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Another Bob Archer VOR Antenna Question

asw20c

Well Known Member
The installation instructions make it fairly clear that for the antenna to function as intended it must be well grounded to the wing. To do this, the instructions say you should sandwich the grounding strip of the antenna between the fiberglass wingtip and the wing skin. I realized last night (yes, I'm building in my sleep too) that this is physically impossible. The wingtip fits inside the wingskins, and the antenna is inside the wingtip, therefore it isn't possible to sandwich the grounding strip between the wingtip and wingskins. Since there are others flying with the same antenna, how have you guys grounded the antenna? Are you simply relying on the nut plate screws that penetrate the grounding strip to be adequate? Perhaps rivet the antenna grounding strip to the wingtip by sandwiching the grounding strip between the nutplates and wingtip?
 
Perhaps rivet the antenna grounding strip to the wingtip by sandwiching the grounding strip between the nutplates and wingtip?

That is what I did. plus, made sure the wingtip attach screws had no paint between the screws and the aluminum wing. Others have attached an aluminum angle to the rib, and the antenna to the angle. This has the advantage that the tip can be removed without disconnecting the coax.
 
Don't over think it...

I laid the antenna into the bottom of the left wingtip about 1" away from the nut plate/attach strip and ran a ground wire (22ga) from the angled leg (ground plane) of the antenna (also where the coax shield attaches), to a ground lug/nut plate I installed on the wing tip rib (W-712)

Range is better than 100NM, and been solid for dozens of VOR & ILS approaches with Garmin GTN 650 in this configuration.


Cheers.
 
Here's a photo of my install. Reception is adequate for me - I'm haven't tested for long distance reception but easily pick up VOR's 30-40NM.


IMG_0011.jpg
 
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Mine is very similar. I get VOR out further than what I did in a tail antenna on my old Arrow.

On mine the wiring for the AeroLED light/strobe didn't lay exactly like the plans because I put the antenna further back in the tip. I made sure the light wiring stays forward of the antenna; but it doesn't seem to affect the antenna at all in any configuration of light/power/VOR range.

I think the light wiring is an issue if you let it lay or coil over the long fore/aft portion of the antenna.
 
I have an Archer antenna in each wingtip- one for each NAV- following Bob's directions to ground the antenna through the nutplate screws. The nav frequency VSWR, a measure of the quality of the RF power transmission, is shown below. Bob spec'd VSWR better than 2 for 108-127Mhz, so grounding through the nutplates look acceptable. A VSWR of 2 means 10% of the antenna power is lost due to mis-termination.

As8vNf5BQZnsAERLjwVMVlvsJk4Wc6JNsHePUgyYNDFn1S2bbqPGxI29rQRrJCRTlEymXfVH7xM0PfSX6mlacc7OgrVm5RZuIIlpq0OM_2VVR-_oieAOt_qlb0QICLlQ36gNslCJAEasFCJ5clS16k_-Ma_XDIj6jb2Qp5o7dLKy6qciItBrO07VlqNa2yuquE0cLC7kHNKFrdoQL7Z3HjeMVvrLukxh399K17baGUViYKpBegyA2V5riWyWTla6_HFDc_w3gLgQpzCThxgw7pEUEhqySRgeVj54pDD-J0G3Eso4rxVMEBqaEifHMyO8Bfqk79OiemaSzQf0Q_HPaCsuCnTY7XGLdCMFTK0soAqwf8Us8JaFMRVoXAFXN19DQ3vvKfyGEImB28qbZSe8FfHAqADMk5-SF3UfTNPjnHcP3REE3ObtNiuIssPJc-LSddCS3ZdBBQqqLpMi0eThQEEZ76vjX4CgAy1QP2pjbQK9P_AUO7t4rxD64UuR6GMmqjmT5G40nxzm74O2kvAxxfgLAE6G-M7fHsD1yb5lecvwo4wQvD-KggaccsGnAlAhjVw2S_RTxQpB9vml1PQNBQG3efi_09cb2uULkNtfcj5u5X_G_MBSsEBg3MMrOIP8IRB2FXgyx6XyG2wO75QFPTfHXyxSBwwiG3UBdEXODSfk1y_kwkvJ0lc=w500-no


The glide slope VSWR is the next photo- Bob didn't spec this frequency band; the glide slope frequencies are ~330-334Mhz, shows a VSWR range of 4 to 6 or 20% to 50% antenna power lost due to mis-termination.

RK7IMGw95JQnlnOj7_FykkFI07MULxNyt3HEIN6Efhsy4yFZ4WvMk8XgqGJnFomHdNLWY_qOx5lC9Kvuv2hZBjasW3ZZMBUDIOaww9fBenchRSCLi1gAd5mWtkQemmAmJtmvJzFdDTvLpfUEOoesukqgjxfi6QBGO-KMtit2P_gjXbm0CXg_vsejsWTTG2C4VhlhhB7itW-reUuvUEuXfe21J1PuP-HGUCwYRGNV3tAEi1FbnZM5Z86f-K3IezDocqQrgD0u-S7xe-BRjo5HC43tlt7OvfFoSM6EOLf-YXMyb5cPR0hNuMKWFIzdcjUEq_7c4uYl-vT2d2oVfYHWB_cXL1czyoMLhVAD7jxUO0EMuavjAaJK0ywJezE75k7qnCrd_DfofIUvDhaNzS_KFGO6FauMYHzDacS1R9Vy5Y2priecvFLedEkZ5Qg6KbdSC8UywPydnjXFzczQ_GPZ2F3Eme_gQQpu9nWmFDARahmcbHmaAlJpD3Mqslg_Z6NqtEy05kAPbAJrIcWKD8be-l07Kw8j3JutW-vmaVrBjAt70y1t4xusyEUpNqqFGm-zLGkWjSErgZqkMHo07tE_tpT5TKHh1ugRLiVV5zUhPSiJ5TVirgybFo2bY_InYKKkphCJRjah6tb-wRIEaYKKInAj2OfWgkUlbaFJTb9yGGZh034geMzuNRA=w400-no
 
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Good data. In my plane the GS always comes thru perfect. The power of the signal overcomes the poor gain of the antenna.
 
That's right, the sensitivity of the radio, plus the power of the ILS transmitter will win the day. I did discover a lower bound to signal loss- originally had a single Archer antenna feeding two nav radios through a splitter. The glideslope needle on some days was scalloping from 1/4 to 1/2 FS deflection. A 50% splitter power reduction, combined with a 50% loss from the antenna, is not a place to be in the clouds!
 
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Here's a photo of my install. Reception is adequate for me - I'm haven't tested for long distance reception but easily pick up VOR's 30-40NM.


IMG_0011.jpg

If you don?t have the right antenna test equipment, it is hard to beat installing an Bob Archer antenna exactly as the instructions lay out.

Note however how this antenna does not use the full width of the wingtip. The most important part of the antenna is the first third or so that angles away from the wing rib. This is the high current part. The ?tail? that runs aft in the wingtip is high voltage - together they bring the antenna into resonance.

Below is a homemade version of this antenna being trimmed to resonance using an antenna analyzer. The dimensions have been changed to extend the angle arm all the way to the outboard edge of the wingtip. I prefer mounting the antenna on a piece of 0.063 angle connected to the wing rib. The wingtip just slides over the antenna. Note also my preference to move the antenna aft from the landing light and NAV/Strobe wires. No need to risk creating an unnecessary problem.

I?m made several of these for various RVs. I?m more than satisfied with the performance.

Carl
7-D7-C77-E6-92-E5-4114-A5-AB-BE42-D8-E0069-A.jpg
 
Here's a photo of my install. Reception is adequate for me - I'm haven't tested for long distance reception but easily pick up VOR's 30-40NM.


IMG_0011.jpg

My Archer antenna is like this on the TOP of my RV-6 wingtip. I can pick VORs up over 80-miles away. Worked great for over 22-years.
 
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