2 EAMs At the Same Time?

CSL126 · #1 (**permalink**) 03-19-2007, 12:08 PM

I am currently hearing two EAMs on 11.175, they are talking over each other. Andrews is broadcasting one of them, I'm not sure what station is broadcasting the other. I've never heard this before...

eorange · #2 (**permalink**) 03-19-2007, 12:31 PM

Could it be the same EAM, but you're receiving one via short path and the other via long path?

kf4pep · #3 (**permalink**) 03-19-2007, 12:53 PM

Quote:

Originally Posted by eorange

Could it be the same EAM, but you're receiving one via short path and the other via long path?

I have heard that before.

mtindor · #4 (**permalink**) 03-19-2007, 01:31 PM

Or, it could be that they are purposefully keying multiple transmitter sites on the same frequency to broadcast that EAM. I heard an EAM also last night that came in very strong and was echoing like made because likely two or more xmitters at different ground locations were transmitting the EAM.

I read somewhere about OFFUT (and maybe others) being able to take control of the whole network and transmit on one or more freqs from one or more sites simultaneously if they desired.

The one I heard was from Andrews.

Mike

CSL126 · #5 (**permalink**) 03-19-2007, 02:18 PM

Quote:

Originally Posted by eorange

Could it be the same EAM, but you're receiving one via short path and the other via long path?

I should have said this in my original post. One EAM was being read by a female and the other was being read by a male. The broadcast from Andrews was most definitely coming in stronger than the other.

N0JRD · #6 (**permalink**) 03-19-2007, 05:41 PM

Are thoose usb or lsb from Andrews?

eorange · #7 (**permalink**) 03-19-2007, 06:30 PM

All EAMs are USB.

nexus · #8 (**permalink**) 03-19-2007, 08:24 PM

to back up eorange, all military HF is going to be USB. Most if not all Government, Military stations will be USB.

kb2vxa · #9 (**permalink**) 03-19-2007, 11:52 PM

To put it simply only Amateurs use voice LSB on 160, 80 and 40 meter bands, everything else is USB.

It's not uncommon to hear two completely different transmissions simultaneously on the same frequency depending on propagation conditions and your location. It happens to hams all the time, two stations may be having a conversation when another puts out a call on top of them because he hears neither one, to him the frequency is clear.

eorange · #10 (**permalink**) 03-20-2007, 08:13 AM

But I thought all USAF HF-GCS locations now simulcast the same broadcast, with the EAM originating from Andrews. I think there was a recent MT article about that.

In part - see the Modernization section in the Wiki entry -> http://wiki.radioreference.com/index...cations_System

lurking · #11 (**permalink**) 03-20-2007, 08:56 AM

Yes, one station can control the whole network. BUT, Offutt can broadcast remote to Ascension Island while Andrews is broadcasting their message. At the same time, McClellan could be using Guam.

3 stations on the same frequency, thousands of miles apart, but some overlap can occur due to propagation.

K3GI · #12 (**permalink**) 03-20-2007, 12:31 PM

Most EAMs are exercise messages used to simply give aircrews and radio operators practice in transmitting and receiving (aircrews) them with accuracy. In my day (30+ years ago) we would wait (usually) for aircrews to "request traffic" and then transmit the latest one. So it is entirely possible for two stations to be transmitting the same message at about the same time and not know they are walking on each other (as KB2VXA points out--it happens all the time to amateurs).

gcgrotz · #13 (**permalink**) 03-20-2007, 02:31 PM

Quote:

Originally Posted by kb2vxa

To put it simply only Amateurs use voice LSB on 160, 80 and 40 meter bands, everything else is USB.

Warren: I'm betting you know the reason why that is the case, but I wonder how many others on here know?

w0fg · #14 (**permalink**) 03-20-2007, 04:05 PM

At least one more.

K3GI · #15 (**permalink**) 03-20-2007, 04:12 PM

Make that two, and a third off topic post. lol

eorange · #16 (**permalink**) 03-21-2007, 08:08 AM

I think it had something to do with when you guys were crossing high voltage wires to make sparks or something.

zz0468 · #17 (**permalink**) 03-21-2007, 09:10 AM

Quote:

Originally Posted by gcgrotz

Warren: I'm betting you know the reason why that is the case, but I wonder how many others on here know?

Add another dinosaur to the herd that knows why! =)

LouisvilleScanMan · #18 (**permalink**) 03-21-2007, 03:10 PM

Hi I don't do much shortwave listening.I'm guessing that these "EAMs" that you are talking about are Emergency Action Messages from the military to planes and ships giving them new orders,what I want to know is why are you able to receive them? One would think that something like that would be encrypted and not open to monitoring.

ampulman · #19 (**permalink**) 03-21-2007, 04:00 PM

Quote:

Originally Posted by Bluegrass1dcr1

Hi I don't do much shortwave listening.I'm guessing that these "EAMs" that you are talking about are Emergency Action Messages from the military to planes and ships giving them new orders,what I want to know is why are you able to receive them? One would think that something like that would be encrypted and not open to monitoring.

While EAMs (as far as I know) are broadcast in the clear, traffic on the HF-GCS system can and has been 'altered' by various means. During the active stage leading up to the taking of Baghdad, I monitored many such transmissions.

AM

LouisvilleScanMan · #20 (**permalink**) 03-21-2007, 04:12 PM

What does the average EAM consist of?