[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem was considering HF as a solution. Watson, I think he's got it... maybe. Howard --- In digitalradio@yahoogroups.com, kh6ty [EMAIL PROTECTED] wrote: Howard, We already achieved successful, error-free, VHF communication (with no repeated blocks) using NBEMS software over a 70 mile path in flat country between two 50 watt FM transceivers, one with a 7.5 dBi antenna at 10 feet off the ground and the other with a 7.5 dBi antenna 25 feet off the ground. I have also developed a DOX interface for FM transceivers which have no VOX. A schematic is here: http://home.comcast.net/~hteller/Interface%20schematic.jpg We are now in the process of determining just how much farther we can go using FM. However, using SSB with DominoEX, we have already reached 100 miles consistently between a 9 dBi antenna and a 13 dBi antenna. We think that a 100 mile capability is sufficient to reach outside connectivity for email or phone delivery and confirmation. If so, then VHF can be used most of the time. By using 2m, if the S/N is sufficient, we can also use phone and data interchangably on the same frequency, which is not permitted on HF. When the terrain is too hilly for VHF, NBEMS also supports Hf using NVIS antennas with several modes specifically tailored to work under very high static conditions. However, it obviously easier to put up a small beam than it is to always find supports for a NVIS antenna for portable use. A picture of my 2m portable setup is here: http://home.comcast.net/~hteller/sideview.jpg. By using a two section mast, everything will fit in the trunk or in the back seat. NBEMS does not support push emcomm email, because there is no confirmation of delivery. Instead, there must just be an operator present at each end of the link. This also helps prevent transmitting on an already active frequency. As you correctly note, VHF FM transceivers cost only a couple of hundred dollars instead of a thousand for SSB-capable transceivers, however, it is absolutely necessary to use horizontally-polarized, gain, antennas to go farther than a repeater can go. The portable station antenna is usually going to be near the ground, and at 10 feet off the ground, there is a huge 6 dB penalty to using vertical polarization. We are now changing the emphasis of NBEMS from SSB to FM with DominoEX in order to make it possible for more people to use NBEMS and also take advantage of the low cost FM-only transceivers in the field. There appears to be a 3 dB or greater disadvantage to using FM over SSB, even with horizontally-polarized antennas, but that can be made up with increased antenna gain or power. Phone will not work on VHF over the same long distances as DominoEX or MFSK16 will work, because the noise level is often so high, the voice just cannot be understood or even heard at all. However, DominoEX and MFSK16 can still decode when the S/N is 10 or 12 dB UNDER the noise level, and that is how we get such long distance communication on 2m. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Tuesday, November 25, 2008 6:58 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of VHF range? If the base station has a 100 watt VHF radio like the 746pro - you might be able to still reach the volunteer, but he may not have enough power to get back to you. Or he may be out of VHF range. HF is the way to go - but both ends of the conversation need NVIS antennas. HF antennas tend to be large, and NVIS
[digitalradio] RFSM8000 new version
There is a relatively new version of RFSM8000 #535 In the email server mode - email would go out on the internet to someone's personal or bussiness email without a FROM address. Thus how to reply was difficult or non obvious. This is now fixed. The FROM address is now the email address the RFSM8000 email server uses. The person replying still needs to start the subject with the call-sign of the RFSM8000 user who originated the message. Howard.
[digitalradio] Re: RFSM8000 new version
There is another problem with RFSM8000 which I hope the author will correct. It seems impossible to start a subject with //MARS R to send an email message to winlink.org to a MARS account. MARS winlink accounts do not have functional whitelists, and all messages must have a subject starting with //MARS R or //MARS P. Howard N3ZH
[digitalradio] Re: RFSM8000 new version
There is another problem with RFSM8000 which I hope the author will correct. It seems impossible to start a subject with //MARS R/ to send an email message to winlink.org to a MARS account. MARS winlink accounts do not have functional whitelists, and all messages must have a subject starting with //MARS R/ or //MARS P/. Howard N3ZH
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Howard, If you respond to someone's response to a question, with asking questions of your own, then it might be reasonable for some to respond as Skip did. It seems reasonable to me considering you asked Is the volunteer out of VHF range? You also asked about setting up something in the bed of a truck and asked about setting up something on HF after arrival at the destination. All good questions. While your particular job situation does not seem relevant to this discussion, the use of VHF, especially SSB VHF does seem particularly relevant since it is the only other way to get increased distance of communication between a mobile and fixed/portable/mobile station if HF is not workable. The most expensive HF equipment may of of no value when you are trying to communicate between two points that do not have NVIS propagation. It can be frustrating, especially during high QRN as well as the skywave signal just going through the ionosphere and not reflecting back down. For those experienced with Section level nets that only use 75/80 meters, you know what I mean. Going higher in HF frequency doesn't work any better (actually shorter ground/direct wave), and that is why STANAG systems won't work for local communication. VHF simplex with FM and with minimal antennas are not going to go all that far as you point out. In fact, in our area, it is difficult enough for mobiles to repeaters. Sometimes 15 to 20 miles is the best you can do in shaded areas. With 2 meter SSB, we seem to be able to still get through when FM can not get through although signals can be very weak. That is using half wave base to quarter wave mobile antennas. With improved antennas, depending upon terrain, the distance is going to extend out to as much as 50 to 100 miles. This is important because you reduce QRN problems from lightning static and other noise (admittedly less likely though during a time when power has failed), and you rarely would need that much distance for Incident Command to the dispatched mobile. Bottom line is that HF may not be able to do it 24/7, but 2 meter SSB may be the best choice. With today's relatively low cost multimode/multiband rigs, the cost is around $700 or so for 50 watts on 2 meter SSB. As you point out, these rigs are more expensive than 2 meter FM, but tremendously more flexible and a very good value since you also get an HF rig too. 73, Rick, KV9U Moderator, HFDEC yahoogroup Howard Z. wrote: SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem was considering HF as a solution. Watson, I think he's got it... maybe. Howard
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Howard, First of all, there is no need to shout! My old eyes are still fine for reading without your using caps! :-) This group is for the purpose of discussion about using digital modes in amateur radio, all opinions are welcome, and nothing should not be held against a person for posting a contrary opinion. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. Your statement that VHF is nice for 10-20 miles, is what we find also (using phone, and a 5/8 wavelength vertical whip on a car), but I was only tryng to point out that if you use horizontal polarization and sensitive digital modes, you can go much, much, farther, and we have established that over flat country. Vertical polarization with omnidirectional antennas are perfect for mobile use, and that is why we have repeaters today, but the range is very limited, as you point out. However HF is also often not reliable, especially during the time of day that 40m fades out and 80m comes up, or later, when 80m fades also, even using NVIS antennas. We have made many months of NBEMS tests on HF to realize that. In contrast, when VHF can be used, propagation is always consistent up to about 100 miles away. We are continually looking for ways to provide the most dependable messaging system at any time of day or night, and using VHF is one of those ways. I also clearly stated, When the terrain is too hilly for VHF, NBEMS also supports Hf using NVIS antennas with several modes specifically tailored to work under very high static conditions. However HF is not the only way reliable communications can be achieved, at least in non-hilly country. I was not trying to give you any advice, or make someone elses problem yours, but only to address the opinions in your own post. It is not necessary to be sarcastic - if my post, opinions, or findings displease you, simply use your delete key! ;-) For everyone else, please take note that it is a significant finding that long-range communications using FM and DominoEx can more than triple the range of FM phone communications in flat country, but we still have to find out what ranges are possible in hilly country compred to phone communications. Perhaps someone will explain it better, but my guess that when all signals encounter an obstacle such as the curvature of the earth (line of sight?), they diffract and scatter, losing most of their original strength. However, sensitive digital modes can still recover information from the very weak scattered waves, and that is why we can still copy with digital modes when you cannot even tell that a phone signal is no longer present. Since VHF phone signals are limited in general by the encounter with the curvature of the earth, it just makes sense to see what can be done with those weak scattered waves, and that is what we are trying to find out. If anything in my previous post is useful to anyone, please feel free to use it. Even the digital interface for FM transceivers can be useful, as it can be built for $10, which is much less than the $100 SignaLink USB, which also has its own DOX. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 1:42 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem was
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Hi Rick, Thank you for your comments on Howard's and my posts. Of course, we prefer using SSB on VHF, because the range is longer. First tests indicate that DominoEX with SSB has at least a 3 dB advantage over using FM with DominoEx. We are arranging more tests to be sure. However, the fact that today, maybe half of the U.S. amateurs hold only a Technician license, and do not have access to full HF priviledges, together with the fact that many hams only have inexpensive FM-only transceivers (but only a relative few may have VHF or multimode 2m transceivers with SSB capability), we have decide to explore ways that more hams can participate in emcomm activities, which means finding out how to use FM-only transceivers without repeater assistance. Although you have previously pointed out that many hams already have vertical antennas, the fact remains that a vertical antenna close to the ground (2 wavelengths), has about 6 dB less gain than the same antenna horizontally polarized. At VHF, a 6 dB disadvantage is an enormous disadvantage, plus many of the directive antennas used for FM are fixed on a particular repeater, and cannot currently be rotated anyway. Just model a vertically-polarized antenna over real ground at 2 wavelengths and compare the gain to the same antenna rotated 90 degrees to horizontal polarization to see the difference. In order to confirm Cebik's assertion about the gain difference, I did the modeling myself and found that he is absolutely correct. No difference in free space, but a huge difference over real ground. So, putting it all together, we can get significantly more range by simply investing in a horizontally-polarized antenna, using the same FM transceiver that people already have, and, better yet, in an inexpensive TV antenna rotator so we can communicate in any direction. The optimized two-element quad that we used for the FM/DominoEx tests (7.5 dBi in free space) can be built for less than $15 in an hour with all parts from Lowes, plus a SO-239 connector, and turned with a $60 Philips TV antenna rotator from Walmart, because its wind loading and boom length (13) is so small. A picture of the little quad is here: http://home.comcast.net/~hteller/OptimizedQuad.jpg. It is only 20 x 20 x 13, so it will fit in the trunk of a car without having to be dismanteled. Construction uses schedule 40 PVC, fiberglass driveway markers for spreaders, and #14 insulated house wire, so it is very rugged. I wish that all existing equipment could be used intead, but without a gain antenna and horizontal polarization, range without repeater assistance appears to be just too limited. It would be useful to know how much range you can get in your hilly rural area by using FM, DominoEx, and horizontal antennas on 2m. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Rick W [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 3:38 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Hi Howard, If you respond to someone's response to a question, with asking questions of your own, then it might be reasonable for some to respond as Skip did. It seems reasonable to me considering you asked Is the volunteer out of VHF range? You also asked about setting up something in the bed of a truck and asked about setting up something on HF after arrival at the destination. All good questions. While your particular job situation does not seem relevant to this discussion, the use of VHF, especially SSB VHF does seem particularly relevant since it is the only other way to get increased distance of communication between a mobile and fixed/portable/mobile station if HF is not workable. The most expensive HF equipment may of of no value when you are trying to communicate between two points that do not have NVIS propagation. It can be frustrating, especially during high QRN as well as the skywave signal just going through the ionosphere and not reflecting back down. For those experienced with Section level nets that only use 75/80 meters, you know what I mean. Going higher in HF frequency doesn't work any better (actually shorter ground/direct wave), and that is why STANAG systems won't work for local communication. VHF simplex with FM and with minimal antennas are not going to go all that far as you point out. In fact, in our area, it is difficult enough for mobiles to repeaters. Sometimes 15 to 20 miles is the best you can do in shaded areas. With 2 meter SSB, we seem to be able to still get through when FM can not get through although signals can be very weak. That is using half wave base to quarter wave mobile antennas. With improved antennas, depending upon terrain, the distance is going to extend out to as much as 50 to 100 miles. This is important because you reduce QRN problems from lightning static and other noise (admittedly less likely though
[digitalradio] Correction on URL for Optimized Quad
The correct URL for the picture of the two-element Optimized Quad is http://home.comcast.net/~hteller/OptimizedQuad.jpg A period at the end of the link in my email accidentally got included in the URL. Skip KH6TY - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 1:42 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? SKIP SKIP SKIP READ READ READ I, HOWARD, AM not not NOT NOT not THE PERSON WITH THE QUESTION NOR THE PROBLEM. GEEZ, I TRY TO ANSWER SOMEONE'S QUESTION, AND SUDDENLY IT BECOMES MY QUESTION AND MY PROBLEM. If you are going to address someone - address the individual who has the problem or question in the first place. Personally - I don't care. Personally, I am an emergency worker who will never ever be sent to help in an ARES/RACES HAM group, because my agency will need me here. If it snows 20 feet one day, I'll be disciplined if I do not get to work - lose all bonuses and raises for a year. Personally, I already own expensive HF equipment and consider VHF short range no matter what you do with it - compared to a few hundred miles one gets via HF with a NVIS antenna 10 feet above ground. Personally, I think VHF is nice for 10 to 20 miles - you can go further - nice for you. I'll keep it in mind if anyone gets a team of bulldozers and makes Maryland flat - I can't walk a block or two with reaching a hill. I am not the one who asked the question. I am not the one who asked the question. Don't try giving me advise when I am not the one who asked the question. The original poster who posed the question and who has the problem was considering HF as a solution. Watson, I think he's got it... maybe. Howard --- In digitalradio@yahoogroups.com, kh6ty [EMAIL PROTECTED] wrote: Howard, We already achieved successful, error-free, VHF communication (with no repeated blocks) using NBEMS software over a 70 mile path in flat country between two 50 watt FM transceivers, one with a 7.5 dBi antenna at 10 feet off the ground and the other with a 7.5 dBi antenna 25 feet off the ground. I have also developed a DOX interface for FM transceivers which have no VOX. A schematic is here: http://home.comcast.net/~hteller/Interface%20schematic.jpg We are now in the process of determining just how much farther we can go using FM. However, using SSB with DominoEX, we have already reached 100 miles consistently between a 9 dBi antenna and a 13 dBi antenna. We think that a 100 mile capability is sufficient to reach outside connectivity for email or phone delivery and confirmation. If so, then VHF can be used most of the time. By using 2m, if the S/N is sufficient, we can also use phone and data interchangably on the same frequency, which is not permitted on HF. When the terrain is too hilly for VHF, NBEMS also supports Hf using NVIS antennas with several modes specifically tailored to work under very high static conditions. However, it obviously easier to put up a small beam than it is to always find supports for a NVIS antenna for portable use. A picture of my 2m portable setup is here: http://home.comcast.net/~hteller/sideview.jpg. By using a two section mast, everything will fit in the trunk or in the back seat. NBEMS does not support push emcomm email, because there is no confirmation of delivery. Instead, there must just be an operator present at each end of the link. This also helps prevent transmitting on an already active frequency. As you correctly note, VHF FM transceivers cost only a couple of hundred dollars instead of a thousand for SSB-capable transceivers, however, it is absolutely necessary to use horizontally-polarized, gain, antennas to go farther than a repeater can go. The portable station antenna is usually going to be near the ground, and at 10 feet off the ground, there is a huge 6 dB penalty to using vertical polarization. We are now changing the emphasis of NBEMS from SSB to FM with DominoEX in order to make it possible for more people to use NBEMS and also take advantage of the low cost FM-only transceivers in the field. There appears to be a 3 dB or greater disadvantage to using FM over SSB, even with horizontally-polarized antennas, but that can be made up with increased antenna gain or power. Phone will not work on VHF over the same long distances as DominoEX or MFSK16 will work, because the noise level is often so high, the voice just cannot be understood or even heard at all. However, DominoEX and MFSK16 can still decode when the S/N is 10 or 12 dB UNDER the noise level, and that is how we get such long distance communication on 2m. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Tuesday, November 25, 2008 6:58 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? Is the volunteer out of
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department.
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
One obvious choice for pushing messages to the field would be multicast ( on any band, depending on the range you are after, etc.. ) One transmitter pushes the data to an unlimited number of recipients, who all get it at the same time. No point-to-point system can compete with it, multicast is much, much faster for distributing the same data to many locations. Learn about multicast at these plasces: http://uspacket.org/smf/index.php?board=6.0;sort=subject http://uspacket.org/smf/index.php?topic=9 The second link is only for the truly curious - the article is long-winded! Pardon my typing, my vision is not good today and I'm a hunt 'n peck typist. 73 DE Charles Brabham, N5PVL - Original Message - From: John Becker, WØJAB To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 4:41 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department.
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
I deleted that posting soon after I made it. However, I suppose those who get emails still got it. My posting was not appropriate. I appologize. Howard
[digitalradio] Skip - Quad detials?
Could you provide sufficient details on the quad to allow building it? Rud Merriam K5RUD ARES AEC Montgomery County, TX http://TheHamNetwork.net
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
No hard feelings, Howard! Your passion for the hobby is appreciated, and many of us have hit the Send key, wishing immediately afterward that we had not! Regardless, I thought many of your points were well made and bared repeating. 73, Skip KH6TY NBEMS Development Team - Original Message - From: Howard Z. [EMAIL PROTECTED] To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 6:32 PM Subject: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? I deleted that posting soon after I made it. However, I suppose those who get emails still got it. My posting was not appropriate. I appologize. Howard Internal Virus Database is out of date. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.9.2/1785 - Release Date: 11/13/2008 9:12 AM
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
I deleted the posting a few minutes after I made it. I realized it was inappropriate. I somehow felt I was being challenged to a debate, All I did was give someone my 2 cents, and dozens of others would also likely give their opinions. I don't know why, but I reacted badly to the post directed to me. I thought the identity of the original person with the problem who posted the question had been lost and I had been nominated in his place. But, I re-read my posting, and considered it inappropriate, and I deleted it hoping nobody would read it. Howard --- In digitalradio@yahoogroups.com, kh6ty [EMAIL PROTECTED] wrote: Howard, First of all, there is no need to shout! My old eyes are still fine for reading without your using caps! :-)
[digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Yes indeed - I have found that nothing on HF is reliable 24/7. One can not reliably reach another country at will regardless of equipment. Local NVIS operation also has problems. In my MARS group before DST ended, conditions were pretty bad because we started before sunrise - and then everything was find after sunrise. Sometimes we change frequencies which can help, but few members have antennas for 2 Mhz, so there are limits to that approach. I used to use an inverted dipole 10 to 20 ft above ground. I found one member who always sounded great and could always hear me no matter what. Turns out he uses a one wavelength loop, and that is what I use now. I think just about everyone hears me fine - I get good reports, but I don't hear everyone well under those occassional bad conditions. I am using a 1:1 balun, and I read that a balun is unnecessary with a one wavelength loop antenna, so I'm going to try eliminating the balun next month to see if it makes a difference. MARS uses NVIS SSB HF from 2 Mhz to 30 Mhz as the primary emcomm mode. Voice, digital, and winlink. I do admit it does not work 24/7, but nothing on HF does. Since morse code is eliminated, it is relatively easy for people to upgrade to General licenses - but it does take some effort. If VHF can get the job done for your circumstances - it's cheaper, antennas are smaller, mobile use is easy, etc etc. Howard
RE: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department. I passed the question to my ARES crew that is posted in the subject area as it is an important question and with great scenarios. We just went through the largest mass exercise in Ontario called Trillium Exercise here in Thunder Bay Ontario. ARES was not involved as much as they should have been but we did have a chance to pass traffic via radio during the time. Anyhow, we too are in an area where we have a large mass of land and few hams to fill it. I have many areas in my ARES district that are vacant, so again getting those messages there are going to be tough both ways if all power and communications are down. Consensus here has MT63 as the mode of choice in digital traffic and use of NVIS antennas. We use it for CFARS as well Anyway, I think it is a great question and some good answers have come out of it. Regards Fred VE3FAL -Original Message- From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On Behalf Of Charles Brabham Sent: Wednesday, November 26, 2008 6:22 PM To: digitalradio@yahoogroups.com Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? One obvious choice for pushing messages to the field would be multicast ( on any band, depending on the range you are after, etc.. ) One transmitter pushes the data to an unlimited number of recipients, who all get it at the same time. No point-to-point system can compete with it, multicast is much, much faster for distributing the same data to many locations. Learn about multicast at these plasces: http://uspacket.org/smf/index.php?board=6.0;sort=subject http://uspacket.org/smf/index.php?topic=9 The second link is only for the truly curious - the article is long-winded! Pardon my typing, my vision is not good today and I'm a hunt 'n peck typist. 73 DE Charles Brabham, N5PVL - Original Message - From: John Becker, mailto:[EMAIL PROTECTED] WØJAB To: digitalradio@yahoogroups.com Sent: Wednesday, November 26, 2008 4:41 PM Subject: Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field? In this county you can sum up the biggest problem in one word manpower. Within my zip code there is 3 hams living in town. One is up in the years and has not been on the air in years as well as to weak to do much. As far as the other 2, one is chief of police. The other is #2 in command on the fire department.
Re: [digitalradio] Re: How Can We Push HF Emcomm Messages to the Field?
Skip, Have you found that DominoEX is the best overall digital mode for FM? I know that PSK modes can have doppler errors from aircraft, but otherwise seem pretty good for weak signal. Your point is well taken that many of the hams who participate in public service activities, may tend to be the younger ones who are Technician class and can mostly operate on 6 meters and up with their vertical antennas and FM only rigs. The number of hams with the multimode/multiband rigs is increasing, at least in our area. It is not easy to get them to try SSB, much less SSB digital though. The claim about the ground gain for horizontal antennas may be true but I have not seen this definitely tested. Have you done some comparisons with low 2 meter antennas, such a mobile to low base antenna with V and H and found H consistently better? I don't hold too much stock in software modeling and only would go with empirical data for that kind of test. We will probably bite the bullet eventually and put a rotor back up on the low tower and maybe go with a Gulf Alpha 11 element V and H antenna for some reasonable gain. Then we could do the test. The ham that was going to help us lost his QTH and will not be able to relocate his VHF antenna farm. Of course they are quite high so maybe there would not have been as much difference in such a case. One of the best known VHF ops in my Section says that after running many tests he has never found either polarization is any different. But he has high antennas so maybe that accounts for it. We hope at least soon do some digital mode comparisons on 2 meters, whether SSB or FM. 73, Rick, KV9U kh6ty wrote: Hi Rick, Thank you for your comments on Howard's and my posts. Of course, we prefer using SSB on VHF, because the range is longer. First tests indicate that DominoEX with SSB has at least a 3 dB advantage over using FM with DominoEx. We are arranging more tests to be sure. However, the fact that today, maybe half of the U.S. amateurs hold only a Technician license, and do not have access to full HF priviledges, together with the fact that many hams only have inexpensive FM-only transceivers (but only a relative few may have VHF or multimode 2m transceivers with SSB capability), we have decide to explore ways that more hams can participate in emcomm activities, which means finding out how to use FM-only transceivers without repeater assistance. Although you have previously pointed out that many hams already have vertical antennas, the fact remains that a vertical antenna close to the ground (2 wavelengths), has about 6 dB less gain than the same antenna horizontally polarized. At VHF, a 6 dB disadvantage is an enormous disadvantage, plus many of the directive antennas used for FM are fixed on a particular repeater, and cannot currently be rotated anyway. Just model a vertically-polarized antenna over real ground at 2 wavelengths and compare the gain to the same antenna rotated 90 degrees to horizontal polarization to see the difference. In order to confirm Cebik's assertion about the gain difference, I did the modeling myself and found that he is absolutely correct. No difference in free space, but a huge difference over real ground. So, putting it all together, we can get significantly more range by simply investing in a horizontally-polarized antenna, using the same FM transceiver that people already have, and, better yet, in an inexpensive TV antenna rotator so we can communicate in any direction. The optimized two-element quad that we used for the FM/DominoEx tests (7.5 dBi in free space) can be built for less than $15 in an hour with all parts from Lowes, plus a SO-239 connector, and turned with a $60 Philips TV antenna rotator from Walmart, because its wind loading and boom length (13) is so small. A picture of the little quad is here: http://home.comcast.net/~hteller/OptimizedQuad.jpg. It is only 20 x 20 x 13, so it will fit in the trunk of a car without having to be dismanteled. Construction uses schedule 40 PVC, fiberglass driveway markers for spreaders, and #14 insulated house wire, so it is very rugged. I wish that all existing equipment could be used intead, but without a gain antenna and horizontal polarization, range without repeater assistance appears to be just too limited. It would be useful to know how much range you can get in your hilly rural area by using FM, DominoEx, and horizontal antennas on 2m. 73, Skip KH6TY NBEMS Development Team
