I noticed JC's comment below about a low dipole as a receiving antenna. Did I interpret that correctly? I've read of a Dipole on the ground as a low noise receive antenna for 160 but.........can a non resonant dipole installed at low heights be better, as a receive antenna, than a vertical or L antenna? How about a non-resonant dipole, say, two feet above ground, at a length of 100 feet? Would you feed it with coax or figure out the Zo at 160 and use a suitably wound xfmr to match to 50 ohms??? Just athinkin' of ways to use available low horizontal space, albeit the available space is insufficient for a beverage. Thoughts??? 72, Jim Rodenkirch K9JWV
> From: [email protected] > To: [email protected]; [email protected] > Date: Wed, 17 Dec 2014 23:11:10 -0500 > Subject: Re: Topband: 8 circle: DXE vs Hi-Z > > Hi guys > > Polarization does play a lot on 160m for two reasons. I can say that because > I am using my HWF (two horizontal flags end fire) since 2009. The first one > is local man made noise that propagate only vertical due the attenuation on > the horizontal component near the ground. And Second the DX signal always > come in both polarization. > The result form the two reasons is an optimized signal to noise ration using > horizontal polarization. > > I have both WF with the same RDF, during SR or SS there is almost no sky > noise coming from the back because of the darkness, however local man made > noise comes from any direction, especially if you live in a city lot like I > do. Most of the time the noise is coming at the same direction you want to > hear the DX, and if you add power line noise the situation deteriorates a > lot for the VWF due vertical polarization. Using my HWF I normally get 10 dB > better SNR than my VWF that has the same RDF and same aperture of 74 degree > measures, I can turn the antenna and measure it, they are not optimized for > best F/B, I optimized them for maximum rejection of local man made noise. > > The HWF is not a dipole. The two phased loops take of angle us 40 degree and > there is a huge attenuation for signals above 60 degree. Low dipole is a > huge issue if the dipole is resonant, it will interact with all other > receiver antennas and will destroy directivity of all of them, if you want > to use a low dipole make it not resonant. Gain in not important so it can > be short as a 30 m dipole and still will hear the same way. Another issue > with low dipoles is the amount of energy absorbed from the TX antenna. If > you connect a power meter and a 50 ohms load o the low dipole and transmit > KW on the TX antenna, you can measure several WATTS at the low dipole . You > can burn you front end with a low resonant dipole. > > Adding to all that there is another very interesting observation from my > last 5 year using a high RDF horizontal RX antenna, when the TX signal > refract on the ionosphere the signal split in two waves, that was very well > explained by K9LA. What I observed is that these two waves does propagate in > different directions. I normally receive VK6 near my SR with better SNR > horizontal from 210 degree SSW and with better SNR from 280 degree vertical. > Sometimes the horizontal peak is 20 minutes before the vertical peak that is > most of the time at my SR. > > 73's > N4IS > JC > > > > > > > > > -----Original Message----- > From: Topband [mailto:[email protected]] On Behalf Of John > Kaufmann > Sent: Wednesday, December 17, 2014 8:59 PM > To: [email protected] > Subject: Re: Topband: 8 circle: DXE vs Hi-Z > > Good points about polarization. If the signals and/or noise are polarized > predominantly in one state, then RDF may not be a good predictor of SNR > performance, particularly if the antenna receives predominantly in an > orthogonal polarization. On the other hand, if the polarization state of > the signals and noise evolve randomly with no preference for any one state, > which is often assumed for skywave signals, then RDF will be--on average--a > good receiving metric, subject to the previous stated qualifications about > the spatial distribution of the received noise. However, some of the past > discussions on this reflector about preferential polarization of skywave > signals on 160 may call into question the assumption of randomly polarized > signals. > > 73, John W1FV > > > -----Original Message----- > From: Topband [mailto:[email protected]] On Behalf Of Richard > (Rick) Karlquist > Sent: Wednesday, December 17, 2014 3:19 PM > To: Lee K7TJR; 'Terry Posey'; 'John Kaufmann'; [email protected] > Subject: Re: Topband: 8 circle: DXE vs Hi-Z > > All this discussion about RDF overlooks the issue of polarization. If you > make an array of verticals with a certain RDF (assuming noise comes from all > directions uniformly), the array will be better than an individual vertical > by the RDF factor. However, what I have found is that a horizontally > polarized antenna, such as a low dipole frequently receives considerably > better than a vertical. In that case, you would be better off using an > array of low dipoles. The reason why horizontal polarization can be better > is that the horizontal component of terrestrial based noise is highly > attenuated over distance as a ground wave. > > Rick N6RK > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
