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## Re: Topband: Suggestions for vertical at HG0R

 To: Steve HA0DU Re: Topband: Suggestions for vertical at HG0R Dave Cuthbert Sat, 7 Nov 2020 05:49:21 -1000
 ```Steve, *I believe there is a measurement error. * 1. The reactive part of the input impedance should not become more inductive as the frequency is decreased. 1904kHz --> Z=68.1 + j0.3 and 1844kHz -->48.9 + j21.5. 2. An EZNEC model over 0.005/13 GND shows resonance at 1750kHz and the real part of the input impedance to be 17 ohms. Real-world will be a bit higher due to this being NEC-2. So, the real part of the input impedance is too high and I don't think can be accounted for by ground loss. Resonance is off by 150kHz. Questions: How are you measuring the antenna base impedance? What instrument are you using? Are there any strong LF/MF broadcast station signals at the QTH? Dave KH6AQ On Sat, Nov 7, 2020 at 5:08 AM Steve HA0DU wrote: > HI All, > > Today we finished installing a vertical with a top hat at HG0R, but it > is not perfect (yet). > > The vertical part is about 20.5m (67 ft) tall, starts with 10m of 50mm > (2") pipe at the bottom, and ends with 28mm (1.1") OD pipe on top. > > There are 8 quarter-wave radials below the antenna at each 45 degs, soil > is wet black earth. > > Top hat wires are connected to a small aluminum plate. The four (4) top > hat wires are about 12m (39 ft) long each, and are sloping at an angle > between 60 and 45 degrees. > > We measured the antenna, and found the following: > > *1904 kHz* (minimum SWR and also ain inflexion point in phase): > > *Z=68.1 + j0.3 SWR 1:1.36 Phase 0 deg* > > *1844 kHz* (resisitive Z closest to 50 ohms) > > *Z=48.9 + j21.5 SWR 1:1.54 Phase 23 degs* > > */One step before, with shorter top hat wires (approx. 10.2m wires) the > SWR was lower at the 0 phase point, but it was at 2005 kHz./* > > Please tell me what shall we do: > > - tilt the antenna again, add more lengths to the top hat wires, so that > phase 0 point comes down to about 1840 kHz (R will be still higher than > 50 ohms), and add more radials, perhaps radiation resiastance comes > closer to 50 ohms? > > - add a series capacitor to compensate the +j21.5 at 1844 kHz, and leave > it as is? > > Or any aother suggestions? > > 73/DX > Steve HA0DU > > > > -- > Ezt az e-mailt az Avast víruskereső szoftver átvizsgálta. > https://www.avast.com/antivirus > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector ```
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