Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar)
It seems as though if data were taken as to categorize the (average or typical) noise temperature with the angle of intensity of atmospheric noise that this could be utilized as part of the RDF equation. For instance, if at 20 degrees, the noise temperature was 5 dB higher than at 80 degrees, then we might have a *more* accurate measure of comparison of performance increase. Take the data every 5 degrees for city, urban, and rural areas and the user can determine which RDF model to use. My experience like K9LA and others, is that some antennas that should work better by the numbers, just don't. Jim - KR9U -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of donov...@starpower.net Sent: Friday, March 04, 2016 12:04 PM To: Topband@contesting.com Subject: Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar) Hi Tim, While RDF is helpful, nothing substitutes for devoting the effort to analyze the detailed antenna pattern. RDF is especially useful in quiet rural areas with very few homes and power lines and within several miles of our antenna, but its insufficient for most of us. Very few of us live in an extremely quiet local RFI environment any more, especially now that just one RFI generating electrical or electronic device in a single home within a mile (or more) can suddenly ruin our previously quiet RFI environment. Life was much easier when we only had to worry about power line RFI. RFI caused by a high efficiency heating and air conditioning system in a home a mile from my QTH caused me to install the 8-circle W8JI receiving arrays at W3LPL to provide a much narrower main beam than I could achieve with Beverage antennas. The 8-circle often provides a tremendous improvement compared to my 580 foot Beverages which I still have and use. I don't have adequate space for longer Beverages or arrays of phased Beverages. Most of us care more about narrowing the beamwidth of the main beam at elevation angles below about 30 degrees while also inimizing RFI arriving at all azimuths outside the main beam at low angles. RDF doesn't do that for us, it optimizes over the entire hemisphere, often at the expense of better RFI rejection at low angles. Better RFI rejection usually results in a different optimization than RDF alone can provide. RDF provides a good starting point, but it doesn't provide the complete answer for most of us. 73 Frank W3LPL - Original Message - From: "Tim Shoppa" <tsho...@gmail.com> To: "Richard (Rick) Karlquist" <rich...@karlquist.com> Cc: Topband@contesting.com Sent: Friday, March 4, 2016 2:59:34 PM Subject: Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar) The RDF seems to be the best we have at the moment, for taking a 3-dimensional pattern and turning it into a single number. Of course the details of the 3-dimensional pattern are lost. In addition to the quantitative RDF or S/N numbers, the qualitative change in pattern as you move up the RDF is remarkable. We go from * no directivity * a null in back with not much differentiation between forward and side * increasing side rejection * near-complete side rejection * increasing rejection of directions near forward but not quite forward The 8-circle is mind-blowing. Tim N3QE On Fri, Mar 4, 2016 at 12:37 AM, Richard (Rick) Karlquist < rich...@karlquist.com> wrote: > In this webinar, it was asserted (without explanation) that for every > 1 dB increase in RDF, you get 1.5 to 2.0 dB improvement in S/N ratio. > I've never heard that before and don't even see how it makes sense. > Actually, I don't even know how you can make generalizations like that > unless you are describing a theoretical QTH with uniform isotropic > noise. I'd like to believe this is true. > Can someone educate me as to why I should believe this? > > 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
Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar)
Hi Frank I agree with you. I'm near Fort Lauderdale in a city lot, directivity from my Vertical WF did help me a lot on 160, some rare DX like 4W6 was possible only direct and using the vertical WF. 9M0 first time was also direct using the VWF but next year 9M4 was only possible to work using my HWF long path SSW. 80 and 40m is very easy from here ,over 300 using only a R7 for TX on 40m and tuning my 160m TX antenna on 80m, not all the time, it is hard to tune it. The noise around me is increasing every year and I am not using my VWF anymore, only the HWF( 11.5) dB RDF) due horizontal polarization the HWF rejects most of the city noise. I tuned the HWF for maximum rejection of vertical signal and the size is just big enough so I can hear some man made noise, It is not tuned for maximum RDF(12 dB) or F/B. My average noise here during the day is around -85dBm, a rural location noise can be as low as -125 dBm, all 500 Hz BW. It is a 40 dBm more noisy. My 160m station is on my back yard, 150Ft x 50Ft , including the 64 radials in between 25 Ft (70%) to 120 Ft (30%). Doug NX4D QTH is only 1/5 of an acre for his WF and TX vertical. We are getting close to 300 countries on 160m, Doug is 298 and I'm 283 now. Regards JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of donov...@starpower.net Sent: Friday, March 04, 2016 12:04 PM To: Topband@contesting.com Subject: Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar) Hi Tim, While RDF is helpful, nothing substitutes for devoting the effort to analyze the detailed antenna pattern. RDF is especially useful in quiet rural areas with very few homes and power lines and within several miles of our antenna, but its insufficient for most of us. Very few of us live in an extremely quiet local RFI environment any more, especially now that just one RFI generating electrical or electronic device in a single home within a mile (or more) can suddenly ruin our previously quiet RFI environment. Life was much easier when we only had to worry about power line RFI. RFI caused by a high efficiency heating and air conditioning system in a home a mile from my QTH caused me to install the 8-circle W8JI receiving arrays at W3LPL to provide a much narrower main beam than I could achieve with Beverage antennas. The 8-circle often provides a tremendous improvement compared to my 580 foot Beverages which I still have and use. I don't have adequate space for longer Beverages or arrays of phased Beverages. Most of us care more about narrowing the beamwidth of the main beam at elevation angles below about 30 degrees while also inimizing RFI arriving at all azimuths outside the main beam at low angles. RDF doesn't do that for us, it optimizes over the entire hemisphere, often at the expense of better RFI rejection at low angles. Better RFI rejection usually results in a different optimization than RDF alone can provide. RDF provides a good starting point, but it doesn't provide the complete answer for most of us. 73 Frank W3LPL - Original Message - From: "Tim Shoppa" <tsho...@gmail.com> To: "Richard (Rick) Karlquist" <rich...@karlquist.com> Cc: Topband@contesting.com Sent: Friday, March 4, 2016 2:59:34 PM Subject: Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar) The RDF seems to be the best we have at the moment, for taking a 3-dimensional pattern and turning it into a single number. Of course the details of the 3-dimensional pattern are lost. In addition to the quantitative RDF or S/N numbers, the qualitative change in pattern as you move up the RDF is remarkable. We go from * no directivity * a null in back with not much differentiation between forward and side * increasing side rejection * near-complete side rejection * increasing rejection of directions near forward but not quite forward The 8-circle is mind-blowing. Tim N3QE On Fri, Mar 4, 2016 at 12:37 AM, Richard (Rick) Karlquist < rich...@karlquist.com> wrote: > In this webinar, it was asserted (without explanation) that for every > 1 dB increase in RDF, you get 1.5 to 2.0 dB improvement in S/N ratio. > I've never heard that before and don't even see how it makes sense. > Actually, I don't even know how you can make generalizations like that > unless you are describing a theoretical QTH with uniform isotropic > noise. I'd like to believe this is true. > Can someone educate me as to why I should believe this? > > 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
Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar)
The RDF seems to be the best we have at the moment, for taking a 3-dimensional pattern and turning it into a single number. Of course the details of the 3-dimensional pattern are lost. In addition to the quantitative RDF or S/N numbers, the qualitative change in pattern as you move up the RDF is remarkable. We go from * no directivity * a null in back with not much differentiation between forward and side * increasing side rejection * near-complete side rejection * increasing rejection of directions near forward but not quite forward The 8-circle is mind-blowing. Tim N3QE On Fri, Mar 4, 2016 at 12:37 AM, Richard (Rick) Karlquist < rich...@karlquist.com> wrote: > In this webinar, it was asserted (without explanation) that > for every 1 dB increase in RDF, you get 1.5 to 2.0 dB > improvement in S/N ratio. I've never heard that before > and don't even see how it makes sense. Actually, I don't > even know how you can make generalizations like that > unless you are describing a theoretical QTH with uniform > isotropic noise. I'd like to believe this is true. > Can someone educate me as to why I should believe this? > > Rick N6RK > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar)
Hi Rick As I told in the webinar it is a measured practical result, not a math calculation.. I have a DDC SRD and several receiving antennas in a very clean environment, only one TX antenna detuned, not other tower or Yagi etc. I can switch from one receiving antenna to another and see how much the signal is above noise. When you remove noise for every direction due RDF, increasing RDF the noise floor decrease. I can pick up a signal and measure db. above noise listening my TX vertical. Then I switch to my vertical WF and the signal to noise ratio increase average by 10 db., it has nothing to do with gain, just signal level against noise level. Then I switch to my HWF and the SNR increase another 10 db. from the vertical WF , it is average 20 db. better them the same signal against noise on my TX antenna. That is observations and measurements since 2009. Any time I can detect a improvement I stick with it, and try something else to get another new improvement. Looking into my records and associating it with RDF, comparing with 5dB RDF from a vertical TX antenna, I come up with average 1,5 to 2 db. increase on SNR for each dB increase in RDF against a vertical TX. I it a practical empirical result, you can try and check it by yourself. Regards JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Richard (Rick) Karlquist Sent: Friday, March 04, 2016 12:38 AM To: Topband@contesting.com Subject: Topband: Comments on High Performance RX Antennas for a Small Lot (Webinar) In this webinar, it was asserted (without explanation) that for every 1 dB increase in RDF, you get 1.5 to 2.0 dB improvement in S/N ratio. I've never heard that before and don't even see how it makes sense. Actually, I don't even know how you can make generalizations like that unless you are describing a theoretical QTH with uniform isotropic noise. I'd like to believe this is true. Can someone educate me as to why I should believe this? Rick N6RK _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
