Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Page 2 of 3 FirstFirst 123 LastLast
Results 11 to 20 of 28

Thread: Antenna wiring

  1. #11
    Senior Member SkyPirate's Avatar
    Join Date
    Apr 2009
    Location
    Edgar Springs MO
    Posts
    1,841

    Default Re: Antenna wiring

    My 5 has a plate about 1/2 way between the rear edge of the turtle deck and the vertical stab, thats where im mounting my com antenna
    Chase
    Model 5 OutBack
    912 UL

  2. #12
    Senior Member jrevens's Avatar
    Join Date
    Aug 2009
    Location
    Arvada, CO
    Posts
    2,146

    Default Re: Antenna wiring

    I'm certainly no expert on this subject, but I have been told that relatively small antenna mounting plates (compared to what is generally recommended on aircraft by people who DO know what they're talking about), connected to the welded tube structure seem to work very well on Kitfox aircraft. It has been suggested to me that perhaps the steel tubing of the fuselage structure augments or effectively increases the effective size of the metal mounting plate itself, creating a larger ground plane than you would think. The plate itself has to be welded to, or otherwise well connected electrically to the rest of the structure of course. I don't have any personal experience with this yet, but I have mounted my ELT antenna on a very small aluminum plate that is connected to the welded structure with a wired connection. A very similar plate on a friend's Kitfox, with the same ELT, was proven to work very well during an unintended activation.

    My fuselage was built before the factory was welding on the "razorback" with the plate at the front end of it, just behind the turtle deck. I fabricated & welded on a plate for my com antenna approximately halfway between the vertical fin & the turtle deck, like Chase's, as I like that location for the antenna. I then installed a little different "semi-razorback" tube from the fin to that plate. It may not look as nice as the factory set-up, but I hope it will work & look OK when everything's covered.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  3. #13
    Senior Member SkyPirate's Avatar
    Join Date
    Apr 2009
    Location
    Edgar Springs MO
    Posts
    1,841

    Default Re: Antenna wiring

    Your correct John with your analysis of the airframe being an enlarged ground plane, the materials in the structure work well distributing the RF signal were in wooden or composite structure would need to fabricate an "X" ground plane out of copper or another conductive material and connect it to the ground side of the coax ,

    The obstacles that can deflect or reflect the RF are any vertical ( vertical stab) components of the airframe within 18" to 20" suggested in some of the literature i have found on the matter which locating the antenna between vertical stab and turtle deck should be adequate
    Chase
    Model 5 OutBack
    912 UL

  4. #14
    Senior Member HighWing's Avatar
    Join Date
    May 2009
    Location
    Goodyear, AZ
    Posts
    1,743

    Default Re: Antenna wiring

    Back in the days of my Ham hobby, many vertical antennas had ground "Planes" constructed out of four horizontal wires parallel to the ground - sometimes buried so you could still mow the lawn. Where we build light for short field or fair for speed, Hams build for distance. If six were better, you would have seen six or even more. You will often see this type of antenna on the roofs of fire houses and other structures that house radio transmitters - the four horizontal whiskers are the ground plane. I agree that the fuselage is a great ground plane if using the welded antenna mounting plates. With the Dorsal Fins that some are adding that extend from the vertical stabilizer to the turtle deck, the plates become unusable and a suitable ground plane needs to be installed. I terminated the dorsal fin tube to the aft edge of the plate for this reason. A ground plane can be made using appropriate lengths of adhesive backed copper tape soldered to a brass ring that mounts to the base of the antenna. I don't think you need a round metal plate. Also keep in mind - and this is from my aluminum wired house days. Aluminum will corrode next to dissimilar metals unless well protected and will eventually cause lots of buzzes and sparks.

    With regard to Coax runs. My current radio install manual says separate. Whether it is a wives tale, or not I followed that recommendation. And regarding Bob Knuckolls recommendations in general. He was a participant in the first Kitfox email list years ago and made some comments that implied to me that he had opinions just as we all do. Example: He couldn't understand why anyone would want to put in expensive circuit breakers when simple cheap light weight fuses did exactly the same thing. Well, I love my Klixon Circuit breakers that allow me to simply pull the button to turn off a circuit for testing or just because sometimes without having to find and pull a fuse and remember where I put it when I need to re-energize the circuit.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  5. #15
    Senior Member jrevens's Avatar
    Join Date
    Aug 2009
    Location
    Arvada, CO
    Posts
    2,146

    Default Re: Antenna wiring

    Thanks, Chase & Lowell. Just a few follow-up comments -
    The aluminum mounting plate for my ELT antenna is mounted with rubber lined Adel clamps, then electrically grounded to the airframe with a wire connection, all carefully cleaned & sealed against moisture & air. I've had a lot of successful aluminum airplane experience.
    You're exactly right about Bob N., Lowell... I guess we're all human. In reading his work & monitoring his thoughtful replies to questions & comments however, I believe that there is a good reason that he has directly & greatly affected the way that aircraft electrical systems are designed & installed in the majority of homebuilt aircraft today. I must also say that your craftsmanship & ideas have been an inspiration to me, Lowell. This forum is a wonderful asset!
    I've also seen the admonition to run the antenna wires separated from the rest of the wiring on printed installation instructions for avionics. I still have to believe that Bob is correct in his statement, and I have had experience which seems to confirm it. By the way, my antenna cables in the T-18 are not even the good RG-400 stuff, with better shielding, that is mostly used today.
    I too love the Klixon breakers in my Thorp, but I've come around to the AGC fuses as my choice for the Fox. I could count on one hand the times I've had to pull one of those breakers in the 23 years I've been flying that airplane. The fuses are lighter, probably more accurate, & certainly more available & cheaper by far. I can put the fuses for ALL of the fused circuits in one easily accessed location on the panel, using less space, at a fraction of the cost. I just wanted to talk about why I am doing some of the things on this project the way that I am. We all have to do what is right & appeals most to us... the beauty of homebuilt aircraft!
    Thank you both again.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  6. #16
    Senior Member Dorsal's Avatar
    Join Date
    Sep 2008
    Location
    Central, MA
    Posts
    1,511

    Default Re: Antenna wiring

    I must say I also used fuses based on Bob's book and like the result. I like the clean panel and have yet to replace a fuse. But as you point out the cool thing about experimental is we each get to do what works for us. I also used the standard antenna mount (on the 7) which appears to work well.
    Dorsal ~~^~~
    Series 7 - Tri-Gear
    912 ULS Warp Drive

  7. #17
    Senior Member HighWing's Avatar
    Join Date
    May 2009
    Location
    Goodyear, AZ
    Posts
    1,743

    Default Re: Antenna wiring

    I understand the fues idea and it is a practical choice. I guess the closest thing I can think of to illustrate my preference are the guys who put valves just below the wing tanks. I don't have them and need to use clamps if I want to service the fuel system between the tanks and the main shut off. I like the simplicity and the disadvantage is fine for me.

    With my breakers, I also have never had a breaker trip or had any electrical issues while underway and that's with about a thousand hours with two airplanes. Keep in mind that the fuses or breakers protect the wireing and accuracy is pretty much a non issue if the breakers are selected properly. But, I will often turn on the master to do some of the tinkering I do and get real tired of hearing the Turn Coordinator screaming at me or seeing the low oil pressure light flashing, or with the new fangled no on off switch com radio. I can stop that from booting every time I power up the system - just pull the breakers and quiet. A simple thing, but worth the $150 or so and the few ounces of extra weight. Speaking of weight, I helped a friend finish a Series V and he used fuses with a very nice fuse box in the panel. I don't know of the set-up is suggested by Bob, but I would guess my breakers weigh less than that set-up and likely not much more expensive. There are definitely pros and cons to any choice, but I guess I would have been a bit more apreciative if Bob had mentioned any of the advantages of breakers. I haven't read his book and don't know if he does acknowledge any - my experience with his ideas is all historical.
    Lowell Fitt
    Goodyear, AZ


    My You Tube Channel

  8. #18
    Senior Member jrevens's Avatar
    Join Date
    Aug 2009
    Location
    Arvada, CO
    Posts
    2,146

    Default Re: Antenna wiring

    I sure can appreciate and respect your comments and agree with your reasoning. My comment about fuses being more accurate was grasping at straws on my part, and you're absolutely right about the weight. Bob has certainly talked & written quite a bit about breakers and this issue. As far as I can tell, he has evidently come to the personal conclusion that fuses are a more practical choice for most homebuilt aircraft, but acknowledges that some builders/designers prefer breakers. He explains his reasoning quite thoroughly in his book. It's a good discussion - thanks Lowell!
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  9. #19

    Join Date
    Oct 2011
    Location
    Canada
    Posts
    187

    Default Re: Antenna wiring

    Quote Originally Posted by jrevens View Post
    I'd like to revisit this subject based on a recent post by Bob Nuckolls on the Matronics AeroElectric List. This was Bob's reply, on 10/18/13, to a question about separating antenna wiring from power wiring:

    "There is no demonstrable value in separating antenna coax wires and other ship's wiring. The idea that 'noise' escapes ships wiring to invade the inner-sanctum of your coax is a popular myth morphed into sage advice."

    This has been my real-life experience for 23 years with my Thorp T-18, where I ran the antenna wires tightly & parallel with other wiring. I have never been aware of any "issues" because of that, & Bob's knowledge & experience gives me a better (warm & fuzzy) feeling about how I've run the wires in my Kitfox project. I just thought some of you builders might like to know this.

    Her is one that works 100%
    https://www.youtube.com/watch?v=k-Ah9Ei2N2k

    https://www.youtube.com/watch?v=AFqmXk8wEoE

    Enjoy

  10. #20

    Join Date
    Jan 2013
    Location
    NATCHEZ, MS
    Posts
    6

    Default Re: Antenna wiring

    Quote Originally Posted by jrevens View Post
    The aluminum mounting plate for my ELT antenna is mounted with rubber lined Adel clamps, then electrically grounded to the airframe with a wire connection, all carefully cleaned & sealed against moisture & air.
    I am at the point of installing antennas in my SS7 so this thread has been pertinent. A couple questions:
    1) What is the best method to seal the connections against moisture and air?
    2) My fuselage has two welded antenna mounts under the baggage compartment, one on each side. I was going to use one for the transponder (Dynon SV) and the other for the ADS-B (also Dynon SV). However, the Dynon manual says these two antennas need to be at least 24" apart. The placement of the welded mounts won't get me but about 22" or 23" between the two if the holes are drilled at the very outboard edges. Is an inch or two really that significant? If so, I may need to mount one of the antennas further forward under one of the seats.

    My Com antenna is going to be on the welded mount at the front end of the razorback.

    With using the Dynon Skyview system my solution to the antenna cable runs (as well as to keep the area behind the instrument panel as clean as possible) was to mount the transponder, ADS-B module and the Com transmitting unit on a panel behind the pilot's seat (similar to where the header tank is mounted on the copilot's side). The antenna cable runs will be very short, especially for the ADS-B and the transponder since the antennas will be on the bottom of the fuselage. The Com antenna cable run will be a little longer since it has to go behind the baggage area and on top. Consequently none of the cables will be running parallel or in conjunction with any other wires. I ran a length of 3/4" thin wall PVC from the tail to the front of the cabin, through the center console and up behind the instrument panel that will accommodate trim motor wires (I may consider replacing that with shielded wire), trim position sensor cable, wintip landing lights and position/strobes wiring, along with the Skyview Network cables connecting the remotely mounted radios. (I think it is all going to fit -- I'll know pretty soon.) The only thing outside the PVC conduit is an eight conductor shielded cable from the ELT to a remote switch on the panel which will be routed under the copilot's door frame.

    The Skyview ADAHRS module will be mounted at the left wingtip and its network cable routed through the rear spar to a network hub near the remotely mounted radios outlined above. I realize this places the ADAHRS module is outside the recommended parameters called out in the Dynon manual. In case that mounting arrangement does not work out as hoped, I have constructed a second mounting shelf just outboard of the fuel tank (i.e., nearer the aircraft CG) with necessary PVC conduits to route the cable and pitot/static tubing to the new location along with an access panel under the wing to facilitate the necessary mounting and connections.

    I mounted my ELT along with its antenna (Emerging Lifesaving Technologies 406 ELT with internal GPS - the antenna is huge) inside the fuselage on two shelves - on the copilot's side beside the baggage compartment - just behind the flaperon control rod.

    Any comments or suggestions are welcome.
    Peter B
    Natchez, MS (HEZ)
    Cessna 182 (1970)
    Building S7 Super Sport

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •