[MRCA] URC-4

[Peter Gottlieb]

Originally the Emergency Locator Transmitters for aircraft and boats (they 
called them EPIRBs) were on 121.5 along with voice emergency comms.  LEO 
satellites monitored 121.5 and could get a rough position fix by the use of 
doppler techniques.  Some years ago the locator beacons were relocated to the 
406 MHz area and the satellite monitoring discontinued, although there are still 
a lot of 121.5 ELTs out there.  Most all aviation control towers still monitor 
("guard") 121.5 but mostly for voice use, and many airlines also guard that 
channel as well.  If you are an aircraft in distress you can use that frequency 
but many times the controllers will just have you stay on their frequency if it 
isn't busy.  I've had a few times where I was flying in the middle of nowhere 
and been asked to go to 121.5 to test comms with the ground station.

After 9-11 when they created all these restricted flight areas, if you wander 
into one the fighters (if capable of VHF) or ground stations will try and reach 
you on that frequency.  I've heard that many times in the northeast as I always 
make a habit of guarding it while flying.

Civil Air Patrol generally does DFing for the beacons and it can take hours.  If 
you're going to test, it won't raise alarms but PLEASE keep it VERY short (as in 
a second or two) and preferrably use a dummy load.  If there is an aircraft in 
distress (which you might not even be able to hear) you might very well be 
interfering with the comms.

Peter


On 8/19/2014 3:46 PM, Ray Fantini wrote:
>
> Do not use it on 121.5!!! Bad things will happen.
>
> *From:*MRCA [mailto:mrca-bounces at mailman.qth.net] *On Behalf Of *Robert Newberry
> *Sent:* Tuesday, August 19, 2014 2:54 PM
> *To:* mrca at mailman.qth.net
> *Subject:* Re: [MRCA] URC-4
>
> OK well one just makes a tone when I hit the RX button. The PTT doesn't seem 
> to do anything other than draw a 1/4 of an amp.
>
> The other one does make static, it also draws the same amount of current on 
> TX. I have a 121.5 xtal installed. So I guess these are going to require some 
> more digging before I can make a signal.
>
>
>
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