Bob archer antenna

[Denok]

First, I hate having things sticking out of my 7 so I thought a Bob Archer wingtip com antenna would do the trick. Turns out it preforms ok when the wingtip is off and I use a bonding strap to ground the antenna to the aircraft but when I install the windtip with all screws I see gremlins everywhere. My Dynon HTX engine monitoring quits and all engine parameters go wild, a real mess. Hints anyone?

[Carl Froehlich]

I suspect you have an end of a wingtip screw touching the antenna.

Carl

[Xkuzme1]

I might be wrong... and it happens a lot...

I believe is you are talking about the NAV antenna, it?s made so that the screws and nut plates should be the same ones that connect the plane to the wingtip (so hard connected and not grounding strap). It?s made so that it it actually turns the aircraft into the directional of one side, and the wingtip is the other side.

Maybe with a try of reinstalling.

X

[Pilot8]

Does the instruments go wild event happen when you activate the PTT?

[BobTurner]

1. As mentioned by others, the Archer has a "ground leg" which should be electrically tied to the end rib of the wing by as short a route as possible. Some have riveted that leg directly to the rib, or an angle on the rib; design calls for that ground leg to be under the wingtip screws (make sure there is no paint under the screws - you want a short electrical path to the rib. If mounted correctly I'm not sure how the tip mounting screws could subsequently make contact with the radiating part of the antenna.
2. Mount the ground leg as high as you can, and bend the leading edge down around 30 deg or so, as far as the tip will allow, to get as much vertical polarization as possible. (You can also mount the ground leg near the bottom of the rib, and bend the antenna up, and hold it up with fiberglass.). This is for the com antenna; for the nav version, just lay it flat (you want horizontal polarization for the nav).

Any chance of a photo? worth a 1000 words.

[gmcjetpilot]

Originally Posted by Denok

First, I hate having things sticking out of my 7 so I thought a Bob Archer wingtip com antenna would do the trick. Turns out it preforms ok when the wingtip is off and I use a bonding strap to ground the antenna to the aircraft but when I install the windtip with all screws I see gremlins everywhere. My Dynon HTX engine monitoring quits and all engine parameters go wild, a real mess. Hints anyone?

I'm a simple man so let me ask these dumb questions. The antenna is for NAV? Where does the coaxial go, a NAV unit (VOR/LOC/GS) somewhat separate of the Dynon. What does NAV have to do with the engine monitoring side of your glass display except provide some basic VOR/LOC/GS data Left/Right/Above-Below GS ? Just asking.

Even if it is a COM antenna is attached to a COM transceiver, I don't see the connection (no pun int ended) between the antenna and your Engine monitoring function.

[BobTurner]

Originally Posted by gmcjetpilot

Even if it is a COM antenna is attached to a COM transceiver, I don't see the connection (no pun int ended) between the antenna and your Engine monitoring function.

This is not an uncommon symptom of RF energy radiating where it's not wanted. What happens is the antenna or antenna coax is screwed up. As a result the RF is reflected back up the coax along the outside of the shield where, like an antenna, it radiates. If enough is picked up by the EGT, oil sensor, etc., wires, trouble follows. Curiously enough, old fashioned current gauges were pretty immune to this. Not so modern electronics.

[Sam Buchanan]

The Archer COM antenns has never been considered to be a very good performer in our RVs due to the wingtip shape. The NAV antenna on the other hand is a good option.

I think at some point you will decide to mount a conventional COM antenna....

[Aiki_Aviator]

Originally Posted by Sam Buchanan

The Archer COM antenns has never been considered to be a very good performer in our RVs due to the wingtip shape. The NAV antenna on the other hand is a good option.

I think at some point you will decide to mount a conventional COM antenna....

Not really sure that this comment is correct. I have a Bob Archer and from my experience it is very good. I do know that users who have made their own antenna from plans and have had issues. I do know that Bob was a Communications specialist and custom tuned each antenna before sending out. My understanding was that the originals operated to a very high standard.

That being said, for my own interest and comfort, do you have any details, reference material or statistics to support the comment "The Archer COM antenns has never been considered to be a very good performer"?

[BobTurner]

Originally Posted by Aiki_Aviator

That being said, for my own interest and comfort, do you have any details, reference material or statistics to support the comment "The Archer COM antenns has never been considered to be a very good performer"?

1. There are some poor installations, that of course work poorly. I’ve seen a photo of a ‘poor performer’ that was installed upside down-the ground leg was out in the wing tip, the radiator up against the rib!!
2. I’ve seen some home brews that don’t understand and/or fail to replicate the matching capacitor.
3. Some don’t get it that you need to maximize the vertical distance of the leading edge, to maximize the vertical polarization. This is really the main issue. In some not well controlled tests (different receivers/com transmitters) I’d say my Archer has 75% of the useful range of my belly whip. Is this ‘not a good performer’? Opinions vary.