AMSAT-BB April 2013

117 participants
172 discussions

FUNcube Project - Your advice requested
by Graham Shirville 09 Apr '13

09 Apr '13

Hi All, As part of the FUNcube project we now need to urgently decide which is going to be the best type of antenna to propose for use at schools and colleges to receive the 145MHz downlink signals from both FUNcube-1 and FUNcube-2 on UKube after launch. Both spacecraft will be transmitting approx 300mW of BPSK 1k2 telemetry with FEC – FC1- will be using a dipole antenna and will have passive magnetic attitude control. FC-2 on UKube will use a single monopole antenna and the spacecraft is intended to have active attitude control. This is primarily to ensure that the deployed solar panels are illuminated and that the face with the S band patch is usually earth pointing. We believe that the resultant signal should be easily usable using an omnidirectional antenna but the questions is which would be the best type to use. Obviously ease of construction, cost, robustness and safety in a school environment will also be important factors as well as suitable “gain” and circularity from horizon to horizon. We envisage that some operations may be from fixed installations with the antennas mounted permanently but some will be temporary - perhaps hand held or bolted to a step ladder or similar. We know there are many AMSAT members around the globe with great experience in this field and, we suspect, with some strongly held views. So please let us have some constructive input about which type is likely to be best for this purpose - your comments, ideas and lessons learnt will be very valuable for us. Thanks in advance for your support 73 Graham G3VZV - for the FUNcube Project team As part of the FUNcube project we need to decide which is going to be the best antenna to propose for use at schools and colleges to receives the 145MHz downlink signals from both FUNcube-1 and FUNcube-2 on UKube after launch. Both spacecraft will be transmitting approx 300mW of BPSK 1k2 telemetry with FEC – FC1- will be using a dipole antenna and has passive magnetic attitude control. FC-2 on UKube will use a single monopole antenna and the spacecraft is intended to have active attitude control to ensure that the deployed solar panels are illuminated and that the face with the S band patch is usually earth pointing. We believe that the resultant signal should be easily usable using an omnidirectional antenna but the questions is which would be the best type to use. Obviously ease of construction, cost, robustness and safety in a school environment will also be important factors as well as suitable “gain” and circularity from horizon to horizon. We know there are many AMSAT members with experience in this field and, we suspect, some strongly held views but all constructive input would be very welcome.

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Re: FUNcube Project - 7 dBi omni
by Robert Bruninga 09 Apr '13

09 Apr '13

> ... which is going to be the best type of antenna... > to receive the 145MHz downlink signals There are lots of good hemispherical satellite antennas that provide equal gain for all satellites in view. However, these designs ignore the fact that satellites on the horizon (LEO passes spend almost 70% of their time below say 22 degrees) are so far away, most of them are too weak to be decoded until they get closer (and higher) anyway. Given the weak downlink (300mw) of FunCube there is no -omni- antenna that is going to decode that signal at the horizon when the satellite is over 1500km away. In this light, it is better to simply sacrifice low angle coverage and concentrate the gain higher up to make sure that when the satellite does get to high angles, then there is plenty of gain to decode it. The simplest and best performance (for LEO satellites) and easiest to construct is a 3/4 wave vertical over a ground plane. It has over 7 dBi gain above 25 or 30 degrees and requires no matching circuit. Just shield to ground plane and center coax to the 3/4 wave whip. The antenna pattern is ideal for LEO satellites because it concentrates the gain above 30 degrees and does not waste gain down on the horizon where satellites are 6 to 10 dB farther away and not decodable on an omni anyway unless the satellite has decent power (which the fun cube does not). Background: In the past, a 19" whip is an ideal 3/4 wave gain vertical for UHF (over 7 dBi) and also acts as a 1/4 wave vertical (5 dBi) for VHF. A nice dual band antenna for satellite work with weak UHF downlinks. But then Funcube is not UHF, but VHF. So you want more gain on the VHF downlink, so you would want to make this antenna almost 58 inches long to be 3/4 wave on VHF (and ignore it for UHF where the gain pattern would be too narrow). Also, by having reduced gain on the horizon, the VHF link will have less noise to contend with. You don’t you see this excellent antenna more often because it is useless for terrestrial operation (negative gain on the horizon), and for satellites, most people think they want omni-gain on the horizon even though for anything other than the 10W transmitter on the ISS, they still won't decode anything on the horizon until the satellite gets higher (and closer) anyway. So my receommendation is the 3/4 wave vertical for unattended fixed omni operation with high gain above say about 25 degrees and use a gain YAGI and tracking antenna if you need to have coverage down to the horizon. The over 7 dBi gain of this simple 3/4 wave antenna plus the nearly 5 dB path-loss (and noise) gain of VHF over UHF for omni antennas makes this link over 12 dB better than a comparable UHF downlink to-an-omni experience with cubesats. My opinion anyway. You can see some of my early writings on this antenna about 80% down this page: http://aprs.org/astars.html Bob, Wb4APR -----Original Message----- From: amsat-bb-bounces(a)amsat.org [mailto:[email protected]] On Behalf Of Graham Shirville Sent: Tuesday, April 09, 2013 3:47 PM To: AMSAT BB Subject: [amsat-bb] FUNcube Project - Your advice requested Hi All, As part of the FUNcube project we now need to urgently decide which is going to be the best type of antenna to propose for use at schools and colleges to receive the 145MHz downlink signals from both FUNcube-1 and FUNcube-2 on UKube after launch. Both spacecraft will be transmitting approx 300mW of BPSK 1k2 telemetry with FEC – FC1- will be using a dipole antenna and will have passive magnetic attitude control. FC-2 on UKube will use a single monopole antenna and the spacecraft is intended to have active attitude control. This is primarily to ensure that the deployed solar panels are illuminated and that the face with the S band patch is usually earth pointing. We believe that the resultant signal should be easily usable using an omnidirectional antenna but the questions is which would be the best type to use. Obviously ease of construction, cost, robustness and safety in a school environment will also be important factors as well as suitable “gain” and circularity from horizon to horizon. We envisage that some operations may be from fixed installations with the antennas mounted permanently but some will be temporary - perhaps hand held or bolted to a step ladder or similar. We know there are many AMSAT members around the globe with great experience in this field and, we suspect, with some strongly held views. So please let us have some constructive input about which type is likely to be best for this purpose - your comments, ideas and lessons learnt will be very valuable for us. Thanks in advance for your support 73 Graham G3VZV - for the FUNcube Project team As part of the FUNcube project we need to decide which is going to be the best antenna to propose for use at schools and colleges to receives the 145MHz downlink signals from both FUNcube-1 and FUNcube-2 on UKube after launch. Both spacecraft will be transmitting approx 300mW of BPSK 1k2 telemetry with FEC – FC1- will be using a dipole antenna and has passive magnetic attitude control. FC-2 on UKube will use a single monopole antenna and the spacecraft is intended to have active attitude control to ensure that the deployed solar panels are illuminated and that the face with the S band patch is usually earth pointing. We believe that the resultant signal should be easily usable using an omnidirectional antenna but the questions is which would be the best type to use. Obviously ease of construction, cost, robustness and safety in a school environment will also be important factors as well as suitable “gain” and circularity from horizon to horizon. We know there are many AMSAT members with experience in this field and, we suspect, some strongly held views but all constructive input would be very welcome. _______________________________________________ Sent via AMSAT-BB(a)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

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2M1EUB/P OPPS UPDATE WEDNESDAY IO97CM
by paul robinson 09 Apr '13

09 Apr '13

Tomorrow wednesday,ill be driving to Peterhead Aberdeenshire,on the N.E coast corner of Scotland, grid sq IO97CM which is a rare grid to be had....fo29 and ao7 ,please make the qso as quick as poss as there may be lots of interested stations looking for me and time is short...ill only be there for a few hours in day light ,mid day passes,GMT.after that ill be back to io87nc till saturday.Hope this works out for every one who is interested ill be around 145.950 a07 and 435.850 fo29,if for any reason ao7 is in mode A ill be around 29.450mhz ...de paul 2M1EUB/P.... QSL dirrect via 2E1EUB

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Bill Tyan, W3XO in May QST
by JoAnne Maenpaa 09 Apr '13

09 Apr '13

Check out page 13 of the May 2013 QST ... there is a nice photo and write up of Bill Tynan, W3XO, receiving the Barry Goldwater Award from the Radio Club of America. The ARRL posted the initial announcement at: http://tinyurl.com/Bill-Tynan-W3XO (www.arrl.org) The AMSAT News Service announcement can be found at: http://amsat.org/pipermail/ans/2012/000651.html -- 73 de JoAnne K9JKM k9jkm(a)amsat.org Editor, AMSAT Journal

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demo help
by Nick Pugh 09 Apr '13

09 Apr '13

Thanks to all that help on the demo yesterday there were 7 very excited kids Thanks nick ARS K5QXJ EM30xa 30.1N 92.1W Office 337 593 8700 Cell 337 258 2527 Helping UL become a world Class Engineering and Educational School

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io97 sq opps WEDNESDAY 2M1EUB/P
by paul robinson 08 Apr '13

08 Apr '13

Hope to be qrv wednesday this week day time only from io97 sq in north east aberdeenshire scotland,ao7 and may be fo29 ...i will be driving to this sq special.Hope to find a good spot to park up .Heavy snow is forcast here for thrusday,so if it comes early we wont be going..im opperating holiday style...ie the xyl is understanding! 73 de paul 2M1EUB/P

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7330 Km contact on FO-29!
by Hector Luis HLMS. Martinez Sis 08 Apr '13

08 Apr '13

Hello to all! Today on the 1338z pass, I beat my distance mark on FO-29. David, EA4SG (grid IN80cp) and I (grid EL92sd) completed a SSB contact successfully. Based on QRZ.com, the distance between the two stations is 7330.6 km. We had just a 88 seconds window. I was operating portable from on top of a tall building as before. Satellites are always fascinating! Thanks very much to David for this great contact and new grid! 73! Hector, CO6CBF EL92sd --- Consulte la Enciclopedia Colaborativa Cubana http://www.ecured.cu/

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greetings
by Gail A Mcdaniel 08 Apr '13

08 Apr '13

http://www.hugobusinesses.com/includes/newsphoto.php?mfqfrmli712shlgy ********************** You can do better than that. Fracture, shatter, pulverize and atomize it. Don't kid around. -- Ari Rapkin

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demo help
by Nick Pugh 08 Apr '13

08 Apr '13

The Children Museum of Acadiana and the AARA will be presenting handhelds to 7 6th graders who just passed the tech license. If someone on this list could connect to ECHOLINK node 370324 at 1915 z Monday and have a QSO with the kids for their 1st Q. DX stations would really excite the kids. Most f the kids are learning French. Please reply to me if you can come up on Echolink. Thanks nick ARS K5QXJ EM30xa 30.1N 92.1W Office 337 593 8700 Cell 337 258 2527 Helping UL become a world Class Engineering and Educational School

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Keps Downconverter
by Angelo Glorioso 07 Apr '13

07 Apr '13

I am trying to repair my Keps 13lnc72-db 2.4 gig dowmconverter and I am unable to find any document or schematic. Do anyone have any documents on this unit??? I have looked on the web but the site looks like it is down. Any help would be appreciated. Thanks in advance, Angelo

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AMSAT-BB April 2013