Batboard

I live in Central Florida, on the east coast, about 20 miles south of Port Canaveral.

My VHF radios have marine channel 16 in the scan list. Sometimes I hear
something interesting enough to be worthwhile.

I've got to wonder just what sort of transmitters the Coast Guard uses.
I've heard both the Jacksonville and Miami Coast Guard stations get
on the channel and practically blow me out of my chair. 200, maybe 300
mile signal paths, and they're at full quieting on ANY receiver I have, and
practically heating up my receiver antenna.

Whatever they're running, it's insane. And I want to know what it is.

Power, antenna type and gain, altitude, ERP, and radiation pattern.

Does anyone know what they're running to be able to virtually blanket
half the state with a single transmitter? It must be something really
extraordinary.


Elroy

http://www.gdc4s.com/content/detail.cfm ... 0e9f7972fa

should answer your question.
It's not a single site, its a network

Elroy,

CG radio sounded like you describe the current ch.16 when
they were on HF years ago, 2182 kHz AM if I remember right.
When a call was heard the coast stations would all call back
in turn, trying to get a response. I was in NYC and would
hear CG at Groton, New London, Nantucket, etc. all calling.
Lots of good radio discipline and a signal that was so strong
you could hear the hum in their power supplies.

Regards,

The Coast Guard recently published a request for public comments related to their interest in shutting down all HF radio operations including SITOR, weather fax, and so forth, citing maintenance issues on the equipment, lack of spare parts, and so forth.

with stat comms who can blame them when the cg is just an iridium or an inmarsat call away.

last time i was at the port ops office at the pcan coast guard office...


they had a 50w spectra on a 100ish foot tower...

that's it - nothing more, nothing less...




d

Canaveral's signal is vastly overmodulated but not particularly powerful.


Jacksonville heats up my antenna!

Miami is almost as strong. And those are two LONG hauls.



Elroy

Most of the installs that I have seen in CT where 50watt W9 Astro Spectra's.

There was a shot of the CG station at Dutch Harbor in the Deadlist Catch not too long ago which also showed a W9 Astro Spectra in a console. Didn't see what the display said though..

Mush be a nice LOS with the flatland of FL.

I think that they USED to run 300 watt Motorola base stations (rack mounted) but I can't remember what model they were. And I'm sure they're long
gone as they seemed to be of early 70s vintage.


But even 300 watts from an 1800 foot tower might not be enough to
account for the monster signals I've heard from them.

They probably are NOT using multiple transmitters in different locations
as that would cause multipath issues, and there are none that I can determine. No fluttering as I'm in motion, or stationary, or anything
else that might indicate multiple transmitters on the same frequency.



Elroy

Hi Y'all,

All the new "Rescue 21" CG stuff is Quantar - while the older radios were a hodgepodge, depending on where you are. Out west, it is/was mostly Mastr II, while the eastern stuff has been reported as both Motorola (Mitrek bases thru Astro Spectra) and GE. But the new stuff is all supposed to be Quantar. All the linking is digital, instead of the older leased lines - most of the over/under modulation and distortion problems were related to those lines, not the equipment itself.

73 DE Hartley

They have tons of remote sites. They could be 200 miles away from the transmitter you are listening to.

Elroy Jetson wrote:They probably are NOT using multiple transmitters in different locations
as that would cause multipath issues, and there are none that I can determine. No fluttering as I'm in motion, or stationary, or anything
else that might indicate multiple transmitters on the same frequency.
Elroy

Unless it was a good, properly phased simulcast, which if that was the case, you'd never know there were multiple transmitters.

could also be voting with transmitter steering

In this neck of the woods, the radios themselves are nothing spectacular: largely (to my observation) a mix of mid- and high-power Spectras and one MSF5000. However, they have some good high sites (Pilgrim Monument: 343 MSL in Provincetown, and Newport-Jamestown Bridge superstructure, for examples) which are connected by TRC and phone lines. Receivers are voted; transmitters are operator steered. Limited (possibly inadvertent) simulcasting.

Last time I serviced it in 2000 or so..

USCG TX in Flagler Beach, FL used a multi channel 100 watt Micor base with a dedicated monitor RX on channel 16. This could be operated by tone remote from Jacksonville, Cape Canaveral and several other sites. I think it has been upgraded since then to a Quantar. Antenna was a DB 224 at 250 feet with all the elements directed offshore.

Dave

Lets also keep in mind that line-of-sight on the coastline and over the water is very uninhibited. There is no terrain or obstructions to get in the way. So if you put your 100 watt transmitter on a 6 or 10db gain antenna 180ft up in the air on the coast, it is going to go pretty far.

These monster signals are often noted quite a few miles inland. If I'm just picking up the backside of the radiation pattern, it makes the setup even more awesome still.



Elroy

I know here in Atlantic Canada they are switching out all their current base stations (whatever they may be) with 100W MTR2000s. They have their own techs, so information is limited, but I know it's some sort of linked system. Total number of base stations east of Montreal number in the 500 range.

Todd

the speculation in this is driving me mad so lets state the information sofar.

They have quantars maybe 350 watt and MTR2000 at 100 watts.
They have many linked sites through a system called Rescue 21(link above)
They have high towers
They have high gain antennas mainly pointed at sea.

Now they are PS so sites probably overlap for redundency.
Okay put this together and you have a high power VHF system with great coverage along the coast.
Now any one in a coastal area should recieve the CG strong.Remember they are a PS as well as defence.
But as the system is multi site, they could be in Key West or New England.
or depending on the config they could be in Seattle and boom in like there next door in West Palm.

I mean in the end I have a 9db antenna at 260 ft with a MTR200 pushing 100 watts through 7/8 heliax.
Our centre can recieve 25 watt boats 80 miles away without a problem.

nmfire10 wrote:Lets also keep in mind that line-of-sight on the coastline and over the water is very uninhibited. There is no terrain or obstructions to get in the way. So if you put your 100 watt transmitter on a 6 or 10db gain antenna 180ft up in the air on the coast, it is going to go pretty far.

True Line of sight signals dont care power power levels once you have enough to overcome signal loss. a base antenna at 200ft talking to a ship with an antenna at 30ft only gives 28mile range lOS. Even 200ft base to base is only 40miles LOS.

in the Annapolis area, Coast Guard Group Baltimore can and does use at least two transmitters, selected as a function of which receiver is voted up and down the Chesapeake Bay.

During marine safety broadcasts on 22A they manually key up both. I've been in an area where the capture effect waggles back and forth, with different audio characteristics telling me one or the other.

I understood that their console panel indicates which of the receive sites is hearing a given vessel, to aid in tracking calls and deploying resources.

...a.k.a. manual transmitter steering.

when I worked on a rail project in Australia (V\Line for the Aussies)
we had base stations covering whole lines.
These fed back via spaz attacks and main comparators to centracom I's
There was some stuff in there that auto steered so the controller would page the train on simulcast and the system would autosteer to the closest sitecould easilly be the same stuff using voting auto steer

Rescue 21 is not fully operational yet, although some units have had equipment installed. The system is not in widespread use.

Most USCG small boat stations have Astro Spectras in a console with a modest tower arrangement. You will also sometimes see a direction finder antenna on their towers as well. Some stations like Rio Vista, CA have a large area of responsibilty and use what are called high sights. Their voice is sent over a leased line to a transmitter on a tower, in the case of Rio Vista 200 miles away from the actual station. The station watchstander can select which transmitter to use.

When I was stationed at Governors Island in the early 90s the watch center had 5 separate radios connected to high sights up and down the Hudson River all the way to Albany NY. The watchstander had to actually pick up a different mic depending on which high sight he needed. It was not uncommon to hear them transmitting on the wrong high sight.

We also had the AMVER center on the island back then. They had HF gear capable of speaking with vessels over much of the globe. They were able to coordinate rescues all over the world. They have since been privatized.