On this evening's net the topic was NVIS. After a brief description of Near-Vertical Incident Skywave (much like the post below this one), we opened the net for check-ins.
ke5okt, Jim, checked in with a question. He has a KendeCom, model KRP-5000 repeater and can't find much information on it. He asked if anyone has information on this brand, such as how to find parts and documentation. kb5vdb, Ron, mentioned that aa5v, Steve, may have a repeater of that brand in his garage, and may know something more about them. Steve is a member of TRO and may be contacted through the club. If anyone has information they think Jim might be able to use about the KendeCom repeaters, he can be contacted at jim@mounds.org.
n5tda, Rex, mentioned that he has a G5RV up at about 25 ft., which would be less than 1/4 wavelength and would fall into the NVIS category. He mentioned that he was not able to get within the 500 mile skip zone at that height.
ke5lnn, Dave, asked if NVIS is in wide use by any particular amateur radio groups. In addition, Dave has a TE Systems 1412G, 2 meter amplifier. He says it works fine on two meter but doesn't work on 70cm. He has heard of a mod that can be done to allow it to work on 70 cm and wants to know if anyone knows how to install that mod. w5ydl, Dan, says he also has one of those amplifiers and that he too would like it to work on 70 cm, but doesn't know how to install the mod. Dave mentioned that he may be able to reach someone at TE tech support who can help.
ka0oxn, Rich, said that he had a 160M installed at about .o4 wavelength height that was good out to about 400 miles. He also had a 40M installed at 10 ft. that was good to about 300 miles.
na5dw, Dan, said that he would like to find a way to get his HF signal from Fairplay, CO to Denver, CO, about 90 miles. He tried a dipole hooked up to his truck's tailgate, on one end, and to a signpost on the other end, about 3 ft. high, 20M or 40M, and couldn't quite make the trip.
ae5ft, Gene, said that n5fem, Steve, was talking into the Dallas, Texas area on 40M, on the NVIS dipole mounted at 5 ft. at the last Route 66 event in Chandler Park. He also mentioned that he uses an NVIS antenna every day to check into the Oklahoma Sooner Traffic Net, which is a part of the National Traffic system Net. His antenna, he calls an "extreme" NVIS antenna, which is a G5RV mounted along the top of his wooden fence at about 6 ft, with about 10 ft. of wrap on each end, fed with about 30ft. of twin-lead and a short piece of coax. He says that he is about 90% effective getting into the net on 80M. He says he's worked both coasts during the Route 66 Contest where folks were trying to make contact with him as a Route 66 station. So it may not be all that good of a test, coast to coast.
ae5mn, Hank, mentioned that this might be an HF solution to his problem of finding something that would fit in with his neighborhood covenants.
kk5edd, Ed, said that he's in the process of building an NVIS antenna, from plans of Dr. Carl Gellenik, n6vng, with two 38ft. elements and then at 90 degrees from them, two 25 ft. elements. The design calls for a threaded center conductor on a SO-239 plug, which Ed is having trouble finding/fabricating. Ed would appreciate hearing back from anyone who might have information on how to find a threaded SO-239 center connector such as this.
ae5ft, Gene, mentioned also that in NVIS applications, we have to look at the maximum usable frequency. That is the maximum frequency that will bounce of (versus penetrating) the ionosphere. That "maximum frequency" can depend a lot on conditions, sunspot activity, and etc. Gene mentioned that 40 M is "iffy" on NVIS, which may explain na5dw's, problem making a 90 mile trip in Colorado. The other thing Gene mentioned, is that when you're looking at 80M NVIS, that's what most dipole installations are, to at least some degree. Few of us can afford to construct 120 ft towers for your dipole!
ke5und, Travis, checked in and mentioned that he's used NVIS technology inadvertently. He understands the principle but now knows what to call it. Travis asked if NVIS relates more to angle of take off. ae5ft, Gene, answered that yes, angle of take off is one of the parameters that NVIS defines. Travis mentioned also that this is probably why he can make it in to Albuquerque, NM but can't quite make the trip into Arizona.
No comments:
Post a Comment