For a 20 Mile path to the server I use 28 MHz ground wave, works with 5 Watts pskmail day and night. That is with PSK 250. The server has a horizontal dipole on the roof of a 65 meters high building.
When I am at our contest location in Germany, 100 Miles away, I use 80 meters NVIS with 80 Watts from the camper to my home with a horizontal linear loaded antenna. Also with PSK250. Difficult during the night because of high qrm levels. 73, Rein EA/PA0R/P -via pskmail server PI4TUE - > -----Ursprüngliche Nachricht----- > Von: digitalradio@yahoogroups.com > Gesendet: 29.02.08 16:30:39 > An: digitalradio@yahoogroups.com > Betreff: Re: [digitalradio] Some thoughts on antenna polarization for > emergency use > > > > > Thanks for the comments, Ralph, > > Most of us OT's have known about the cross polarization for decades. But > it really does hit home when you try it out for yourself. I had never > had both horizontal and vertical antennas available to me at one time as > I only had horizontal back in 1964 when I was first on 2 meter AM. Later > on I only had vertical. > > I spent some time searching the web for some solid information on the > distance issue. Some practical numbers perhaps? There just does not seem > to be that much advantage to horizontal the closer the stations are to > each other. Some difference on the over 100 mile paths perhaps, but I > wonder how often we will use that long a path on VHF for this kind of > work. My recent SSB contact to north of Chicago to a high end weak > signal operator to my 50 watts with a 4 element beam at a very good > location tells me that this 180 mile path might have even been difficult > for digital modes. Lots of very warbly audio and severe QSB making phone > contact barely possible. But it would have been most interesting to try > digital on that path to get a feel for it. > > For digital modes I can operate 160 meters up thru 6 meters, but not 2 > meters at this time. Perhaps some of you have tried calling CQ on PSK31 > or other modes on say, 6 meters? I have done this many times on 50.290, > but no luck and have never heard anything either. I have heard some > PSK31 on 28.120 but nothing "local" as it was likely all Es. > > Using repeaters is absolutely not an option since we are specifically > trying to operate without infrastructure and if the repeaters are > operational, other communications are likely to be operational as well > in an emergency situation that we are preparing for. > > And with our terrain, 20 miles on VHF FM through a repeater, can be > difficult. Our repeater drops out in several directions when you > approach that point when operating mobile, even though the repeater > location is on a high water tower at about the highest point in the > county. We will find out a lot more this spring/summer when we do the 2 > meter SSB tests and find out for myself. Maybe I can convince someone to > operate VHF digital? > > We hope to do something with 6 meters too, but Skip recommends 2 meter > SSB equipment for NBEMS digital. We will also be trying several HF > antennas to compare portable operation. We have mobile HF operation with > my wife's vehicle, but you lose ground wave on 75 meters within 10 to 15 > miles. Since there is minimal NVIS pattern from a vertical HF antenna, > mobile operation does have its downsides for close in work. Much of what > hams think is "ground wave" on HF, can be NVIS. > > If the FoF2 drops down to 2 MHz at night, I have found it impossible to > try and communicate on 80 meters with a station only 20 miles away. And > that is using CW! > > To give you an idea of the problem that an ARES ham faced this summer > during the 1000 year flood, he was stationed at a remote location that > was well out of range of the repeater. I just measured the distance and > it is only like 15 to 18 miles and yet he had no way to hit the repeater > from that location, even though he had a very good portable setup. The > only way he could contact the DEC to coordinate ARESMAT help was with > cellphone. He later admitted that this was a ridiculous situation. I > pointed out that if he is serious about an amateur radio solution, he, > and others in ARES/RACES, really need to give consideration to getting > their General class license and having HF capability and have the > equipment and know how to use it. The only other possibility that I can > think of is 2 meter SSB phone/digital, but as I have said, no one has > tested the efficacy as yet. > > In terms of the EOC, we have had several Field Day activities at the > site and we tried to set up an 80 meter dipole but the building really > does not fit that kind of antenna very well and is festooned with many > other antennas that we don't want to interfere with. So if we absolutely > must set up HF at that location, we can quickly install a sloper dipole. > Not pretty as you point out, but will work. An alternative would be to > have a VHF ink to a home station that has emergency power. Or both as > needed. > > 73, > > Rick, KV9U > > Ralph Mowery wrote: > > YOu are finding out what others have known for years. > > There is around a 20 db differance in cross > > polarization. > > > > MOst hams that are serious on ssb on vhf and above > > will be using horizontal for several reasons. It > > seems to give slightly more distance and the mast > > going to the boom is not in the antenna patern. > > > > Also 20 miles is nothing to vhf ssb. It seems many of > > the weak signal ssb stations are not too interisted in > > emergency service. Unless you have unusual > > requirements, vertical antennas for short distances on > > FM, and use repeaters. For longer distances just drop > > the the low bands. > > > > I have seen posts as to where the emergency building > > owners do not want to have their building's beauty > > messed up by ugly antennas. When that hapens, I would > > be tempted to remind them of New Orleans an just pack > > up and leave them. > > > > > > > > __________________________________________________________ > > Be a better friend, newshound, and > > know-it-all with Yahoo! Mobile. Try it now. > > http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ > > > > > > > > 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 > > > > > > > > > > > > > > > > > > -- http://pa0r.blogspirit.com 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! 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