This is something that would likely be more at home at the HFDEC yahoogroup that discusses disaster and emergency communications but lets look at some of the practical aspects.
Distance was not specified, but it would be rare to send someone out at night, under dangerous conditions, in unfamiliar territory, to handle communications at a shelter. It would be unusual to be out of range of the EOC unless a very rural area with difficult terrain (OK, maybe not too unlike my region, HI). After recent testing that my wife and I have been doing with 6 meters vs 2 meters with different modes, we have found that 2 meters works the best when there are any possible noise problems (less likely with power lines inoperative though), and using SSB is superior to FM when signals become weak. This can give you a significant coverage area, especially if the base station has some gain. We also use HF mobile since Judy has a Texas Bug Catcher that can be attached to the receiver hitch. While not optimum according to expert mobileers, this is the way we are willing to do HF. Contrary to some claims that bending the antenna over will improve signals, we have not found this to be true and it does not give you NVIS signals. Using an extended wire might be of help but we have yet to test that as it can not be used in motion. There are very large and expensive antennas that are claimed as operating NVIS, but not something that most of us would consider. And I have not seen any tests done to show how efficient or how vertical the radiation really is. When Judy came back from our daughter's home (200 miles) last week, as is our usual custom, we again performed a number of tests at different distances and as long as the FoF2 is above 4 MHz, things are often OK with daytime signals of S5 to S8 (almost no QRN) when she is at the maximum distance. As she gets closer, her signal often drops lower in strength since she is likely transmitting with lower angle radiation than we would like on 75 meters. Her signal got worse and worse and at 100 miles out things became unusable at times. Even when she was only 15 miles out, she was barely able to communicate. And then even at only 7 or 8 miles where she refueled and had to take off the quick release top whip on her last transmission she was extremely difficult copy. The FoF2 had dropped below 2 MHz by then. Some of you may have noticed that lately we have had barely 1 MHz FoF2 in the evening. I just checked and at about ~8 pm CST, almost the entire U.S. is at 2 MHz. This means that you may find HF to be of very limited value in the evening. Since higher frequencies are even worse at close distances, other than ground wave, (which is only a few miles), and since 160 is so difficult to use for mobile, I am convinced that there really needs to be more of a focus on VHF SSB. One other supporting point is that many new mobile transceivers now include VHF and UHF SSB. 73, Rick, KV9U Howard Z. wrote: > 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 > > > --- In digitalradio@yahoogroups.com, "expeditionradio" > <[EMAIL PROTECTED]> wrote: > >> The following questions are asked to the amateur >> radio Emcomm community... how can we work together >> on this? >> >> THE TYPICAL SCENARIO >> It is a dark and stormy night... >> You are an amateur radio operator, volunteering >> with a relief organization, for communication >> to set up shelters in a hurricane disaster. >> >> There has been no power in the area for 24 hours. >> There is no mobile phone service, and all >> the VHF/UHF repeaters and digipeaters in the >> area are out of range or out of service. >> >> It is 3AM. You are driving in your vehicle, >> half-way to your first shelter destination, >> making your way on back roads. The >> main highway is flooded. You use your >> chain saw to pass a downed tree. The road >> ahead looks worse. >> >> THE CALL >> The relief organization wants to call you now. >> They have new information since you left on >> your mission, and they now want to change your >> destination, to divert you to another shelter >> location not far from your route. They want you >> to give the workers at the other shelter a list >> of supplies that are on the way. They want you >> to check the shelter's status. They want to know >> where you are, and if you can possibly divert >> to the other shelter, so they won't need to >> send out yet another expedition to the other >> shelter. >> >> THE QUESTIONS >> How will the relief organization call you? >> How will they get the actual message to you? >> How will they know where to route the message >> to be sure it gets to you? >> How will they get urgent feedback from you? >> >> THE BACKGROUND >> In the past, Ham radio has generally been >> very good at a "One Way Traffic" situation. >> >> We can initiate messages. >> We can pull messages into the field using >> automatic email systems. >> >> It is easy to send messages initiated from >> the field. But, not as easy to call someone in the >> field, unless the operator in the field decides >> to actually initiate some sort of 2-way contact. >> >> CAN WE PUSH MESSAGES? >> >> What about pushing calls and messages to the field? >> >> What are the types of ham radio methods >> presently in place to call hams in the field >> when the ham in the field doesn't initiate >> the contact? >> >> What are the existing techniques, and how >> can these be improved? >> >> How is the ham in the field alerted to a call? >> >> Can we devise standard method(s) for routing >> Emcomm "push messages" to the field? >> >> Is ham radio HF viable for pushing messages? >> Can we make the call day or night, without >> prior notice? >> >> Bonnie VR2/KQ6XA >> >> P.S. In case you are wondering, the scenario >> above was taken from the Katrina Hurricane Disaster. >> >> . >> >>
