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Stripped coax vs Diplexer

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birddog486

Well Known Member
Cost aside is there any reason to go with the Diplexer over a stripped coax inside the gear fairing to receive the Glideslope. I'll be using an archer antennea in the wing tip and my radio requires a separate GS connection.
 
Use the one wingtip NAV antenna with a diplexer. The signal loss of the diplexer is less than can be noticed in any practical application. The gear leg antenna however would be, under the best circumstances, a poor performer.

Carl
 
birddog486 said:
Cost aside is there any reason to go with the Diplexer over a stripped coax inside the gear fairing to receive the Glideslope. I'll be using an archer antennea in the wing tip and my radio requires a separate GS connection.
Click to expand...

Need more information. Antennas along metal gear legs in my opinion/experience be it for Com or Nav would be useless. I'm not aware of this being done, and it does not sound like a good idea. Please gang correct me if I am wrong. This topic has been discussed before.

Home Made GS Antenna

Duplexer on single hidden wingtip NAV antenna, I don't know how it would work. May be someone else has experience, but you can try it. Just test it well in VFR conditions. I think those Archer hidden wingtip antennas are a compromise.

However GS antenna under the cowl on shelf or attached to lower forward cowl has been done and seems to work well, since the only time you need it is flying toward the runway, so signal is coming from one direction.

GS Antenna under Cowl

A small dipole in the windscreen or on dash for GS works well. Some have put them under cowl on shelf or bottom near the front, but windscreen is a known solid installation. GS frequency (330Mhz) is 3 times higher than LOC and VOR (110Mhz). So the length of antenna is about 8.25". You can two 8.25" wires/foil tape in the windscreen or cowl. You see Cessna's with GS antennas in the windscreen, center top.

Store bought GS antenna Click Here

I've had no issue with GS duplex off a standard VOR/LOC Cat whiskers driving the VOR/LOC and GS. I had that setup in my RV-4. When I "raced" my RV-4 I took the VOR antenna off in about 5 minutes. The dipole was on the belly near the tailwheel under horizontal stab. It worked well.

Unlike GS antenna putting the NAV (VOR/LOC) antenna in cowl it does not work well to the rear.
NAV Antenna in Lower Cowl?

Cat I ILS to low mins is serious business. I'd be somewhat concerned about accuracy. Whatever you do please test it. There are cases in commercial airliners where GS was off during certification, and they had to make adjustments.
 
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I think some have good luck, some have poor...with both configurations. I have had less than stellar performance splitting off an Archer - and very good GS results with a stripped coax down a gear leg. Others have too....and others have not.

Unless you decide to go with a fully certified and tested (expensive) antenna suite, you’re experimenting, and should experiment until you are satisfied with the performance.

Paul
 
gmcjetpilot said:
There you go, it is great....

What kind of VOR/LOC range do you get?

Blind spots?
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FWIW, my experience with a PROPERLY INSTALLED Archer Nav antenna is that it?s performance is on par for VOR, LOC and GS with externally mounted traditional antennas. I freely admit that I have a limited number of places that I?ve flown an ILS into with an Archer nav antenna, and it?s certainly possible that local conditions might cause issues.

Many years ago I talked with Bob Archer himself and he was adamant that following the install directions was critical for max performance, particularly grounding and wingtip wire routing. Many times when people talk about their particular installation details, their explanation includes statements like ?instead of...? or ?Just like the directions said, except...?.
 
bcondrey said:
FWIW, my experience with a PROPERLY INSTALLED Archer Nav antenna is that it?s performance is on par for VOR, LOC and GS with externally mounted traditional antennas. I freely admit that I have a limited number of places that I?ve flown an ILS into with an Archer nav antenna, and it?s certainly possible that local conditions might cause issues.

Many years ago I talked with Bob Archer himself and he was adamant that following the install directions was critical for max performance, particularly grounding and wingtip wire routing. Many times when people talk about their particular installation details, their explanation includes statements like ?instead of...? or ?Just like the directions said, except...?.
Click to expand...
+1
I have seen some photos here on vaf of unbelievably bad installations.
 
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