Re: Topband: 75 meter 1/4 wave vertical on160
Doug, If you have the room, here is an alternative that I am using now at ZF9CW. I believe this would be better than a coil at the base. Make that vertical your 160m transmit antenna by adding two wires attached to the top and going out as far as you can so the ends are as high as you can get them. Make it symmetrical with the wires going East/West or North/South, etc. Those wires will be 60 feet plus or minus each. For 80m have a quarterwave wire with a good insulator spaced a few feet out coming off the vertical at 45-50 feet up. That wire can come out from the vertical by 10 feet or more and then back to the base. Use separate feedlines and same radial field. Match with a hairpin for each antenna. My 80m vertical looks a lot like a > sign but the top line is longer than the bottom one. I am just guessing mine comes from about 50 feet, comes down to about 20 feet up and 20 feet out and then back to the base. You could put a vacuum relay at the top to switch the wires out for 80, which I have done, but I like the flexibility of current scheme better. If you are going to make a coil and have modeling software, Hamwaves Inductance calculator is a good tool. Coils are nice but can be a pain to weatherproof. 73... Stan, ZF9CW On Sat, Nov 17, 2018, 12:04 PM doug dietz Gentlemen, > I have been lurking in the background for over a year there have been some > excellent learning possibilities. > Thank you all. now on to my question. > > I have a 1/4 wave vertical (about 66 feet) for 75-80 meters I would like > to try and make it resonate on 1.825. If I put the analyzer on it I don't > understand the reading.I know the swr is bad on 160 because the > kpa-1500 will not match it. If possible I would like to add a coil at the > bottom with a relay to switch in and out. Any ideas length of wire, > diameter, of coil, and size of wire, for 1500 watts I am not worried > about receive only transmit. > > Doug WD8Z > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: 75 meter 1/4 wave vertical on160
Hi Doug, I've got exactly the same setup. I use two coils, a 2uH shunt coil, one side of which is grounded, and a 22uH loading coil that connects to the top of the shunt coil at the bottom of the antenna. You drive the antenna where the two coils intersect. Realistically, you'll probably have to tweak the coil settings bit to minimize the SWR and to bring the resonance where you want it. My vertical resonates at 3.530 MHz and 1.815MHz, with a 1.1 VSWR on 160 and a 1.45 on 80. I use a toroid for the loading coil to make it compact. It consists of two 2.25" cores T42 material wrapped with fiberglass tape and wound with RG-316U , with the shield and braid soldered together. It all fits in a weatherproof NEMA enclosure. I'll send a photo separately. 73, Jim w8zr Sent from my iPhone. > On Nov 17, 2018, at 10:04 AM, doug dietz wrote: > > Gentlemen, > I have been lurking in the background for over a year there have been some > excellent learning possibilities. > Thank you all. now on to my question. > > I have a 1/4 wave vertical (about 66 feet) for 75-80 meters I would like > to try and make it resonate on 1.825. If I put the analyzer on it I don't > understand the reading.I know the swr is bad on 160 because the > kpa-1500 will not match it. If possible I would like to add a coil at the > bottom with a relay to switch in and out. Any ideas length of wire, > diameter, of coil, and size of wire, for 1500 watts I am not worried > about receive only transmit. > > Doug WD8Z > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: 75 meter 1/4 wave vertical on160
Gentlemen, I have been lurking in the background for over a year there have been some excellent learning possibilities. Thank you all. now on to my question. I have a 1/4 wave vertical (about 66 feet) for 75-80 meters I would like to try and make it resonate on 1.825. If I put the analyzer on it I don't understand the reading.I know the swr is bad on 160 because the kpa-1500 will not match it. If possible I would like to add a coil at the bottom with a relay to switch in and out. Any ideas length of wire, diameter, of coil, and size of wire, for 1500 watts I am not worried about receive only transmit. Doug WD8Z _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
