Hi Low Band people, Nice presentation Steve. I would like to point out that Beverage users or even other phased antenna users should not use paralleling two 75 ohm coaxes and then matching them back to 75 for the receiver. While on the surface that all sounds good there is a little problem for the individual antennas. If you look from the wire through the Beverage transformer to the parallel junction the antenna transformer actually sees the other antenna at 75 ohms in parallel with the rig matching transformers 75 ohms. This causes the real load impedance on the Beverage transformer to be 37.5 ohms and not 75. This may cause the Beverage to not have the anticipated impedance flat curve or possible performance problems. This could also make the end load resistor not be an anticipated value. If you use a delay line in one antenna for stagger, the following should be noted. It has been my experience that although theoretically you only need to match at least one end of a coax for the phase delay in circuit to match the proper terminated value, I have found that terminating both ends reduces problems from component tolerances not terminating the proper coax impedance causing unwanted phase shifts. Using a Magic Tee will help terminating the coaxes with their proper impedance keeping the phase delay where you expect it. Early designers of passive 4 or more element receiving arrays missed this point when making combiners for arrays using paralleled transmission lines. Bottom line is to yes yes, use a Magic Tee or some version of a hybrid combiner for combining which will isolate between antennas.. Then the antennas as well as the receiver will see the 75 ohm load as likely designed. Here is a nice technical tutorial on the Magic Tee. https://michaelgellis.tripod.com/magict.html Lee K7TJR OR
-----Original Message----- From: Topband <topband-bounces+k7tjr=msn....@contesting.com> On Behalf Of donov...@erols.com Sent: Tuesday, February 9, 2021 3:28 PM To: topband <topband@contesting.com> Subject: Re: Topband: The Magic-T This is the corrected URL for Steve's Magic-T video www.youtube.com/watch?v=_Bbt1IcC4bk 73 Frank W3LPL ----- Original Message ----- From: "VE6WZ_Steve" <ve...@shaw.ca> To: "topband" <topband@contesting.com> Sent: Tuesday, February 9, 2021 10:29:54 PM Subject: Topband: The Magic-T Today I uploaded a video to my RX series which explains the Magic-T combiner. I have received a few emails asking me “how do I make the magic-T”? so I thought a video would be helpful. I show the method for winding and building the Magic-T combiner and I explain how it is used in phased RX antennas. The associated 2:1 impedance transformer is discussed, and I show the difference between an isolated and auto-transformer architecture. I also discuss an error that can be made when building phased RX antennas if care is not taken to avoid an unintentional 180 phase shift at one of the elements, especially if using home-brew matching boxes. YouTube video: https://youtu.be/_Bbt1IcC4b <https://youtu.be/_Bbt1IcC4b>- 73, de steve ve6wz _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
