Not only are EOC's that far away, but when a hurricane hits the Gulf Coast, you can have all communications interrupted for much more than 100 miles.
73, Walt/K5YFW John Bradley wrote: > on occasion less than 100 miles on VHF and sometimes as little as 30 miles > on 80M HF > > > > I disagree with the assumption that for Emcomms we only need span 100 miles. > That may be true in higher population areas, and where the state is broken > down into counties. Up here we will be working into provincial EOC's, which > could be up to 500km away (300 Miles), too far for VHF point to point. > Furthermore we don't have the density of hams in the rural areas which we > allow for relay points. > > > > We have good cellular coverage along our highways, but once off the major > roads rural cellular service is very spotty. Internet access via cellular to > pass text messages cannot be relied upon, so that throws us back to HF as > the most likely link (besides sat Phone) > > > > I really don't understand the restrictions that you have in the USA on baud > rate and mode restrictions. Your mode works well but would be wonderful a > little faster. RFSM 8000 works well, but is wide, and am still not sure how > it will work under poor HF conditions. > > ALE400 works well into the weeds, and it would be great to see you and > Patrick team up to combine NBEMS and Ale400 in one package. > > > > John > > VE5MU > > > > From: digitalradio@yahoogroups.com [mailto:[EMAIL PROTECTED] On > Behalf Of kh6ty > Sent: Sunday, March 02, 2008 9:13 PM > To: digitalradio@yahoogroups.com > Subject: Re: [digitalradio] Re: Keeping NBEMS in mind > > > > John, > > Over what distance are you getting flutter or Doppler on VHF? I only get the > > flutter (usually all the time!) when I try to work Charlotte, NC from > Charleston, SC on 70 cm, which is 173 miles away, but I am not far enough > north for Aurora. For emcomm, we only need to span up to 100 miles. I am > interested to know if you also find flutter on VHF within 100 miles. > > Skip KH6TY > > ----- Original Message ----- > From: "John Bradley" <[EMAIL PROTECTED] <mailto:jbradley%40sasktel.net> > > To: <digitalradio@yahoogroups.com <mailto:digitalradio%40yahoogroups.com> > > Sent: Sunday, March 02, 2008 9:30 PM > Subject: RE: [digitalradio] Re: Keeping NBEMS in mind > > >>This may be true at lower latitudes, but up here at 50 degrees north, we >>get >>sustained aurora flutter or Doppler on HF and VHF. Sometimes the audio has > > >>a >>distinct echo. PSK125 and 250 are worse. >> >>we do have days where we have strong signals but cannot decode anything. >> >>it would be nice to have something a little faster than regular MFSK for a >>robust mode >> >>John >>VE5MU >> >> >>-----Original Message----- >>From: digitalradio@yahoogroups.com <mailto:digitalradio%40yahoogroups.com> > > [mailto:digitalradio@yahoogroups.com <mailto:digitalradio%40yahoogroups.com> > ] > >>On >>Behalf Of kh6ty >>Sent: Sunday, March 02, 2008 4:18 PM >>To: digitalradio@yahoogroups.com <mailto:digitalradio%40yahoogroups.com> >>Subject: Re: [digitalradio] Re: Keeping NBEMS in mind >> >> >> >>>I have seen some multiipath, especially when I have tested PSK31 on VHF, >>>but much of that was from aircraft. I am not sure how I can discern >>>multipath when on HF. Is there any clue in the waterfall or do you go by >>>the sound? >>> >>>73, >>> >>>Rick, KV9U >> >>You will see three kinds of multipath on VHF, which you can see on the >>waterfall. >> >>One is reflections from airplanes, which tends to look like a ghost signal >>accelerating across the main signal. When it coincides with the main >>signal, >> >>all copy will be momentarily lost, no matter how strong the signal. >> >>The second correlates with wind conditions, and the ghost signal moves >>slightly in and out of the main signal during wind gusts, especially when >>a >>weather front is moving through. >> >>The third is reflections from fixed objects, and the ghost signal tends to >>stay a fixed distance away from the main signal. >> >>PSK63 is less affected by multipath reflections than PSK31 is on VHF, and >>PSK125 even less so. When cancellation does occur, if you are using ARQ, >>that frame is just resent and the transfer is delayed by that much. Of >>course, only ARQ is going to guarantee error-free copy. FEC only helps, >>but >>does not insure no errors. >> >>QRN seems to be the biggest problem on HF and QSB second. During a period >>of >> >>thunderstorm activity, as we often have in South Carolina, and more >>especially in Florida, PSK125 is greatly disturbed and PSK250 so much that >>it is unusable, but PSK63 not nearly as much. All the decoders seem to >>have >>this problem, and there may be a way to improve that cascaded loss of sync >>in the faster modes, due to QRN, but we have not yet tackled this problem. >>Fortunately, for our 100 mile emcomm uses, QRN and QSB are not problems on >>VHF, and ARQ takes care of the multipath reflection problem. >> >>73, Skip KH6TY >> >> >> >> >> >> >>Announce your digital presence via our Interactive Sked Page at >>http://www.obriensweb.com/sked >> >>Check our other Yahoo Groups.... >>http://groups.yahoo.com/group/dxlist/ >>http://groups.yahoo.com/group/contesting >>http://groups.yahoo.com/group/themixwgroup >> >>Yahoo! Groups Links >> >> >> >> >> >>-- >>No virus found in this incoming message. >>Checked by AVG Free Edition. >>Version: 7.5.516 / Virus Database: 269.21.3/1306 - Release Date: 3/1/2008 >>5:41 PM >> >> > > > ---------------------------------------------------------- > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.21.3/1306 - Release Date: 3/1/2008 > 5:41 PM > > > >
