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 >
