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VOR/ILS antenna

togaflyer

Well Known Member
I saw an article that was posted on Beech Talk. Some owners are eliminating the cat wiskers or older style type antennas for a pair of blade VOR/ILS antennas. The blades are being located on the aft portion of the tail cone, below the horizontal stabilizer (positioned approximately 4 to 5 inches below the leading edge of the horizontal) The blade style are more expensive then the wiskers, but it appears to be a clean installation with reported outstanding reception. Is there acessibility to that area of the tail cone once the tail is assembled. Are there any issues with a set of blade antennas location in that portion of the tail cone, i.e interference on the inside with cables etc.
 
I would say you certainly have access to this area to install blades if you wish, without interference (if you plan well)... Or... you could install a set of Bob Archer NAV antennas in the wingtips, avoiding the extra drag and cost of the blades and whiskers all together...;)
 
There's access, but it ain't easy. I have the aforementioned cat whiskers mounted on the bottom of the tailcone and installed them after the tailcone was mated to the fuse. However, I provisioned for that beforehand. During the tailcone build I located where the antenna would go and made and installed a doubler and ran wiring. So when I was ready all I had to do was bolt the antenna on.
 
There's access, but it ain't easy. I have the aforementioned cat whiskers mounted on the bottom of the tailcone and installed them after the tailcone was mated to the fuse. However, I provisioned for that beforehand. During the tailcone build I located where the antenna would go and made and installed a doubler and ran wiring. So when I was ready all I had to do was bolt the antenna on.

I did the same as Todd. The blades are nicer, but significantly more expensive. For me, it wasn't worth the expense. My whiskers are hidden under the horizontal to keep them out of the way. Commant recommends pointing them forward, but many including myself point them aft.
 
Over the years I've had to repair cracked skins around/under the blades on several airplanes. Once on a bonanza. The blades are heavy.
 
no-drag antenna

Any reason we couldn't embed the VOR/GS dipole Vee in the cabin top - copper foil or wire under a bed of micro (or covered with a console / head liner if on the inner surface?) Seems workable and invisible, drag free and no risk of injury or damage vs. the whiskers. Anyone done this?
 
Any reason we couldn't embed the VOR/GS dipole Vee in the cabin top - copper foil or wire under a bed of micro (or covered with a console / head liner if on the inner surface?) Seems workable and invisible, drag free and no risk of injury or damage vs. the whiskers. Anyone done this?

Don't know for sure, but it seems plausible but I've never heard of anyone doing it that way. I did embed three 24" runs of 1/4" copper foil in the top of my cabin to extend one of my Com antenna's ground plane (the antenna is mounted just aft of the baggage bulkhead on top of the tailcone hence the need).

But IMO the work isn't worth the reduction in drag. YMMV...
 
Any reason we couldn't embed the VOR/GS dipole Vee in the cabin top - copper foil or wire under a bed of micro (or covered with a console / head liner if on the inner surface?) Seems workable and invisible, drag free and no risk of injury or damage vs. the whiskers. Anyone done this?

You could. Depending on your panel and such, this might pick up some RFI - especially if you are running electronic ignitions.

There is little advantage (and some disadvantages) to any VOR/ILS antenna install over a properly tuned wingtip antenna. No need to reinvent the wheel.

Carl
 
Bill, I have used copper strip VOR antenna glasses to the inner cabin surface twice now. Reception is perfect, you can run the cable through the windshield brace and hide the terminals under the overhead console.
 
Using copper foil tape nav antennas in the canopy was old school before there were RV's to install them in. I bought an old Mustang II project back when I started flying, and there were plans for installing that type of antenna in newsletters and magazines I got with the project, from back in the '70s & '80s.

Obviously very inexpensive to do, shorter coax run, etc etc.

Charlie
 
Just spitballin' here

most of my antenna playtime has been at 3.8-29 MHz on automobiles, but I've tried a few VHF designs on my RV over the years, most of which ended in the scrap bin including an Archer wingtip copy (comm, not nav).

I don't think the installation of a foil dipole antenna on the inside of the cabin cover would be problematic, but admit I have not yet finished an RV-10 cabin, and many of you have. From an RF standpoint the antenna install seems pretty straightforward and bulletproof - mostly need to know the effect of the dielectric it's embedded in or glued to on resonant length. For a receive-only VOR/ILS antenna, that can probably be ignored with no adverse effect. Shading would be anticipated as nonexistent vs the wing rib issue some report with the Archer design. Feedline is considerably shorter run to the cabin top. Other DC electrics in the overhead console can probably be run through the center of the vee area, perpendicular to the antenna elements, with next to no coupling effects. Drag reduction vs external whiskers is not nothing, nor are there any unfavorable cost or CG considerations I can think of vs running RG-400 to the vertical stab tip or under the horizontal stab and putting in doublers for the puck, etc.

Just looking for the elegantly simple way to skin this cat. Todd, I saw your post about the embedded ground plane radials in the top for your comm whip, and that is what got me to thinking about this stuff. Now I'm wondering if there's room in the sides of the cabin lid for a mostly-vertical comm dipole to be embedded. 10 watts at 130 MHz can't be that hard to safely tame near people's heads :D
 
most of my antenna playtime has been at 3.8-29 MHz on automobiles, but I've tried a few VHF designs on my RV over the years, most of which ended in the scrap bin including an Archer wingtip copy (comm, not nav).

I don't think the installation of a foil dipole antenna on the inside of the cabin cover would be problematic, but admit I have not yet finished an RV-10 cabin, and many of you have. From an RF standpoint the antenna install seems pretty straightforward and bulletproof - mostly need to know the effect of the dielectric it's embedded in or glued to on resonant length. For a receive-only VOR/ILS antenna, that can probably be ignored with no adverse effect. Shading would be anticipated as nonexistent vs the wing rib issue some report with the Archer design. Feedline is considerably shorter run to the cabin top. Other DC electrics in the overhead console can probably be run through the center of the vee area, perpendicular to the antenna elements, with next to no coupling effects. Drag reduction vs external whiskers is not nothing, nor are there any unfavorable cost or CG considerations I can think of vs running RG-400 to the vertical stab tip or under the horizontal stab and putting in doublers for the puck, etc.

Just looking for the elegantly simple way to skin this cat. Todd, I saw your post about the embedded ground plane radials in the top for your comm whip, and that is what got me to thinking about this stuff. Now I'm wondering if there's room in the sides of the cabin lid for a mostly-vertical comm dipole to be embedded. 10 watts at 130 MHz can't be that hard to safely tame near people's heads :D

I don't think there's enough room on the fiberglass part to get a full vertical dipole mounted - half of it would below the edge of the metal "bathtub". Also, I don't think that I would volunteer to sit next to it, but I know nothing factual about the biophysics!
Remember if you put in a real dipole (horizontal) for a VOR that reception off the end (90 deg to the airplane, I presume) will be poor. My Archer nav is not as good as an external antenna, but not too bad, either, even when looking thru the airframe. On an ILS it works just fine.
I do have an Archer com. It is not as good as the external whip, but not as bad as some would have you believe. It is important to get as much vertical polarization into the high-current front leg as possible. In this respect the thicker wingtips in the -10 are better than in other RVs (-14 excepted).
 
Sounds like a plan, then.

I wrote my second post without refreshing and therefore did not see the replies about having been done successfully before. Not surprised, and glad to hear it is worthwhile. I think I will do this.

Bob, the foil tape dipole for VOR would probably be a Vee, as are the whiskers we use externally. I suppose the vee shape allows for less of a null off the ends, since it's not a truly linear dipole. Without doubt it allows the dipole feedpoint Z to be 50 ohms versus the 72 ohms of a straight (180*) dipole, and offers a somewhat streamlined form factor when mounted with the whiskers in trail (though some say this is "backwards" to the intended direction of mounting.) At any rate, I intend to make mine with whatever included angle gives a match to 50 ohm coax (and I need to look that up).

The vertical dipole in the cabin side could be more of a 1/4 wave monopole against a pair of ground radials (ideally drooping, for reasons mentioned above) or working against the metal fuselage side or even a folded or coiled counterpoise - scaled down version of this: https://www.google.com/search?q=fol...unterpoise+foil+antenna&imgrc=DXRZCKC8b8iaCM:

I'm not worried about biological effects of low level VHF radiation so much as the issue of that much field strength so close to the headsets, which offer a path back into the radios. Untoward and unpredictable things might happen when you key down. :eek: Still, it's an attractive place to hide a stealth antenna. I will give it more thought.
 
Look at the second post again: Mike had the right answer. The Bob Archer antenna is cheap, no interference, easy installation and access, and works perfectly. No need to reinvent the wheel.
 
I suppose it depends who you ask.

I gather that the Archer works well when established on the ILS. At those distances there is less left to chance. I'm not sure how great they work when transiting an MOA where there is active GPS jamming and EFIS's are having cascading failures and VOR/pilotage is all you've got and the VOR is a good ways away :eek: No one, myself included since I've tried one, is touting them as a fully workable solution for comm - although I admit that discussion is true thread drift, tied together only so far as it shares the theme of using the cabin top as a radome / antenna substrate.

The motive behind my contribution to this thread is my inner angst - as I close up the baggage and rear seat areas with no doublers or plans for same to mount any belly antennas. I _think_ I'll have no regrets there, but at the same time I'd better have a plan for where those antennas are, in fact, going to end up.
 
I gather that the Archer works well when established on the ILS. At those distances there is less left to chance. I'm not sure how great they work when transiting an MOA where there is active GPS jamming and EFIS's are having cascading failures and VOR/pilotage is all you've got and the VOR is a good ways away :eek: No one, myself included since I've tried one, is touting them as a fully workable solution for comm - although I admit that discussion is true thread drift, tied together only so far as it shares the theme of using the cabin top as a radome / antenna substrate.

The motive behind my contribution to this thread is my inner angst - as I close up the baggage and rear seat areas with no doublers or plans for same to mount any belly antennas. I _think_ I'll have no regrets there, but at the same time I'd better have a plan for where those antennas are, in fact, going to end up.

My $2 homebrew wingtip VOR/ILS antenna picks up VORs beyond 100nmi. No reason any properly made wingtip antenna should not do the same.

You have option to install comm antenna doublers in the bottom of the tunnel, so no fear about having the other areas already closed. The bottom of the tunnel also provides for easy cable routing and inspection. Bias the antennas to the left and right side of tunnel bottom, one forward and one aft, to avoid interference. I did a bend on the doublers so that one edge overlapped the tunnel wall flange and used the same rivets as the skin.

Carl
 
If you place your terminals overhead approx in line with the. Rear doorpost, you can run the V aft and they fit with just the last couple inches curving down a bit. I embed a pair of nuts in the glass and solder the copper element ends to them. Hide the balun right there in the console. Kinda hard to argue with a $1 hidden VOR antenna that works perfect, is invisible, is unbreakable, and won't poke her dam eye out.
 
Just curious

Is there a "roll your own" kit for sale that comes with the balun, copper foil and coax connector somewhere online? Also, if you go with a VOR/ILS antenna of this kind in the canopy, does it preclude you from being able to install pucks on the canopy top or COMM antennas on the top od the tail cone?
 
Aerhed!

I like the way you think.;)

Carl, I've had at least one -10 pilot tell me not to depend on an Archer nav antenna. I get that yours has worked well, and that the installations are frequently not to spec - not idiot=proof. I see no reason not to go with the cabin-top integral foil VOR antenna, as in my mind it's less controversial and more easily fab'd. I sincerely wish the Archer comms had a good reputation for performance, but that polarization thing rears its ugly head every time. I am busy brainstorming an alternative shortened/fractal vertical dipole design for wingtip as well as cabin mounting. may play with it in the 6 this summer; if it will work in that shallower wingtip, piece of cake in the 10 and 14.
 
Is there a "roll your own" kit for sale that comes with the balun, copper foil and coax connector somewhere online? Also, if you go with a VOR/ILS antenna of this kind in the canopy, does it preclude you from being able to install pucks on the canopy top or COMM antennas on the top od the tail cone?

Don't know about the kit. jim Weir used to sell that sort of thing. Balun probably not needed in a receive application anyway. Would be easy to wind on a tiny toroid core.

As for the two antennas nearby, they will be somewhat separate as well as cross-polarized, but the VOR might still get clobbered during comm transmit; would probably immediately recover but that would be an experiment in receiver front-end robustness for sure. Common sense would favor a forward location for the VOR and an aft one for the tailcone top skin comm antenna to minimize this.
 
My $2 homebrew wingtip VOR/ILS antenna picks up VORs beyond 100nmi. No reason any properly made wingtip antenna should not do the same.

You have option to install comm antenna doublers in the bottom of the tunnel, so no fear about having the other areas already closed. The bottom of the tunnel also provides for easy cable routing and inspection. Bias the antennas to the left and right side of tunnel bottom, one forward and one aft, to avoid interference. I did a bend on the doublers so that one edge overlapped the tunnel wall flange and used the same rivets as the skin.

Carl

Carl, I'm not to the point of having my elevator push-pull tube in the tunnel forward of the battery box, so wasn't sure how much clearance there was in the
tunnel above the belly skin before control hardware got in the way of antenna fittings, etc. Good to know it's doable. Thanks!
 
I like the way you think.;)

Carl, I've had at least one -10 pilot tell me not to depend on an Archer nav antenna. I get that yours has worked well, and that the installations are frequently not to spec - not idiot=proof. .

I've seen these things with all kinds of crazy installations, from one where the ground leg was a foot away from the rib, to one which was installed upside down (radiating arm up against the rib). Little wonder there are some reports of it not working well. Like Carl, I'm happy with mine.
 
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