September 2007 - AMSAT-BB - mailman.amsat.org

FO-29 sked Sep.21~Oct.21
by Mineo Wakita 20 Sep '07

20 Sep '07

UTC Sep. 21 03:00- 22 03:50- 23 None 24 03:45-, 05:31- 25 02:52-, 04:35- 26 03:40- 27 04:30 28 03:36- 29 02:43-, 04:25- 30 03:30-, 05:17- Oct. 1 None 2 03:27-, 05:12- 3 04:17- 4 None 5 04:12 6 03:18- 7 04:08- 8 03:15-, 05:00- 9 None 10 03:10-, 04:55- 11 04:00- 12 None 13 None 14 03:00-, 04:45- 15 None 16 04:40- 17 03:45- 18 02:52-, 04:35- 19 03:41- 20 02:47-, 04:31- 21 03:37-

1 0

Re: New Preamp
by k0vty＠juno.com 20 Sep '07

20 Sep '07

Thanks to Dom and Ed. >From you two gentlemen, a few words please on field proofing antenna systems using sun noise and a EME signal should add nicely to this discussion. Joe K0VTY Amsat #860 =========================== On Tue, 18 Sep 2007 22:18:32 -0800 Edward Cole <kl7uw(a)acsalaska.net> writes: > Thanks Domenico, > > I was about to insert my comments to Gary. > > I would challenge his belief that manufacturers achieve better NF, > as > the evidence shows the contrary. If you can show me a commercial > radio with 0.5 dBNF on the 150-MHz band, then I would love to know > it. Almost all commercial two-way radios have a sensitivity of > about > 0.15 to 0.25 uV at 15-KHz BW. This will result in about MDS of > > -124 dBm and a NF well over 3-dB. Commercial equipment is designed > > for immunity from high RF/noise urban environments and that trades > off noise figure in the process (commercial radios are designed for > > strong signals - hams* are the crazy weak-signal nuts!) *and a few > > weird radio astronomers, NASA engineers, .... > > My 2m eme station has a sensitivity of -147.5 dBm with 2.2 KHz SSB > BW; that is a receiver temp= 58K or NF=0.79 dB. This is assuming > 0.5 > dB loss ahead of the preamp. A good ham radio VHF satellite > receiver > will be about 100K or NF=1.2 dB with a sensitivity of -145 dBm at > 2.2 > KHz SSB BW. > > Now if you add sky noise, industrial noise, and antenna noise, the > system sensitivity (Te) will suffer: Te = Tr+Tsky+Tant+Tindustrial > e.g. using Tsky = 210K, Tant = 45K (very good low sidelobe eme class > > antenna), and no man-made noise (my situation): > Te = 313K, and Pn = -140 dBm (note no antenna gain is included in > this number) > so my environment cost me about 7.5 dB in sensitivity. Obviously if > > you have several hundred degrees of industrial noise then things do > > get worse which will minimize the advantage of the low NF > preamp. Here the use of well engineered filters may help. Preamps > > with better strong signal characteristics (though a bit higher NF) > may also help. > > Tradeoffs of NF vs gain are made in low noise amplifiers (preamps) > usually in favor of low NF. As long as there is sufficient gain to > overcome the higher NF of the following receiver the overall system > > will benefit. Usually this means a min of about 16 dB gain. This > will lower the noise contribution of the following circuits by > 1/40. > > For the majority, a good low-noise preamp mounted at the antenna > will > result in significant increase in hearing ability. > caveat emptor > > 73 Ed > > At 12:33 PM 9/18/2007, i8cvs wrote: > >----- Original Message ----- > >From: "Gary Memory" <gmemory(a)tks-net.com> > >To: "'i8cvs'" <domenico.i8cvs(a)tin.it>; "'Amsat-BB'" > <amsat-bb(a)amsat.org> > >Sent: Tuesday, September 18, 2007 8:26 PM > >Subject: RE: [amsat-bb] Re: New Preamp > > > > > Domenico: > > > > > > Greetings once again. You sent me a note some time ago that > helped to > > > amplify my current belief concerning SNR. > > > > > > I am willing to bet two things. > > > > > > First, it is difficult (not impossible, just difficult) to > obtain a better > > > front end noise figure than what the original receiver > manufacturer has > > > created. > > > >Hi Gary, N7BRJ/DA1BRJ > > > >This is why we use a low noise preamplifiers antenna mounted. > >Make an example: > >The noise figure of a commercial receiver like a TS-736 is about > NF=6.5 dB > >corresponding to an equivalent noise temperature T1= 1005 kelvin > >If you add a low noise preamplifier antenna mounted with a NF= 0.5 > dB and > >if the overall noise figure of the system is degradated to NF= 0.7 > dB > >corresponding to T2 = 51 kelvin then using the same antenna the > improvement > >of S/N using the above preamplifier is: 10 log (1005/51) = 13 > dB > > > 10 > > > > Almost certainly the addition of an outboard amp will add more > > > noise. And this is not always a bad thing. > > > >In the above example the more noise that you see on your S-meter is > only > >apparent because the gain of the system probably is too great but > you can > >reduce the noise reading of the S-meter without reducing the S/N > ratio > >adding an attenuator and this is particularly easy to do if you use > a > >preamplifier + downconverter + attenuator + IF receiver > > > > > A preamp can be a great > > > addition despite the addition of more noise. > > > >If you get more noise degrading the S/N it meens only that the NF > of your > >preamplifier is greater then the NF of your receiver or its gain is > too low. > > > > > But then you get into a curve > > > of cost vs true value of gain. Is it worth it? Maybe so. > > > >Adding a low noise preamplifier with the capability of improving > the S/N > >ratio is always wortwhile. > > > > > Second, it is very unlikely that maximum signal strength will be > at the > > > same > > > point as maximum signal to noise ratio (SNR). > > > >The best noise figure NF of a preamplifier cannot correspond to the > maximum > >gain as the S-parameters of a device for the lowest NF are > showing. > > > > > Again, maybe this is not a > > > bad thing in any one individual case. Almost certainly the best > SNR will > > > be > > > at a point of gain somewhat less than maximum. > > > >The important of the point is that even if the lowest noise factor > F1 > >do not correspond to the maximum gain the gain G1 obtained from it > be > >sufficient to get a satisfactory overall noise factor Ft of the > system as > >the formula for more stages in series is showing: > > > > F2-1 F3-1 > >Ft = F1 + --------+ --------- + .................. > > G1 G1xG2 > > > > > I work with receivers and preamps that cost dozens of thousands > of > > > dollars. > > > Cost and receive noise figure is almost a logarithmic curve. > And it seems > > > that only with the very best front ends are SNR and gain at the > same > > > point. > > > >This is not strictly mandatory for as Radio Amateurs. > > > > > > > > Once you get the best receiver, coax and antenna you can afford, > that is > > > all > > > you can do....which seems like a dumb and obvious thing to say. > Beyond > > > that, true magic is hard to come by. And I am not knocking the > preamp. > > > Again, I own and use them all the time. > > > >Once I get the best receiver and the best antenna I must reduce the > thermal > >noise of the coax cable wich noise factor is F1 in the above > formula so that > >to improve the S/N ratio I have to add a low noise preamplifier in > F1 with > >the maximum possible gain in G1 > > > > > > 73! > > > > > > Gary, N7BRJ/DA1BRJ > > > > >Best 73" de > > > >i8CVS Domenico > > > > > > > >_______________________________________________ > >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 > > 73, > Ed - KL7UW > ====================================== > BP40IQ 50-MHz - 10-GHz www.kl7uw.com > 144-EME: FT-847, mgf-1801, 4x-xpol-20, 185w > DUBUS Magazine USA Rep dubususa(a)hotmail.com > ====================================== > > _______________________________________________ > 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 > >

4 3

QSL Cards
by Clint Bradford 20 Sep '07

20 Sep '07

Anyone have a favorite QSL card printer...one with the AMSAT logo already ready to print? Clint Bradford, K6LCS / KAF3359 909-241-7666

5 4

More on the preamp
by Bob Stewart 19 Sep '07

19 Sep '07

I guess I'm being a bit noisy lately, but I'm kinda excited about the results I'm getting from the preamp. I switched the turnstiles out and put the crossed moxons back in the attic (it's a walk-in attic) and I managed a couple of contacts in the West at just over 10 degrees elevation on AO-27. I heard some of the guys trying to rustle up some contacts down to maybe 7 degrees. Good stuff! Bob

1 0

REMINDER
by Martha 19 Sep '07

19 Sep '07

A reminder to make your room reservations for the 2007 AMSAT Space Symposium in Pittsburgh as soon as possible.Any rooms that have not been reserved by October 8th will be released to the hotel. For the reservation code, go to the AMSAT website and click on the left hand side - AMSAT Symposium. If you have any problems making a reservation, please call me (301-589-6062). -- 73- Martha

1 0

Re: USB to RS232 Conv
by George Henry 19 Sep '07

19 Sep '07

Unfortunately, I really don't know. I put out a request on the RTTY list, and the only response I've received so far is for the Conceptronics brand, model CCSERU. The BAFO unit I have seems to work okay. The critical factor for use with SatPC32 is that it properly recognizes the CTS signal. You may also need to check that Flow Control for the serial port created for your adapter is set to "Hardware". George, KA3HSW ----- Original Message ----- From: "Stan,WA1ECF" <stanwa1ecf(a)verizon.net> To: <ka3hsw(a)earthlink.net> Sent: Sunday, September 16, 2007 11:35 AM Subject: USB to RS232 Conv > Can you tell us what brands are compatible with SatPC32 ? > > Thanks Stan, W1LE >

3 2

AMSAT Awards
by Bruce 19 Sep '07

19 Sep '07

Awards this week are: We would like to welcome the following to the satellite community. They have made their first satellite contact and are now members of the AMSAT Satellite Communicators Club. Richard Silva, WA6ES AMSAT Communication Achievement Award Jeffery Thomas, K7WIN, #454 Douglas Papay, KD8CAO, #455 South Africa AMSAT Communication Achievement Award Jeffery Thomas, K7WIN, #US112 Douglas Papay, KD8CAO, #US113 To see all the awards visit http://www.amsat.org or http://www.amsatnet.com Bruce Paige, KK5DO AMSAT Director Contests and Awards ARRL Awards Manager (WAS, 5BWAS, VUCC), VE Houston AMSAT Net - Wed 0100z on W0KIE Intelsat Americas, T1, 6.8Mhz Also streaming MP3 at http://www.amsatnet.com

1 0

Fw: New Secretary for the IARU--Region 2
by Andrew Glasbrenner 18 Sep '07

18 Sep '07

Just saw this on another list, congratulations Ramon! For those who don't know, Ramon is an active satellite op, goes on many dxpeditions taking sat gear, and is an all around friend of AMSAT. 73, Drew KO4MA > Ramon Santoyo, XE1KK, was just elected to the new position of the > Secretary for the IARU---Region 2. I hope with his help things can improve > in the issure of licensure and operation in countries south of the > border...Who knows??? de YLZ

1 0

G5400 meter lamp mod
by charter 18 Sep '07

18 Sep '07

Hello...does any one have a copy of replacing meter lamps with LED's. Any help appreciated. Tks Bruce ke0lx Amsat #30873

2 1

Re: Subject: TS 790a 70cm. display
by Mark L. Hammond 18 Sep '07

18 Sep '07

Hi Scott, There are 2 small bulbs on the SUB band side of the TS-790--that is what you mean, right? The 70cm can be set to MAIN or SUB...the SUB is on the RIGHT side of the rig. I've had to replace the little bulbs in there several times. I found small 12V bulbs at Radio Shack and spliced them in...it's not a horrible task by any means. There are --------------------------- Date: Mon, 17 Sep 2007 23:07:24 -0700 From: scott smith <ve6itv(a)shaw.ca> Subject: [amsat-bb] TS 790a 70cm. display To: amsat <amsat-bb(a)amsat.org> Message-ID: <000601c7f9ba$321c0980$e8ec4118@VE6ITV> Content-Type: text/plain; charset="iso-8859-1" Hi, for some reason (maybe old age) The 70cm display does not work. I have done a full reset but to no availe. Has anyone had this problem happen to them?, is there something i have not checked?, or should i just send it to Kenwood to fix or replace the diplay. Any help appreciated. 73 de ve6itv Scott -- Mark L. Hammond [N8MH]

1 0