Conditions just now are at night hostile to even NVIS. We sometimes eke out ground wave between MARS members here with vertical antennas below -- well below -- 3.5 MHz. Some nights I'd like something below 1.8! Nevertheless, my mobile setup, when I have it installed, covers 160-440. MARS frequencies too, of course. I dont rely on the mobile antenna, with a spool of telco CO wire cheap and handy. I have Elk 2/440 LPDA's and painters poles, too.
Making a communication system work requires forethought as to HOW it can be done for the requirement of the time. Frequency coordination that doesn't allow for propagation can hobble even a California Kilowatt, assuming anyone had a big enough generator and a 6X6. -- and ravine comms on VHF is really not a good idea. Some prior planning and practice is needed. A club I used to belong to supported bicycle rides over some pretty poor VHF radio paths. It helped when we TESTED those paths. Sometimes a remote cross band mobile repeater was needed. Sometimes an FRS radio link (but the Feds can't legally use those) to the rest stop or aid station from a nearby hill. But we can't rely on such things appearing from thin air. Or helping when large amounts of message traffic must be passed. There has been some discussion involving communication to customer WiFi and Bluetooth. Where it has been tried it has apparently been well received and these are of course well suited for digital traffic. The holes in our planning are not yet all known, either. Cortland KA5S AAR5UT > [Original Message] > From: Howard Z. <[EMAIL PROTECTED]> > To: <digitalradio@yahoogroups.com> > Date: 11/25/2008 6:59:21 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 >
