must add the Earth's radius to altitude to get orbital radius) Gotcha! > Gravity can be simplified by using a constant MU = 398600.4418 km^3/sec^2 > > For any radius you can compute g by: > > g = MU / r^2 > > But make sure you use radius and not altitude. Mean Earth radius at > mid-latitudes is approximately 6371 km and is 6378 at the equator. > > The speed (v) for an elliptical orbit can be computed from the current radius > (r) and semi-major axis (a): > > v = sqrt(MU*(2/r - 1/a)) > > This can be simplified for a circular orbit (r = a): > > v = sqrt(MU/a) These are the formulas they did not tell us at school, thank you! > The more important thing is what Dan Schultz pointed out. At 300 km > altitude, atmospheric drag is a significant factor in a continuous drain of > orbital energy. This is less at 500 km and almost insignificant starting > around 800 km. The drop off is because drag is: > > 1. proportional to atmospheric density which drops off quickly with increased > altitude. > 2. also proportional to the square of the speed relative to the atmosphere. > > If you can get above 800 km without using up a lot of your fuel, you have a > chance to make something workable. >From the last few cubesat rides I reckon that going there instead of only to 300 km is not that impossible. Regards Patrick -- Engineers motto: cheap, good, fast: choose any two Patrick Strasser ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: Fermi Avoids Near Miss In Orbit
--- On Thu, 2/5/13, Greg D wrote: > Um, the dates in the article are from > 2012 (that be last year). > Interesting stuff, but why is NASA posting it now? Perhaps they are lobbying for funding for a debris mitigation program ? 73 Trevor M5AKA ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Call for Papers: 2013 Digital Communications Conference
Amateurs are invited to submit papers for publication in the conference proceedings of the ARRL/TAPR Digital Communications Conference that is taking place September 20-22 in Seattle, WA. You do not have to attend the conference to submit a paper for consideration. Send papers by July 31 to: Maty Weinberg ARRL 225 Main St Newington, CT 06111 . . . or by e-mail to m...@arrl.org Submissions will not be edited and authors will retain all rights. 73 . . . Steve Ford, WB8IMY QST Editor in Chief and Publications Manager ARRL -- the National Association for Amateur Radio tel 860-594-0287 sf...@arrl.org ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: [Forum] S-Band Downlink auf HEO/GEO noch sinnvoll?
Hi Peter, DB2OS I am still using a 120 cm (4 foot) parabolic dish for 2400 MHz and I noted that when the elevation is about 10 degres above the horizon here in the bay of Napoli there are not heavy interference from WiFi tuning between 2400 to 2402 MHz so that actually the old OSCAR-40 (P3-D) S band is still usable here. We need not a new S band but a new P3E satellite. Best 73" de i8CVS Domenico > Hi there, > > many of us will certainly remember the Mode S downlink of AMSAT > OSCAR-40 (P3-D) remember. > > After initial skepticism, especially after the 2m transmitter > failed, Mode-S was indeed an amazing encouragement and was > bad out of "Easy Mode". > I myself can not in experiments with different antennas and > Feeds remember, through the bathroom window in the direction of AO-40 ... > The signals were glaskar and the tape clean, even weak stations > were easy to understand .. > > 10 years later, each more than a 2.4 GHz WiFi wireless router, > Laptop and smartphone in the house, the neighbors and office buildings > around a > around all ... > In the country there are also many "citizen networks" with Wi-Fi to all > Villages to provide them with inexpensive internet ... > > Probably the noise level is now very high, and even > when working with parabolic antennas to heaven, you will be on the > Sidelobes surely still a mess from all of WLANs > Receive directions ... remains of the actual desired > Useful signal probably little left .. > > Under these conditions would have an S-band downlink like you would with > AO-40 > still have a chance? > > Has anyone had any experience in this regard and perhaps collected with > a connected spectral antennas in all the times > Rotated directions? > > Under https://www.facebook.com/amsat.deutschland there is a small > To vote .. > > > 73s Peter DB2OS > > > - Original Message - > From: "Peter Guelzow" > To: "AMSAT - Forum" > Sent: Wednesday, May 01, 2013 8:33 PM > Subject: [Forum] S-Band Downlink auf HEO/GEO noch sinnvoll? > > > Hallo zusammen, > > viele von uns werden sich bestimmt noch an die Mode-S Downlink von AMSAT > OSCAR-40 (P3-D) erinnern. > > Nach anfänglicher Skepsis, insbesondere nachdem der 2m-Sender > ausgefallen war, fand Mode-S ja einen erstaunlichen Zuspruch und war > schlecht hin der "Easy Mode". > Ich selbst kann mich noch an Versuche mit verschiedenen Antennen und > Feeds erinnern, durch das Badezimmer-Fenster in Richtung AO-40... > Die Signale waren glaskar und das Band sauber, selbst schwache Stationen > waren problemlos zu verstehen.. > > 10 Jahre später hat jeder mehr als einen 2,4 GHz WiFi WLAN-Router, > Laptop und Smartphone im Hause, die Nachbarn und Bürogebäude um einen > herum auch alle... > Auf dem Lande gibt es ja auch viele "Bürgernetze" mit WLAN um ganze > Dörfer preiswert mit Internet zu versorgen... > > Wahrscheinlich ist der Grundrauschpegel inzwischen sehr hoch und selbst > wenn man mit Parabolantennen gegen Himmel arbeitet, wird man über die > Nebenzipfel sicher noch ein Durcheinander von WLAN's aus allen > Richtungen empfangen... dann bleibt von dem eigentlich gewünschten > Nutzsignal wohl wenig übrig.. > > Hätte unter diesen Bedingungen eine S-Band Downlink wie eben bei AO-40 > noch eine Chance? > > Hat jemand diesbezüglich schon Erfahrungen gesammelt und vielleicht mit > einem angeschlossenen Spektralanalyse mal die Antennen in alle > Richtungen gedreht? > > Unter https://www.facebook.com/amsat.deutschland gibt es eine kleine > Abstimmung dazu.. > > > 73s Peter DB2OS ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] VHF Amps (Smaller) for Sale
Cleaning out extra & backup items from the shack in an attempt to stave off bankruptcy and the poor-house while paying for my daughter's wedding. :-) Selling off a few small amplifiers that may be of use to other VHF Weak Signal fans. All amps are in good working condition. Cosmetically, they are "USED", meaning that they have the usual scratches, etc. No major dents, paint loss, etc. Perfectly acceptable and XYL approved , but not mint from the factory. If you're not happy we'll make it right. Relax, it's just a hobby. Prefer Paypal payment or USPS Money Order. Shipping via UPS Ground is included in the price. TE Systems Model 0510G 50-54 MHz (6 Meter) Linear Amplifier (SSB/CW/FM) Serial #A7173 10 Watts input-150 Watts Output. The amp is rated for 170 Watts Output, but I never drove it that hard. This amp was modified by TE Systems to provide an RCA rear panel input jack for PTT keying. You simply connect a footswitch, handheld PTT, or amp keying line to this jack, close to ground, and the amp keys. Saves wear and tear on the relay. $225 TE Systems Model 1412G 144-148 MHz (2 Meter) Linear Amplifier (SSB/CW/FM) Serial #38482 10 Watts input-190 Watts Output This amp includes heavy duty power connector with Anderson Power-Poles. TE Systems plug including RCA female PTT keying circuit. Simply attach a footswitch, handswitch or amp keying line to this connector, close to ground and amp keys. Saves wear and tear on the relay. $250 Mirage A1015 50-52 MHz Linear Amplifier (SSB/CW/FM) Serial #93-234 10 Watts Input-150 Watts Output This amp includes heavy duty power connector with Anderson Power-Poles. This is the non-G model, with the older brown face. Does not include RF sensing switching, so you HAVE to use the RCA plug on the rear to key the amp using a footswitch, handswitch, or amp key line. But then again, who does weak signal work and doesn't do that anyway. Great workhorse amp at a good price. Used mine with a Flex 1500. 5 watts input pushes about 80 watts output. $225 Advice to OM's with daughters. Start saving now!!! :-) -- -- 73, Les Rayburn, N1LF 121 Mayfair Park Maylene, AL 35114 EM63nf 6M VUCC #1712 AMSAT #38965 Grid Bandits #222 Southeastern VHF Society Central States VHF Society Life Member Six Club #2484 Active on 6 Meters thru 1296, 10GHz & Light ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: [Forum] S-Band Downlink auf HEO/GEO noch sinnvoll?
Hi Domenico, thanks - this is indeed very valuable input for me ! Maybe we are still lucky at the very low end of 2400,00 MHz of our satellite band, because this is also the edge of the WiFi band... No, I'm not considering a "new S-Band"... I just want to be sure that when we will have a Downlink there, that it is desirable and still usable... best wishes Peter DB2OS On 02.05.2013 18:24, i8cvs wrote: > Hi Peter, DB2OS > > I am still using a 120 cm (4 foot) parabolic dish for 2400 MHz and > I noted that when the elevation is about 10 degres above the horizon > here in the bay of Napoli there are not heavy interference from WiFi > tuning between 2400 to 2402 MHz so that actually the old OSCAR-40 > (P3-D) S band is still usable here. > > We need not a new S band but a new P3E satellite. > > Best 73" de > > i8CVS Domenico > >> Hi there, >> >> many of us will certainly remember the Mode S downlink of AMSAT >> OSCAR-40 (P3-D) remember. >> >> After initial skepticism, especially after the 2m transmitter >> failed, Mode-S was indeed an amazing encouragement and was >> bad out of "Easy Mode". >> I myself can not in experiments with different antennas and >> Feeds remember, through the bathroom window in the direction of AO-40 ... >> The signals were glaskar and the tape clean, even weak stations >> were easy to understand .. >> >> 10 years later, each more than a 2.4 GHz WiFi wireless router, >> Laptop and smartphone in the house, the neighbors and office buildings >> around a >> around all ... >> In the country there are also many "citizen networks" with Wi-Fi to all >> Villages to provide them with inexpensive internet ... >> >> Probably the noise level is now very high, and even >> when working with parabolic antennas to heaven, you will be on the >> Sidelobes surely still a mess from all of WLANs >> Receive directions ... remains of the actual desired >> Useful signal probably little left .. >> >> Under these conditions would have an S-band downlink like you would with >> AO-40 >> still have a chance? >> >> Has anyone had any experience in this regard and perhaps collected with >> a connected spectral antennas in all the times >> Rotated directions? >> >> Under https://www.facebook.com/amsat.deutschland there is a small >> To vote .. >> >> >> 73s Peter DB2OS >> >> >> - Original Message - >> From: "Peter Guelzow" >> To: "AMSAT - Forum" >> Sent: Wednesday, May 01, 2013 8:33 PM >> Subject: [Forum] S-Band Downlink auf HEO/GEO noch sinnvoll? >> >> >> Hallo zusammen, >> >> viele von uns werden sich bestimmt noch an die Mode-S Downlink von AMSAT >> OSCAR-40 (P3-D) erinnern. >> >> Nach anfänglicher Skepsis, insbesondere nachdem der 2m-Sender >> ausgefallen war, fand Mode-S ja einen erstaunlichen Zuspruch und war >> schlecht hin der "Easy Mode". >> Ich selbst kann mich noch an Versuche mit verschiedenen Antennen und >> Feeds erinnern, durch das Badezimmer-Fenster in Richtung AO-40... >> Die Signale waren glaskar und das Band sauber, selbst schwache Stationen >> waren problemlos zu verstehen.. >> >> 10 Jahre später hat jeder mehr als einen 2,4 GHz WiFi WLAN-Router, >> Laptop und Smartphone im Hause, die Nachbarn und Bürogebäude um einen >> herum auch alle... >> Auf dem Lande gibt es ja auch viele "Bürgernetze" mit WLAN um ganze >> Dörfer preiswert mit Internet zu versorgen... >> >> Wahrscheinlich ist der Grundrauschpegel inzwischen sehr hoch und selbst >> wenn man mit Parabolantennen gegen Himmel arbeitet, wird man über die >> Nebenzipfel sicher noch ein Durcheinander von WLAN's aus allen >> Richtungen empfangen... dann bleibt von dem eigentlich gewünschten >> Nutzsignal wohl wenig übrig.. >> >> Hätte unter diesen Bedingungen eine S-Band Downlink wie eben bei AO-40 >> noch eine Chance? >> >> Hat jemand diesbezüglich schon Erfahrungen gesammelt und vielleicht mit >> einem angeschlossenen Spektralanalyse mal die Antennen in alle >> Richtungen gedreht? >> >> Unter https://www.facebook.com/amsat.deutschland gibt es eine kleine >> Abstimmung dazu.. >> >> >> 73s Peter DB2OS > ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Rising Price of Flights to the ISS
New price for flights to the ISS will be $71 million per person from 2017. Current price paid by NASA is $55.8 million per person and that is due to rise to $62.75 million next year, a year or so ago they were paying $51 million, see http://www.aviationweek.com/Article.aspx?id=/article-xml/asd_05_01_2013_p01-02-575108.xml 73 Trevor M5AKA ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: Rising Price of Flights to the ISS
On 5/2/13, M5AKA wrote: > New price for flights to the ISS will be $71 million per person from 2017. > > Current price paid by NASA is $55.8 million per person and that is due to > rise to $62.75 million next year, a year or so ago they were paying $51 > million, see > > http://www.aviationweek.com/Article.aspx?id=/article-xml/asd_05_01_2013_p01-02-575108.xml > Virgin Galactic might raise its prices, too: http://www.parabolicarc.com/2013/04/29/reserve-your-spaceshiptwo-seat-now-big-price-increase-coming-soon/ http://www.newspacejournal.com/2013/05/01/is-virgin-galactic-raising-its-ticket-price/ 73s Bernhard VA6BMJ @ DO33FL ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] satellite metallic cross boom
Hi all, Am down in Peru working on the club station. The antennas are mounted on a metallic cross boom. The antennas are carbon copies of each other in terms of position. I read on the internet that one should be rotated 45 degrees. Is this an old wives tale? I can fix the problem as one of the antennas will partially down to rehab it. Thanks, Norm n3ykf ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: satellite metallic cross boom
Norm, I'm assuming you're talking about circularly polarized antennas. The short answer is yes, you can use a metallic cross boom if you: (1) mount both antennas in an X orientation to the boom, *and* (2) avoid having the cross boom 0.5-wavelength, 1.0-wavelength, etc. away from the driven element. The full article written by Kent Britain (of cheap-yagi fame) is on Howard Long's (of LVB Tracker and FUNcube dongle fame) web site: http://www.g6lvb.com/fibermetalboom.htm Good luck with your project; have a great trip! 73, Steve N9IP -- Steve Belter, s...@wintek.com On 5/2/13 9:18 PM, "Lizeth Norman" wrote: >Hi all, >Am down in Peru working on the club station. The antennas are mounted on a >metallic cross boom. The antennas are carbon copies of each other in terms >of position. I read on the internet that one should be rotated 45 degrees. > >Is this an old wives tale? I can fix the problem as one of the antennas >will partially down to rehab it. > >Thanks, >Norm n3ykf >___ >Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. >Not an AMSAT-NA member? Join now to support the amateur satellite program! >Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
