AVSIG: Uh, ok... wwswsigarch.jpg (7236 bytes)

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Mac Tichenor (DAL)
Top Gun


Reged: 06/04/04
Posts: 1857
Uh, ok...
      #403352 - 01/27/15 01:37 AM

I made my first stop at KTUS (Tuscon) the other day and came across this note on the taxi chart: All aircraft use upper antenna until airborne.

That is a good rule to live by, but I've never seen it prescribed on an airport chart before. It made me wonder what I was taxiing over that might be inconvenienced or aggravated by VHF RF coming off the bottom antenna. Zombies? Or maybe they tracked down communication problems that arise with the bottom antenna. But is there some reason it's worse at TUS than anywhere else?

Anybody know the genesis of that note?

Mac


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Russell Holton
AVSIG Member


Reged: 07/07/05
Posts: 14136
Re: Uh, ok... [Re: Mac Tichenor (DAL)]
      #403353 - 01/27/15 03:26 AM

Quote:

It made me wonder what I was taxiing over that might be inconvenienced or aggravated by VHF RF coming off the bottom antenna.



Strong RF can create problems with audio and digital control circuits. However, I wouldn't trust using the top-side antenna to solve that problem.

I'm wondering if the location of the ground antenna and geography creates dead zones if the lower antenna is used. Possibly due to multipath or when taxing between/behind other airplanes.

Each airport has a unique RF environment. If that dead zone falls at a spot where communication frequently takes place, well, that would be aggravating.


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Scott Dunham (RDU)
Top Gun


Reged: 04/29/04
Posts: 6470
Loc: Chapel Hill, NC
Re: Uh, ok... [Re: Russell Holton]
      #403389 - 01/27/15 03:54 PM

That's my guess. Some airports have a well-known dead spot or two.

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B. Butler (Oregonian)
Top Gun


Reged: 05/15/04
Posts: 9760
Loc: Ashland, Oregon
Re: Uh, ok... [Re: Mac Tichenor (DAL)]
      #403400 - 01/27/15 05:10 PM

Quote:

I made my first stop at KTUS (Tuscon) the other day and came across this note on the taxi chart: All aircraft use upper antenna until airborne.


Anybody know the genesis of that note?

Mac




Dead spots are not unusual, often created or moved by construction on the airport; the usual cure is to move the (ground) antennas. In the case of TUS, they may not have been able to find the right spot.

--------------------
"Why not be a nihilist? A man has to believe in something."
-Bernie Gunther


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Jeff Hartmann CIC
Top Gun


Reged: 05/18/04
Posts: 7323
Loc: Chico,CA
Re: Uh, ok... [Re: B. Butler (Oregonian)]
      #403431 - 01/28/15 04:11 PM

There used to be bad area at AVL when I flew a King Air there. The King Air had the #1 on the top, #2 on the bottom antenna. Since I always used #1 for flying and #2 for ground and Clearance, I switched the leads.

I wonder (because it was not readily clear), how many people know which radio goes to which antenna.

I also think the prop arc could somehow disturb the signal from the belly antenna....not real sure.

--------------------
Jeff

nothing clever to say right now...

Edited by Jeff Hartmann (EXX/SVH) (01/28/15 04:12 PM)


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Ralph Jones
Top Gun


Reged: 08/31/01
Posts: 21214
Loc: 4CO2
Re: Uh, ok... [Re: Jeff Hartmann CIC]
      #403433 - 01/28/15 04:27 PM

Quote:

I also think the prop arc could somehow disturb the signal from the belly antenna....not real sure.



Dunno, but I've heard transmissions from helicopters being chopped by the rotor.

--------------------
Ralph Jones
LS-4a N49LS 6R


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Mac Tichenor (DAL)
Top Gun


Reged: 06/04/04
Posts: 1857
Re: Uh, ok... [Re: Jeff Hartmann CIC]
      #403453 - 01/29/15 12:01 AM

Quote:

I wonder (because it was not readily clear), how many people know which radio goes to which antenna.




Agreed - it's often not easy to find that information.

Mac


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