April 2011 - AMSAT-BB - mailman.amsat.org

Re: Preamp Distance from Antenna
by i8cvs 02 Apr '11

02 Apr '11

Hi Matthias, DD1US I know that the negative effect of the added losses in front of a preamplifier and thus reduced sensitivity is also a function of the noise level due to the Antenna Temperature. In a terrestrial system for 70 cm the antenna at zero degrees elevation sees at best a Noise Temperature equal to the ambient temperature of 290 kelvin if you are fortunate enough to live in a rural area. In a satellite system a good antenna with low side lobes when aimed at high elevation sees a "cold sky" and thus the " Antenna Temperature" is around 50 kelvin i.e. much lower than the ambient temperature of 290 kelvin. Now suppose that the loss of the coax cable betwen the antenna and the preamplifier input is 0.7 dB and the Noise Figure of the preamplifier is 0.55 dB and the antenna is used for terrestrial use at zero degrees elevation so that the antenna sees at best 290 kelvin Coax cable 0.7 dB = 51 kelvin Preamp NF 0.55 dB = 39 kelvin Antenna temperature = 290 kelvin -------------- Total system Temp. = 380 kelvin ( for terrestrial use) Now suppose that the antenna is aimed at the satellite and sees a "cold sky " at 50 kelvin so that the total system Temperature is reduced to 51+39+50 = 140 kelvin ( for satellite use ) The improvement of sensitivity of the same receiving system looking at the satellite against terrestrial use is 10 log (380 / 140 ) = 4.3 dB 10 in Signal to Noise Ratio. By the way now suppose that the preamplifier is NOT antenna mounted and the line losses between the antenna and the shack where the preamplifier has been mounted is tipically 3 dB = 290 kelvin For terrestrial use at zero degrees elevation the total system Temperature is 290 + 39 + 290 = 619 kelvin For satellite use with high antenna elevation the total system Temperature is 290 + 39 + 50 = 379 kelvin With 3 dB of loss of coax cable between the antenna and preamplifier the improvement of sensitivity of the same system looking at the satellite against terrestrial use is reduced to 10 log (619 / 379 ) = 2.1 dB ONLY 10 in Signal to Noise Ratio This is why prescinding from where the antenna is aimed or towards the horizon or towards the sky in order to gain in sensitivity it is necessary to keep the losses between the antenna and input of preamplifier as low as possible. Best 73" de i8CVS Domenico ----- Original Message ----- From: "Matthias Bopp" <matthias.bopp(a)gmx.de> To: <AMSAT-BB(a)amsat.org> Sent: Saturday, April 02, 2011 12:22 PM Subject: [amsat-bb] Re: Preamp Distance from Antenna Hi Zack and Domenico, I would like to add, that the negative effect of the added losses in front of the preamplifier and thus reduced sensitivity of your system is also a function of the noise level: in terrestrial systems where your antenna typically sees a noise temperature equal to the ambient temperature all written below is reflecting the negative effect quite well. However in a satellite system where your antenna sees the noise of the sky the "Noise temperature" is a function of frequency and at VHF/UHF/SHF the sky is "quite cold" and thus the "noise temperature" is much lower than the ambient temperature. Therefore the negative effect of the degraded noise figure is much higher. Please keep this in mind. Best regards Matthias www.dd1us.de -----Ursprüngliche Nachricht----- Von: amsat-bb-bounces(a)amsat.org [mailto:[email protected]] Im Auftrag von i8cvs Gesendet: Donnerstag, 31. März 2011 00:03 An: Zachary Beougher; Amsat - BBs Betreff: [amsat-bb] Re: Preamp Distance from Antenna Hi Zack, KD8KSN The loss in dB of the coax cable from the antenna to your preamplifier adds directly to the Noise Figure NF of your preamplifier. As an example if the loss of the coax cable is say 0.7 dB and the Noise Figure of the preamplifier is 0.55 dB as specified by the manufacturer then the overall Noise Figure of the system antenna plus preamplifier is 0.7+0.55=1.25 dB This is why to reduce the overall Noise Figure of any receiving system it is necessary to install the preamplifier as close as possible to the antenna connector. By the way the gain of a ARR SP432VDG preamplifier is 16 dB and as connected in front of your 70 cm receiver you will see an increase of noise level of about 3 S-units in your S meter but the overall Noise Figure of your receiving system will be much lover than the Noise Figure of the 70 cm receiver alone. In this condition using a preamplifier the 70 cm receiving system will be more sensitive but it will be more susceptible to intermodulation and overloading when you transmit to a satellite in the 2 meters band. If you suffer with intermod the only cure is to add a 6 dB attenuator from the preamplifier output to the 70 cm receiver input but if you use a 70 cm tranceiver don't forget to remove the attenuator before to transmit in 70 cm I hope this helps. 73" de i8CVS Domenico ----- Original Message ----- From: "Zachary Beougher" <zack.kd8ksn(a)hotmail.com> To: <amsat-bb(a)amsat.org> Sent: Wednesday, March 30, 2011 4:24 PM Subject: [amsat-bb] Preamp Distance from Antenna > Hi, > I am in the process of getting the ARR SP432VDG preamp for my mobile setup (and just to have around), and I have read that the closer to antenna you mount the preamp, the lower noise figure you will have. My question is, what is close to the antenna - 1ft., 5ft., 10ft.? Ideally, I would probably mount it about 5-6ft. from the antenna (1/4 wave) - would this be acceptable? > > Any additional advice would be appreciated! > > Zack > KD8KSN > _______________________________________________ > 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 > _______________________________________________ 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 _______________________________________________ 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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Log/Grids
by Kevin Deane 02 Apr '11

02 Apr '11

I am hoping there is a nice logbook thinga ma jig program out there. Does anyone know where I can get one? I really like doin the cards, I feel bad for sending out some pretty hokey ones now that I am getting some really nice ones... Anyway I figured that someone must have some easy/cool way to keep track of all this stuff. Thanks, Kevin KF7MYK

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Wisp DDE Client
by Howard Kowall 02 Apr '11

02 Apr '11

Hello All Does anyone know what the last version of Wisp DDE Client is. As far as I can tell it's 4.3.7 Thanks to all who read and respond Howard VE4ISP

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Icom IC-910H using SatPC32
by KE4KOL 02 Apr '11

02 Apr '11

Is anyone using the Icom IC-910H with SatPC32? Any pros or cons? Will it give VFO feed back to the software? Thanks, Jim, KE4KOL

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SwissCube satellite videos + PW Sat
by Trevor . 02 Apr '11

02 Apr '11

See http://www.southgatearc.org/news/march2011/swisscube_video.htm IARU Satellite Frequency Coordination pages have an update on PW Sat due to fly on Vega later this year, see http://www.amsatuk.me.uk/iaru/formal_detail.php?serialnum=132 It's planned to carry an APRS transceiver which will be good. I had a look at the Warsaw University of Technology site but couldn't locate any PW Sat pages. Anyone know if there's any further info on the sat available? 73 Trevor M5AKA Daily Amateur Radio Email/RSS News: http://www.southgatearc.org/ Email Your News To: editor at southgatearc.org Or Upload At: http://www.southgatearc.org/news/your_news_1.htm ----

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KL7CN QRV Caribbean next week
by KL7CN 02 Apr '11

02 Apr '11

Hello, all: I will be active in a holiday-style DXpedition on the FM satellites from various Caribbean locations next week starting Sunday 3-April-2011. We will start /KP4 from San Juan, and then operate /MM from as many grids as we can, followed by J6/ from St. Lucia, then as V25CN from Antigua, then as a very special FS/PJ7/ operation from the border monument on St. Martin, then /KP2 from St. Croix, and finally again as /KP4. I will attempt to send a note at the beginning of each day indicating if, when, and how operation will occur. Special thanks to Patrick WD9EWK for answering many questions, Sawson KG6NUB for equipment checks, and Allen N5AFV for the original inspiration. Special thanks also to the AO-51 control ops for agreeing to keep the satellite in V/U mode for the week. We'll see how it goes! Thanks in advance for your patience! -- bag Sent from an iPhone; replies are brief, but still attempt to be witty.

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Paccomm PSK-1 firmware discovery
by Greg Beat 01 Apr '11

01 Apr '11

I am checking out a couple of surplus Paccomm PSK-1 this weekend. I was told that there was only one version of the PSK-1 firmware, BUT I have discovered that is not true. S/N are hand written on the PSK-1 printed circuit board. S/N P10511 *********************************************** * P a c C o m m P S K M o d e m * * Software version 2.01 CSUM: 6717 * * COPYRIGHT 1989 Digital Signal Systems * * -with Kansas City Tuner REALTIME Support- * *********************************************** <1> Mode: Manchester (Satellite) <2> Modem: Out-of-Line (TNC's modem) <3> Joint/Split: Joint (VHF RX, VHF TX) <4> AFC: None (Provide no AFC outputs) <5> Mic-Click Sense: Active-Low <6> Clicks-per-Step: One <7> Maximum Step Rate: 2 per second <8> DCD Output Sense: Active-Low <9> RS232 Speed: 1200 8N1 <A> KC Tuner Radio Type: None Enter Function# or ESCAPE to exit... ----- This earlier 1989 version (2.01) supports the KC Tuner function This version of the PSK-1 will turn ON (slave operation), when the host TNC-2 is tuned ON ----- S/N P10809 *********************************************** * P a c C o m m P S K M o d e m * * PSK Firmware version 2.10 CSUM: 2A05 * * (C) 1990 Digital Signal Sys, 1991 PacComm * *********************************************** <1> Mode: Manchester (Satellite) <2> Modem: Out-of-Line (TNC's modem) <3> Joint/Split: Joint (VHF RX, VHF TX) <4> AFC: None (Provide no AFC outputs) <5> Mic-Click Sense: Active-Low <6> Clicks-per-Step: One <7> Maximum Step Rate: 2 per second <8> DCD Output Sense: Active-Low <9> RS232 Speed: 1200 8N1 <A> Help: Enter Function # or CONTROL-C or ESCAPE to exit... ----- This later 1990 version (2.10) removes the KC Tuner support and replaces it with a Help function. This version of the PSK-1 will NOT turn ON, when the host TNC-2 is tuned ON. Power ON function has to be separately performed with each modem. ===== Interesting discovery and behavior. Any thoughts? Greg w9gb

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[Fwd: FW: AMSAT-BB Digest, Vol 6, Issue 184 [Sec=Unclassified]]
by vk0kev＠ontoit.biz 01 Apr '11

01 Apr '11

I have been following this discussion with some interest. I too have experienced working AO-51 in areas where the footprint is over relatively low population areas. Despite being thrilled by my first contacts from VK4 (my home state) my enthusuiasm on AO-51 operation quickly wained due to a few "big gun" operators who seemed to consider AO-51 a private chat channel. Often passes would be completely monopolised by two or three operators leaving no gaps for other stations. Sadly when these "guns" were out of footprint there was seldom anybody to the north to contact. Down here in VK0 I'm pretty sure I'm the first to get the footprint and have noticed the same beahviour. Unless of course I call first (which I have done on only a few occassions). Being a "rare" stations has it's advatages! I guess the bottom line is to spend more time listening, have a little patience, courtesy and respect for other hams. This needs to apply to the "guns" as much as anybody else. Whilst there has been a lot of discussion about how to reign in the rogues surely the simplest solution is to ignore them? It's a practice I use in any pile-up and is an opportunity for people to change their operating behaviour. 73' Kevin Message: 2 Date: Fri, 01 Apr 2011 06:32:49 +1100 From: Tony Langdon <vk3jed(a)gmail.com> Subject: [amsat-bb] Re: More Echo Madness To: K5OE <k5oe(a)aol.com>, amsat-bb(a)amsat.org Message-ID: <4d94d6e8.9d7bdc0a.053d.2cdc(a)mx.google.com> Content-Type: text/plain; charset="us-ascii"; format=flowed I remember in the UO-14 days many late night passes, where I ended up talking to myself for an entire pass. If I got lucky, one or two others would show up and we'd have a ragchew for the entire pass (with long breaks for those breaking in). The biggest problems I've heard on the FM birds down this way are (1) long range cordless phones, there seems to be millions of these things in SE Asia - I'm assuming it's phones by the tempo of the speech, and (2) new operators who don't realise they're not hearing the 70cm downlinks on their vertical antennas, and accidentally stomp on the uplink. Unfortunately, due to the large distances here, there's often no one else within their simplex range to give them pointers. I have personally elmered a couple who I did find within simplex range, and got them on the birds successfully. I'm not so active on the satellites these days, but that's due to subtle lifestyle factors that brings the short passes at differing times of day into conflict with other things that happen here, rather than anything fundamental about the sats themselves. One of the things I notice here is that not only is the population density much lower, but there's none of the grid chasing down here. We do have satellite awards, but these can be completed with a modest amount of contacts (VK0 can be a challenge to work - it's the only VK call area I haven't worked). I've never understood the rationale behind increasing the pressure on an already limited resource by encouraging grid square chasing. One would have thought the FM birds should be the "WARC bands" of the satellite world. Keep the grid chasing to SSB/CW, where more operators can be supported (and maybe encourage a few to upgrade to SSB :) ). >I spent most of last year in Papua New Guinea (V29OE) and the only >satellite traffic I ever heard was on AO-51 V/U FM (VK's of >course). I never completed a QSO as I just could not make it with a >bad battery in my FT51R (less than a Watt) and a whip antenna. And the only P29s I've worked on the birds have been Americans who were working in PNG! :) Unfortunately, you weren't one of those I've worked. >The thing that really annoys me, though, is that I saw Drew's >posting, I wrote down the new uplink frequency, I had it in front of >me on a sticky note, and I still didn't connect the dots when I >couldn't hear myself in the downlink! I deserved to miss that grid :-) In the famous words of Homer Simpson... "DOH!" :D 73 de VK3JED / VK3IRL http://vkradio.com

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Android satellite tracking app
by George Henry 01 Apr '11

01 Apr '11

Looking for an Android tracking app that: Doesn't require GPS (which lots of tablets don't have); Has a world map (groundtrack and footprint) display instead of a sky watcher type display, and; Is available to download from someplace other than the Android Marketplace (which doesn't support most tablets, only phones). Does such a thing exist?? George, KA3HSW * Open in Google Docs Viewer * Open link in new tab * Open link in new window * Open link in new incognito window * * Download file * Copy link address * Edit PDF File on PDFescape.com

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Short notice plans from EK99xp this afternoon - ZF2AE/ZF8
by Adrian Engele 01 Apr '11

01 Apr '11

Fellow ops, I was originally not planning on getting on the satellites this afternoon but we are coming back early from our neighbor island trip. I will try to make the following passes: FO-29 @ 2153UTC AO-51 @ 22:11UTC assuming it is still on the end of March Schedule AO-07 @ 22:31 UTC. I will have some blockage after TCA and will only make half of the pass. 73, Adrian ZF2AE/ZF8

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