April 2009 - AMSAT-BB - mailman.amsat.org

AO-51 S band reception
by Luc Leblanc 25 Apr '09

25 Apr '09

On the current AO-51 S band downlink i notice the "always" present deep fades period during a pass as the S band antenna are Dual band L/S Open Sleeve (1/4 wave stub) it confirm why my actual linear "WI-FI" stacked yagi perform better than my BBQ grill and dish with circular polarisation. Foliage and blocking structures "seems" to have a lesser effect on the yagi than on the circular polarisation antenna. On one QSO with Clare VE3NPC we noted that theses fades does not happen at the same time at our respective QTH (Ottawa and Sorel-Tracy) making the following excerpt quite accurate. >From down to earth web site: http://www.docstoc.com/docs/5178447/down-to-earth Satellite antennas are usually whips or dipoles. The satellite may slowly tumble, changing the orientation of the antennas. If you happen to be "off the end" of its antenna, the signal may be too weak to work. Even if you remain out of its "null", the direction of the linear polarization of the satellite downlink signal changes relative to you during the pass. If the polarization at some instant happens to be perpendicular to the polarization of your receiving antenna, there is about a 20dB (100x) signal loss. I think i will give up in the fades elimination fight 100X signal is nearly impossible to compensate at the receiving side. It is probably an AO-51 S band limitation. Could be the internet can be a solution if each station can feed their downlink audio on Skype or echolink it will be possible to listen on theses various downlink sources making possible to have a full pass reception as there will be always one receiving station out of the fades. DSTAR on S mode As the first DSTAR satellite transmission has been made on AO-27 i don't know if the same test can be perform on AO-51. If someone with DSTAR capabilities is interesting to "test" it on mode V/S just let me know. Why on mode V/S it's because i will have to be in half duplex as my DSTAR transceiver is a monobander. It is a very "dangerous experiment" here as i will have to manually TR switching between the VHF antenna and the downconverter line. But it will be interesting to know if a DSTAR digital signal can passed through AO-51 first? I can try to send a couple of CQ on the last mode V/S evening pass listening what goes out too? "-" Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE

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AO-51 U/S
by w7lrd＠comcast.net 25 Apr '09

25 Apr '09

Lots of fun using my old AO-40 (sobsob) gear. Worked Scotty-VE6ITV solid contact. Heard XE2BHL, I think he sorta heard me, near his LOS. Tracking the fast moving AO-51 with a three foot dish by manually is tricky, I have a LVB tracker on order. Thankyou Drew, and the other control ops, this is neat stuff. 73 Bob W7LRD

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AO-51 U/S
by w7lrd＠comcast.net 24 Apr '09

24 Apr '09

At 1707Z, (next pass) I will be looking for W. coast US & Canada, KL7 for anyone with U/S capability. 73 Bob W7LRD

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Re: FLTSATCOM Hacked
by Alan Sieg WB5RMG 24 Apr '09

24 Apr '09

Dan N8FGV said > Mark's original point is still a valid one and has not been addressed... > An amateur-built bent pipe transponder in geosynchronous... > orbit will be vulnerable to the same sort of unlicensed abuse... > how exactly do we protect it from this sort of abuse? This may have been worked to death, but the discussion quickly changed to '-wish we had a GEO-', then came back around to '-how do we protect-'. It's not like we are gonna arrive quickly at a perfect solution. It has always seemed to me that some of the best protection we have had, is in the simple fact that a moving target is less likely to be of value or interest to pirates. Our feeble low-powered, fast-moving, doppler- shifting transponders are not very attractive targets for freeloaders. Just like internet hackers, they are not interested in a 386 w/4MB ram. Something like an antique Navy GEO with lots of power is an easy mark. I'm not suggesting we only deploy obscure low-power LEO birds, but the higher we push the frequencies, and stay in motion, the less attention we attract. As much convenience as GEO offers, it would also bring a following of pirates. A GTO like AO-13 that requires at least scheduled pointing, would likely not be seen as such an easy mark. A small flock of APRS birds like BobB mentions would probably not appear of much interest to pirates either. No easy answers, but maybe we can avoid making it too easy to hijack. Thanks /;^) -- <- Licensed in 1976, WB5RMG = Alan Sieg * AMSAT#20554 -> <- http://www.somenet.net * http://wb5rmg.somenet.net -> <- http://www.linkedin.com/in/alansieg * My 'Day Job' ->

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Re: FLTSATCOM Hacked
by RFI-EMI-GUY 24 Apr '09

24 Apr '09

I think it is less important to worry about technology that can't be hacked and more important to devise a scheme to locate the source of an interferer be it deliberate or accidental. With a bent pipe transponder scheme, if there are two or more satellites having overlapping footprint, you can monitor the downlink of each satellite and derive a time of arrival fix from each. Do some trig and get a fix on the possible locations. I am sure this is exactly what the DOD is doing to locate these pirates. -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Use only Genuine Interocitor Parts" Tom Servo ;-P

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AG-35 smoke test
by RFI-EMI-GUY 24 Apr '09

24 Apr '09

FYI for operators using the IC-970 radio. I blew my AG-25 preamp once as a result of switching the satellite mode knob while PTT was still engaged. I never tried to duplicate this action of course, but it seems the radio logic got confused during the change and the sequencer did not kill the TX power. > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 23 Apr 2009 20:45:40 -0600 > From: "Yokshs" <yokshs(a)sbcglobal.net> > Subject: [amsat-bb] AG-35 smoke test > To: "Amsat BB" <amsat-bb(a)amsat.org> > Message-ID: <0CD166CE3BF94D2B91D05ECD6D2CCCBC@main> > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > reply-type=original > > > Luc, > > Thanks for the reply. > > Did you have to remove the relay to replace the FET? Just curious. I've got > my AG-35 down off the tower and on the bench now. The FET is so close > to one of the relays, I'm pretty sure it'll have to be removed to replace > the FET.. Any suggestions? > > Thanks, > > Kyle > K0KN > > > --- Original Message --- > > I fried my UHF one too...I order a couple from ICOM. With my very limited > electronics building skills i cut the dead one leaving as much > legs as possible and i resolder the replacement over the cut legs. Not > elegant but quick and effective. Is this is achieving the same > overall previous gain figures? that i don't know but it works. > > I have another one to replace in a different type of preamp but the FET is > below a lot of other components and he's flat mounted (No legs) > i don't come up with a solution with this one? > > > "-" > > > Luc Leblanc VE2DWE > Skype VE2DWE > www.qsl.net/ve2dwe > WAC BASIC CW PHONE SATELLITE > > > > > > -- Joe Leikhim K4SAT "The RFI-EMI-GUY"© "Use only Genuine Interocitor Parts" Tom Servo ;-P

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Re: FLTSATCOM Hacked
by Daniel Schultz 24 Apr '09

24 Apr '09

Mark Spencer wrote >Kind of makes you wonder what would happen if there was a geo stationary >amateur satellite that was easy to use.?? If pirates will hack military >satellites then I doubt they would have any qualms about using an >amateur satellite.?? Mark's original point is still a valid one and has not been addressed yet in this discussion. An amateur-built bent pipe transponder in geosynchronous orbit will be vulnerable to the same sort of unlicensed abuse that FLTSATCOM is experiencing, and we amateurs will not have the same ability to prosecute the offenders that the US military has. If we build such a system, how exactly do we protect it from this sort of abuse? Dan Schultz N8FGV

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Re: ANUSAT heard
by Mineo Wakita 24 Apr '09

24 Apr '09

I heard and saved ANUSAT carrier wave (2.8MB). This is a very very weak signal with a doppler. ANUSAT, 13:00-13:11UTC, Mel 57, 137.400MHz http://www.ne.jp/asahi/hamradio/je9pel/90424anu.wav http://www.ne.jp/asahi/hamradio/je9pel/90424anu.jpg ANUSAT information, Telecommand : VHF(PCM/FSK/AM), 100 bits/sec, 149.2 MHz Telemetry : VHF(PCM/FSK/AM), 256 bits/sec, 137.4 MHz ANUSAT 1 34808U 09019B 09113.18398593 -.00000289 00000-0 00000+0 0 127 2 34808 041.2102 148.9969 0109770 026.6096 083.2692 15.29388015 488 http://www.isro.org/pressrelease/Apr20_2009.htm http://beswaminathan.googlepages.com/Anusat.pdf http://bsidharth1205.googlepages.com/research Thanks your these information for ANUSAT. JE9PEL, Mineo Wakita

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ANUSAT heard
by Mineo Wakita 24 Apr '09

24 Apr '09

I heard and saved ANUSAT carrier wave (2.8MB). This is a very very weak signal with a doppler. ANUSAT, 13:00-13:11UTC, Mel 57, 137.400MHz http://www.ne.jp/asahi/hamradio/je9pel/90424anu.wav http://www.ne.jp/asahi/hamradio/je9pel/90424anu.jpg ANUSAT information, Telecommand : VHF(PCM/FSK/AM), 100 bits/sec, 149.2 MHz Telemetry : VHF(PCM/FSK/AM), 256 bits/sec, 137.4 MHz ANUSAT 1 34808U 09019B 09113.18398593 -.00000289 00000-0 00000+0 0 127 2 34808 041.2102 148.9969 0109770 026.6096 083.2692 15.29388015 488 http://www.isro.org/pressrelease/Apr20_2009.htm http://beswaminathan.googlepages.com/Anusat.pdf http://bsidharth1205.googlepages.com/research Thanks your these information for ANUSAT. JE9PEL, Mineo Wakita

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Re: Cross Boom
by Roy 24 Apr '09

24 Apr '09

It seems that this subject comes up once or twice every decade. I have never used anything but a metal cross boom since I joined AMSAT in 1974. Later there were some tests run by Kent Britain, WA5VJB. His measurements resulted in the following recommendations: 1. Mount the antenna with the tips of the elements as far from the support boom as possible. Instead of mounting them in a + form, mount them as an X in relation to the cross boom. 2. Saw off any excess cross boom so that it doesn't extend past the antenna boom. 3. Avoid mounting the boom 1/2 or 1 wavelength from the driven elements. (I would modify that to multiples of 1/2 wavelength) 4. Run the coax out the metal boom and down the antenna boom. Keep the turning radius of the coax small but not to the extent of damage to the coax. I have never detected any bad effects of this arrangement and had stumbled into this configuration years before Kent published his findings in the 1993 AMSAT Symposuim Proceedings. I did it to avoid having the coax from hanging off the rear of the antennas and dragging on the roof of my house and changing fore/aft balance with ice loads. Incidentally, I think I recall that Jim, G3RUH was also using this method. If anyone wants a photo of the antenna setup and contacts me directly I will send it to him. Roy -- W0SL AMSAT 410

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