antenna suggestions

I will have two navs for vor reception, and two comms in my RV. I will also have a transpoder and marker beacon. Looking fo suggestions on antenna selection and location. Speed is my goal so if anybody has a some suggestions.....Also, can one antenna work for both comms or navs??

Splitter

I know you can use a splitter for the nav antenna. I believe your coms have to be separate and spaced apart or have a cut out to keep from burning up the other receiver when you transmit. Also location can depend on if your building a slider or not, and if speed or reception are your main goals.

Mike,

I suggest you search "Antenna Decisions" by Ironflight on this forum for a very lucid start to your quest for antenna knowledge. It certainly helped this "antenna-challenged" individual

http://www.vansairforce.com/community/showthread.php?t=40633&highlight=antenna+musings

As a quick hit, this is what I'm planning on doing:

Two RAMI bent comm antennas on the belly, just forward of the seat belt anchors.
One 'bare coax' MB antenna in a wingtip.
One Archer Nav antenna in another wingtip.
One Garmin GPS antenna on top just aft of the canopy (tip-up).
One ELT antenna on top after of the GPS antenna.
One RAMI Transponder antenna on forward bottom of fuse (next to fuel vent).

If you can split the nav antenna, it could be used to feed both nav units - I only have one (SL30), with a 300XL GPS for my backup nav source.

marker beacon

I would be interested to see if you can find a marker beacon antenna that can go behind fibreglass and be placed in the wing tip or the cowl or the wing fuselage fairings?

My MB antenna is installed in my wing tip and it is working very well. No issue with fiber glass, just make sure you install it facing down.

Yes....

jay.pearlman said:

I would be interested to see if you can find a marker beacon antenna that can go behind fibreglass and be placed in the wing tip or the cowl or the wing fuselage fairings?

Click to expand...

...42" of stripped coax in the wingtip works well for MB. Used in my -6A.

18" of stripped coax in the top if windshield, hidden by bow for GS antenna (Courtesy Paul Dye),

Best,

I have Comant.....

Bent whip antenna's under my RV6 and towel bars in the wingtips, all seem to work well. My friend has used stripped coax in the gear leg fairings for comm ant.'s and this seems to work well. I think ultimately I will try the comm. coax in the gear legs too. If you do this, I think you need to use double sided tape to close the fairings rather than the hinge arrangement. When done the only exposed ant.s I will have is the marker & transponder ant.s. Every little bit helps.

antenna locs

About the same as ccrawford above:
- 2 bent whip comants for comm1/2 on belly.
- stripped coax for mb in wing tip
- bob archer nav antenna in same wingtip. (don't have 2 navs myself)
- (3) GPS and (2) XM pucks are all mounted on tip up glare shield. (insure a little spacing between pucks)
- ELT antenna just aft the seats, slightly bent along the canopy frame
- el cheapo TED xpdr antenna on belly. (I put it behind baggage bulkhead, but would probably install between comants next time to minimize coax run.)
- diplexer for g/s and vor (CI-507). allows archer nav antenna to do both.

comm split

Archer makes a switch for comm so that two comms can use a single antenna.

Antenna locations

A 1/4 wave monopole antenna above a counterpoise, the so-called ground plane, needs to have a lot of very conductive metal in the direction of transmission in order to get good TX/RX in that direction. When you mount one of this type of antenna on the top of an airplane, the majority of the radiation pattern is upward; not too bad when you're on the ground speaking to the tower or another plane in flight, but a bummer when you're in the air trying to reach a station below you. For most purposes when you're trying to contact someone within 10 to 20 miles it probably doesn't make much difference where you mount an antenna. But if you want superb long distance TX/RX, mount your antennae on the bottom. Here's a location that will probably make you choke, but if you put a comm antenna on the bottom of each wing just outboard of the fuel tank you will get a good pattern and much isolation between the two. But a big part of TX/RX problems lies in using lossy coax. The best coax for the job, especially for the higher DME and transponder frequencies, is Andrew FSJ1-50. It is about the same diameter and weight as RG58U, has a total solid outer metal jacket so its EMI-RFI is as low as you can get, has half of the loss of RG58U, and can be bent in a 1" radius. The last time I checked you could get it for about $1.29/ft. So why spend big buck$ on radios and then scrimp on coax? 'Doesn't make sense, does it?

On the RV-8 I'm currently working on, we've installed the Bob Archer VOR antenna in the left wingtip, a Comant bent whip COM antenna on the belly, and instead of using a splitter to divide the VOR antenna into VOR and Glideslope for the Garmin 430, I'm going to try a variation of Paul Dye's homemade GS antenna, similar to what Pierre described about 5 posts up... my homemade GS antenna is a simple strip of aluminum, 1/2" wide and 16" long, and fiberglassed onto the floor of the inside of the right wingtip. It'll stick straight out horizontally as possible, the outboard tip tilted aft slightly and not quite perpendicular straight outward to the end of the wing in order to fit it inside the wingtip. If 16-18" of stripped coax works well for GS, then I figure that a same length strip of aluminum ought to work as well too, since there'll be about an inch or so of stripped coax from where the shield braid ends to reach the screw post connector I made on the inner end of the antenna strip. I'll be grounding the shield to the rib at the end of the metal wing and the aluminum strip antenna will start with a couple inches of fiberglass separating it away from the wing. We're using ordinary incandescent landing lights, so no worries about EM interference from HIDs. There will be wingtip strobes in the front corners of the wingtips, but the GS antenna will be pretty far aft of the strobes.

GS antenna.

Neal@F14 said:

...my homemade GS antenna is a simple strip of aluminum, 1/2" wide and 16" long, and fiberglassed onto the floor of the inside of the right wingtip. It'll stick straight out horizontally as possible, the outboard tip tilted aft slightly and not quite perpendicular straight outward to the end of the wing in order to fit it inside the wingtip. If 16-18" of stripped coax works well for GS, then I figure that a same length strip of aluminum ought to work as well too, since there'll be about an inch or so of stripped coax from where the shield braid ends to reach the screw post connector I made on the inner end of the antenna strip. I'll be grounding the shield to the rib at the end of the metal wing and the aluminum strip antenna will start with a couple inches of fiberglass separating it away from the wing. .

Click to expand...

Here's a design for a glideslope antenna that you migt try; it's a little more compact than your design and you may be able to get it a little more aligned with the wingspan. It consist of two thin aluminum triangles each having a height of 6.5" and a base of 3.75". Cut off about 1/8" on the pointy end of each and connect these two opposite each other with their ends about 1/4" apart on a small piece of plastic to form a bow-tie configuration. Slip a couple of ferrite beads over the stripped end of the coax to form an isolator for antenna currents on the shield then join the cable shield to one triangle and the center conductor to the other.You will find that it will have a very low VSWR across the 329-335 MHz GS band.