Hello KD9SV made a great Magic T
https://www.dxengineering.com/parts/svp-sv-rsc 73, Jorge CX6VM/CW5W El mar, 9 feb 2021 a las 23:02, Lee STRAHAN (<[email protected]>) escribió: > 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 <[email protected]> On Behalf Of > [email protected] > Sent: Tuesday, February 9, 2021 3:28 PM > To: topband <[email protected]> > 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" <[email protected]> > To: "topband" <[email protected]> > 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 > -- 73, Jorge CX6VM/CW5W _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
