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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QUBCQLGAR6W4NYGDX6CUWP4BAVAQWECI/", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/", "message_id": "[email protected]", "message_id_hash": "QUBCQLGAR6W4NYGDX6CUWP4BAVAQWECI", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/3WIEZSGMO32TAU5SDYNPME34FNCTQA2G/", "sender": { "address": "jonny290 (a) gmail.com", "mailman_id": "bed0432ae6e64c0493fa6343553c3746", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/bed0432ae6e64c0493fa6343553c3746/emails/" }, "sender_name": "Jonny 290", "subject": "[amsat-bb] Re: Station not coming together - the full post (sorry\tfor repost, reply to this)", "date": "2007-03-07T05:01:02Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ITDBJQ2VKUZQGU5I5NLBPTX3DTMN3TE6/", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Bruce, Gould and Les,\n\nSincere thanks for your thoughts so far. I'll let this topic percolate for a\nbit, but I had to comment on one thing:\n\n<<<Unlike in HF, where the RF sometimes just gets through, here you're\ndealing\nwith the Hard Numbers, and they will crush you into silence.>>>\n\nTHIS is why I love satellite operation. It's a huge challenge, and the\nionosphere largely has NOTHING to do with it. No 'magic' involved. I know\nit's anathema to ye olde Amateur Radio meme of \"operating in a dim room with\na small transmitter\", but I am finding that this satellite station is the\ngreatest engineering challenge of my life, to date - and I'm going at it\n100% solo NOBODY in my area knows anything gives a rip about the birds. Yet.\n\n\n\nOn 3/6/07, Bruce Robertson <[email protected]> wrote:\n>\n> Quoting Jonny 290 <[email protected]>:\n>\n> > LONG LONG LONG post ahead.\n> >\n> > OK, the situation is: I'm building up a satellite station to get\n> > familiar\n> > with LEO sats and to get ready for the phase 3E fun to start soon.\n> > Here's my\n> > station, and I'll post my thoughts after that.\n> >\n> > The \"too long, didn't read\" version: I've built good antennas, fed them\n> > with\n> > good feedlines and into a supposedly good receiver, but I just can't\n> > keep\n> > solid copy on LEO birds, and cannot get a QSO. I am jealous of the\n> > \"Satellites worked with HT and 5/8 wave\" articles, and want to figure\n> > out\n> > what the weak link in my station is.\n> >\n> >\n> > RX path:\n> >\n> > Eggbeater II antenna mounted at 15 feet. This is built to the K5OE\n> > Eggbeater\n> > II spec (http://members.aol.com/k5oejerry/eggbeater2.htm) using RHCP\n> > but\n> > uses a 100 ohm phasing line using two 50 ohm coax lines done in\n> > parallel,\n> > used in a balanced configuration, instead of 93 ohm RG-62. Antenna was\n> > 'redesigned' in MMANA-GAL to match exactly 100 ohms and to use 6mm\n> > diameter\n> > copper tubing instead of AWG 12 house wire. It is peaked for SWR < 1.1\n> > at\n> > 436 MHz, and is less than 1.5 at 435.0 and 437.0.\n> >\n> > Our lot is lightly treed, but there is no wood (natural or otherwise)\n> > within\n> > six feet of this antenna. A good chunk of the sky, mainly northwesterly\n> > looking, is partially obscured by a large tree, but right now the leaves\n> > are\n> > off and it shouldn't kill the signal that much...should it?\n> >\n> > This antenna is the secondary antenna on this mast and is mounted on a\n> > 3\n> > foot PVC stand-off pipe. The primary antenna is a Diamond F22A mounted\n> > at\n> > approximately 18 feet. It has a 10 foot vertical element and three 1/4\n> > wave\n> > horizontal radials. It is not used in the satellite station but I wanted\n> > to\n> > describe it, in case it is interfering (I suspect it is.)\n> >\n> > Eggbeater is fed through29 feet of 213 spec coax (5.1 dB loss/500 MHZ)\n> > terminated in well done PL-259 connectors. I have verified this\n> > particular\n> > cable's loss at less than 2 dB at 432 MHz, using my Icom PCR-100's\n> > accurate\n> > S-meter and a known signal source.\n> >\n> > My latest upgrade: RX chain goes into a homebrew bypass relay / Ramsey\n> > preamp box (the relay is DPDT and switches the preamp in or out of the\n> > RX\n> > signal path). The preamp provides approximately 18 dB of gain when\n> > inserted\n> > and using a test signal around 432 MHz. It has proven somewhat\n> > beneficial,\n> > giving me 2-3 S-units advantage at certain points from the LO-19 CW\n> > beacon\n> > (Which I recently received at up to S9 with the preamp on a ~60 degree\n> > pass,\n> > a new record so far).\n>\n> Matt:\n>\n> Thanks for submitting your antenna system to the scrutiny of this list.\n> For\n> many of us, planning and organizing these systems are good fun. I have\n> some\n> direct experience that pertains to some part of your system; I hope those\n> with other experiences will concur or debate.\n>\n> As you probably already know, it is considered a requirement of satellite\n> work that a low noise preamp. be placed before your receiver, especially\n> on\n> 70cm. One measurement that indicates the quality of this is its gain, and\n> you have indicated the Ramsey unit's declared value in this dimension.\n> However, an equally important measurement of quality is the noise figure.\n> I\n> believe most advise that this be below 1 dB, and the lower the better. The\n> math on this issue is really very revealing, and I'll leave it to you, if\n> you're interested, to pursue it with Davidoff, _The Radio Amateur's\n> Satellite Handbook_. However, it's important to note that a high-gain\n> preamp with an inappropriate noise figure likely will do nothing to\n> improve\n> your reception of satellite signals.\n>\n> In hopes of getting an inexpensive preamp for my satellite work, I built\n> the 2m version of the Ramsey preamp you described. I quickly concluded\n> that\n> it didn't do what I wanted. Now that I own a mast-mounted ARR preamp., I\n> am\n> certain that the unit I built doesn't have the appropriate noise figure.\n> Now 2m is way less touchy in all this than 70cm, so I have to say that I\n> suspect your preamp. is simply not up to the task. I highly recommend you\n> buy a known quantity for this part of your system: Advanced Receiver\n> Research and SSB USA are both well-liked. Once you know what one of these\n> can do, homebrew to your heart's content until you get something that\n> performs as well or better. Then sell your commercial preamp on this list!\n>\n> Secondarily, it is very important that the preamp be as close to the\n> antenna as possible. That 2 dB of loss on the cable is killing you. You\n> can\n> effectively negate it by putting the preamp before it; but you never get\n> it\n> back if you put the preamp after it. Again, I recommend playing with the\n> simple formulae and seeing for yourself how the configurations of\n> equipment\n> are very important.\n>\n> I know mast-mounted preamps are a big pain; and I know bias tees are not\n> fun. But given your cable and your antenna, you don't have a choice, you\n> really don't.\n>\n> Finally, your antenna. This is one I would very much like to build myself;\n> it seems very carefully designed. However, due to its slightly complex\n> construction I have my doubts about using it as a first satellite antenna.\n> I have advocated elsewhere that everyone have on hand a simple 1/4 wave\n> vertical to use as a known-good antenna. Outside, tilted and in the clear,\n> it may well only pick up very little intelligible audio of an FM bird's\n> pass with an FM-only radio (a CW one will get the warbling tone quite\n> nicely), but it should quiet the radio a bit and give some general\n> indications of life. You should then expect your egg-beaters to be better.\n>\n> By using fixed antennas, you are, of course, limiting your gain. That\n> means\n> everything after your antenna has to be spotless: no 2 dB here, 2 dB\n> there.\n> Unlike in HF, where the RF sometimes just gets through, here you're\n> dealing\n> with the Hard Numbers, and they will crush you into silence.\n>\n> > Receivers:\n> > IC-208H dual band radio, rated at <0.18 uV for 12dB SINAD\n> > OR\n> > PCR-100 computer controlled receiver, rated at <0.34 uV for 12dB SINAD\n> >\n> > The TX setup is currently an IC-271 pushing from about 4 to 38 verified\n> > FM\n> > watts into a simple RHCP turnstile, recently built. It is mounted on a\n> > slightly shorter PVC mast about 10 feet away from the \"big mast\". It is\n> > the\n> > only antenna on this pole, and is fed through 27 feet of 213 spec coax.\n> > Peaked at 145.8 MHz with SWR less than 1.1 . I know the turnstile\n> > pattern\n> > has most gain directly overhead and has some shortages towards the\n> > horizon,\n> > but I have plenty of theoretical EIRP to get on the LEO sats, I believe,\n> > and\n> > I'm not worried about the TX path right now.\n>\n> Don't worry about the uplink. You're fine there.\n>\n> > I'm just not getting the signal strength and intelligibility that I\n> > expect\n> > from this setup. For example, there was a theoretically perfect SO-50\n> > ascending pass today at about 5:15 PM Central, 15 minutes plus duration\n> > and\n> > it peaked at almost 80 degrees elevation. I received the signal\n> > faintly\n> > starting at 2 degrees, and it steadily improved to a 'fluttering S3\" at\n> > about 8-10 degrees. I attempted to come back to a station that finished\n> > a\n> > QSO, because I thought it cleared - turns out,the signal DIED. I could\n> > just\n> > barely track it for the rest of the pass, even when it was almost\n> > directly\n> > overhead at less than 900 miles altitude. Gave up when it was five\n> > minutes\n> > before LOS, with no contact made.\n> >\n> > So, given my station description, what am I facing? Is my Eggbeater's\n> > 'overhead 10dB null' design killing it? I would think that, as designed,\n> > the\n> > greatly decreased path loss as the bird comes overhead should compensate\n> > for\n> > this shortage, and then some.\n> >\n> > As mentioned earlier, I'm also concerned that the Diamond F22's radials\n> > are\n> > destroying the radiation pattern of this antenna. I'm in a rent house\n> > and\n> > have to conserve masts as much as possible, but if it's killing me, I\n> > can\n> > move the satellite antennas to a ~12 foot PVC mast instead of trying to\n> > piggyback them on my metal vertical mast.I've copied beacons and\n> > various\n> > carriers from birds as low as 0.5 degrees, so I know the antenna 'gets\n> > out'\n> > okay at lower elevations. It's the high elevation periods that are\n> > disappointing me.\n>\n> I honestly don't think this is your first worry. It's all about the\n> preamp,\n> mate :-)\n>\n> > How does my IC-208H compare to more refined receivers? Is it too deaf?\n> > I've\n> > considered feeding my IC-735 HF radio with a 435 MHz receive converter.\n> > This\n> > would allow all mode 70cm reception with a very good radio (comments on\n> > the\n> > Hamtronics converter boxes would be great). I'd love any comments on\n> > the\n> > Hamtronics receive converters from those who have tried them out.\n>\n> This is super-great fun. I bought one of these when I started out and used\n> it with my IC-728. FO-29 is an amazing bird. Worth the price of admission.\n> One warning, though. Be sure the converter can do 435 MHz. Mine was 432\n> only, and I had to buy a new crystal for it. Alas, I sold it this summer\n> in\n> the Great Kenwood Purchase of 2006.\n>\n> > I'd appreciate any comments and advice from the great minds on this\n> > list.\n> > Thanks for taking the time to read up and give any advice or comments.\n> >\n>\n> No great mind; just a fellow-traveler.\n>\n> 73, Bruce\n> VE9QRP\n>\n", "attachments": [] }