Peter, one long radial running under the horizontal section appears to be quite beneficial, at least in simulation. The other radials should be as about long as the vertical section is tall. The ques
George, I tried an L-network and it will match your antenna on 80 and 160 meters. The L is configured as a series inductor at the source end and a shunt capacitor at the load end. Values to match you
How to quickly troubleshoot the plasma TV RFI? Disconnect all of the cables (except the AC power) from the TV. If I needs video to keep the screen active you can connect a source of NTSC video. Many
Hi Jim, I might not have been clear that my statement of bonding the case to earth GND pertains to the safety issues (covered in standard UL60950 and IEC60950) and not the EMI issues. Dave WX7G _____
Rune, the 16.5 m vertical with three horizontal, 9 m top hat wires has a radiation resistance of 12 ohms. A base loading inductance of 15 uH will tune the antenna to 1.8 MHz. This antenna is resonant
I checked the Triplite site but they do not list the attenuation for their products. An example of an industrial line filter is the Tyco 20ESK6, available at Digikey. It is $60 and needs to be instal
Jon, Tom's experience with plasma TV's supports my theory of the coupling mechanism. He found that common mode impedance was not very effective. Theory: A possible equivalent circuit for the plasma T
Mike, The Wireman stocks two lengths of the Spiderbeam fiberglass masts. 40' and 60' for $99 and $279. I recently bought the 40' version and I am very impressed with it. I plan to buy the 60' and giv
Merv sounds like top band heaven to me. Tell me if I'm wrong, but I assume the towers are 1/4 wavelength tall, base fed at 870 kHz. I can run a "real" tower model later when I get the dimensions from
Armin, there are many ways to proceed. Here is one way to do it that is simple. A simulation of a 60' vertical with twelve 70' radial wires, 12' above the ground, shows that it wil resonate with 64 u
There is a free download of the book RADIO ANTENNA ENGINEERING, by Edmund A. Laport, at lulu.com. This book has a large section on low and medium frequency antennas that should be of interest to top
Speaker wire and AC line cord (zip cord) are close to 100 ohms. The ARRL ran some loss tests on zip cord 10-15 years ago and reported fairly high losses. On top band RX this should not be an issue. T
Ollie and the gang, And the winner is.... The vertical antennas were modeled with 15 ohms of extra ground loss to account for NEC-2 not fully modeling ground losses. One 90-deg radial is run along th
Dan, five wavelengths will be far enough. An indirect measurement can be as good as a field strength measurement. If you can accurately measure the base impedance at resonance you can calculate the c
Tom, I think you missed the point of my post. The end result desired is to determine how effective the added radials are. My method involves relative measurements. In this case we are comparing X num
Dave, let's see if we can obtain an accurate change in field strength from added base resistance in NEC-2. Here's a 7 MHz vertical mounted 1' above average Sommerfield GND. The vertical has 16 resona
Right you are Sinisa. I think we are having a semantic issue here. I know that you understand what I'm saying and I'm saying it just to try to clarify the issue. Did Tom, W8JI, mean 100% horizontal p
Rick, that is a good antenna for 160 meters. I was thinking in terms of a 180 degree dipole terminated into 50 ohms. Like we use for EMC measurements. To "calibrate" one of these in NEC I radiate it
Rick and Tom (W8JI), thanks for the great information! In NEC I have not been able to create a symmetrical radial field in which the impedance rises with additional radials. The radial lengths explor
Tom, thanks for the excellent data.We have two things were are discussing; whether a decrease in input impedance follows the field strength trend and how well NEC-2 can model all of this. I ran a sim