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#1
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weatherfax
So I have a laptop and a receiver (Yaesu) that covers the frequencies
from 2 Mhz to 30 Mhz. What kind of black box and software do I need to display weather fax maps on my laptop screen ? I want to use that on my 26' trailerable boat during a cruise, it will not be a permanent installation. Thanks in advance, Klaus |
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#2
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weatherfax
For starters, ask around locally. IIRC, we didn't have terribly good
luck with Australian weatherfax crossing the Tasman -- I don't remember why, but my memory is that it wasn't useful. We did use weatherfax across the Pacific and the Atlantic, so it probably wasn't our installation that was the problem. That was in 1997, so it may be different now. For equipment, at the low end, a demodulator that plugs into the headphone jack on the receiver and into the serial port on your laptop and software to run it. West sells one for US$200+, but there are others, cheaper (do a Web Search -- I don't know about Oz vendors). This will do fine if you're relatively close to the transmitter (100s of miles) and have limited needs. It's also possible to plug the headphone output into the sound card on your computer, with suitable software -- I've never used this, but I suspect the bandwidth is fairly low. At the high end, a demodulator that uses a PCMCIA slot, a USB, or a parallel port on the computer (much higher data rate, hence better detail) and some sort of image processing program (Corel PhotoPaint, Adobe PhotoShop, etc.). Fairly sophisticated image processing is helpful when you're getting a fair amount of static with your image -- it can pull a usable picture out of a mess. Make sure you have a good antenna installation. SSB transceivers have sophisticated antenna tuners which make the antenna look like a different length when you change bands. I don't think the antenna on the radio will do the job so you'll probably need insulators in the backstay. A good antenna also includes a good ground -- at radio frequencies, this is not just a wire, but a copper strip maybe 4" wide going down to your keel (if the keel is outside the glass) or a large area of copper screen just inside the glass below the waterline. Bonding all the metal on board, including life lines, rail, prop shaft, engine, and keel, will help and is a good idea for other reasons. For starters, you'll know you're in reasonable shape when you can hear a really solid signal from the weatherfax station of your choice -- it's a very characteristic sound as it scans across the page. Operate the rig a number of times ashore before you set out. As you probably know, the faxes come only a few times a day and the computer has to be set up and running before the transmission starts -- I wouldn't count on using the computer for anything else while it's receiving one. Also look to your electrical system -- you'll have to run the receiver and computer while receiving, and, if you want to set it up to receive while you're sleeping, even longer. This may tax the battery on a 26' boat. Jim Woodward www.mvfintry.com Klaus wrote in message ... So I have a laptop and a receiver (Yaesu) that covers the frequencies from 2 Mhz to 30 Mhz. What kind of black box and software do I need to display weather fax maps on my laptop screen ? I want to use that on my 26' trailerable boat during a cruise, it will not be a permanent installation. Thanks in advance, Klaus |
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#3
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weatherfax
Software such as JVcomm will probably do the job for you. You can get a
demo version of the software from http://www.jvcomm.de/indexe.html The software utilizes the soundcard to receive fax transmissions. The demo version will imprint "demo" on the received faxes, but other than that works well. I had problems with JVcomm stair-stepping the faxes and could never get it resolved. I now use the SailMail companion program GetFax, but that requires a Pactor HF modem which is probably overkill for you at $800. -- Geoff Klaus wrote in news:3F39F8C3.C392DD12 @curtin.edu.au: So I have a laptop and a receiver (Yaesu) that covers the frequencies from 2 Mhz to 30 Mhz. What kind of black box and software do I need to display weather fax maps on my laptop screen ? I want to use that on my 26' trailerable boat during a cruise, it will not be a permanent installation. Thanks in advance, Klaus |
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#4
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weatherfax
Thanks Jim, for you very informative reply. I will do some more research on the lines you suggested.
Klaus Jim Woodward wrote: For starters, ask around locally. IIRC, we didn't have terribly good luck with Australian weatherfax crossing the Tasman -- I don't remember why, but my memory is that it wasn't useful. We did use weatherfax across the Pacific and the Atlantic, so it probably wasn't our installation that was the problem. That was in 1997, so it may be different now. For equipment, at the low end, a demodulator that plugs into the headphone jack on the receiver and into the serial port on your laptop and software to run it. West sells one for US$200+, but there are others, cheaper (do a Web Search -- I don't know about Oz vendors). This will do fine if you're relatively close to the transmitter (100s of miles) and have limited needs. It's also possible to plug the headphone output into the sound card on your computer, with suitable software -- I've never used this, but I suspect the bandwidth is fairly low. At the high end, a demodulator that uses a PCMCIA slot, a USB, or a parallel port on the computer (much higher data rate, hence better detail) and some sort of image processing program (Corel PhotoPaint, Adobe PhotoShop, etc.). Fairly sophisticated image processing is helpful when you're getting a fair amount of static with your image -- it can pull a usable picture out of a mess. Make sure you have a good antenna installation. SSB transceivers have sophisticated antenna tuners which make the antenna look like a different length when you change bands. I don't think the antenna on the radio will do the job so you'll probably need insulators in the backstay. A good antenna also includes a good ground -- at radio frequencies, this is not just a wire, but a copper strip maybe 4" wide going down to your keel (if the keel is outside the glass) or a large area of copper screen just inside the glass below the waterline. Bonding all the metal on board, including life lines, rail, prop shaft, engine, and keel, will help and is a good idea for other reasons. For starters, you'll know you're in reasonable shape when you can hear a really solid signal from the weatherfax station of your choice -- it's a very characteristic sound as it scans across the page. Operate the rig a number of times ashore before you set out. As you probably know, the faxes come only a few times a day and the computer has to be set up and running before the transmission starts -- I wouldn't count on using the computer for anything else while it's receiving one. Also look to your electrical system -- you'll have to run the receiver and computer while receiving, and, if you want to set it up to receive while you're sleeping, even longer. This may tax the battery on a 26' boat. Jim Woodward www.mvfintry.com Klaus wrote in message ... So I have a laptop and a receiver (Yaesu) that covers the frequencies from 2 Mhz to 30 Mhz. What kind of black box and software do I need to display weather fax maps on my laptop screen ? I want to use that on my 26' trailerable boat during a cruise, it will not be a permanent installation. Thanks in advance, Klaus |
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#5
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weatherfax ANTENNA
Klaus, Jim's advice is sound for a SSB install, but a good antenna for your
little installation is to simply run a wire from the receiver's antenna connection to a convenient point somewhere on the standing rigging. I use a stout alligator clip to the backstay or backstay chain plate. Make a great RECEIVE antenna! You don't need to isolate the backstay with insulators for a receive antenna.....as you've got a damn elaborate high performance RECEIVE antenna with all of the standing rigging as it is! My receiver lights up like a Christmas tree on ALL bands. While in the MARINA, however, there is so much stray current floating around that the noise level is s-9 PLUS......but out away from the marina it's pretty amazing. Keep this in mind during your testing. You might try a ground to keel bolts, inboard engine, tanks, or whatever ....to improve performance, but on my present boat, a MacGregor 26x (with no seawater or capacitive ground at all,) it still works very well. The BEST performance I've ever seen for a receive-only antenna was on my old keelboat....with the standing rigging (mast) solidly grounded to the keel bolts. This is the most quiet (as far as noise) antenna for HF receive I've ever played with. Many short-wave listeners use this trick on land as well. BTW....I've not tried any of them, but I hear there are some FREEWARE soundcard weatherfax programs out there you may want to search around for....... Fair winds......Joe S/V "South of 80" Charlestown, MD "Jim Woodward" wrote in message om... For starters, ask around locally. IIRC, we didn't have terribly good luck with Australian weatherfax crossing the Tasman -- I don't remember why, but my memory is that it wasn't useful. We did use weatherfax across the Pacific and the Atlantic, so it probably wasn't our installation that was the problem. That was in 1997, so it may be different now. For equipment, at the low end, a demodulator that plugs into the headphone jack on the receiver and into the serial port on your laptop and software to run it. West sells one for US$200+, but there are others, cheaper (do a Web Search -- I don't know about Oz vendors). This will do fine if you're relatively close to the transmitter (100s of miles) and have limited needs. It's also possible to plug the headphone output into the sound card on your computer, with suitable software -- I've never used this, but I suspect the bandwidth is fairly low. At the high end, a demodulator that uses a PCMCIA slot, a USB, or a parallel port on the computer (much higher data rate, hence better detail) and some sort of image processing program (Corel PhotoPaint, Adobe PhotoShop, etc.). Fairly sophisticated image processing is helpful when you're getting a fair amount of static with your image -- it can pull a usable picture out of a mess. Make sure you have a good antenna installation. SSB transceivers have sophisticated antenna tuners which make the antenna look like a different length when you change bands. I don't think the antenna on the radio will do the job so you'll probably need insulators in the backstay. A good antenna also includes a good ground -- at radio frequencies, this is not just a wire, but a copper strip maybe 4" wide going down to your keel (if the keel is outside the glass) or a large area of copper screen just inside the glass below the waterline. Bonding all the metal on board, including life lines, rail, prop shaft, engine, and keel, will help and is a good idea for other reasons. For starters, you'll know you're in reasonable shape when you can hear a really solid signal from the weatherfax station of your choice -- it's a very characteristic sound as it scans across the page. Operate the rig a number of times ashore before you set out. As you probably know, the faxes come only a few times a day and the computer has to be set up and running before the transmission starts -- I wouldn't count on using the computer for anything else while it's receiving one. Also look to your electrical system -- you'll have to run the receiver and computer while receiving, and, if you want to set it up to receive while you're sleeping, even longer. This may tax the battery on a 26' boat. Jim Woodward www.mvfintry.com Klaus wrote in message ... So I have a laptop and a receiver (Yaesu) that covers the frequencies from 2 Mhz to 30 Mhz. What kind of black box and software do I need to display weather fax maps on my laptop screen ? I want to use that on my 26' trailerable boat during a cruise, it will not be a permanent installation. Thanks in advance, Klaus |
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#6
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weatherfax ANTENNA
I'm not sure I understand. You got good antenna performance with the
antenna wire connected to the standing rigging and the mast solidly grounded to the keel (as it should be)? That goes against all I know about radio -- that antenna is antenna and ground is ground and they must be separate. I might go so far as to suggest that if your standing rigging works well as an antenna that it's not well grounded and is therefore asking for trouble with lightning. Keep in mind as well that weatherfax is not voice radio. Many of the voice stations on MF radio operate with large power and directional antennas to make them heard in specific areas. Weatherfax stations tend to be lower power and broad antenna patterns. Hearing lots of voices on MF doesn't necessarily mean you'll be able to recieve good weatherfax. Jim Woodward www.mvfintry.com "JAD" wrote in message ... Klaus, Jim's advice is sound for a SSB install, but a good antenna for your little installation is to simply run a wire from the receiver's antenna connection to a convenient point somewhere on the standing rigging. I use a stout alligator clip to the backstay or backstay chain plate. Make a great RECEIVE antenna! You don't need to isolate the backstay with insulators for a receive antenna.....as you've got a damn elaborate high performance RECEIVE antenna with all of the standing rigging as it is! My receiver lights up like a Christmas tree on ALL bands. While in the MARINA, however, there is so much stray current floating around that the noise level is s-9 PLUS......but out away from the marina it's pretty amazing. Keep this in mind during your testing. You might try a ground to keel bolts, inboard engine, tanks, or whatever ...to improve performance, but on my present boat, a MacGregor 26x (with no seawater or capacitive ground at all,) it still works very well. The BEST performance I've ever seen for a receive-only antenna was on my old keelboat....with the standing rigging (mast) solidly grounded to the keel bolts. This is the most quiet (as far as noise) antenna for HF receive I've ever played with. Many short-wave listeners use this trick on land as well. BTW....I've not tried any of them, but I hear there are some FREEWARE soundcard weatherfax programs out there you may want to search around for....... Fair winds......Joe S/V "South of 80" Charlestown, MD "Jim Woodward" wrote in message om... For starters, ask around locally. IIRC, we didn't have terribly good luck with Australian weatherfax crossing the Tasman -- I don't remember why, but my memory is that it wasn't useful. We did use weatherfax across the Pacific and the Atlantic, so it probably wasn't our installation that was the problem. That was in 1997, so it may be different now. For equipment, at the low end, a demodulator that plugs into the headphone jack on the receiver and into the serial port on your laptop and software to run it. West sells one for US$200+, but there are others, cheaper (do a Web Search -- I don't know about Oz vendors). This will do fine if you're relatively close to the transmitter (100s of miles) and have limited needs. It's also possible to plug the headphone output into the sound card on your computer, with suitable software -- I've never used this, but I suspect the bandwidth is fairly low. At the high end, a demodulator that uses a PCMCIA slot, a USB, or a parallel port on the computer (much higher data rate, hence better detail) and some sort of image processing program (Corel PhotoPaint, Adobe PhotoShop, etc.). Fairly sophisticated image processing is helpful when you're getting a fair amount of static with your image -- it can pull a usable picture out of a mess. Make sure you have a good antenna installation. SSB transceivers have sophisticated antenna tuners which make the antenna look like a different length when you change bands. I don't think the antenna on the radio will do the job so you'll probably need insulators in the backstay. A good antenna also includes a good ground -- at radio frequencies, this is not just a wire, but a copper strip maybe 4" wide going down to your keel (if the keel is outside the glass) or a large area of copper screen just inside the glass below the waterline. Bonding all the metal on board, including life lines, rail, prop shaft, engine, and keel, will help and is a good idea for other reasons. For starters, you'll know you're in reasonable shape when you can hear a really solid signal from the weatherfax station of your choice -- it's a very characteristic sound as it scans across the page. Operate the rig a number of times ashore before you set out. As you probably know, the faxes come only a few times a day and the computer has to be set up and running before the transmission starts -- I wouldn't count on using the computer for anything else while it's receiving one. Also look to your electrical system -- you'll have to run the receiver and computer while receiving, and, if you want to set it up to receive while you're sleeping, even longer. This may tax the battery on a 26' boat. Jim Woodward www.mvfintry.com Klaus wrote in message ... So I have a laptop and a receiver (Yaesu) that covers the frequencies from 2 Mhz to 30 Mhz. What kind of black box and software do I need to display weather fax maps on my laptop screen ? I want to use that on my 26' trailerable boat during a cruise, it will not be a permanent installation. Thanks in advance, Klaus |
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#7
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weatherfax ANTENNA
Jim, in answer to question #1...we are talking a simple RECEIVE antenna
here. Insulated backstays and whips are used with HF-SSB TRANSCEIVERS. In another vein, there are a whole slew of boaters here (mostly hams for recreational use) that "load up" the ENTIRE standing rigging (on fiberglass sailboats) against a good ground for a really fine antenna. No good for offshore where salt water may ground the rig at the chainplates....or where someone my grab something during TX.....but it does work and it works well (again, for RECREATIONAL HF use.) Shoot...there was a thread here not long ago about guys loading the entire standing rigging against the lifelines and toe rail......and THAT supposedly works, too. Building a good capacitive ground can be difficult on some boats.....but sure is the best choice. Any boat doing serious offshore cruising should have a properly insulated backstay or large whip for an HF antenna. As far a question #2 is concerned....see Meindert's post above. The ARRL handbook presents some antenna designs....but not ALL of them...and not all of the GOOD ones....... I can tell you, as in my original post...connecting a receiver to my old boat GROUNDED (to keel bolts....lead keel....encapsulated somewhat,) standing rigging, produced one of the quietest, best performing receive antennas I have ever played with. I did not ground the rig on purpose for this arrangement....is just the way it was. In the marina...where stray currents and noise abound....the receiver worked like a champ on ALL HF bands. And...to the guy who says receiving broadcast stations and HF telefax is different......I say..NUTZ! If you have a good antenna, the signal is there....AND there is good signal / noise ratio...you should receive quality faxes. Simple as that. Knowing the wefax broadcast schedule and location / frequencies of the stations would help........ Fair winds....'73 Joe "Jim Woodward" wrote in message om... OK. I know just enough to be dangerous here. In an effort to learn enough to be even more dangerous, I ask two questions: 1) If this arrangement yields a satisfactory signal and a better SNR, then why does virtually every crusing boat use an insulated backstay or a whip? Remember that we're talking about weatherfax, which is often difficult to receive. 2) I note that the ARRL Antenna Handbook devotes a full chapter to loops. All are carefully isolated from ground at all corners -- the ground comes after the matching network. Am I missing something? Jim Woodward www.mvfintry.com "Meindert Sprang" wrote in message ... In this configuration, the mast and standing rigging work as a magnetic loop antenna, which *should* have something you would call a short-circuit to ground in order to close the loop. A loop antenna picks up the magnetic component of a radio signal and is far less suscebtible to noise than a whip antenna (single isolated backstay too). Meindert |
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#8
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weatherfax ANTENNA
Joe:
Please take this OK -- there are parts of boating in which I consider myself expert -- but this isn't one of them. I flunked out of the EE school at Cornell a long time ago, so I'm really trying to learn here, not be argumentative. I have two questions about what you wrote below: First, am I correct that as far as choice of antenna is concerned, receiving and transmitting are the same problem -- an antenna that receives well will transmit well, and vice versa? If so, I don't understand why you start off with, "...we are talking about a simple RECEIVE antenna here." If you're trying to pick a weak signal out of the noise, I should think you'd want as good an antenna as possible. Which brings me to the second question, or perhaps I should say "objection" to your comment. My experience with receiving weatherfax is considerable -- in several oceans, from many different stations, on a daily basis. It was all in 1995-98, which, IIRC was a low sunspot year. We had both an insulated backstay on an 82' mast and a 23' whip and a lot of well bonded copper screen for the ground under a Furuno 1502. The weatherfax stations were never as loud as medium frequency broadcast stations and were often much more difficult to copy successfully. Now, I can't speak directly to how good our installation was -- a professional did it, but that might be good and might be bad, so all I can say is that we did talk to people all over the Pacific with no problem. Now for a question on which I am soliciting opionions as widely as I can. We're going to have SSB on Fintry (as well as Inmarsat C and, probably, one of the low orbit services -- Iridium or one of its cousins.) The usual choice would be a tall whip hung top of the wheelhouse about six feet from the mast. We could also do a long wire from the jackstaff on the bow to the top of the mast -- 44 feet at about a 20 degree angle from horizontal. Which would you chose and why? Thanks, Jim Woodward www.mvfintry.com "JAD" wrote in message ... Jim, in answer to question #1...we are talking a simple RECEIVE antenna here. Insulated backstays and whips are used with HF-SSB TRANSCEIVERS. In another vein, there are a whole slew of boaters here (mostly hams for recreational use) that "load up" the ENTIRE standing rigging (on fiberglass sailboats) against a good ground for a really fine antenna. No good for offshore where salt water may ground the rig at the chainplates....or where someone my grab something during TX.....but it does work and it works well (again, for RECREATIONAL HF use.) Shoot...there was a thread here not long ago about guys loading the entire standing rigging against the lifelines and toe rail......and THAT supposedly works, too. Building a good capacitive ground can be difficult on some boats.....but sure is the best choice. Any boat doing serious offshore cruising should have a properly insulated backstay or large whip for an HF antenna. As far a question #2 is concerned....see Meindert's post above. The ARRL handbook presents some antenna designs....but not ALL of them...and not all of the GOOD ones....... I can tell you, as in my original post...connecting a receiver to my old boat GROUNDED (to keel bolts....lead keel....encapsulated somewhat,) standing rigging, produced one of the quietest, best performing receive antennas I have ever played with. I did not ground the rig on purpose for this arrangement....is just the way it was. In the marina...where stray currents and noise abound....the receiver worked like a champ on ALL HF bands. And...to the guy who says receiving broadcast stations and HF telefax is different......I say..NUTZ! If you have a good antenna, the signal is there....AND there is good signal / noise ratio...you should receive quality faxes. Simple as that. Knowing the wefax broadcast schedule and location / frequencies of the stations would help........ Fair winds....'73 Joe "Jim Woodward" wrote in message om... OK. I know just enough to be dangerous here. In an effort to learn enough to be even more dangerous, I ask two questions: 1) If this arrangement yields a satisfactory signal and a better SNR, then why does virtually every crusing boat use an insulated backstay or a whip? Remember that we're talking about weatherfax, which is often difficult to receive. 2) I note that the ARRL Antenna Handbook devotes a full chapter to loops. All are carefully isolated from ground at all corners -- the ground comes after the matching network. Am I missing something? Jim Woodward www.mvfintry.com "Meindert Sprang" wrote in message ... In this configuration, the mast and standing rigging work as a magnetic loop antenna, which *should* have something you would call a short-circuit to ground in order to close the loop. A loop antenna picks up the magnetic component of a radio signal and is far less suscebtible to noise than a whip antenna (single isolated backstay too). Meindert |
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#9
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YOUR "trawler" HF ANTENNA
Jim, first off, no argument intended! Just discussion! Perhaps my use of
caps???? Anyway, my original post was to answer the guy's question about a simple receiving antenna for his weatherfax on a small sailboat...thus my comments on my experience with receive ONLY antennas. YES....receive only antennas and antennas that are required to transmit AND receive are different. More on this in a moment... As to the fact that broadcast stations were easier to copy then weatherfax stations at THAT given time, location, propagation, and goodness knows other factors....there is no surprise to me....BECAUSE of so many factors involved. I'll be willing to say that the transmitter power of those fax stations was FAR less than the comparable broadcast stations....but that would only be ONE factor describing your reception at that time, location, propagation etc... See where I am going? Impossible to predict everything, or explain everything in long-distance radio. By the way, FINTRY is one gorgeous boat! I had a look at her on your site to see where (I) would put an HF antenna. Here's what (little) I know as a sailor: First....your boat looks like a trawler...a general description of this style boat, that has become VERY popular with serious motor-cruisers as of late. You are going to find many other folks with HF stations on this style boat...and I would sure get in touch with some of these people to find out what THEY are using. I'll bet most use a WHIP antenna.....but the true rule-of-thumb for an HF antenna is to go as LONG as possible to get the best performance! MY GUESS would be to go with the (insulated) WIRE for the reason of LENGTH alone.....but this wire at 20 degrees off of the horizon might not give you all of the "local" (50-200 mile) performance you might desire, due to polarity being mostly horizontal, and MOST other marine HF stations antennas out there being polarized somewhat vertical. Someone (hopefully from EXPERIENCE) may comment on NVIS and other factors to support / poo-poo my thoughts here....PLEASE DO! That is why I titled the post that way....hopefully other "trawler" style boaters will contribute something. The BEST signal I have ever heard coming from a boat (given the distance and propagation conditions at the time,) was from a STEEL sailboat with a 33ft !!!??? whip off of the transom, according to the operator. 33ft whip? Who makes such a beast....I've never seen or found them advertised. BUT...a BIG doggone whip well supported up on that wheelhouse might be the ticket! NOT the little 23ft whips commonly available.... It seems that you know something about a proper capacitive ground, and it's ABSOLUTE NECESSITY for a good TRANSMIT signal....she's a WOODEN boat, eh? Build the most elaborate ground you can, with AS MUCH area below the waterline (and bond the engine, tanks, metal through-hulls ad nauseum) as you can. Whatever long antenna you choose, the ground will be the MOST IMPORTANT factor in signal output besides the transmitter and antenna tuner. Take the ground stud of the radio itself to some point in the ground with a wide copper foil (as well as the tuner,).....the tuner should be as close to the FEED POINT of the antenna as possible. Bring AS MUCH of the ground complex to the ground of the tuner as possible, using multiple legs of copper if need be....with the tuner as the "apex." Steel yachties have it easy....and often have the best signals on the water....a near perfect ground with the whole damn hull for signal to "push against." LEARN TO USE the antenna tuner properly. MOST of them will bypass the "tune" function in some way....most common is to cut the power to the tuner and then turn it back "on". (THIS circuit breaker goes separately right next to the radio operation position, if the electrical panel is elsewhere!) Puts the tuner into a "bypass" mode in which the transceiver is connected directly to the antenna. Try this for reception when tuning across different bands looking for something. That way, you are not tuned to only the last frequency in use....to the detriment of others (sometimes, to the detriment of others in the same band!) If your "tune" button on the transceiver works (hopefully with very low TX power) on all frequencies....in theory...if the tuner tunes to resonance...it should RECEIVE better while tuned....but is easier to find a broadcasting station in the bypass mode FIRST. I am by no means suggesting that you should transmit (even for a second or two, even at low power) on frequencies that you are not licensed on. THAT'S what the "bypass" feature is for! Hope this helps just a little bit, as I'm no "expert" either, Jim! There are quite a few guys on this group that will contribute more direct answers to your good questions, and if I've scared them up from the deep...I have done OK! Good luck with that wonderful boat! Joe "Jim Woodward" wrote in message m... Joe: Please take this OK -- there are parts of boating in which I consider myself expert -- but this isn't one of them. I flunked out of the EE school at Cornell a long time ago, so I'm really trying to learn here, not be argumentative. I have two questions about what you wrote below: First, am I correct that as far as choice of antenna is concerned, receiving and transmitting are the same problem -- an antenna that receives well will transmit well, and vice versa? If so, I don't understand why you start off with, "...we are talking about a simple RECEIVE antenna here." If you're trying to pick a weak signal out of the noise, I should think you'd want as good an antenna as possible. Which brings me to the second question, or perhaps I should say "objection" to your comment. My experience with receiving weatherfax is considerable -- in several oceans, from many different stations, on a daily basis. It was all in 1995-98, which, IIRC was a low sunspot year. We had both an insulated backstay on an 82' mast and a 23' whip and a lot of well bonded copper screen for the ground under a Furuno 1502. The weatherfax stations were never as loud as medium frequency broadcast stations and were often much more difficult to copy successfully. Now, I can't speak directly to how good our installation was -- a professional did it, but that might be good and might be bad, so all I can say is that we did talk to people all over the Pacific with no problem. Now for a question on which I am soliciting opionions as widely as I can. We're going to have SSB on Fintry (as well as Inmarsat C and, probably, one of the low orbit services -- Iridium or one of its cousins.) The usual choice would be a tall whip hung top of the wheelhouse about six feet from the mast. We could also do a long wire from the jackstaff on the bow to the top of the mast -- 44 feet at about a 20 degree angle from horizontal. Which would you chose and why? Thanks, Jim Woodward www.mvfintry.com "JAD" wrote in message ... Jim, in answer to question #1...we are talking a simple RECEIVE antenna here. Insulated backstays and whips are used with HF-SSB TRANSCEIVERS. In another vein, there are a whole slew of boaters here (mostly hams for recreational use) that "load up" the ENTIRE standing rigging (on fiberglass sailboats) against a good ground for a really fine antenna. No good for offshore where salt water may ground the rig at the chainplates....or where someone my grab something during TX.....but it does work and it works well (again, for RECREATIONAL HF use.) Shoot...there was a thread here not long ago about guys loading the entire standing rigging against the lifelines and toe rail......and THAT supposedly works, too. Building a good capacitive ground can be difficult on some boats.....but sure is the best choice. Any boat doing serious offshore cruising should have a properly insulated backstay or large whip for an HF antenna. As far a question #2 is concerned....see Meindert's post above. The ARRL handbook presents some antenna designs....but not ALL of them...and not all of the GOOD ones....... I can tell you, as in my original post...connecting a receiver to my old boat GROUNDED (to keel bolts....lead keel....encapsulated somewhat,) standing rigging, produced one of the quietest, best performing receive antennas I have ever played with. I did not ground the rig on purpose for this arrangement....is just the way it was. In the marina...where stray currents and noise abound....the receiver worked like a champ on ALL HF bands. And...to the guy who says receiving broadcast stations and HF telefax is different......I say..NUTZ! If you have a good antenna, the signal is there....AND there is good signal / noise ratio...you should receive quality faxes. Simple as that. Knowing the wefax broadcast schedule and location / frequencies of the stations would help........ Fair winds....'73 Joe "Jim Woodward" wrote in message om... OK. I know just enough to be dangerous here. In an effort to learn enough to be even more dangerous, I ask two questions: 1) If this arrangement yields a satisfactory signal and a better SNR, then why does virtually every crusing boat use an insulated backstay or a whip? Remember that we're talking about weatherfax, which is often difficult to receive. 2) I note that the ARRL Antenna Handbook devotes a full chapter to loops. All are carefully isolated from ground at all corners -- the ground comes after the matching network. Am I missing something? Jim Woodward www.mvfintry.com "Meindert Sprang" wrote in message ... In this configuration, the mast and standing rigging work as a magnetic loop antenna, which *should* have something you would call a short-circuit to ground in order to close the loop. A loop antenna picks up the magnetic component of a radio signal and is far less suscebtible to noise than a whip antenna (single isolated backstay too). Meindert |
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