Re: Topband: FCP Question
Ted, Read through Jim K9YC’s "Power Point slides for a presentation about 160M antennas at Pacificon in October 2012. Getting On 160M From a Small Lot (and Larger Ones Too). October 2012” http://k9yc.com/160MPacificon.pdf K2AV Folded Counterpoise information begins on page 68 of the PDF. 73, Jim WI6X > On Jan 4, 2021, at 9:47 AM, Salvatore [Ted] K2QMF wrote: > > Hello Topbanders, > > I have an inverted "L" with 4 elevated radials! > I seem to have too much ground losses! > I am wondering if I can add an 160 FCP to help with the ground losses?? > Any info would be much appreciated! > Thanks and 73, > Ted K2QMF > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
> > To model radials, we must use Real High Accuracy Ground, with NO connection > to Ground. Read the EZNEC manual Yes! That is what I need to change. Thank you! Solution: I was connecting the radials to ground using EZNEC. I need to create the radials just above ground. Page 90 of the User Manual. "Buried radials can be directly modeled only with EZNEC Pro/4 using an NEC-4 calculating engine (see Buried Wires). With EZNEC, EZNEC+, and EZNEC Pro/2 they have to be simulated.” Buried radials with EZNEC have to be simulated. “...model buried radials by substituting radials just above the ground surface. This does a moderately good job of predicting the ground system efficiency as well as whatever pattern modification results from the radial system. With this approach, the High Accuracy Real ground type must be used. See Connecting to High Accuracy Ground for more information.” Page 127 of the User Manual "With program types other than EZNEC Pro/4 the best way to approximate a buried radial system is by creating horizontal radials just above the ground, and make the "ground" connection to the radials. A height of between about 1/100 and 1/1000 of a wavelength is suitable, but in any case no less than several wire diameters. If a low impedance connection is required, make the radials about a quarter wavelength or odd multiples long, and avoid lengths approaching a half wavelength or multiples. These aren't free space wavelengths, however, but wavelengths for a wire at the radial height. A half wavelength for a wire very close to the ground will be less than in free space, though. You can determine the wavelength by modeling a dipole at the height of the radials and adjusting its length until it's resonant. Be sure you're seeing the lowest (series) resonance, which for very low wires will occur with a dipole length somewhat less than a free space half wavelength. The best radial length will be about half the resonant dipole length. Radials can easily be constructed using EZNEC's automated radial creation feature. Above ground radials will show resonant effects more sharply than buried radials, but will provide a reasonable approximation of a buried radial system." _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
Thank you everyone. The radials as modeled have End1 Ground connection and no End 2 connection. Should they be connected to another wire? --- WIRES --- No. End 1 Coord. (ft) End 2 Coord. (ft) Dia (in) SegsInsulation Conn. X Y Z Conn. X Y Z Diel C Thk(in) 1 GND0, 0, 0W2E10, 0, 40 #14 17 10 2 W1E20, 0, 40 143, 0, 40 #14 17 10 3 GND0, 0, 00, -100, 1 #14 17 10 4 GND0, 0, 00,100, 1 #14 17 10 5 GND0, 0, 0 -100, 0, 1 #14 17 10 6 GND0, 0, 0 100, 0, 1 #14 17 10 I have a field of 100+ 70’ to 20’ #14 wire radials under my lawn that I will use. I stopped inputing radials in the model at four radials when my numbers seemed off. I’m using EZNEC Ver. 6 (NEC-4). I do not have room for proper elevated radials. I only have room to elevate about six, and they could only be about 5’ above ground. I used Jim K9YC’s Pacificon 160 on Small Lots slideshow to get started with this antenna and his cookbook for the balun. Thanks! FCC’s ground conductivity map indicates 15 millimhos per meter, and I’m on predominantly clay soil. Transmission line is 75’ of RG213, so it is not an issue. Thanks again for helping. Jim WI6X > On Dec 9, 2020, at 1:16 PM, Jim Brown wrote: > > On 12/9/2020 12:00 PM, wi6x...@gmail.com wrote: >> My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but I >> don’t have enough experience to know if what what I am doing is correct or >> not. I’m a neubie, at EZNEC and 160m. > > Those numbers tell you that the antenna is resonant below the band, and the > dimensions also show. It's a common trick to tune the antenna low so that R > is 50 ohms and X is inductive; we can then tune out the inductance with > series C. I'm using this technique with my Tee vertical for 160M. > > Feedline loss on 160M is pretty low unless the line is pretty long, so if > your rig or power amp will drive it, I wouldn't worry about it. > > Another important observation. Four radials isn't enough of a counterpoise > unless they are well elevated -- N6BT, who's done lots with verticals and is > a fine antenna engineer, says at least 16 ft. A lot of the R in your model > could be ground loss. If those radials are on-ground, you need a LOT more > than four; they don't need to be any specific length or even close to the > same, but 100' is pretty close to a quarter wave (thanks to soil modifying > their VF), and more copper on the ground is better. > > Also, soil parameters strongly affect that loss component -- try to learn > what your soil is like, and plug those parameters into the model. In the soil > parameters window, right click on the entry screen to get a list of them. > > Here are slides for a talk I've done at Pacificon, Visalia, and to several > clubs. It's mostly about antennas and counterpoise/radial systems. No > original work, just summarizing a lot of great work by others. > http://k9yc.com/160MPacificon.pdf > > 73, Jim K9YC > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.
I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire. My gut tells me the 60.25197 + J 18.63926 ohms impedance is to high, but I don’t have enough experience to know if what what I am doing is correct or not. I’m a neubie, at EZNEC and 160m. Thank you in advance for your advice and recommendations. 73, Jim, WI6X SOURCES: Wire #1, 0% From E1 GROUND TYPE: Real/High Accuracy EZNEC ver. 6.0 160m Inv L 12/9/2020 11:38:28 AM --- SOURCE DATA --- Frequency = 1.83 MHz Source 1 Voltage = 314.7 V at 17.19 deg. Current = 4.99 A at 0.0 deg. Impedance = 60.25197 + J 18.63926 ohms Power = 1500 watts SWR (50 ohm system) = 1.470 (75 ohm system) = 1.422 EZNEC ver. 6.0 160m Inv L 12/9/2020 11:21:01 AM --- WIRES --- No. End 1 Coord. (ft) End 2 Coord. (ft) Dia (in) SegsInsulation Conn. X Y Z Conn. X Y Z Diel C Thk(in) 1 GND0, 0, 0W2E10, 0, 40 #14 17 10 2 W1E20, 0, 40 143, 0, 40 #14 17 10 3 GND0, 0, 00, -100, 1 #14 17 10 4 GND0, 0, 00,100, 1 #14 17 10 5 GND0, 0, 0 -100, 0, 1 #14 17 10 6 GND0, 0, 0 100, 0, 1 #14 17 10 _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
