Hmm -- The drawings suggest that this is correct - and cable clamps are included at this location to facilitate this routing.

However, I agree - keep all the wires as far as possible from the radiator (small piece of aluminum on top of the fiberglass) - and route the RG-400 back and away from the radiator.

B

It is as per instructions.

Hi Denis
I got the photos you emailed, thanks- the antenna side coax connection looks good. A few questions, still trying to figure out what is going on with your installation:

1. Did you use the single point ground forest of tabs on the firewall?
2. Is your wing painted?

Sam

Sam,
No. Equipment is grounded at multiple locations and yes, the aircraft is painted and screws make good contact.

The instructions are for when you cannot avoid running wires across the antenna, use the provided clamps. But bypassing the antenna completely, by a foot or more, is better.
The first part of the radiating element (the piece that the feed arm attaches to) appears to be horizontal. For a com you have to bend the entire antenna up or down (depending if the ground leg is riveted low or high) to get as much vertical component in the first part of the antenna (the part that attaches to ground leg) as possible. Otherwise the polarization will be all horizontal, you need vertical.

Noted difference
 

Hi, From looking at this photo, against my installation per the original installation details, I noticed that this is also attached to a Aluminium strip along the bottom of the Wing Tip.

Now I am not sure of whether this would have an impact, however, mine was not connected to any other metal along that strip other than the aircraft via the screws.

As I said, not sure of the impact, just something I noticed and have no idea if that would affect the way in which a signal is then translated.

This should be fine. It will just act as part of the wing skin. What?s important is a good electrical contact from the antenna ground leg to the wing skin to the rib.

a finding
 

I have a Archer antenna in my right wing tip and a marker beacon antenna (a length of stripped coax). I installed my GPS antenna in the right wing tip also and used the coax from my marker beacon and left the marker beacon wire in place disconnected. I noticed my CDI would not capture the ILS as well and VOR performance was diminished. I removed the marker beacon antenna today and low and behold my ILS is smoother than ever.

As an update to my antenna problems, I have modified the installation in the windtip to reflect the Sportcraft antennas instructions in order to increase the verticality of the antenna. I have also improved the grounding of the antenna but to no avail. Engine monitoring still goes haywire when PTT is depressed.
see: https://photos.app.goo.gl/TaoYR2oZ7ALdenzp7

One thing that cought my eye in the installation instructions is this (Bob speaking:) )

"It has recently been brought to my attention that some folks have experienced problems with RF interference with trhe late model panel devices. These new devices operate on lower voltages and when the RF energy gets on the bus wires it can travel back to the panel area and cause all kinds of problems. SO, It is recommended that the cable used for the transmitted signals be the double shielded type and the cables should be run as far from Bus wires as possible."
Is return energy normal in well shielded cable?
I guess rerouting the RG400 will need to be looked into. Any (other) ideas?

[quote=SNIP...
Is return energy normal in well shielded cable?
I guess rerouting the RG400 will need to be looked into. Any (other) ideas?[/QUOTE]

?Return Energy? is a problem if the path of least resistance for the RF energy is not the antenna.

What I do:
- Assume the antenna is not resonant at the desired frequency unless you verified it so. Simple task with an antenna analyzer.
- Assume the antenna lead and connectors are an issue unless you verified them good. Again a simple task with an antenna analyzer.
- NEVER run the nav/strobe wires along the antenna like the instructions say. Move the antenna a little aft a little on the wing root to gain some separation. A few inches can make a world of difference. I suspect this is a common problem with both RF energy going back to the panel and LED noise getting into the radio.
- Assuming you are using modern LED Nav/strobes, feed these strobes via a three #20 conductor shielded wire (leads are power for the Nav, strobe and a strobe sync line, the shield is the ground lead).
- The RG-400 antenna coax can be run in the same bundle as the other wing wires. It will not typically be an issue unless there is a bigger problem with the antenna itself.

Bob Archer type antennas are a good design - I?ve made several (but modified to use the full width of the wing tip). I note however that to get them to work well you should to have an antenna analyzer. Each EAA chapter should have one of these in their shared tool bin: https://www.dxengineering.com/search...swr-analyzers?
autoview=SKU&sortby=Default&sortorder=Default

Carl