ATIS Reception Problems ?

[air-scan]

Hi,

Have a new Uniden SDS 200 scanner.

Live fairly close to Hanscom AFB (Bedford, Mass.) and about 15 miles from Logan Airport (Boston).

I can hear lots of Tower comms, Tracon, etc. from both.

But, If try to pick up any ATIS from either, nothing but continuous static.

Was wondering:

Have they (both ?) perhaps gone to digital ?
Or, extremely low low power ?
Or, ?

Was wondering why this might be ?
Any thoughts on this ?

Regards,
Bob

I live a few miles from KOKC-Will Roger's World Airport. I can't hear ATIS on 125.850MHZ in the building. When I take the scanner with me I can barely hear it. I think it has to do with angle of radiation or signal takeoff of the transmitting antenna. that's meant for solid reception for quite a far distance for aircraft inbound about 80-100nm away approaching the airport. Weather is dynamic, always changing, the report can change. ATIS signals usually will just keep going upward.

 

[prcguy]

There is nothing unusual or upward favoring with most aircraft comm antennas. They generally don't have much if any gain and have a wide lobe that peaks at the horizon, which is what you want for distance like 80-100nm or more away. When an aircraft is directly overhead at 35,000ft it can be in a major null of the antenna, but at that point is only about 5.8nm away line of sight and can probably be picked up with a paper clip. That same aircraft at 35,000ft altitude but 100mi away is at a very low look angle.

That's why you want your aircraft ground antenna or scanner antenna to have a radiation pattern that is primarily at the horizon, to get the most distance and don't worry about what's overhead, that will work just fine.

I live a few miles from KOKC-Will Roger's World Airport. I can't hear ATIS on 125.850MHZ in the building. When I take the scanner with me I can barely hear it. I think it has to do with angle of radiation or signal takeoff of the transmitting antenna. that's meant for solid reception for quite a far distance for aircraft inbound about 80-100nm away approaching the airport. Weather is dynamic, always changing, the report can change. ATIS signals usually will just keep going upward.

 

[air-scan]

I am not here to argue nor debate. What I said is true mr @prcguy.

That lobe HAS an upward angle

I didn't say the word 'unusual' I said 'usually'.

 

[belvdr]

I don't think they are upward facing.

The ATIS antenna at my local airports are simply verticals on a tower. Maybe the larger airports do something different but I doubt it.

 

[air-scan]

I am not about to argue the take off angle of a vertical antenna at different wavelengths. The longer the wavelength of the antenna the lower the take off angle of the signal closer to the horizon at VHF. The shorter the wavelength the higher the take off angle of the signal at VHF. It's line of sight NOT a perfect level line per se. All that theory behind it gives me a headache even thinking about it.

 

[prcguy]

I've had most every kind of airport base antenna over the years and my garage still has a bunch of surplussed airport antennas in the rafters, some still new in box. I know for a fact they put most of the radiation at the horizon and are not engineered to put any extra signal upwards.

Anybody need an airport base antenna? I gotta clean the garage out some day.

 

[air-scan]

I find it to be unique with the ATIS frequencies because if they are all vertical why are we all able to hear the vertical antenna for the Tower, some airplanes talking to the tower on the ground but we have a hard time receiving ATIS with scanners with rubber duck antennas or telescoping antennas. I think it's the way they have the antenna mounted or something else happening. It gets stronger if at least 3 miles out from the transmitting antenna. I am not about to go to KOKC and ask them if I could have a look at their antennas. Funny looks and a quick bye bye would be the only thing I could accomplish from them.

I tried searching for a license but none found. Wanted to see the output power. I don't think the FCC publishes airport licenses or I don't know the right keyword.

 

[trentbob]

I've been following this thread and I did participate in the beginning. I have a Regional Airport about four miles from me.

I use a VHF UHF 800 megahertz ground plane quite high up... About 40 feet. I have three different antennas located on different parts of my roof. Only one of them works on that airports ATIS, not the best reception but clear enough.

Everybody's making qualified statements here and I agree with all of it as indicated by my reactions.

As with any of these situations there are so many variables including topographical environment, surrounding interference, location and characteristics of the antenna, overall conditions in general.

My Aviation monitoring for many many years has been area Helo Unicom over Philadelphia. Any helicopter entering the area announces themselves and communicates with the others. I also monitor 4 different news helicopters all on the same news helicopter coordination frequency so when they are hovering over a scene they can maneuver with each other and of course gossip about their news desk and share all of the news information they have with each other lol.

Nobody's right or wrong in this discussion, there are just so many variables.

 

[nd5y]

I find it to be unique with the ATIS frequencies because if they are all vertical why are we all able to hear the vertical antenna for the Tower,

The ATIS/AWOS transmitter might be only 2.5 watts and might be at ground level where the weather instruments are located and not at the same location as the tower, approach, and other transmitters for the airport.
It's not surprising that you can hear one station and not another if they are not in the exact same location.

I tried searching for a license but none found. Wanted to see the output power. I don't think the FCC publishes airport licenses or I don't know the right keyword.

Most of them belong to the FAA and don't have FCC licenses. I posted a link to the federal regulations that contain aviaion station power limits in post #20.

 

[air-scan]

I tried the telescoping antenna I made. It barely received 125.850MHZ. It barely was intelligible. I also checked the distance from my location to airport location which is 7 miles. I don't know about where they station the weather related equipment. My impression was it all came from the airport. 2.5 watts isn't much at VHF. Planes can hear it fine and that's all that matters.

 

[nd5y]

If you want to know about FAA spectrum management and engineering then read these.

https://www.faa.gov/documentLibrary/media/Order/6050_12A.pdf

https://www.faa.gov/documentLibrary/media/Order/6050_32B_WITH_CHG_1_AND_2_INCORPORATED.pdf

One of them says an ATIS station should not exceed 10 W and ASOS/AWOS should not exceed 2.5 W.

 

[air-scan]

It's limited by TRACON* airspace 100' AGL* is 2-5nm 25,000ft AGL is 60 nm. if below 100' AGL you need good antenna setup! VHF Yagi

*AGL = Above Ground Level Departure ATIS
*TRACON=Terminal Radar Approach Control

 

[dlwtrunked]

The ATIS/AWOS transmitter might be only 2.5 watts and might be at ground level where the weather instruments are located and not at the same location as the tower, approach, and other transmitters for the airport.
It's not surprising that you can hear one station and not another if they are not in the exact same location.

Most of them belong to the FAA and don't have FCC licenses. I posted a link to the federal regulations that contain aviaion station power limits in post #20.

The above is true. Often a few watts atop a 1 or 2 story building. I can barely hear 2 AWOS within 10 miles of me but if I go 50 miles further away atop 2000 ft mountains I can easily hear them and many others.

 

[spanky15805]

Lobing from a no gain vertical.

ATIS is FAA, AWOS is NWS. AWOS's don't have a certified output power like ATIS's do.