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tonyjohnson

Well Known Member
I am building an 8A. I am trying to determine what antenna to use for:

Garmin 430 Nav/com: I am considering the bent whip antenna for the belly (in front of the spar) for the comm function. Does anyone know of a performance difference between the various makers?

For the VOR function I have considered the archer type for inside the wingtip. I understand there is some loss of signal as a tradeoff for the antenna being outside the wind stream. Since I will use the airplane for IFR flights, I am probably less likely than others to accept the loss of signal. Does anyone know how much the archer type antenna reduces the signal strength?

What do I need for marker beacons, localizer and glideslope information?

Is there some type of combination antenna for NAV purposes?

Transponder- The little ball type is simple and inexpensive. I assume that the fin type is more aerodynamic. Does anyone think it worth it to use the fin type? I will need two, one for my garmin 327 and the other for the monroy traffic detector.

Thanks
 
My solutions

Tony,

I've only got 1.8 hours on the plane in one day so far, but I did pick up the ILS at Galveston from about 30 miles away....

Comm 1 Antenna is a standard faired-bent whip (from Van's) on the belly, behind the spar - if you put it ahead of the spar, the wiring will be under your legs. GPS is under the cowling, attached to the firewall on a shelf-type bracket. GPS #2 on the glareshield (a Garmin 18 all-in-one receiver/antenna "hockey puck" - very small). VHF Nav antenna is an Archer in the the right wing tip (does VOR/LOC/GS), and Number 2 Comm is an Archer in the left tip, made as "vertical" as possible for the polarization. Worked well for my chase pilot's yesterday. No marker beacon - not required much (or at all) these days. Oh, Transponder is the little ball on a stick, just ahead of the left wing rear spar attach bolt.

As usual, YMMV, but you can keep it simple!


Paul Dye
N188PD
 
For IFR ops, I wouldn't go with the wingtip antenna. Call me old fashioned, but a chance of not getting adequate performance in the clouds doesn't sit well with me.

The localizer will come in through your VOR antenna, a whisker antenna that many put on the VS.

The marker beacon and Glideslope antennas are very small, and will go on the belly.

Transponder antenna, you can use either one. I used the shark fin, but it was probably overkill.

Comm antenna, bent whip in front of the spar on the belly. I had a comant, and never had problems with the tower hearing me when I was on the other side of the field. Others have said that if it's on the belly, they have to turn the aircraft sometimes so that the tower can hear you if you are at a large airport. I had a Garmin GNC250XL for my comm/gps, and it was plenty powerful enough with the comant antenna on the belly. The only antenna I had on top was GPS. I didn't have a VOR, but if I did, I'd probably put it on the VS.
 
antenna

Thanks Paul for your input. Did I understand that your NAV is an archer in the wingtip and you picked up the localizer from 30 miles? If you make any observations during future flights I would appreciate hearing about them I wonder how the range differs between that installation and the cats whiskers.
I like the fact that the archer does everything, VOR/LOC/GS.

Congratulations BTW, on the completion of your 8.

Tony
 
Wingtip VOR antenna works fine

I don't know what the hesitation to use a wingtip VOR antenna would be. Mine (Bob Archer VOR antenna, right wingtip, RV-7) works perfectly. Stronger, clearer reception (as far as I can tell) than any other externally mounted antenna I've ever used.

I fly IFR with it. Get it out of the slipstream and out of the way!

)_( Dan
RV-7 N714D
http://www.rvproject.com
 
Yes Tony - wingtip VOR/LOC/GS antenna, and got the Localizer at GLS from about 30 miles out. I had forgotten I had the G-430 tuned to it,and was surprised to see the indicators move onthe EFIS!

Paul Dye
 
Here's Mine

First I want to point out the the "V" navigation antenna at the top of the vertical stabilizer receives the VOR/LOC/GS signals and they are routed through splitters to the appropriate receivers. Mine is located up there and it provides "expected" performance (not measured but used on IFR flights).

I mounted my communication antennas aft of the spar for the reason mentioned earlier. They are bent whip Comants. The minimum separation recommended was researched at one time (something like 21" as I recall but that may be low) and I placed mine on the bottom skin with doublers with the connectors in the bays between the outer seat support structure. They worked well. Then I had to move the left one inboard one bay because in an RV-6A the trutrak autopilot servo mounts where I had the antenna. I believe you need an autopilot for this airplane in single pilot IFR operations by the way. Both comms still work well. Before I moved the one antenna I had one case at the John Wayne Airport in Santa Ana where I had to rotate the plane to communicate with Ground because of the blanking by the wings etc. In RV-8s I have seen the bent whips mounted on the bottom with a fwd and aft arrangement to provide the necessary separation.

My marker beacon "slim boat" antenna in on the bottom (with a doubler) aft of the second bulkhead behind the bagage compartment. I'm not sure how you report the outer marker without it by the way.

My transponder is the traditional balled spike in the center between the two com antennas. No interference experienced with the coms with this spacing and widely seperated frequencies.

My Apollo GPS antenna is on the upper skin aft of the bagage bulkhead. When the canopy opens it lifts and passes directly over this antenna. It works well of course in this location.

With all of these antennas, two steel steps and the rudder controls hanging in the breeze I'm still seeing TAS in the low 170s with a stock O-360-A1A and a standard two blade Hartzell C/S prop. It is a small vertical stab & rudder model but I have 1.5' more wing than standard so I'm not sure of the net drag difference from the later RV-6 models (parasitic is certainly higher but induced may be lower). If you do put everything outside you are still going to go fast. I went through tha same decision making process as you and I was going to go with all inside antennas for speed. However, when I called the manufacturer of the ones I was interested in the owner of the company told me he does not recommend his antennas for serious IFR operations. I over reacted to that input and stuck everything outside. There is probably an ideal compromise but my antennas are very reliable and I do not plan to change any of them.

Bob Axsom
 
Marker Beacon

You only need to be able to ID the Outer Marker location, and this can be done with an actual MB reciever, crossing radial, ADF (if there is an NDB co-located), or IFR GPS. So if you already have an IFR GPS, there is no need to have a MB receiver.

Of course, there is nothing preventing you from choosing to have one, and I support everyone's personal choice in what they need for IFR operations. My decision was to do away with it, since I'm flying with a Garmin 430 and a backup GPS as well.

Paul Dye
RV-8 N188PD - Flying
 
Comant Antenna

Comant has come out with a new line of antennas that are combination units, several types in one mast. I do not know which combo's are available but it might help.
 
Thanks

Thanks to all of you who have responded to my request for information. It has been a great help in my planning.
 
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