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 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 needs to be > horizontal. I'm not sure there exists an NVIS antenna for a car or > truck. Maybe something horizontal can be setup in the bed of a pick > up truck? In general HF antennas for vehicles do not perform very > well - but they are better than nothing. > > There are portable NVIS HF antennas available that can be setup > rather quickly. Perhaps this is something to be done when he > arrives at his destination, and then call the base on HF? > > Also keep in mind that HF radios typically cost over a thousand > dollars compared to maybe two hundred for a VHF radio. > > Howard > N3ZH > 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
