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VOR/LOC/GS

P

paul330

Well Known Member
I hi-jacked a previous thread concerning antenna location but never really got a satisfactory answer. So, I'll try again.

Certain antenna (like the Comant 215) are described as LOC/VOR/GS. They are all either twin blade or V-whip and presumably designed to be fitted on the side or top of the VS. Is there a single blade or whip antenna that can be fitted under the fuselage that will give me VOR/LOC/GS with suitable diplexers? Or are the physics such that it has to be a dual type antenna?

If that is the case, is it possible to build a small housing to fit a V-whip under the fuselage? More accurately, I know it is possible but would it work?
 
I am using a single antenna for VOR/LOC/GS (2 actually, one for each radio), but have it in the wing tip. It has to do with signal polarization, the signals are polarized in the horizontal plane......where the com signals are vertical. I am not a comm engineer...but I have spent a night in a Holiday Inn.

You should be able to find other discussions in this archive or Matronics.
 
Yes, the orientation has to be horizontal. My plan is to put the V-whip under the fuselage just aft the HS leading edge. I haven't decided yet if I will attempt to use the removable whips and penetrate the fuselage side or if I will simply mount it on the bottom with a blister fairing.
 
under rear fuse- works

paul330 said:
Is there a single blade or whip antenna that can be fitted under the fuselage that will give me VOR/LOC/GS with suitable diplexers? More accurately, I know it is possible but would it work?
Click to expand...

Had a V-Whip mounted under the Fuse in the rear as you described- It did work great with the KX125 when we had it installed- Removed and went to GPS radio and more speed. (every MPH counts as I will always want to pass Flion!) :p I think that under fuse point is probably the best place to install for reception since there is nothing to degrade the ground signal- But top of tail (AKA Cessna -Piper) always seems to work well also. :cool:
If I where to go back to VOR/ILS/GS I would consider the engine cowl as a fiberglass Antenna(???)
I know: bad ground plain- too much noise- forget about tracking away from station etc etc-BUT- has anyone tried it??? could be the lightest install as yet for a VOR/ILS antenna
 
I installed the wing tip Archer antenna in my previous RV8 and have one for the RV10 I am building as well. Simple and clean.

Pat Stewart
 
Of course, horizontal polarization ....duh! Should have known that :eek:

OK, so it looks like I can mount a v-whip under the fuselage in a suitable blister or housing. Now, why does everybody prefer the rear?

Thanks, as always, for the prompt info.
 
Tradition, probably. Production aircraft used to put them back there; I've commonly seen the v-whip or the towel racks back and high, out of the way. When you're planning the installations in your small aircraft, seems a lot of people like the COMM(s) between the mains, then transponder. Tail top is popular to keep people from running into them; my plan of under the HS is for a similar reason. I've also investigated the 'wing' antenna but it's just too expensive; I mean the little COMANT wings not the Archer wingtip antenna. The Archer seems to do just fine in my -6A but I was strongly advised to go with external antennae with the G900 for the -10. Brad's idea is interesting but I'd worry about noise from the engine (Brad, wait 'til I get the intersection fairings done and paint on...). Anyway, bottom line is there's a lot of places you can put an antenna but you have to keep it away from other antennae, interference sources, etc. so what you see is a common compromise.
 
Paul, I have done two RV7A's with a V type (like a CI-175P) wire antenna. One with the antenna on the VS and one below the HS. Both worked fine. On the 10 I am going below the HS because the wire run is less complicated and slightly shorter. Just remember that you will also nee a CI-507 or similar to get both the VOR and GS signal needed. Here is an example http://www.edmo.com/index.php?module=products&func=display&prod_id=18806
 
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Diplexer not always required

I don't think you need a diplexer for all radios. Although one would be required with a 430/530, I beleive the SL-30 has an internal diplexer built-in thus eliminating the requirement for one like the CI-507.
 
Happy New Year guys and thanks for the info - think we are almost there. Just another couple of questions:

The Comant CI505 diplexer takes one Nav input and puts out 2 Nav and one GS. Now the SL30 has an internal diplexer. Does that mean I can take one Nav output to the SL30 and get ILS/GS and put the other Nav and GS outputs to the 430?

Secondly, what do I need to get a DME?
 
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And with GPS, I'm not sure I'd want to bother with DME. A friend has been comparing the two in his aircraft and they are both pretty good. But the GPS is consistently to center of runway while the DME depends on where the equipment is set up on the field.
 
paul330 said:
The Comant CI505 diplexer takes one Nav input and puts out 2 Nav and one GS. Now the SL30 has an internal diplexer. Does that mean I can take one Nav output to the SL30 and get ILS/GS and put the other Nav and GS outputs to the 430?
Click to expand...

I am trying to solve this same issue. According to Paul at Steins, I need two splitters.

My understanding is you first need to split the signal using a CI-5120, with one side going to the SL30 (which has the built in diplexer) and the other side going to a CI-507 which is the external diplexer for the 430, allowing the 430 one feed for VOR and one feed for GS.

If you use the CI-505 it looks to me like you would get VOR and GS for the 430, and only VOR for the SL30. You would lose the option of getting GS for the SL30.
 
OK, the diplexer thing sounds right. I was wondering whether I would lose the G/S to the SL30 with the CI505.

As for the DME, does either the SL30 or 430 have a built in receiver? A seperate aerial is simple enough but another reciever looks expensive. I'd prefer to have a DME for co-located ILSs although I appreciate the advantages of GPS.
 
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