Luke AFB ATIS VHF vs. UHF

[N9JIG]

Today when I visited the Luke AFB area to watch some F-35's screaming around I verified the current Luke UHF ATIS of 269.850 (it had been 269.900 before, database has been updated). VHF remains on 134.925 as it has been for quite a while.

In the decade I have lived here I have always been able to pick up the VHF ATIS at home, from roughly 20 miles NW and across the White Tanks. The VHF comes in very strong, 4 bars on the Unidens and about half the scale on my R8600's spectrum display. I am not however been able to hear the UHF ATIS from home at all, never have.

Anyone know if the power level, antenna height or something else is different for the two ATIS freqs? Is there a similar propagation difference at other facilities with both UHF and VHF ATIS stations?

 

[RaleighGuy]

Anyone know if the power level, antenna height or something else is different for the two ATIS freqs? Is there a similar propagation difference at other facilities with both UHF and VHF ATIS stations?

I'm sure you looked here but just in case...

Airport Data and Information Portal

 

[N9JIG]

Yes, the ADIP is a great resource but they do not give any info on the antenna or power output of the various radio aids.

 

[MiCon]

N9JIG, I'm sorry I missed you. I've been giving some thought the past couple of days to driving to LAFB tomorrow. I need to get out of the house, and I haven't visited Luke since I moved here.

Re your question: I'm no expert. I've been monitoring and occasionally using two way radios since the early 1960's. To be brief, I've always been under the impression that, all things being equal (location, output power, terrain, etc), the higher the frequency, the less distance the signal will travel. Thus, if the VHF and UHF transmitters are using the same output power, the VHF signal will travel farther, under normal conditions.

An example that comes to mind is my CB use in the 1960's. Using a 4 watt transmitter and roof mounted antenna, I would easily get 15 miles talking to a similar user set-up. Under those same conditions, a four watt transmitter on 800mhz would be lucky to get one-fourth of that distance.

RE your last question: Yes, my experience is that I can usually hear the VHF ATIS signal better and farther than the UHF ATIS signal, no matter which airport I'm listening to.

 

[DudleyG]

I live exactly 8.5 miles east of the Lexington, KY airport. On my ICOM R30, I can hear the Lex Tower (VHF) controller extremely well, I can hear the Lex APR/DEP East (VHF) controller extremely well, and I can hear the LEX APR/DEP West (VHF) controller extremely well. By well, I mean the signal strength meter on the R30 is FULL (all the way across the screen). Obviously, I can also hear the airplanes. There is an ATIS (VHF) frequency but no UHF ATIS. I hear the ATIS (VHF) frequency extremely well also.

However, on my R30, I can barely hear the Lex Tower (UHF) controller -- only 1 bar on signal strength. I ever so often I can hear the Lex APR/DEP East (UHF) controller, but it doesn't even register 1 bar. I can usually barely hear the Lex APR/DEP West (UHF) controller, but it is only 1 bar. The Lexington Airport controllers use "paired" VHF/UHF for Tower, APR/DEP East, and APR/DEP West. Thus, when I hear the controllers on UHF frequencies, they are almost always talking to civilian airplanes on VHF frequencies. There is almost no Military activity at the airport except when the KY National Air Guard out of Louisville flies their C130 over to Lexington for VOR Approach practicing and touch and goes at the airport, but they almost always operate on VHF instead of UHF so every airplane in the air knows they are nearby.

Thus, there is a very significant drop off from just 8.5 miles from the airport. At the airport in the "Cellphone Waiting Area", I have no trouble receiving the UHF frequencies on even my weakest (worst receiving) scanners and receivers.

 

[GlobalNorth]

My understanding on UHF ATIS is that it is broadcasted upwards and slightly above the horizon for maximal coverage aloft.

 

[N9JIG]

My understanding on UHF ATIS is that it is broadcasted upwards and slightly above the horizon for maximal coverage aloft.

That makes sense!