Twitchy Glide slope

RV8iator · #1 01-19-2012, 05:39 PM

I'm running an SL30 with a GRT Sport SX. I'm using a Dave Archer antennae for the VOR, LOC, and G/S in the left wing tip.
VOR and LOC signals are solid but the glide slope jumps up and down like crazy.
Any ideas out there?

Bill.Peyton · #2 01-19-2012, 06:39 PM

I believe the sl30 has a built in gs splitter, so you can't substitue another. How about loose connection on antenna. Does it pick up the GS and pull the flag at at a good distance and then loose the signal during the approach? Define jumps up and down.

johnfurey · #3 01-19-2012, 06:58 PM

I have the exact same set up and had the same problem. I check everything I could think of and spoke directly with Bob Archer several times with no improvement. In desperation I removed the aluminum tape from inside the wingtip that Vans supplies as a heat shield for the twin landing light bulbs and the problem went away

RV8iator · #4 01-19-2012, 08:46 PM

Quote:

Originally Posted by Bill.Peyton

I believe the sl30 has a built in gs splitter, so you can't substitue another. How about loose connection on antenna. Does it pick up the GS and pull the flag at at a good distance and then loose the signal during the approach? Define jumps up and down.

Never get a flag, good ident, loc is stable. The GS needle oscillates up and down almost full scale deflection.

Bill.Peyton · #5 01-20-2012, 06:12 AM

I know the installation of the archer antenna is critical on wire routing and metallic objects. Maybe a call to Bob Archer, or maybe try removing the insulation. The GS freq. at 325 mhz is lower than the loc at 110. So the single antenna never does as well as an individual antenna due the mismatch. With that said, the GS is so close that it most times does not really matter. It sounds like you have a mounting issue, I would review the prior post and maybe try rmoving the heat shield and also review the installation instructions. I have one of these in each wing tip for my two radios and I hope I don't see these types of issues
Good Luck, and let us know what you find out so we can avoid similar problems.

RV8iator · #6 01-20-2012, 07:13 AM

I don't have lights in the wingtips so no heat shield. I routed the nav and strobe light wires in the mounts provided on the leading edge of the antennae and grounded it to the end of the wing like the instructions said.
The only odd man out is that I have an APRS antennae in the wingtip also. I'll try turning it off and see if that helps with the GS reception.
I'll keep you posted on the results.

RV8iator · #7 01-27-2012, 03:36 PM

OK, Bob Archer's instructions say to slide the antenna between the wing tip and the wing for a good grounding plane.

I didn't want to unrivet the plate nuts that held the wing tip on so I butted tt against the wing and ran a 12 ga. grounding wire from the antennae's to the wing.
The VOR and LOC were rock solid with good range on the VOR. As stated above the Glide Slope was erratic all the way down the chute.

I talked to Bob and he said that a single wire ground would probably not be a big enough grounding plane and in fact, with it slipped in between the wing tip and the wing that the wing itself would be a grounding plane as well as act like part of the antennae.

I removed the tip and drilled out the platenuts and slid the antennae under the aluminum strip in the tip, drilled it all out and reinstalled the platenuts and,,

Success..the glide slope doesn't even flicker.. Both the LOC and GS were rock solid. VOR reception was excellent at 3500 feet for a station 45 miles away. Didn't go any higher to check range but I'll bet it's better too.

When all else fails, RTFI!

Bill.Peyton · #8 01-27-2012, 05:28 PM

I hope mine works ok. I used piano hinge to attach the wing tip and ran the antenna ground plane under the piano hinge, which eventually gets connected to the other hinge piece, which is riveted to the wing.

RV8iator · #9 01-27-2012, 08:22 PM

According to Bob you just need a good ground spread across the entire width of the ground side of the antennae so that should work fine. In fact, you will probably have more surface area than I do with just the nut plates and screws. I slipped the antennae under the 1/2 inch wide strip on aluminum inside the tips and reriveted the plates in.
Sure made a huge difference.