Stepping on other airport CTAF?

[Matthew]

It's not uncommon to hear CTAF announcements (around here anyway) from airports over 100NM away.

There is one airport at a lake resort area 112NM away that, during the summer and on weekends, is pretty busy. It also shares the same freq as one of our local airports.

I've usually tried waiting for a break in the action to do my announcements, but it gets annoying listening to conversations about who's stopping where for lunch a hundred miles away. It's even more awkward when an a/c at a lower altitude (who can't hear those transmissions) is trying to communicate with an a/c at a higher altitude who can.

My question - Just how far away is 'far enough' to go ahead and transmit even though someone else is already talking?

 

[Dean]

We have some airports with-in 30nm of ours with the same CTAF (122.7) one is NE the other SE. If you would wait for the freq to clear, you would be on the ground before that happened. At that distance you will not cover them up with the low power radios that planes use.

 

[RotaryWingBob]

My question - Just how far away is 'far enough' to go ahead and transmit even though someone else is already talking?

Since our comm radios are AM, any stepping on a stong signal, regardless of the distance is likely to produce squeals and other rude noises. And everybody on the freq is gonna hear them, too. I'd suggest trying to get a break before keying the mic...

 

[AdamZ]

Sigh! Matthew some folks just don't understand common radio etiquette and never will. Several Fields share our CTAF and it can be a pain especially the jump planes making frequent announcments. But ater all it is a legit communication. What really irks me is the inane chatter about Vern having lunch with Bubba yesterday. I want to tell those folks to cram it but that would just take up more valuable airtime.

 

[Matthew]

I can live with the fact that airports within 50 miles have the same freq and can wait my turn, that's just the cost of doing business.

It's the airports half a state away that I wonder about. If I can hear them, maybe they can hear me, and I don't want to interfere. On the other hand, there has to be some kind of power/AM interference limitations.

Dean, I noticed from your profile you are in Sullivan, MO. I'm on the other side of the state, just ssw of Kansas City. I can hear Lake of the Ozarks traffic all the time, how 'bout you? (This is the basis of my question)

 

[markb5900]

I am based in Jeff city. On the weekend I can hear sullivan easy from here. And the lake and all the others too. It is hard to get a word in!!!

Went to Sullivan for one of my PPL XC's. Nice airport you have there.

 

[silver-eagle]

Depending on the day, it's common to hear airports 100 miles away out on Long Island or north to Maine, I figure they can hear me just as well as I can hear them so I try to wait. You do have a fairly good chance of being heard locally even it you do get walked on by a remote airport.
It's pretty strange to hear those kinds of calls when you're on the ground.

 

[SJP]

We have some airports with-in 30nm of ours with the same CTAF (122.7) one is NE the other SE. If you would wait for the freq to clear, you would be on the ground before that happened. At that distance you will not cover them up with the low power radios that planes use.

I knew it was bad...didn't realize quite how bad...

I looked at my (old, wall mounted) Detroit Sectional - just the section between 83'30W 42'00" N and 85'00W 44'00N...

Out of approximately 35 un-towered, hard runway fields...

There are 15 airports that share 122.80
There are 9 that share 123.0
122.9 boasts 2
122.7 has 4.


I guess I dont understand :

a) why they dont spread some of the love around a bit ?
b) surely the freq-band isn't THAT full that they couldn't add a few extra ?
c) Who the heck is Vern, and why do I care whether he gets his lunch

I am always competing with MOP traffic calls when trying to call into D98 - 50+ miles, and you still get squeals.

 

[ScottM]

The fields can apply for another CTAF if there are too may people on a freq. This happened a few years ago at 3CK which is near me. We had several nearby airports that were on 122.8. On weekends you could not get a word in edgewise. The airport management rightfully decided this was a safety issue and applied for and was granted a freq change for the CTAF to 123.05. That is hardly used at all and most of the time all you hear is lifeguard helicopters calling down information to their base.

 

[Dave Krall CFII]

The fields can apply for another CTAF if there are too may people on a freq. This happened a few years ago at 3CK which is near me. We had several nearby airports that were on 122.8. On weekends you could not get a word in edgewise. The airport management rightfully decided this was a safety issue and applied for and was granted a freq change for the CTAF to 123.05. That is hardly used at all and most of the time all you hear is lifeguard helicopters calling down information to their base.

If it's on the new sectional why wouldn't the new Fx be used?

 

[Matthew]

The best I could find, so far:

From the AIM -
vvv

4-1-11. Designated UNICOM/MULTICOM Frequencies
Frequency use
a. The following listing depicts UNICOM and MULTICOM frequency uses as designated by the Federal Communications Commission (FCC).
(See TBL 4-1-2.)​

[SIZE=-2]TBL 4-1-2[/SIZE]​

Unicom/Multicom Frequency Usage

Use
Frequency ​

Airports without an operating control tower. ​

122.700
122.725
122.800
122.975
123.000
123.050
123.075 ​

(MULTICOM FREQUENCY) Activities of a temporary, seasonal, emergency nature or search and rescue, as well as, airports with no tower, FSS, or UNICOM. ​

122.900 ​

(MULTICOM FREQUENCY) Forestry management and fire suppression, fish and game management and protection, and environmental monitoring and protection. ​

122.925 ​

Airports with a control tower or FSS on airport. ​

122.950 ​

NOTE-
1. In some areas of the country, frequency interference may be encountered from nearby airports using the same UNICOM frequency. Where there is a problem, UNICOM operators are encouraged to develop a "least interference" frequency assignment plan for airports concerned using the frequencies designated for airports without operating control towers. UNICOM licensees are encouraged to apply for UNICOM 25 kHz spaced channel frequencies. Due to the extremely limited number of frequencies with 50 kHz channel spacing, 25 kHz channel spacing should be implemented. UNICOM licensees may then request FCC to assign frequencies in accordance with the plan, which FCC will review and consider for approval.

2. Wind direction and runway information may not be available on UNICOM frequency 122.950.
b. The following listing depicts other frequency uses as designated by the Federal Communications Commission (FCC). (See TBL 4-1-3.)​

[SIZE=-2]TBL 4-1-3[/SIZE]​

Other Frequency Usage Designated by FCC

Use
Frequency ​

Air-to-air communications & private airports (not open to the public). ​

122.750
122.850 ​

Air-to-air communications (general aviation helicopters). ​

123.025 ​

Aviation instruction, Glider, Hot Air Balloon (not to be used for advisory service). ​

123.300
123.500 ​

^^^

Note: This specifically adresses UNICOM, which, at my airport is NOT the same as CTAF. At my airport, the CTAF is the same as tower, when tower is closed. (We have problems with folks late at night, unfamiliar, using UNICOM because "that's what the GPS says", when everybody else is properly using CTAF. I haven't found out how they plan on turning on the lights with the wrong freq, but that's another story.)

Another note: I've flown to areas where there are so many airports so close together that they use the same CTAF on purpose. They are close enough that arrivals/departures may take you through the patterns at the adjacent airports. Some of these airports use one freq for CTAF, and another for the lights. I learned my lesson about how to use the A/FD when my CFI took me to one of those places one night, just to see how long it would take me to figure it out.

My question is still - How far away is 'far enough'? Should I just adjust the squelch and pretend the problem doesn't exist? It's not like this is a huge problem, and it's not like I'm the only one who puts up with it, but it's just another inconvenience that should have a way around it.

 

[Skip Miller]

Should I just adjust the squelch and pretend the problem doesn't exist?

For my money, don't adjust the squelch. Don't "step on" the loudest calls you hear as it is likely that anyone who might need to hear your call will also have your call partially or completely blocked. But if you can't find a clear spot in the radio traffic, go ahead and step on a weak call as it is likely you will not interfere with it or it with you.

Not the best answer. Not much else you can do, though.

-Skip

 

[ScottM]

If it's on the new sectional why wouldn't the new Fx be used?

To clarify... It hardly used by any other airport but 3CK and a few lifeguard helicopters.

 

[gismo]

Since our comm radios are AM, any stepping on a stong signal, regardless of the distance is likely to produce squeals and other rude noises. And everybody on the freq is gonna hear them, too. I'd suggest trying to get a break before keying the mic...

While what you say is partly true, as long as you are significantly closer to those who you intend to hear you transmissions than you are to the folks at the distant airport, the ones near you will hear you just fine, and your transmission won't really block the distant ones either. FM is much better than AM for this, but since signal strength decreases with somewhere between the second and third power of the distance between transmitter and receiver, the signal level at a receiver 10 miles away from you will be at least 1000 times stronger than one from an airplane a hundred miles distant and that's enough for adequate communication. The folks nearly equidistant are the ones who'll hear the howling. And something that helps is to be as low (pattern altitude for instance) as practical when transmitting.

 

[Dave Krall CFII]

To clarify... It hardly used by any other airport but 3CK and a few lifeguard helicopters.

Ah yes, thanks, that makes sense.
Now if only there was a cat with bunny ears to admire somewhere...