Date: Mon, 11 May 1998 00:49:46 -0400 From: Bill Theeringer Subject: COZY: Antenna Dimensions The formula for a free space half wave dipole is L=3D500/Fmc. The actual= number, which takes into consideration surrounding influences, is 468/Fmc= =2E = Where L=3Dlength in feet and Fmc=3D frequency in Mhz. Bandwidth is a fun= ction of the "Q" of the antenna. Low "Q" antennas are broad banded and are generally defined as having an element thickness to length ratio (K facto= r) in the order of at least 1:100. The center impedance is very close to 5= 0 ohms presenting a good match to RG58 coax cable. The ferrites are made b= y Amidon Associates and are available at any good electronics store such as= Dow Electronics Etc. I had a bunch of them but gave them all away. I ca= n check into getting more if anyone wishes. The com antenna should be mounted in the winglet as vertical as possible with the coax leaving at a= right angle for as long as possible. The voltage nodes on a half wave dipole are at the ends with the current maximum in the center. This mean= s the ends should be as far away from other metal as practical. Not necessarily because of interference, but because of the de tuning effects= =2E = Don't get paranoid about the installation. Just follow the basics and it= will work quite well. You have one big plus going for you and that is altitude. = When I was a kid an old timer told me if I had a dollar to spend on my ha= m radio to put 99 cents in the antenna. He was right. I've been licensed = 45 years and hold ham licenses from 8 countries. Bill Theeringer N29EZ See our award winning Long EZ with = Jim Newmans excellent retractable gear at = http://www.flash.net/~infaero/infgear.htm Composite Aircraft Accessories HOME: 805-964-5454, SHOP: 805-964-5453 E Mail: Composite_Aircraft_Accessories@Compuserve.com PO Box 21645 Santa Barbara, CA 93121 Date: Fri, 05 Jun 1998 09:29:31 -0500 From: Darren DeLoach Subject: COZY: Marker Beacon Antenna in fuselage bottom RST's document, unlike the plans, shows putting the MB antenna in the bottom instead of a Nav antenna. The MB antenna is laid down as a straight line rather than a "V", a line about 78 inches long so our tub is large enough to do this. For those who have done it this way: That pesky landing brake prevents running it down the middle, so I assume you run it along a side of the bottom. How did you route the cable? From the RST booklet which says you should run the coax as far from the antenna as possible, I take it that means the antenna along one side of the bottom (say, the right side) with the "T" coax junction somewhere not beside the landing brake (is this possible?), then the coax running perpendicular across the bottom to the other (left) side of the bottom, then turning towards the front and perhaps entering the interior beside the fuselage side (say, just inside the triangular longeron)? -- Darren DeLoach http://www.deloach.com Chap. 7 From: "Marc J. Zeitlin" Subject: COZY: Marker Beacon Antenna in fuselage bottom Date: Fri, 5 Jun 98 10:54:38 EDT Darren DeLoach writes; > >RST's document, unlike the plans, shows putting the MB antenna in the >bottom instead of a Nav antenna....... I don't have an answer to your questions, but I'll make some general comments about antennae placement. I put the NAV in the fuselage bottom, another NAV in one wing, two COM antennae in the winglets, a GS in the other wing, the transponder antenna in the nose (interior) and the MB in the canard. After doing all this, two things are clear - first, I'll probably never use anything other than one COM and the transponder antennae and second, there's enough room on the top and bottom of the wings to litter them with as many of the the GS, MB, and NAV antennae as you'd like. Only the COM needs the vertical polarization, and there's room in the winglets for one each - should be sufficient. Anyway, I wouldn't sweat trying to force the MB onto the fuse bottom - put in in the canard or on a wing. The GS is small, that could go on the fuse bottom even more easily than the NAV. My $0.02. -- Marc J. Zeitlin Email: marcz@an.hp.com From: cdenk@ix.netcom.com Date: Fri, 5 Jun 1998 10:35:42 -0500 (CDT) Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom Deloach writes I have the antenna dynamics antenna mounted left bottom of the fuseage. It has a balun coil at the center with a BNC connector. The cable protrudes into the botton corner of the rear passenger foot space. I have a small 2 ply BID cover with 3 screws to protect it. The cable then goes up the fuselage side about 5 inches where it joins the wire conduit. It works lovely. I also have the Antenna Dynamics COM (2)(fins), VOR (2)(bottom of canard) and they all work well. From: Don Bowen Subject: COZY: Marker Beacon Antenna in fuselage bottom Date: Fri, 5 Jun 1998 08:42:15 -0700 Marc J. Zeitlin wrote: I wouldn't sweat trying to force the MB onto the fuse bottom - put in in the canard or on a wing. I think this statement should be reconsidered. The orientation of the marker beacon should be along the centerline of the aircraft. This gives a more precise indication of the location of the aircraft relative to the marker beacon. The "shape" of the signal from the marker beacon is not circular, more like an elipse or a bone. The signal is oriented perpendicular to the signal of the localizer. Having the marker beacon antenna oriented 90 degrees from the orientation of the marker beacon signal will give a more precise indication as to when you cross the marker beacon. Take a look at any certfied aircraft on the flightline. The marker beacon antenna is always located so that it is oriented down the centerline of the aircraft. When I spoke with RST engineering, they did not speak highly of putting the VOR antenna in the bottom of the fuselage. This has something to do with the large sacks of salt water (pilot and copilot) interfering with reception. With the close proximity of the marker beacon transmitter to the aircraft (when on approach) this will not be a problem with marker beacon signal reception. Perhaps we can get RST to comment on this. Don Bowen Cozy Mk IV s/n 440 Chapter 9 Date: Fri, 05 Jun 1998 10:48:23 -0500 From: Darren DeLoach Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom At 10:54 AM 6/5/98 EDT, you wrote: >Anyway, I wouldn't sweat trying to force the MB onto the fuse bottom - >put in in the canard or on a wing. >From the RST diagram, the MB antenna (a very long 78 inches total) runs logitudinally front to back. Are you saying that it can also run side to side in the canard (90 degrees rotated)? Is there any disadvantage for doing this? -- Darren DeLoach http://www.deloach.com Chap. 7 Date: Fri, 5 Jun 1998 11:02:32 -0500 From: Tom Brusehaver Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom The cost of the antennas is so little and the work to put them in is minimal. Having more is probably better, after the plane is done, you may wish you had more. The tape antenna is fragile, so it is possible that it quit working, having a spare would probably be a good thing. The future of radio aids to navigation is waaay up in the air. VOR's may be decommissioned sometime, ADF's also. LORAN, well probably first, before VOR's, but as someone pointed out, there will probably be a backup system to GPS. >Anyway, I wouldn't sweat trying to force the MB onto the fuse bottom - >put in in the canard or on a wing. The GS is small, that could go on >the fuse bottom even more easily than the NAV. I think this is a great idea! One other thought about all the antenna's and coax, and all. Make sure you mark which coax is which. Right now you can see the antenna, so you know the GS is in the left wing, and the nav is in the left wing, but after you paint it??? I have a tag on the coax where it comes through the glass, and toward the end (I'll probably cut off the end, because the coax is too long, then I'll loose that tag, and I won't know what was what). Just my $0.02 Date: Fri, 05 Jun 1998 11:11:42 -0500 From: Chris Anderson Subject: COZY: GPS ants. BTW I thought I'd mention to those mounting GPS antennas that as mentioned in a previous post the GPS downlink is a bit higher in frequency than most everything else in our planes. At 1.2GHz the signal loss per foot of coax can be pretty sevear. As such, use only the external antenna kits from the manufactures of GPS's, or research your coax to know how much loss you can expect. Using the wrong stuff (wrong impeadance, sparse braid coverage etc) can easly get worse performace than the hand held antennas on the portables. Belden or another cable manufacture's catalog will have a graph or table of loss per foot at a given frequency. Also note that the RG description number doesn't tell you what you want to know. RG-58A/U can vary in attinuation from 14.5 to 21.5 dB/100 feet (at 1GHz) and still all just be called RG-58A/U. =-=-=-=-=-=-=-=- Chris Anderson andersoc@idcnet.com You can't save everyone folks, just try not to be living next door when they go off... Dennis Miller Date: Fri, 05 Jun 1998 12:34:09 -0400 From: bil kleb Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom Don Bowen wrote: > > When I spoke with RST engineering, they did not speak highly of putting > the VOR antenna in the bottom of the fuselage. i got the same response from RST when i asked about the nav antenna in the bottom of the fuselage on the rec.aviation.homebuilt newsgroup some time ago. (a summary of the response made it into our archives.) basically the response was that RST did not want to be associated with the idea of putting a nav antenna in the bottom of a cozy. RST said that the designer should avail him/herself of RST's offer to provide a detailed recommendation for antenna placement for the design. (nat, can you do this?) AFAIK RST offers this service only to the designer and not to individual builders of the design. (i suppose this is done to minimize the number of times RST has to answer the placement question(s).) -- bil From: Don Bowen Subject: COZY: Marker Beacon Antenna in fuselage bottom Date: Fri, 5 Jun 1998 08:24:05 -0700 Darren DeLoach wrote: RST's document, unlike the plans, shows putting the MB antenna in the bottom instead of a Nav antenna. I have installed the marker beacon antenna in the fuselage bottom. I intend my aircraft to be IFR equiped, and I believe the ILS system will be used well into the future. My VOR antennas will go into the canard and the wing. I placed the marker beacon antenna on the right side of the fuselage bottom. It is located between the outboard edge of the landing brake area and the edge of the fuselage bottom. The antenna cable runs perpendicular from the antenna (at the "T" area) for about 6 inches and then runs parallel with the fuselage center line. It then makes another 90 degree turn towards the centerline of the aircraft. The cable enters the fuselage behind the center "pedistal" of the instrument panel (just behind where the nose wheel well is going to be). It is true, in a technical sense, that the antenna cable should be routed away from the antenna. In the case of the marker beacon antenna, I think it is important to think of the operational factors. When you are over a marker beacon, the aircraft is maybe only a couple thousand feet above the transmitter. The transmitter's antenna is designed to shoot the signal straight up. This signal will be very easy to pick up. The antenna / cable installation does not need to be technically perfect. (You should see some of the installations in "certified" aircraft.) The RST manual is correct that the cable should be away from the antenna. This may be very important for antennas such as the VOR, but I do not think this will be a factor with the marker beacon. I am sure the technical experts can beat this issue to death, but the point to keep in mind is that you are trying to pick up a signal from only a few thousand feet away from the transmitter. Just my two cents worth. I am not a systems expert, just someone who has spent a lot of time around aircraft. Warren, e-mail me direct if you have any questions. If you want, I can snail-mail you a photo of my installation. Don Bowen Cozy Mk IV s/n 440 Chapter 9 donbow@symix.com Date: Fri, 5 Jun 1998 10:11:01 -0500 From: Tom Brusehaver Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom >That pesky landing brake prevents running it down the middle, so I assume >you run it along a side of the bottom. How did you route the cable? From >the RST booklet which says you should run the coax as far from the antenna >as possible, I take it that means the antenna along one side of the bottom >(say, the right side) with the "T" coax junction somewhere not beside the >landing brake (is this possible?), then the coax running perpendicular >across the bottom to the other (left) side of the bottom, then turning >towards the front and perhaps entering the interior beside the fuselage >side (say, just inside the triangular longeron)? I was able to get the "T" junction just ahead of the landing brake. I did run it from f22 -> just in the foam for the NACA duct (about 6 inches or so) along the right side. I wasn't able to keep it straight, so there is a slight "kink" at the "T". I routed the coax under the fuse to just behind the panel on the center right side (figuring the audio panel will be mostly on the right side, and the MB receiver will probably be in there). I put the ground side forward (outer braid), figuring there will be a bit of metal and people in that direction above it. I don't know that it matters. I think the directional 75MHz signals are a little more forgiving than say the GHz GPS signals :-). I think for the distance away from the antenna, you might want to use the 1/4 wave calculation, (~1 meter), but that seems extreem, I know it is ideal. For a transmitter I would keep it a requirement; for a receiver, I'll give up a little. I know especially MB's are quite easy to receive around here. Date: Fri, 5 Jun 1998 11:53:57 -0500 From: Tom Brusehaver Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom >From the RST diagram, the MB antenna (a very long 78 inches total) runs >logitudinally front to back. Are you saying that it can also run side to >side in the canard (90 degrees rotated)? Is there any disadvantage for >doing this? The polarization would be off (not a big loss in this case), I guess I would worry about what is in the nose under the center section of the canard. The nose wheel, and retract mechanism, all metal, might minimize the effectiveness. Then again for the marker beacon, I don't think it'll hurt. From: lschuler@cellular.uscc.com Date: Fri, 05 Jun 98 11:59:51 -0600 Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom Darren DeLoach wrote: >snip How did you route the cable? >snip I have the same RST book. Good stuff!! I will not, at least initially, be doing IFR work, thus not need a marker antenna. "BUT" it seemed prudent that for less than a couple bucks I could put one in now (while not needed) or spend several hundred later if it became a must-have. The choice should be fairly obvious. Best performace from the marker antenna is a straight line fore-aft orientation. Mounted mine along one side of the fuselage bottom. There is room to keep it in a straight line along one side (pick one) of the landing brake. I made mine such that the torroids and "T" are just ahead of the landing brake at about where the front seat angle meets the floor. My coax runs perpendicular from the antenna/torroid "T" to just about where the side of the heat duct would be, then forward to just in front of the instrument panel; then up through the floor to the inside of the fuselage. No dangling wires until reaching the instrument panel. The coax is all imbedded in the fuselage bottom from antenna to instrument panel. I made a trench for the coax to lay in by routing the foam (using my dremel, a 1/4" round bit, and a router attachment). The torroids and the "T" are all trenched in as well. I found that if the round bit is buried in the foam to the level I wanted the coax, the shank would cut through t the thin remaining layer of foam creating a slot a bit smaller than the coax. This slot combined with the round bit made for a neat way to hold the coax in place for microing without worrying about the coax floating up, out of the micro. Just be sure to do all your soldering ***BEFORE*** laying the antenna tape on the foam (unless you like the smell of melted PVC for some reason). Be a bit careful about routing the foam for the torroids; they are right at 3/8" diameter, same as the foam; you could end up cutting through the inside glass. I put a bead of micro in the coax trench using a syringe (flymarket), then laid in the coax and pressed the torroids in. Once the coax, torroids and all are placed into the trench, I filled the trench with micro to just above flush with the foam. After the micro cured, I leveled the micro ridge to flush with my dremel/router attachment. If you intend to hard-shell, you could maybe fill the trench, then hard-shell in the same work session. All my other antennas are going in the wings and winglets. I seriously considered the canard for a couple, but decided against it because I just couldn't seem to come up with a good way to get the coax out from under the skin and into the fuselage without putting a hole (weak spot) in the skin somewhere (personal choice). Lots of room in the wings/strakes/winglets anyway. The marker antenna is really the only one that 'must' be in the fuselage; due to length and orientation. A fuselage side would work ok for the marker, but the RF pattern would be off ideal due to the curvature of the side. Larry Schuler MK-IV plans #500 lschuler@cellular.uscc.com From: cdenk@ix.netcom.com Date: Fri, 5 Jun 1998 12:45:43 -0500 (CDT) Subject: COZY: Glide slope antenna As I wrote previously, I have 2 Antenna Dynamics VOR antennas in the bottom of the canard, one on each side. I do use a splitter for the glide slope. It all work excellent. My friend's Mooney factory installation of King equipment also uses a splitter. I prefer the Antenna Dynamics antenna's to the foil, they are mylar with plated on copper, like a printed circuit, and have some ground plane type matching conductive strips built in. They have preformed flawlessly, well within the published service volumes (FAA for reception distances). From: "Marc J. Zeitlin" Subject: COZY: Marker Beacon Antenna in fuselage bottom Date: Fri, 5 Jun 98 13:43:13 EDT Don Bowen wrote: >Marc J. Zeitlin wrote: >I wouldn't sweat trying to force the MB onto the fuse bottom - >put in in the canard or on a wing. > >I think this statement should be reconsidered. A polite way of telling me I'm full of it :-). >The orientation of the marker beacon should be along the centerline of >the aircraft. > >This gives a more precise indication of the location of the aircraft >relative to the marker beacon. I'm not an RF engineer - I certainly won't argue with these recommendations. I do wonder, however, if there's any data showing what the difference in reception effectiveness or accuracy would be in the case of the MB, where you're REAL close to the transmitter in any case. While the theoretical effectiveness may be better, what's the difference in real world reception - does anyone know? I guess if I ever get IFR rated and put a MB receiver in my plane, I'll be able to do side by side tests with one of you guys that did it correctly :-). -- Marc J. Zeitlin Email: marcz@an.hp.com From: cdenk@ix.netcom.com Date: Fri, 5 Jun 1998 13:03:23 -0500 (CDT) Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom Don Bowen writes I disagree with the requirement: 1: At 100k or thereabouts, is about 170 feet/second, that is one plane length in 0.1 seconds. Anywhere on the aircraft will be adequate for determining location along the localizer. 2: The Marker beacon transmitted signal is a narrow (repect to runway centerline) (possibly 500'), and wide (perpendicular to runway centerline) (1/4 mile or more) beam. The ONLY FUNCTION is to advise the pilot of his location from the end of the runway. The antenna could be on the wing tip of a C-5B, and still do its job. Just yesterday, while downwind at home airport, I found that the audio panel marker switch was on, when the middle marker tones became audible, and that was a normal downwind, just beyond the landing runway threshhold. There are numerous approach plates (charts) that caution of recieving markers from other airports and runways. From: cdenk@ix.netcom.com Date: Fri, 5 Jun 1998 13:08:33 -0500 (CDT) Subject: COZY: VOR Antennas Advantage of the VOR antennas in the Canard: 1: Short Coax lengths. 2: Coax location with respect to noise sources is minimal. a: Not running parallel to other wires the length of the fuselage. b: Not near engine. 3: Only one connector (troublesome) required, and easy to get at. From: Don Bowen Subject: COZY: Marker Beacon Antenna in fuselage bottom Date: Fri, 5 Jun 1998 12:21:45 -0700 Larry Schuler wrote: We want to know when we are exactly over the marker transmiter, not before and not after. Larry's explanation of the marker beacon was much better than mine. What we want to know is precisely when we are over the beacon. If the antenna is perpendicular to the aircraft centerline the antenna will work too well. You will pick up the signal before and after you are over the beacon. If you place the antenna parallel to the centerline of the aircraft you will pick up the signal only when you are directly overhead of the beacon. Anyways, that's how the theory goes. And that's the way RST shows the installation in their book. I thought I was the only person interested in putting a marker beacon antenna in a Cozy. This e-mail group is a great forum for such discussions. Never ment to stir up such a fuss :-) If anyone wants a photo of my antenna installation, e-mail me direct at donbow@symix.com and I will send via snail-mail. Happy building (and flying), Don Bowen Cozy Mk IV s/n 440 From: lschuler@cellular.uscc.com Date: Fri, 05 Jun 98 12:47:20 -0600 Subject: Re[2]: COZY: Marker Beacon Antenna in fuselage bottom Darren DeLoach wrote: >From the RST diagram, the MB antenna (a very long 78 inches total) runs >logitudinally front to back. Are you saying that it can also run side to >side in the canard (90 degrees rotated)? Is there any disadvantage for >doing this? BIG disadvantage! I'll try to keep this simple and short; same time not miss the important stuff. Assuming that the antenna is in a perfect straight line, the radio wave pattern from a dipole antenna (such as the marker antenna) is greatest perpendicular to the wires (copper tape in our case). Without writing a book, a good way to visualize the pattern would be to think of an AN960 washer with a wire right through the center of the hole. The wire is the antenna and the washer is the radio pattern. Good signal strength off the sides of the wire (tape) where the washer is and near nothing along the wire's length except right in the middle where the washer is. With this in mind, a marker antenna mounted perpendicular to the fuselage, such as in a canard will be able to pick up a marker a long way out from the marker transmiter (in line with the washer) and continue to pick it up after we cross the threshold (also still in line with the washer). Not good. We want to know when we are exactly over the marker transmiter, not before and not after. Now change your mental picture of the AN960 with a wire running through the center to a bigger (but still very thin) AN960 with an airplane running through the center. We want the washer (our marker antenna) to pick up the marker beam just as we cross the transmitter. The best way to do that is to make the antenna beam as thin as the washer... Washer idea for antenna pattern does not apply if the antenna is bent like we do for the VOR etc. Different stuff. Hope this helps. Larry Schuler plans #500 lschuler@cellular.uscc.com Date: Fri, 05 Jun 1998 20:12:17 -0400 From: Rob Cherney Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom At 01:43 PM 6/5/98 -0400, Marc J. Zeitlin wrote: >I'm not an RF engineer - I certainly won't argue with these >recommendations. I do wonder, however, if there's any data showing what >the difference in reception effectiveness or accuracy would be in the >case of the MB, where you're REAL close to the transmitter in any case. >While the theoretical effectiveness may be better, what's the difference >in real world reception - does anyone know? I don't have any real-world data, but cross-polarization isolation is typically on the order of 20dB (power factor of 100). With ground reflections, the observable isolation is probably about 10dB (factor of 10). The MB receiver automatic gain control should be able to deal with the extra signal that you will need to receive the marker beacon. Even if this does not work out, it is relatively easy to add a marker beacon antenna either to the inside or the outside of the fuselage. If it is outside, put copper tape on the glass surface and fair the copper tape with micro. If inside, you don't necessarily need copper tape; use insulated (or bare) wire with the torroid balun arrangement in the center. Run the wires along one side/bottom of the fuselage with the center junction just aft of the front seat bulkhead. You can glue them to the fuselage side/bottom with a single ply of bid tape. Route the coax cable toward the opposite side along the intersection of the bulkead and the fuselage bottom and then forward to the instrument panel. Rob- +------------------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@home.com | +------------------------------------------------------------------+ Date: Fri, 05 Jun 1998 20:30:24 -0400 From: Rob Cherney Subject: Re[2]: COZY: Marker Beacon Antenna in fuselage bottom At 12:47 PM 6/5/98 -0600, lschuler@cellular.uscc.com wrote: >With this in mind, a marker antenna mounted perpendicular to the fuselage, >such as in a canard will be able to pick up a marker a long way out from >the marker transmiter (in line with the washer) and continue to pick it up >after we cross the threshold (also still in line with the washer). Not >good. Not exactly. The marker beacon transmitter does not radiate the type of pattern that would occur if you transmitted through one of our copper tape antennas. That is, the transmit pattern is not like your washer analogy. Most of the transmitter energy is directed straight up. In addition, his antenna is cross-polarized with respect to the transmitter. The transmitter station specification calls for a beam that is around 2400 feet wide and 4200 feet long at 1000 feet AGL along the localizer path. If everything is working as designed, a properly aligned antenna and a receiver with the proper sensitivity (500-1000 microvolts at 50 ohms) will receive a marker beacon signal for around 15 seconds, assuming you are moving at 120 MPH relative to the ground. I think that Marc should try his canard-mounted antenna and see if it works. If it does not work out, I don't think it will be difficult to retrofit a marker beacon antenna to his finished plane. Rob- +------------------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@home.com | +------------------------------------------------------------------+ Date: Fri, 5 Jun 1998 21:48:37 -0400 (EDT) From: "C. W. Wright" Subject: COZY: VOR Antennas (fwd) Disadvantage of the VOR antennas in the Canard: 1: Close proximity to GPS/Xponder/NC/ electronically generated noise from the instrument panel. 2: The connector/coax is easy to rip out when you remove the canard and forget the antenna is there. 3: Adverse "tight" EM coupling to the aluminum elevator torque tube which runs parallel to the antenna/canard 4: "Coverage NULLS" in the antenna pattern for VOR's which are 90 degrees to the left and right (which you might be using for crossing radial). Number 1 can be a real problem since most modern avionics generate a fair amount of EM trash which is easily picked up by the nearby antenna. The noise from a gps or loran sounds like "computer music." :-) Wayne Wright From: cdenk@ix.netcom.com Date: Fri, 5 Jun 1998 22:42:08 -0500 (CDT) Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom While flying I haven't noticed any degradation of signal while flying various orientations over a Marker Beacon. Probably it can be oriented anyway as long as it is horizontal. I really like my bottom of the fuselage though, and the canard is just right for 2 VOR's From: cdenk@ix.netcom.com Date: Sat, 6 Jun 1998 05:08:19 -0500 (CDT) Subject: Re: COZY: VOR Antennas (fwd) On 06/05/98 21:48:37 you wrote: > > > >Disadvantage of the VOR antennas in the Canard: > >1: Close proximity to GPS/Xponder/NC/ electronically generated >noise from the instrument panel. > >2: The connector/coax is easy to rip out when you remove the canard >and forget the antenna is there. > >3: Adverse "tight" EM coupling to the aluminum elevator torque tube which >runs parallel to the antenna/canard > >4: "Coverage NULLS" in the antenna pattern for VOR's which are 90 degrees >to the left and right (which you might be using for crossing radial). > > >Number 1 can be a real problem since most modern avionics generate a fair >amount of EM trash which is easily picked up by the nearby antenna. The >noise from a gps or loran sounds like "computer music." > >:-) Wayne Wright > > > > None of the above has proven to be issues, the panel includes (2) KX-155, King transponder, ADF, Audio Panel, IIMorrow Flybuddy GPS, and numerous other electronic goodies. The aircraft has near 600 hours on it and is flown frequently IFR everywhere from flatland Ohio to Jackson Wy. From: "Nat Puffer" Subject: COZY: Antennas Date: Sat, 6 Jun 1998 13:42:00 -0500 Dear Cozy Builders, I have been flying Cozys (3 different ones) since 1982, and have always installed one VOR antenna on the bottom of the fuselage and one in the canard (tips forward, away from torque tube). I have always used the one in the bottom of the fuselage, so I didn't have to disconnect when removing the canard. I have never had a problem receiving the VORs and never had to hook up the one in the canard. In my first 3-place I installed a marker beacon antenna in a wing, and never had a problem with it. I always install com antennas in each winglet, but never had to use more than one, and never had a failure. My radio reception and transmissions are better than most factory builts (I am told repeatedly). My GPS antenna is just under the access door in the nose and it works great! My transponder antenna is in the bottom of the nose, with the probe pointed down thru the bottom, and it works great. I don't understand all this theory that everyone is discussing, all I know is that what I have been doing for the last 16 years works better than most, and I would have no reason to change a thing! Regards, Nat From: cdenk@ix.netcom.com Date: Sat, 6 Jun 1998 18:46:13 -0500 (CDT) Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom There has been considerable traffic about Marker Beacon antenna locations. While in the air at about 1000' above an outer marker transmitter and using the GPS to measure distances here what I observed: flying the localizer centerline inbound, first audio noticed 0.80 miles before the intersection, audio disappeared 0.14 miles after the station. Flying perpendicular to the localizer, the signal disappeared 2.10 miles from intersection. Realizing this isn't terribly scientific or accurate, but indicates that my (Antenna Dynanmics) antenna orientated lengthwise on the fuselage bottom, will receive the signal adequately in any orientation. Date: Sun, 07 Jun 1998 09:42:04 +0100 From: Paul Kuntz Subject: COZY: marker beacon antenna Darren DeLoach wrote: > > RST's document, unlike the plans, shows putting the MB antenna in the > bottom instead of a Nav antenna. Darren, I used the RST reference to arrive at the decision to put a marker beacon antenna on the fuselage bottom, just as you are considering. (I intend to put nav antennas in the wings). I located the antenna on the left side of the bottom, running fore and aft just outside the landing brake. Do this after the brake well and the surrounding 1/8" joggle depressions are sanded into the foam. In order to get the full antenna length in a straight line, but miss the brake well itself, my antenna tape actually runs through the fore-aft 1/8" joggle for the glass that will later line the brake depression in the fuselage bottom. I located the junction of the antenna dipoles just forward of the front edge of the brake hinge , after studying the plans for the brake installation enough to believe that I was going to miss the coax during the brake installation in Chapter 9. I routed the coax perpendicular to the antenna, leading from left to right across the bottom, in front of the brake hinge, then turned it 90 degrees and routed it forward to just in front of the instrument panel at the right side of the panel close to the fuselage side. The only thing I didn't account for in the brake installation steps of chapter 9 is the step where the plans call for two small holes drilled through from inside the fuselage to locate the front edge of the seat back. After crawling under the inverted fuselage to drill those holes, then looking at where they penetrated the bottom, I saw that I hadn't even thought about the coax cable location. Fortunately, I had missed the coax with the drilled reference holes, but by only about 1/32"!! While going through all this, I kept wondering what marker beacon antennas really look like on most aircraft. I can't imagine finding a suitable location for installing a 78" antenna oriented fore-aft, with appropriate separation from metal RF reflectors, on any light aircraft (or even a 747 for that matter). I suppose the more usual MB antenna is some much-shorter fraction of the MB signal wave length. Probably since we only need to receive the signal when directly overhead the MB transmitter at a distance from the beacon of at most a few thousand feet, the antenna does not actually need to be particularly efficient. Anyhow, that's what I did. By the time I actually get around to flying my Cozy, marker beacons, VORs and ILS will probably be obsolete. Nevertheless, these antennas are so cheap and relatively easy to install that I'm going to embed them in the airframe just in case the FAA hasn't gotten around to full dependence on GPS by then. Regards, Paul Kuntz Cozy MKIV Serial 003, England From: cdenk@ix.netcom.com Date: Sun, 7 Jun 1998 15:50:34 -0500 (CDT) Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom Mike Bowden writes First: Most marker beacon antennas are either a long blade or a wire about 2' long, 4 inches parallel to the fuselage. For aerodynamic purposes they are parallel to airflow. >From my personal experience,I recommend that the Antenna Dynamics in the bottom of the fuselage along one side. If RST thinks the human occupants will create a problem, the solution is easy - don't buy the RST! Date: Mon, 8 Jun 98 7:22:04 EDT From: "Nick J Ugolini" Subject: COZY: Marker Beacon Antenna in fuselage bottom >I think that Marc should try his canard-mounted antenna and see if it works. If it does not work out, I don't think it will be difficult to retrofit a marker beacon antenna to his finished plane. When I refitted my LongEZ with a marker beacon antenna, the only place I could put it was on the inside of the longeron (right side) with the antenna running down the back of the pilots seat back. Works great. Another advantage of a marker beacon antenna is that if you are not using it for your beacon receiver, you can use it for your FM radio.... Date: Sun, 7 Jun 1998 13:23:02 -0500 Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom From: mikefly@juno.com (Michael B Bowden) Speaking of large sacks of salt water blocking reception. When looking for an optimum location for my GPS antenna I tested the top of my head rest and checked for any signal degradation caused by the canopy plastic. I even tried to induce static into the plastic by rubbing it with my hand. Signal was lost only when my hand was directly over the antenna Mike Bowden Two EZ MS1 Date: Mon, 08 Jun 1998 09:23:43 -0400 From: Paul Krasa Subject: Re: Re[2]: COZY: Marker Beacon Antenna in fuselage bottom My question is if I run the ground pole leg of the dipole up the pilots seat and the other leg under the pilot's legs, will it work properly. I have to retro the antenna into an existing fuselage, so it is not an option to place it internal to a structure. Any ideas how to retro the antenna would be appreciated. Paul Krasa Long EZ 214LP From: lschuler@cellular.uscc.com Date: Fri, 05 Jun 98 14:17:48 -0600 Subject: Re[2]: COZY: Marker Beacon Antenna in fuselage bottom Tom Brusehaver wrote: >The polarization would be off... >snip >Then again for the marker beacon, I don't think it'll hurt. Moving the marker antenna from fore-aft on the fuselage to the canard wouldn't change the polarization; it would still be horizontal polarization. Moving it to a winglet would change the polarization (orientation relative to the earth). Moving it to the canard does change the antenna pattern relative to longitudinal axis of the airplane [see my earlier note]. The COM antennas are the only ones that need to be vertically polarized for best performance. Those go in the winglets for that main reason (besides moving them away from, as someone so aptly put it, the salt water bags in the seats). Just a thought: Can we also call the salt water bags 'dummy loads'? :-) Larry Schuler MK-IV plans #500 lschuler@cellular.uscc.com From: lschuler@cellular.uscc.com Date: Fri, 05 Jun 98 15:33:27 -0600 Subject: Re[2]: COZY: Antenna polarization loss Tom Brusehaver wrote: >The polarization would be off (not a big loss in this case)... >snip .. >Then again for the marker beacon, I don't think it'll hurt. Thought I'd toss this out FWW for anyone considering putting the NAV antennas in the winglets or the COM antennas in the canard; in other words changing the recommended vertical or horizontal orientation (relative to the earth) of any antenna. (yup, applies to your bookshelf AM/FM radio at home too). Using the incorrect polarization will result in about 30dB of signal loss. For those who don't understand decibels (expressed as: 10*log(ratio)): it would be kinda like cutting the electricity in your house down from the normal 120 Volts to about one-tenth of one volt (considerably less than you get out of a flashlight battery). It'd make your lights pretty dim wouldn't it... On the other hand, if you happen to live under one of those big 100,000 volt power lines, you could lose 30dB from there to your house and still end up with about 120 Volts; which is quite satisfactory. [I'm not suggesting you try to do this by the way.] The point to these two extremes is that the performance degradation may not be readily apparent. It all depends on how close you are to and how big the starting (transmitter) signal is. With us flying around, constantly changing our relative distance to the transmitting stations, it makes good sense to not want any unnecessary losses, such as mismatched polarization, if it can be prevented. [For the scientists out there: I know the numerical examples are not 100% accurate; only used to illustrate the issue.] Just remember, the next time you are talking on your cellular phone, laying down in the lawn chair you would get better phone service by sitting upright, or by standing on your head; either way is better than laying down. Cool. :-) Larry Schuler lschuler@cellular.uscc.com From: lschuler@cellular.uscc.com Date: Mon, 08 Jun 98 13:31:42 -0600 Subject: Re[4]: COZY: Marker Beacon Antenna in fuselage bottom Paul Krasa wrote: >snip >Any ideas how to retro the antenna would be appreciated. Paul, Just a few thoughts and 'rules of thumb' to chew on. I'm sure you'll get other ideas as well. I assume marker antenna only. You would get better perfomance if the antenna is kept in a straight line. Running 1/2 of it up the seat and the other half on the floor would change the pattern somewhat. The best signal in this case would be, shall I say, right through your pelvis and out through the canopy. Doesn't mean you won't be able to pick up the marker; just not ideal. If the fuselage isn't painted yet you could still put the tape on the bottom and fair it in nicely with micro. The inside side of the fuselage would work. You would need to make a notch for it in the front seatback. Keep it as far from other metal stuff as possible (read: practical). A seat belt bracket would be less objectionable than the elevator torque tubes for example. Couple rules for this antenna as you consider location for a retrofit: 1. Keep it staright if possible. If you have to make a bend, bend one or both tips only. 2. Keep it away from other metal stuff if possible; particularly the ends. 3. Keep it away from salt water bags if possible. 4. If you bought the RST book; call Jim and ask his thoughts. 5. Remeber, as in aircraft design; it's a compromise between ideal and what's necessary. 6. Whatever you do will probably work "adequately"; no need for perfection here. The transmitter will be only a few hundred feet or so below you; not like the requirements of a comm or GPS antenna. Larry Schuler lschuler@cellular.uscc.com From: cdenk@ix.netcom.com Date: Mon, 8 Jun 1998 16:26:47 -0500 (CDT) Subject: COZY: Antenna orientation I believe that TV and broadcast FM are orientated horizontal. The aircraft com frequencies are vertical. Just because they are all FM signals in the same frequency bandwidth roughly, doesn't have anything with orientation. It can be changed (without getting into optimization) by unbolting the transmitting antenna and rotating 90 degrees. Date: Mon, 8 Jun 1998 19:44:59 -0400 (EDT) From: DL Davis Subject: Re: COZY: Antenna orientation At 04:26 PM 6/8/98 -0500, cdenk@ix.netcom.com wrote: >I believe that TV and broadcast FM are orientated horizontal. The aircraft com >frequencies are vertical. Just because they are all FM signals in the same >frequency bandwidth roughly, doesn't have anything with orientation. It can be >changed (without getting into optimization) by unbolting the transmitting >antenna and rotating 90 degrees. > Aircraft comm signals are AM. But I agree with your main point. From: cdenk@ix.netcom.com Date: Wed, 10 Jun 1998 15:57:05 -0500 (CDT) Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom My recent reply was NOT knocking RST, but suggesting something that has worked quite satifactorily for me for 600 hours of flying. I felt that the suggestion of someone recently to a builder to experiment and if it doesn't work, then spend effort to change it was out of place. Lets concentrate on doing things that work first. Date: Wed, 10 Jun 1998 21:56:24 -0400 From: Rob Cherney Subject: Re: COZY: Marker Beacon Antenna in fuselage bottom At 03:57 PM 6/10/98 -0500, you wrote: >My recent reply was NOT knocking RST, but suggesting something >that has worked quite satifactorily for me for 600 hours of flying. > >I felt that the suggestion of someone recently to a builder to experiment and if >it doesn't work, then spend effort to change it was out of place. Lets >concentrate on doing things that work first. I believe you were referring to my post and I beg to differ. I opined that Mark Zeitlin's installation of his MB antenna in the canard would, in all likelihood, work just fine. This was within the context of the ease of a retrofit in the event that it did not. So, in effect, Mark had already a thing that would "work first". Nat's post validated my opinion in that his installation of the MB antenna in the wing worked "better than most". In both cases the antennas are aligned the same, but 90 degrees from the ideal. In the event you are not referring to my post, I still beg to differ with your assesment of a post being "out of place". We all have choices. That's why there is chocolate and vanilla. Offering informed opinions and supporting information to allow a builder a choice is never out of place. Respectfully, Rob Cherney +------------------------------------------------------------------+ |Robert Cherney Home Phone: (410)465-5598 | |Ellicott City, Maryland e-mail: cherney@home.com | +------------------------------------------------------------------+ From: wkasty@ix.netcom.com Date: Fri, 12 Jun 1998 06:50:26 -0500 (CDT) Subject: COZY: Chapter 19 antenna I am getting close to glassing the right wing, and plan to embed a VOR antenna on the bottomside. Reading through RST's literature, Jim Weir mentions setting down wax paper over and under the copper tape antenna so it will not stretch with bending of aircraft. Has anyone used this method, or is it unnecessary for the wing and winglet locations? Bill Kastenholz MKIV # 536 From: "Marc J. Zeitlin" Subject: COZY: Chapter 19 antenna Date: Fri, 12 Jun 98 9:14:03 EDT Bill Kastenholz; >........ Reading >through RST's literature, Jim Weir mentions setting down >wax paper over and under the copper tape antenna so it will >not stretch with bending of aircraft. Has anyone used this >method, or is it unnecessary for the wing and winglet locations? I have the RST literature at home, and I installed my antennae a while ago, but IIRC (if I remember correctly), the reason that Jim recommended that was that people were installing the antenna on the landing gear struts. These have a LOT of flex (obviously) and there was a history of antenna stretching and breaking. My belief is that the copper tape is not in danger of breaking if installed in the fuselage bottom, wings, winglets or canard, due to the much smaller levels of strain that would be seen there. (MJZ "antenna comment" flame retardant suit __ON__! :-) ). -- Marc J. Zeitlin Email: marcz@an.hp.com Date: Fri, 12 Jun 1998 15:14:07 +0200 From: Rego Burger Subject: COZY: Chapter 19 antenna In response to Bill's Q? The plans indications have been well researched and used by NAT on three aeroplanes.... naturally you are free to try what you want (at your own risk) but the reason why he has published ( sold ) his advice is because it has worked. Now the way I understand your question it seems two-fold. 1.) Placing it under the wing. 2.) Having it "float" between wax paper. Here are my views. 1.) Placing it up front under the belly of the fuselage is better... it is ridgid with little or no flex. If you do stick it too the wing keep it near the fuselage... least amount of flexing occurs here not that the wings flex too much. 2.) No.... I don't think it's good to have it "loose" why?... Well vibration and movement will no cause serious errosion, this will lead to a serious delam on your wing skin. Rego Burger, web site: http://home.intekom.com/glen/rnb.htm (home e-mail) mailto:rnb@intekom.co.za RSA From: Guy TERREN Subject: RE COZY: Chapter 19 antenna Date: Fri, 12 Jun 1998 16:08:46 +0100 I used it recently. In fact i wrapped the copper into 1 turn and a half of wax paper. The best is to route it with a dremel then. I couldn't do it ( i bought m= y dremel after) and was obliged to sand the part. It works correctly. I didn't do the same for winglets. I don't think wing= lets will bend a lot. Guy -----Message d'origine----- De: wkasty@ix.netcom.com [SMTP:wkasty@ix.netcom.com] Date: vendredi 12 juin 1998 12:50 =C0: cozy_builders@canard.com Objet: COZY: Chapter 19 antenna I am getting close to glassing the right wing, and=20 plan to embed a VOR antenna on the bottomside. Reading through RST's literature, Jim Weir mentions setting down wax paper over and under the copper tape antenna so it will not stretch with bending of aircraft. Has anyone used this method, or is it unnecessary for the wing and winglet locations? Bill Kastenholz MKIV # 536 Date: Wed, 1 Jul 1998 23:48:12 -0400 From: Bill Theeringer Subject: COZY: Winglet antennas After reading so much posted regarding the winglet com antennas I just had to jump in with my .02. I have been doing this sort of stuff for decades so bear with me here. I am a retired engineer whose service has included 13 years with Raytheon's Equipment Development Labs in Wayland Mass. My specialty was high power (megawatt) microwave systems and their antennas. I have also been a licensed (Advanced class) ham operator for 45 years, and have held an FCC Commercial Radio Engineers license for 37 years. My plane looks like a porcupine of antennas and they all work flawlessly. I can communicate routinely for 300 miles on VHF and worldwide on HF. These plastic airplanes present some unique challenges and provide some interesting advantages over our metal brethren. Some of the advantages enjoyed by metal planes are the antennas can be just half the length of the center fed dipoles that we use, but they must stick out in the air stream, preferably at a right angle to their mounting surfaces. They will generally have weaker radiation patterns when the antenna is within the airframe obstructed view of the ground receiver, however It is easier to mount multi antennas of widely different frequencies. The skin of the plane does a good job of keeping these antennas from affecting each other in many ways too deep to go into here. To visualize how your plane would look to an antenna or a radar pulse try picturing your plastic airplane as it would show up on an X-Ray. Anything that is not metal is invisible. The entire strake would consist of the sump screen, filler, vent tubing and wing attach brackets. The wing would just be an aileron torque tube, aileron hinges, rudder cable and bell horn, rudder hinges and strobe wiring. No wonder center can't see you when your not mode C. Any antenna mounted virtually anywhere in this open space will work quite well as long as a few very simple guidelines are are kept in mind. I will list them here in order of their importance. 1) Make the antenna the recommended length and out of the recommended material. 2) Use the torroid baluns on the end of the coax. There does not have to be an air space between them. 3) Run the coax away from the antenna at a right angle for as long as possible avoiding sharp bends. 4) Mount the antenna as close to vertical as practical. Plus/Minus 30 degrees is about optimum. 5) Try to keep the ENDS of the antenna at least several inches away from other metal. 6) Be sure the coax sees ground only at the radio connector. Since the antenna is a half wave vertically polarized dipole out in the breeze ( X Ray, remember?) it will work exceptionally well in spite of almost anything you can do to thwart it. Two things that are a definite no no are a short at the end of the coax or an open in the foil. Stay away from pricey low loss coax as the difference will not be noticed. Can it be mounted in the rudder cutout? Definitely. One of my VHF antennas is a piece of 1/8 brass welding rod secured with plastic clamps in the rudder cutout. I can tune it with a pair of cutters and replace it with a soldering iron. Couldn't ask for a better antenna. Rudder spring? Not a problem. It is not any where near the dipole ends. My other wing has 6 wires buried just under the skin and running full length and tied together at the base of the leading edge of the winglet. This L. E. is an aluminum tube that protrudes out the top of the winglet and accepts the various coils for the HF radio. As a last thought you might mark the exact location of the dipole in your construction log book. Should it ever quit you would be able to poke contact to the foil ends for a continuity check. See you at Oshkosh! Bill Theeringer N29EZ From: mfacchinelli@sogei.it Date: Wed, 7 Oct 1998 17:06:07 +0200 Subject: COZY: Nav-Comm Antenna Hallo Group! I have two questions about the NAV-COMM ANTENNA to be glassed inside the winglets skin: 1- specific models available (Nav-Comm) 2- suppliers with phone number (fax, too) and address Anybody knows if Antenna Dynamics Inc. is still on the market? I need the phone number to contact them. Any suggestion is wellcome ! Thanks and CIAO from Italy ! Massimo e Marcella "ONE KILOMETER ROAD DOESN'T LEAD YOU ANYWHERE, ONE KILOMETER RUNWAY LEADS YOU EVERYWHERE..." From: Don Bowen Subject: COZY: RE: Nav-Comm Antennas Date: Wed, 7 Oct 1998 08:50:55 -0700 Massimo e Marcella wrote: Hallo Group! I have two questions about the NAV-COMM ANTENNA to be glassed inside the winglets skin: 1- specific models available (Nav-Comm) 2- suppliers with phone number (fax, too) and address Anybody knows if Antenna Dynamics Inc. is still on the market? I need the phone number to contact them. Any suggestion is wellcome ! I don't know about Antenna Dynamics, but you might try RST Engineering at http://www.rst-engr.com Their phone number is (530) 272-2203 (9-5 Pacific time, Monday - Friday). Their e-mail is sales@rst-engr.com. Sorry, I don't have a their fax number. Good luck with your project, Don Bowen Cozy Mk IV s/n 440 donbow@symix.com From: "astrong" Subject: Re: COZY: Nav-Comm Antenna Date: Wed, 7 Oct 1998 09:04:58 -0700 Massimo e Marcella, Try this,http://www.rst-engr.com/ .I have been flying my COZY for five years with their antenna trouble free. Alex Homepage"http://www.canard.com/trim" "Live your life so you can look anybody in the eye, and tell him to go to blazes!!" Dr. James Walter Strong (1874-1950) From: cdenk@ix.netcom.com Date: Wed, 7 Oct 1998 11:18:43 -0500 (CDT) Subject: Re: COZY: RE: Nav-Comm Antennas I have the Antenna Dynamics antennas, and am happy with them. >From my records 7 years old: Antenna Dynamics Inc. 9907 Canoga Avenue, Unit O Chatsworth, CA 91311 Phone: 818-773-8102 Can someone with local phone call and see if they are still there. Date: Mon, 12 Oct 1998 14:18:31 -0400 From: "L. Wayne Hicks" Subject: COZY: Antennas Where are people putting the marker beacon antenna? RST says to put it longitudinally in the fuselage belly, but if I do Jim's 1/8th metal within 1/4th distance calculation, then I'm sure the rudder cables are inside that envelope and could cause interference. Wayne Hicks Cozy 678 Chapter 7 Date: Mon, 12 Oct 1998 13:43 -0500 (CDT) From: Michael Pollock Subject: Re: COZY: Antennas Wayne Hicks writes in response to where to put Marker antenna: >RST says to put it longitudinally in the fuselage belly, but if I do >Jim's 1/8th metal within 1/4th distance calculation, then I'm sure the >rudder cables are inside that envelope and could cause interference. Since the marker antenna is used to determine the crossing of a fan marker location, maximum gain is not needed. Therefore, place the antenna along the centerline of the airplane, fore and aft, and do not worry about any interference caused by being too close to metal. This is exactly what we use on our Velocity, and there is plenty of metal around within 1/4 wavelength of the marker antenna, but the antenna works better than any marker antenna I have ever used. Michael.Pollock Flying Velocity N173DT Building Cozy MKIV #643 Date: Mon, 12 Oct 1998 13:54:18 -0500 From: Tom Brusehaver Subject: Re: COZY: Antennas >Where are people putting the marker beacon antenna? The belly or the strake, or the canard, or a wing. >RST says to put it longitudinally in the fuselage belly, but if I do >Jim's 1/8th metal within 1/4th distance calculation, then I'm sure the >rudder cables are inside that envelope and could cause interference. MB's are simple signals that are received only in the airplane. All (most!) the energy emmitted is in a really tight elliptical cone pattern straight up from the point. When you care about a MB, you are usually less than 1/2 mile from it (2000' above it). The dipole antenna's that are in the RST book will receive (and transmit) signals equal in strangth a circular pattern unless there is other metal around the antenna. The cirular pattern will streatch or notch depending on where the signal is, and where the metal is. If you have a larger metal piece between the receiving antenna and the transmitting antenna, there will be a notch in the pattern blanking the signal. If the large peice of metal is behind the transmitter or receiver antenna, then the pattern will stretch in the plane between the metal and the antenna away from the metal. If the metal is smaller (much usually) the patern will stretch in the direction of the metal. There is a whole lotta math to optimize the patterns. If you put the MB antenna in the belly, on one side, the rudder cable will act a a reflector, since they are both in the same plane pointing down at the transmitter. From: cdenk@ix.netcom.com Date: Mon, 12 Oct 1998 14:00:02 -0500 (CDT) Subject: Re: COZY: Antennas On 10/12/98 14:18:31 you wrote: > >Where are people putting the marker beacon antenna? > >RST says to put it longitudinally in the fuselage belly, but if I do >Jim's 1/8th metal within 1/4th distance calculation, then I'm sure the >rudder cables are inside that envelope and could cause interference. > >Wayne Hicks >Cozy 678 >Chapter 7 > > I have the Antenna Dynamics Marker in the belly, and 2" aluminum heater tubing and wiring conduits with lots of wires in addition to the rudder cables within that distance and mine works just fine. Isn't that distance more of an issue for transmitting antennas? Most TSO's marker antennas are much closer than that from the aluminum skin Date: Mon, 12 Oct 1998 15:04:57 -0400 From: "L. Wayne Hicks" Subject: COZY: Marker Beacons - Comment #2 Thanks to those who answered my Marker Beacon location question so quickly. But I do apologize to Marc Z, for I should have checked the archives. All the answers were right there. Thanks for keeping such a great archive for us, Marc! Wayne Hicks Date: Tue, 06 Oct 1998 19:38:36 +0100 From: Jean-Jacques CLAUS Subject: Re: COZY: Nav-Comm Antenna mfacchinelli@sogei.it wrote: > > Hallo Group! > I have two questions about the NAV-COMM ANTENNA to be glassed inside the > winglets skin: > 1- specific models available (Nav-Comm) > 2- suppliers with phone number (fax, too) and address > Anybody knows if Antenna Dynamics Inc. is still on the market? I need the > phone number to contact them. > Any suggestion is wellcome ! Hello, I did them exactly as per plans ( copper foil from Wicks + torroids from RST + rg58 ). After that, i tested them around my favorite airfield ( LFNE ) with an ICOM. I NEVER HAD a better antenna in the past (6/5). Jean-Jacques CLAUS htpp://www.mygale.org/05/jclaus