Coupling Two glide slopes to the same antenna

[yvesg]

Hi guys,

 

I am preparing for the install of a Garmin 430W and the avionics shop asked me how are the current glideslope and nav receivers coupled? This will be added to the current ILS install I have.

 

Here is a picture of the antenna.

 

Would any-one know if this was typically coupled via a diplexer or balun?

How can I find out? 

How did you guys coupled it?

 

Thanks

 

Yves

M20C 1965

Current Radio is a MK12D+

[FoxMike]

Yves,

When I bought my TLS back in 2003 I added a 2nd GS.  I bought a nav splitter that allowed for two GSs to be connected.  I was wondering if the signal would be adequate to split it so many ways.  It does seem to work ok.  I owned a T210 before the Mooney and the second GS antenna was located in the top of the windshield out of the way.  I think this is a better solution but I do not know where you would find such an antenna today.  Ask your shop for suggestions.

[N601RX]

Comant makes them. Usually pretty cheap off e-bay.  I used the ci 1125, it splits the signal into 2 vor's and 2 glideslopes

[Piloto]

I removed the cat whiskers GS antenna and  replaced it with the CI 1125 diplexer that allows two VOR/LOC and two GS slope recivers. The diplexer input is connected to the towel bar antenna on the tail. It works very well with plenty of range for the NAV receivers. You can get one at http://www.aircraftspruce.com/catalog/avpages/ramiav585.php?clickkey=19958 for $133.75. 

 

José

[MARZ]

Diplexer as well - works well.

[orionflt]

I removed the cat whiskers GS antenna and  replaced it with the CI 1125 diplexer that allows two VOR/LOC and two GS slope recivers. The diplexer input is connected to the towel bar antenna on the tail. It works very well with plenty of range for the NAV receivers. You can get one at http://www.aircraftspruce.com/catalog/avpages/ramiav585.php?clickkey=19958 for $133.75. 

 

José

+1

[takair]

That is likely a balun style dipole, but most likely has a duplexer. I have two VORs and two glideslopes and it works fine.

[yvesg]

I removed the cat whiskers GS antenna and  replaced it with the CI 1125 diplexer that allows two VOR/LOC and two GS slope recivers. The diplexer input is connected to the towel bar antenna on the tail. It works very well with plenty of range for the NAV receivers. You can get one at http://www.aircraftspruce.com/catalog/avpages/ramiav585.php?clickkey=19958 for $133.75. 

 

José

José, would it work OK to use that diplexer and the cat whiskers? I do not have a towel bar antenna. takair, this is what I think you have right?

Yves

[Piloto]

José, would it work OK to use that diplexer and the cat whiskers? I do not have a towel bar antenna. takair, this is what I think you have right?

Yves

The cat whiskers that I had was the factory one that was installed on the upper part of windshield center post. This particular small cat whisker was resonant to the GS frequency of 330 MHZ and would not work for the VOR/LOC frequencies of 110MHz. However an antenna resonat at 110MHz such as the one in the tail (large cat whisker, towel bar or blades)  will work at its third harmonic frequency of 330MHz with the diplexer.

 

On large airplanes the GS antenna is mounted inside the radar dome just behind the radar dish. The reason for a separate location is due the relative height of the tail antenna vs the centerline of the airplane.

 

José 

[yvesg]

OK José, I have the large cat whiskers so it should be OK.

Thanks.

Yves

[takair]

José, would it work OK to use that diplexer and the cat whiskers? I do not have a towel bar antenna. takair, this is what I think you have right?

Yves

Yes, that is what I have. Both measured and actual sensitivity have been excellent.