---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Mon 10/23/06: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:44 AM - antenna interference () 2. 01:49 PM - Re: antenna interference (Doug McNutt) 3. 05:08 PM - Re: antenna interference (Noel Loveys) 4. 05:18 PM - Re: antenna interference (Noel Loveys) ________________________________ Message 1 _____________________________________ Time: 11:44:12 AM PST US From: Subject: Avionics-List: antenna interference --> Avionics-List message posted by: 10/23/2006 Hello Bob Nuckolls and other antenna experts, Some time ago a fellow builder installed an Advanced Aircraft Electronics comm antenna in the vertical stab of his composite (fiberglass) airplane. The antenna is a straight one piece dipole with balun in center. The reception was tested with a radio and found to be excellent. In attaching the rudder, a full length aluminum piano style hinge was installed. This is one of the builder's modifications to the original plans that called for separate short segments of aluminum piano type hinge for the rudder. When testing the reception again with the same transmitter the reception was practically nonexistent. The builder would like to retain use of the antenna and come up with a (nearly continuous) hinge solution that will permit adequate transmission and reception. Various solutions have been proposed: 1) Use a continuous piano type hinge made out of plastic. (Guden makes them). 2) Use a continuous piano type hinge made out of carbon fiber. http://www.carbinge.com/index.html 3) Use a basically continuous full length piano type hinge made out of carbon fiber, but cut it a number of times during its length into shorter than full length segments. 4) Use a basically continuous full length piano type hinge made out of aluminum, but cut it a number of times during its length into shorter than full length segments. 5) Abandon the continuous hinge concept and install separate short segments of metal hinge as the plans call for. We would appreciate your inputs and advice. Thanks. OC ________________________________ Message 2 _____________________________________ Time: 01:49:24 PM PST US From: Doug McNutt Subject: Re: Avionics-List: antenna interference --> Avionics-List message posted by: Doug McNutt At 14:41 -0400 10/23/06, wrote: >4) Use a basically continuous full length piano type hinge made out of aluminum, but cut it a number of times during its length into shorter than full length segments. It might be sufficient to cut it once only a few inches away from the center. It might also be enough to cut just the rod into two pieces with an insulator between them You might also try bonding both sides of the hinge to airframe ground. Well. . . that doesn't mean connecting it to the fiberglass. The idea is to move the resonance to longer wavelengths by making the hinge electrically longer as opposed to cutting it to make it shorter. And the # 10 thought. . . . Remove the dipole antenna and put a BNC connector on the hinge. -- --> If it's not on fire it's a software problem. <-- ________________________________ Message 3 _____________________________________ Time: 05:08:46 PM PST US From: "Noel Loveys" Subject: RE: Avionics-List: antenna interference --> Avionics-List message posted by: "Noel Loveys" Plastic or carbon fibre. Any short pieces of metal can be parasitic elements. Pieces shorter than 4" spaced at least 4" apart shouldn't cause the parasitic signal loss you experience. Try holding the short hinge segments to your vertical stab. with string before you commit to an installation. One Question... Is the leading edge of your rudder reinforced with metal ?? If so the hinge is only part of your problem. The system you have installed should be one of the best available. Completely omni directional. Noel > -----Original Message----- > From: owner-avionics-list-server@matronics.com > [mailto:owner-avionics-list-server@matronics.com] On Behalf > Of bakerocb@cox.net > Sent: Monday, October 23, 2006 4:12 PM > To: aeroelectric-list@matronics.com; avionics-list@matronics.com > Subject: Avionics-List: antenna interference > > > --> Avionics-List message posted by: > > 10/23/2006 > > Hello Bob Nuckolls and other antenna experts, > > Some time ago a fellow builder installed an Advanced > Aircraft Electronics > comm antenna in > the vertical stab of his composite (fiberglass) airplane. > The antenna is a > straight one piece dipole with balun in center. > > The reception was tested with a radio and found to be excellent. In > attaching the rudder, a full length aluminum piano style hinge was > installed. This is one of the builder's modifications to the > original plans > that called for separate short segments of aluminum piano > type hinge for the > rudder. > > When testing the reception again with the same transmitter > the reception was > practically nonexistent. > > The builder would like to retain use of the antenna and come > up with a > (nearly continuous) hinge solution that will permit adequate > transmission > and reception. Various solutions have been proposed: > > 1) Use a continuous piano type hinge made out of plastic. > (Guden makes > them). > > 2) Use a continuous piano type hinge made out of carbon fiber. > > http://www.carbinge.com/index.html > > 3) Use a basically continuous full length piano type hinge > made out of > carbon fiber, but cut it a number of times during its length > into shorter > than full length segments. > > 4) Use a basically continuous full length piano type hinge > made out of > aluminum, but cut it a number of times during its length into > shorter than > full length segments. > > 5) Abandon the continuous hinge concept and install separate > short segments > of metal hinge as the plans call for. > > We would appreciate your inputs and advice. Thanks. > > OC > > > > > > ________________________________ Message 4 _____________________________________ Time: 05:18:09 PM PST US From: "Noel Loveys" Subject: RE: Avionics-List: antenna interference --> Avionics-List message posted by: "Noel Loveys" I don't know what kind of plane this antenna is in but it sounds like part of the problem is the hinge is very close to 1/2 lambda (18-20") away from the antenna and is oriented parallel to it. Changing the resonant length of the hinges is a good starting place. Grounding the hinge will probably result in an RF shadow somewhere behind the plane. I think the best thing to do is to look at shorter segments of varying lengths with varying spaces between the segments. Or go straight to plastic or composite hinges... Don't forget the hinge pins also should be non metallic if plastic or composite hinges are used. Noel > -----Original Message----- > From: owner-avionics-list-server@matronics.com > [mailto:owner-avionics-list-server@matronics.com] On Behalf > Of Doug McNutt > Sent: Monday, October 23, 2006 6:14 PM > To: aeroelectric-list@matronics.com; avionics-list@matronics.com > Subject: Re: Avionics-List: antenna interference > > > --> Avionics-List message posted by: Doug McNutt > > > At 14:41 -0400 10/23/06, wrote: > >4) Use a basically continuous full length piano type hinge > made out of aluminum, but cut it a number of times during its > length into shorter than full length segments. > > It might be sufficient to cut it once only a few inches away > from the center. > > It might also be enough to cut just the rod into two pieces > with an insulator between them > > You might also try bonding both sides of the hinge to > airframe ground. Well. . . that doesn't mean connecting it to > the fiberglass. The idea is to move the resonance to longer > wavelengths by making the hinge electrically longer as > opposed to cutting it to make it shorter. > > And the # 10 thought. . . . Remove the dipole antenna and put > a BNC connector on the hinge. > > -- > --> If it's not on fire it's a software problem. <-- > > > > >