Hi Dick "I never noticed any difference in receiving performance"
That's exactly what we should expect using a resonant dipole, it interact with any other antenna because the fiscal length is resonant, does matter if the feed impedance, if it is only a straight wire resonant it is like a director or director. Distance also is something hard to manage on 160m. 120ft is only 1/4 or .25 wave , heavely interact with other resonant elements. A low dipole is like an inverted V, used to be called unidirectional, a high dipole is different because the vertical field change intensity far from the ground, however the feed line is hardtop choke and remove the vertical common mode noise. Ladder line has huge advantage here , but not worth the effort . The low dipole and inverted V is unidirectional only if you disregard the polarization, using EZENEC it is easy to demonstrate that, check Plot Type: 3D plot and select Desc Options Ver.Horiz.Total. When you plot the 2D Azimuth Slice or Elev Slice, the vertical field is the red line and the horizontal a green line. The inverted V or low dipole is horizontal only at broadside with a 8 patter and some RDF, along the wire the Inverted V and low dipole is vertical polarized. Bothe fields are high angle, it means low gain at low angles. Both antennas work like a very short beverage along the wire and does not perform at all. Broadside there is a huge deep null on vertical signals, as a result the manmade noise is also attenuated that direction, the horizontal signal sky wave 20 to 40 degree has less attenuation, that situation there is an increase in the signal to noise ratio. The lobe is very wide and the SNR is better at the center and at 45 degree each side the vertical field is the same as the horizontal field, that's why these antennas are unidirectional, with the two fields the same there is no improvement on SNR after 45 degree from the center The situation where these antennas outperform vertical arrays is because they receive horizontal sky wave signals or high angles vertical or horizontal signals. Any receiver antenna without directivity is works like the attenuator in your radio, just reduce the overall gain decrease the Noise figure of the RX system but increase the IP3 reducing intermodulation. Almost the same thing as reduce the RF gain and increase the audio gain does. Receiver antennas to perform must have good RDF, and keep no other resonant anything around, only one resonant wire will be part of the RX system and change the patter, is the wire works like a director or reflector it would increase the RDF , the odds are not that and most of the cases the interaction makes the RX antenna patter useless. This long answer is to validate your observation, resonant dipoles does not provide any difference in receiver performance than your vertical or TX antenna. 73's JC N4IS -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard Karlquist Sent: Saturday, December 20, 2014 4:49 PM To: topband@contesting.com Subject: Re: Topband: Non-resonant receive antennas On 2014-12-20 13:06, Richard Jaeger wrote: > I guess I should try a low dipole and see what happens. > > Dick, K4IQJ .. > When talking about a low dipole, the question comes up as to why it must be low to work. Actually we don't know that it must be low to work. Very few of us are in a position to put up a "high" dipole, so the question is basically moot. However, in an attempt to gauge the influence of height, I A/B'ed two full size dipoles at 30 and 60 foot heights over a period of 6 months. The one not in use was floating to avoid interaction with the active one. I never noticed any difference in receiving performance. What seems to happen is that the signals are a few dB higher on the 60 foot wire, but the noise is commensurately higher. 30 feet was chosen for the minimum so that the wires didn't look like beverages (and because I have a bunch of 30 foot lengths of pipe). Rick N6RK _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband