Hi Dave, thanks for the analysis. I was using your number 3 model, though I had a small slope in the top wires. When I flattened the top wires I too was getting about 100kc at 24 ohms.
I will to do a sensitivity analysis to see what works best for me. Where I set down the 60 radials (laying on the forest floor) I can’t get the top wires flat due to overlapping tree canopies. The only place with a clearing is above my house and I can’t put the vertical there. Also thanks to all the input on and off the reflector! I will look at the relay option if my idea doesn’t work. I’m running low power so my rig’s tuner can help if I don’t get 100 kc Regards , Kenny K2KW > On Jan 4, 2021, at 1:18 PM, Dave Cuthbert <[email protected]> wrote: > > > > Kenny, your model might have a problem with the acute antenna between the two > vertical wires. I ran EZNEC simulations to test this and compare against a > single vertical wire T reference antenna. Your antenna shows similar > bandwidth, but a different input resistance. > > Antenna 1 reference antenna > 75' vertical wire > from there extend two horizontal 35'wire > SWR bandwidth normalized to the antenna input resistance of 23 ohms > SWR bandwidth is 118kHz > > Antenna 2 your antenna > perfect GND, #12 bare wire, current segments are 1' > 1' vertical wire from GND > from that wire two wires extend to 75' separated by 4' at the top > At 75' the two wires are joined > From each 75' wire extends a 48' wire > SWR bandwidth normalized to the antenna input resistance of 16 ohms > 2:1 SWR bandwidth is 100kHz > > Antenna 3 your antenna modified to conform to the NEC included angle rule > perfect GND, #12 bare wire > 1' vertical wire from GND > from that, 2' horizontal wires extending opposite one another > two wires extend from the ends of those two wires to 75' > at 75' the two wires are joined > from each 75' wire extends a 52' horizontal wire > SWR bandwidth normalized to the antenna input resistance of 25 ohms > SWR bandwidth is 106kHz > > Antenna 4 single vertical wire with a horizontal flat top wires > perfect GND, #12 bare wire > 75' vertical wire from GND > from that, 2' horizontal wires extending opposite one another > two wires extend horizontally from the ends of each of those two wires to 22' > SWR bandwidth normalized to the antenna input resistance of 23 ohms > SWR bandwidth is 72kHz > > Dave KH6AQ > > >> On Mon, Jan 4, 2021 at 5:07 AM Kenny Silverman <[email protected]> wrote: >> Hello and HNY! >> >> I will be converting a wire inverted-L to a T top loading on a 75’ tall wire >> hung from a tree. To improve the bandwidth, I was wondering about going to a >> 2-wire “cage” for the vertical section. I’m actually modeling a skinny >> triangle where the wires connect at a point on the top, but with a 4 foot >> spread of the wires near the ground. This adds about 15-20 kc to the 2:1 >> bandwidth per the model. >> >> Will a 2-wire section like this always behave as a wide/fat conductor or do >> I have to worry about voltage/current in Each wire? >> >> Regards , Kenny K2KW >> _________________ >> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
