Marine Freq's In Boston Area Question, Please

[BOBRR]

Hello,

Live about 20 miles due West of Boston harbor.
Using a Scantenna ST-3 (or is it a -2 ?) up in the attic. "Decent" height probably.

Haven't been very successful picking anything up maritime related.
Have tried the Sector Boston CG freq's, and a bunch of others from the various lists.

Might anyone please suggest a bunch of freq's that I would stand a "reasonable"
chance of actually picking something up on.

Not too particular.
Would enjoy monitoring CG, Commercial, Harbor traffic, etc., etc.

Much thanks,
Bob

 

[mmckenna]

20 miles inland with your antenna only at attic height, it's unlikely you'll hear a lot.

Most of the traffic that is out there is coming from boats with antennas off the water by a few feet. Larger ships may have their antennas up higher, maybe 50 to 100 feet, but that still may not be high enough to hear them.
USCG may have some stuff on higher towers that you could hear, but they are usually focusing that RF out towards the water, not inland.

You may need to get your antenna up higher and in the clear if you want to hear more. Down that low and 20 miles inland is going to be a really hard challenge to overcome.

 

[wtp]

20 miles is pushing it
if i remember the math for possible reception is
the square root of the height of the antennas squared and added together
so if both antennas are 10 feet up
10^2 plus 10^2=200
square root of 200 is about 14 miles apart.
and that is with nothing in the way and some good power (not a handheld)

 

[AM909]

Totally theoretical: FSPL for 160 MHz @ 20 miles is about 107 dB. For a 25W (+44 dBm) transmitter with 0-gain antenna system, that would put -62 dBm at a receiver with a 0-gain antenna system. That's a lot of signal for even a not-great receiver with spec of 0.25 uV (-119 dBm) for decent quieting, with 57 dB of headroom for lossy things in the way, like transmission line loss (net of antenna gain), buildings, walls, dense/smoggy air (?), etc.

Various places I saw in a search talk about range of 50-70 miles for a 25W radio on open water to elevated shore antennas. I have zero experience with marine radio, but these are not unreasonable numbers for VHF over land. As MM said, getting the antenna on the roof instead of below it gets rid of the loss and potential detuning caused by stuff in the attic and the walls, as well as that of your surrounding houses (hopefully).

 

[mmckenna]

Totally theoretical: FSPL for 160 MHz @ 20 miles is about 107 dB. For a 25W (+44 dBm) transmitter with 0-gain antenna system, that would put -62 dBm at a receiver with a 0-gain antenna system. That's a lot of signal for even a not-great receiver with spec of 0.25 uV (-119 dBm) for decent quieting, with 57 dB of headroom for lossy things in the way, like transmission line loss (net of antenna gain), buildings, walls, dense/smoggy air (?), etc.

On paper, yes. But you need to consider distance to horizon from 20 miles inland. An antenna 20 feet of the ground isn't going to work very well when trying to listen to a ship 20-30 miles away with an antenna only 40' off the ground. For a good transmit site up 100-200 feet, you may be able to hear something, but often they'll use stacked folded dipole antennas to direct that signal more towards where it's needed, not inland.

Not to mention that most VHF marine installs are pretty crappy, with cheap RG-58, cheap antennas and twist on PL-259 connectors, and "who the heck ever heard of waterproofing connectors???"

 

[EricCottrell]

Hello,

And not to mention the hills and other obstructions, like buildings, in the path.

73 Eric

 

[AM909]

I'm not disagreeing (certainly not with a guy flying the Coast Guard flag ) – just trying to put some numbers to it and see what the theoretical best case is and I ignored curvature.

So, this Earth curvature calculator seems to say you need ~270 feet of elevation to see the horizon at 20 miles (420' @ 25 mi; 600' @ 30 mi), though it goes on to mention refraction (which also happens for RF), allowing for some wiggle room.

 

[StoliRaz]

Hello,

Live about 20 miles due West of Boston harbor.
Using a Scantenna ST-3 (or is it a -2 ?) up in the attic. "Decent" height probably.

Haven't been very successful picking anything up maritime related.
Have tried the Sector Boston CG freq's, and a bunch of others from the various lists.

Might anyone please suggest a bunch of freq's that I would stand a "reasonable"
chance of actually picking something up on.

Not too particular.
Would enjoy monitoring CG, Commercial, Harbor traffic, etc., etc.

Much thanks,
Bob

I know this is old but I also live in MA about 25 or 30 miles inland. Just a week or two ago I stumbled upon a USCG announcment of the presence of North Atlantic Right Whales spotted in Cape Cod Bay while scanning with my 436HP. I hardly ever hear anything from USCG or marine traffic in general, I was pretty surprised to catch them. Probably 2 bars of signal too. I believe it was the Boston station as opposed to Cape Cod

 

[wtp]

old, yes, but i am back here.
the other thing is how many people actually use their radio.
i lived 1/8 mile from Charlotte harbor and got VERY little action.
in a harbor where you can 'park' and talk to your neighbor, why use a radio ?
in the afternoon i would hear the CAP plane announce they were up and listening.

 

[StoliRaz]

old, yes, but i am back here.
the other thing is how many people actually use their radio.
i lived 1/8 mile from Charlotte harbor and got VERY little action.
in a harbor where you can 'park' and talk to your neighbor, why use a radio ?
in the afternoon i would hear the CAP plane announce they were up and listening.

Also consider the time of year. It'll definitely get busier as the weather warms. More boats on the water

 

[wtp]

i live here all year...
and i am talking about all year.