Best VOR/LOC/GS antenna?

[ewumnrr]

No it isn’t. If that were true then using a horizontal vor wouldn’t work for GS.

Oh good that you mention that. I had it first horizontally polarized with a different modification, then read it was vertically polarized and started over. I just went back and the internet is pretty much split claiming one or the other but I found the FAA document that says it's horizontally polarized. Final answer.
Let me try to recreate what I first had and publish it here.

 

[BobTurner]

hard to tell from your photo of the tip detached, but those power lines to the lights/strobes don’t appear to be IAW archers install instructions which are explicit about routing up the forward element. Looks like they loop around over the top of the element then back outboard.

Agreed. I’d re-route those wires forward inside the rib, then bring them straight out as far forward of the antenna as possible. The instructions for running wires along the antenna are really only when it cannot be avoided.

 

[ewumnrr]

Oh good that you mention that. I had it first horizontally polarized with a different modification, then read it was vertically polarized and started over. I just went back and the internet is pretty much split claiming one or the other but I found the FAA document that says it's horizontally polarized. Final answer.
Let me try to recreate what I first had and publish it here.

Luckily, I found a picture of my first version that was horizontally polarized. Need to recreate it and measure the modification.

 

[gmcjetpilot]

Hi Everyone,
I just bought a beautiful flying 7A and I'm looking for the best solution to add a VOR/LOC/GS antenna. "best" means primarily best functioning, but also decent looking and reasonable cost. Has anyone installed the "do it yourself" kind in the wingtip AFTER the ship has been built? Do they work?
Any other solutions except the Aircraft Spruce black hockey puck looking one?

Thanks!

Andy.

A di-pole on bottom of fuselage under horizontal stabilizer. I am not anti Archer but In my opinion, it's a compromise in performance and it may be more difficult to run coaxial wire from the wing tip into the cockpit versus through the back of the fuselage. The antenna located as I discribed is not noticeable. Drag? 0.01 mph. Seriously don't know but so small you can't measure it.

RAMI AV-532 VOR / Loc / GS Antenna Without Cable | Aircraft Spruce

RAMI AV-532 VOR / Loc / GS Antenna Without Cable This antenna is constructed of taper-ground high-strength stainless steel to withstand the vibration and wind loads with the stability necessary for reliable operation. The insulators are com

www.aircraftspruce.com

You can split the signal for vor/loc/gs. Look at spruce at antennas for ideas. Try any aircraft parts company. Going to Oshkosh? Fly market or every store with show specials. You can try ebay. DIY is fine but antennas are not that expensive and they are guaranteed to work, have good impedance match and be reliable.

 

[airguy]

I hand-made my pair of Archer antennae, one in each wing tip just in case I ever lost one, coax from both coming under the panel. I laid them up inside the wingtip with a little glass to hold them in place, used some copper strap for the ground connection between the antenna and the wing with the screws bonding it to the wing, and routed the light wiring per the instructions. Works perfectly.

 

[rockyfatcat]

Update: Please disregard this post. See further down my mod for horizontal polarization. This one was for vertical glide slope polarization which is wrong for the 330 MHz ones. Only the microwave glide slopes are vertically polarized.

Details:
Adding the second band slightly detuned the VOR part of the antenna. I had to add 2.5 cm to the long end.
The added 330 MHz antenna strip is 16.5 cm long, 7 mm wide, attached to a point on the line between the two nuts that hold the insulation material, 1.4 cm away from the nut closer to the cable attach points, 1.85cm to the nut away from the cable attach points.
View attachment 63594

Just so I understand. You added a vertical strip16.5 cm long, 7 mm wide to better pick up the glideslope signal, and because of the mass of the additional vertical metal strip, you added an additional 2.5 cm to the long end to re-adjust the VOR signal.

If this is correct, wouldn't a thinner wire work better? A similarly sized hole drilled in the horizontal plane, and the wire tacked in place by welding.

I used an antenna length calculator and averaged .740 as a good average length for 328-335 mhz. I do not know the internal vertical distance of the RV7 wingtip, but even if .740 was too long long, wouldn't a simple bend like the bent wire comm antenna on the aircraft belly work?

I'm a mechanic, not an avionics guy.

 

[flyvans.com]

hard to tell from your photo of the tip detached, but those power lines to the lights/strobes don’t appear to be IAW archers install instructions which are explicit about routing up the forward element. Looks like they loop around over the top of the element then back outboard.

I will review this and improve. However, the situation has been unchanged from day 1 and did not seem to cause any issues.
The only recent change (after starting to trouble shoot the GS issue) is the addition of the black grounding strap that improves the ground connection to the wing. Previously that was only established through the nutplates and screws to wing skin contact.

Let me see. SL30, GS always worked. Removed SL30, installed Trig. Unplugged nav coax (one cable), plugged into Trig. Now Trig GS is crap. Did you do anything to the antenna? What makes you think that’s the problem? Installed new ground connection (Is that the black wire that loops out across the antenna, then back to a rib? This is RF, wire lengths matter. This should be as short as possible.) You say the new wire greatly improves nav audio. But that’s the same signal that drives the vor cdi, which you said was already great. There’s something very strange going on here. Return antenna to previous condition (make sure there’s no paint/corrosion under the tip attach screws), re-assemble, get a third loaner from Trig, make sure Archer coax is plugged all the way in, try again.

Practically all correct.
- Only change at the time of the swap was the SL30 Cradle Coax Plugs/Ends on the Nav and Com RG400's were changed by a certified Avionics Technician to Standard BNC plugs, which now attach to the Trig cradle.
- No change was done to the antenna itself.
- Then did several test flights and found the only problem to be the GS reception. (And Nav Audio was rather weak in volume, but still easily detectable)
- CDI/VOR display always worked fine, did not test to max range, but in the order of 50NM from VOR / 18NM from ILS did definitely work. However, GS only at 5-6NM.
- This, irrespective of orientation towards the emitter (thought maybe the fuselage could be shading the wingtip affecting signal strength or so, never was a problem with the SL30 however). No matter whether intercepting from left or right - same result.
- First suspected a serial protocol / display issue between the TX56 and the EFIS as during the first test flight, I never got close enough to the GP, so never received a signal. As I only tested at intercept altitudes / FAF, cruising around waiting for the GS to appear on at least two different ILS's...
- On further flights, once i started visual descents and got close enough to the GP, I did receive the signal and the display on the EFIS became alive and correct. Hence any serial protocol issue appears very unlikely.
- No diplexers or any other kind of active/passive special hardware in the coax path.
- In discussions with Trig we concluded (and the weak Nav Audio hinted to) some kind of Antenna issue / compatibility with the Archer antenna.
- I first wanted to try to improve the grounding, knowing this was somewhat sketchy from the start. The antenna ground leg, metal strip that holds the nutplates and nutplates themselves are all on the inside of the fiberglass wingtip and the connection ot the airframe was mainly established via the screws/nutplates (and the screws over the painted skins, i think i intentionally removed the paint on one of the screw holes!). Yet it worked for all these years, however it could have corroded.
- So decided to add a dedicated grounding strap, connecting the ground side of the wingtip antenna with the outboard wing rib. This did improve the strength of the Nav Audio return (at least I believe it is more than expectation bias *G*).
- The fact that the archer antenna works for most here in the forum, has worked for me in the past and even now works fine for the Localizer & VOR via the exact same cable/installation/plugs, yet not for the GS is extremely puzzling (and on 2 separate TX56 devices, too).
- I doubt that e.g. the new BNC plugs could somehow be "leaking" the 300ish MHz Band while at the same time working perfectly in the 110 range...

 

[Richard Connell]

Apologies, I missed the fact it worked before. That does point to it being a radio issue I suppose. But the fact you added a few more connectors at the same time also could be a factor.

I think an archers get unnecessarily bad press because of two things, poor physical install ( wires crossing etc) and poor coax termination.
Good quality BNCs are harder to get right than people think - so minimizing them and being meticulous in construction is good. If you’ve made a few new connections then that’s also worth looking at.

I’ve had 3 of these antennas. All been great. But I have had one coax termination issue. The symptom? Unsatisfactory (late) GS reception.

In the RV10 I have the archer in the LH wingtip, about mid chord, riveted to the outboard rib. Further back than “ideal” but
it has no BNC connection or any wires anywhere near it. The coax comes out of the nav radio (one BNC) down the wing - out the last rib and straight to the terminals of the antenna.

On the broader question of what’s necessary… Reception is fine. I don’t really know if it will track a radial at 100miles because I’ve never been bothered to test, but 50 is no problem and obviously ILS/LOC are fine. It’s very useful and clear for AWIS etc.

I never use it for en route (other than to get wx), and never will unless something silly happens with GPS. But I’m sure it would be adequate if it was needed.

I’m sure there are many hundreds if not thousands of similar happy installs out there. I’m sure there’ll be a fix for this issue.

 

[Dugaru]

A di-pole on bottom of fuselage under horizontal stabilizer.

+1. I know zilch about the Archer, but can at least say that this setup has worked great for me.

 

[bjdecker]

...I like the antenna outside and ugly. Ha ha.

Thing of beauty eh?

 

[Carl Froehlich]

Antenna work boils down to your objectives. The OP asks what is the best VOR/LOC/GS antenna. I offer the better question is what is the best VOR/LOC/GS antenna for my plane that does what I need.

On four RVs I built a standard wingtip antenna out of aluminum from the scrap box, some fiberglass to make the Gama Match, and perhaps $3 of specialty hardware. It works outside 100nmi for VOR reception, and LOC/GS far beyond useable range.

So what is good enough? As has been posted there is an impedance mismatch on GS frequencies. In practical application however the antenna GS reception is still more than adequate (assuming something else is not wrong).

Some other thoughts I’ve posted in the past:
- The Archer instructions tells you to run the nav/strobe/LL wires along the antenna leg extenteinding into the wingtip. I consider this simply asking for RFI injection into the NAV receive and perhaps the other radios. Move the antenna a foot or so aft and eliminate this issue. While most LED nav/strobe/LL are now much quieter at VHF frequencies they can still be an RFI source.
- Ground straps and such seem to cause more concerns for builders than not. Eliminate the issue by mounting the antenna on the outboard wing rib. The wingtip then just fits over the antenna.
- The Archer antenna does not take advantage of the total width of the typical RV wingtip. The antenna leg going from the wing rib into the wingtip can be extended, and the leg running fore to aft in the wingtip shortened by the same amount. This will enhance performance. Keep in mind for a quarter wave antenna the majority of the work is done by the first third of the antenna (the high current portion). An antenna analyzer is needed to do the final resonance tune and system check of our antennas (store bought or not). I consider this a must have shared tool for all EAA chapters.

Carl

 

[RV7A Flyer]

 

[BobTurner]

To the OP: get back to your certified tech and have them test the BNC connectors they installed. Anyone can screw up, and installing connectors is not quite as easy as you might think.
Full disclosure: when I installed a TNC connector for my Trig transponder, I cut the coax connector’s center wire a bit short. When I assembled the connector, the center pin was too short to snap into place. When I plugged in the connector, the center pin was pushed back a tiny amount and failed to make electrical contact….it can happen.

 

[ewumnrr]

Just so I understand. You added a vertical strip16.5 cm long, 7 mm wide to better pick up the glideslope signal, and because of the mass of the additional vertical metal strip, you added an additional 2.5 cm to the long end to re-adjust the VOR signal.

If this is correct, wouldn't a thinner wire work better? A similarly sized hole drilled in the horizontal plane, and the wire tacked in place by welding.

I used an antenna length calculator and averaged .740 as a good average length for 328-335 mhz. I do not know the internal vertical distance of the RV7 wingtip, but even if .740 was too long long, wouldn't a simple bend like the bent wire comm antenna on the aircraft belly work?

I'm a mechanic, not an avionics guy.

Disregard the vertical strip, the correct solution adds a horizontal strip, see my other post with a picture of that. But, to answer your question: I had to add 2.5 cm to the localizer part of the antenna because my 330 MHz modification de-tuned the 108 MHz part as a side effect. The added length didn't come from math, rather from looking at the network analyzer. I used aluminum tape and cut it until the center frequency was correct again.
The 16.5 cm came from tuning as well. Calculating "F" strip antennas is not as easy as calculating a dipole. Easier to just go for it and measure.
The thickness of the added antenna strip determines the width of the resonant frequency span. If you make that 330 MHz strip very narrow, you won't get all glide slope channels well. I found 7 mm a good compromise. If it's too wideband, you are just pulling in more noise for no benefit. For the final horizontal solution, I'll probably make the strip more narrow than on the picture.
I found that the archer antenna only works as designed, if exactly half of the width of the base leg is overlapping with the adjacent wing metal structure. That gives the receiving part the correct distance to the web of the adjacent rib. The little network analyzers cost less than $50 (https://www.amazon.com/gp/product/B07T6LXNTV) plus the adapters $10 (https://www.amazon.com/gp/product/B078K5563Y). That's all you need to tune an antenna.

 

[ewumnrr]

I recreated adding the horizontally polarized glidslope band to the Archer antenna.
The width of the strip is 6 mm, the length measured from the centerline of the Archer pickup strip to the end is 17.1 cm. It is placed in the center between the two nylon bolts.
Antenna Quality Measurements:
Stock:
113 MHz 333.5 MHz
SWR 1.2 8.7
|Z| 60 Ohm 65 Ohm
S11 -22 dB -1.9 dB

With the mod:
113 MHz 333.5 MHz
SWR 1.2 1.5
|Z| 55 Ohm 61 Ohm
S11 -19.7 dB -13.3 dB

I'll do a CAD design to replace the small cable hookup plate with a plate that has the extra stip. I'll make a few laser cut parts and then we can do some retrofits and see whether the glide slope range increases significantly. I have several ILS runways close-by where I can just drive there and see if it works. If it works on the ground, I'll try in the air.

 

[ewumnrr]

I'll do a CAD design to replace the small cable hookup plate with a plate that has the extra stip. I'll make a few laser cut parts and then we can do some retrofits and see whether the glide slope range increases significantly. I have several ILS runways close-by where I can just drive there and see if it works. If it works on the ground, I'll try in the air.

I am having 12 of these laser cut from 2024T3 for $2.80 a piece. If you want to have one, shoot me a message.

CAD design is here: https://cad.onshape.com/documents/c...renderMode=0&uiState=665891c6a025625f8f60665f

 

[ewumnrr]

If I do the math: If your current archer antenna gets you the glide slope 5 miles out, with the add-on, you would get it 18 miles out. That is a 3x improvement. We'll see what the flight test shows but at least we know what it should be.

 

[flyvans.com]

I will experiment and report back!
Might take a few weeks!

 

[ewumnrr]

The 12 laser cut antenna add-ons came back and they fit perfectly and yield the same specs (SWR 1.1 to 1.3 @ 333 MHz, SWR 1.4 @ 113 MHz) when placed at the edge of a large metal surface simulating the wing. Planning on doing some drive and flight tests in the coming 2 weeks. I'll send out the samples to the ones that contacted me via PM shortly.

 

[RayJr]

All that said, is it reasonable to assume that if I bought an Archer antenna from aircraft spruce, installed per the default instructions in the wingtip of my RV, attached it to a Val Nav2000, it would work? I could shoot an ils with glide slope?

 

[rockyfatcat]

All that said, is it reasonable to assume that if I bought an Archer antenna from aircraft spruce, installed per the default instructions in the wingtip of my RV, attached it to a Val Nav2000, it would work? I could shoot an ils with glide slope?

From what I understand. The archer will pick up the glide slope around 18 miles out. The OP has a laser cut bit of metal that you can rivet to the Archer that will triple that distance.

 

[BobTurner]

All that said, is it reasonable to assume that if I bought an Archer antenna from aircraft spruce, installed per the default instructions in the wingtip of my RV, attached it to a Val Nav2000, it would work? I could shoot an ils with glide slope?

There are a significant number of responders, including myself, who would answer yes. Some however say ‘no’. Personally, I have had the opportunity to see photos of two ‘no’s’, and neither was installed per instructions (in one case the ground leg was out in the wingtip, the radiating leg was rivited to the end rib (!). It was amazing that it worked at all. In the other case the ground leg was 8” out into the tip, attached to the rib with multiple wires (!).

 

[RV6_flyer]

From what I understand. The archer will pick up the glide slope around 18 miles out. The OP has a laser cut bit of metal that you can rivet to the Archer that will triple that distance.

The Archer VOR antenna in my RV-6 connected to my SL-30 has been able to pick up the KPOC ILS Glide Slope 30 Nm from the airport when I was based at KCCB. It may have picked up the signal at a longer distance but I was just outside 30 Nm when I tried it. I was on a VFR flight at the time I tested it.

 

[wjb]

I made an initial run with an Archer type antenna, and had very poor luck getting to tune well in the wingtips (I'm an EE for my day job and have access to good test equipment). Some report great performance, others so-so ... seems to be very installation specific.

I went with a Rami cat whisker, tucked under the tail. The post install antenna tuning checks were spot on, and have not had any issues in flight. I wanted to get on with my IFR training and didn't want to fuss too much with the antenna; I needed a ILS/LOC/VOR receiver to do the check ride in my plane. Got those green needles now!