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General Sailing Forum

How much power does the USCG transmit VHF?

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delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Initially Posted - 06/02/2008 : 13:41:46

I was sitting in my boat last night testing the GPS / VHF interface, had the VHF tuned to 16, and was surprised to hear someone asking for a GPS position. I listened for a while, and then inadvertently switched to another channel (I was playing with the memory function). Eventually I switched back to 16, and heard USCG Port Angeles identify themselves to a boater in distress. I couldn't hear the boater's response, but I had no problems listening to the coastie's side of the conversation. He made several more transmissions confirming position, type of boat, etc., before the conversation petered out. This morning I estimated the distance from their station to my house at greater than 70 miles. Not bad for supposedly line of sight VHF, huh? I wonder how many watts they broadcast at? That signal had to get over the ridge that's just west of my house a couple of miles, then across coastal plains, over Puget Sound, then over the hills between me & Port Angeles. Pretty impressive. I know you get better transmission at night, but the sun was still up although far to the west. Sunset wasn't for another couple of hours.

Anyway, nothing earth shattering, I just thought it was pretty cool. I hope the guy in trouble got out of whatever it was OK.

David
C-250 Mainsheet Editor

Sirius Lepak
1997 C-250 WK TR #271 --Seattle area Port Captain --

Edited by - delliottg on 06/02/2008 13:43:57

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 06/02/2008 : 15:26:12

USCG has more power - I don't know how much, but they have far better antennas.

Sometimes I can hear boat traffic 75 miles away, the atmosphere can refract the radio waves under special conditions.

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John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 06/02/2008 : 16:27:41

My son, who happens to repair radios for our Uncle Sam's Air Force happens to be sitting behind me on leave. He just told me with the right antenna and broadcasting at between 500 and 1000 watts they might reach 100 - 150 miles. Wow. They can't hear that far, but the can shout loud!

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Happy D
Admiral

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921 Posts

Response Posted - 06/02/2008 : 16:49:00

The antennas are way up in the air. That makes a big difference.

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SCnewbie
Navigator

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166 Posts

Response Posted - 06/02/2008 : 21:03:34

Transmission height is a bigger factor than power really. They have big towers so their line of sight is much longer.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 06/02/2008 : 21:33:16

The towers are also in multiple locations along a coast--generally at the top of neaby ridges. I routinely hear the USCG at Sandy Hook, NJ, about 125 miles away with most of Long Island in between. I suspect they have repeaters on Long Island.

Their reception is pretty good, too... Sector Long Island Sound picked up my handheld from what I suspect was 15-20 miles from their antenna. Their new system that includes DSC is supposed to be even more sensitive.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 06/03/2008 : 07:04:27

Our nearest station is Prescott Coastguard Radio. They are about 190 miles from us. I think thre must be a repeater station someplace in between.

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ilnadi
Captain

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452 Posts

Response Posted - 06/03/2008 : 10:18:36

according to USCG website, their fixed stations are "authorized up to 1000W". Many variables affect range: power, antenna height, humidity, cloud cover, solar activity, how well your equipment is installed and operating [one of the biggest contributors], etc.

Here are the [url="http://www.navcen.uscg.gov/marcomms/cgcomms/nds.htm"]NDS coverage maps[/url].

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redviking
Master Marine Consultant

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USA
1771 Posts

Response Posted - 06/05/2008 : 08:04:49

Offshore, we can pick up Coasties well before we can hear the other side. We are in Cape May and we already heard coast guard Long Island Sector calls - and clearly. They do have the ability to increase their power depending on need as we have offered to "relay" transmissions for them when offshore and they have declined and worked something else out.

Their towers and those of NOAA make it possible to be 50 miles offshore and still have the possibility of hearing something or being heard. BTW - DSC distress calls are being recorded in this area and some guy was actually called on his cell phone by th ecoasties after a false DSC distress call was rec'd. We heard the aftermath - so they are on it...

Sten

DPO C25 #3220 "Zephyr", SR, FK
SV Lysistrata - C&C 39 - Cape May, NJ

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.