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Old 04-27-2015, 12:32 PM   #81
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i too often experience much better range from vhfs than what the theory says.
x3!
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Old 04-27-2015, 04:16 PM   #82
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I know from experience that radio signals are also influenced by the atmosphere, there is a bounce effect in certain weather conditions.

Cloudy weather interferres with my work U H F and fine clear days the reception can be extreme in distance. I am sure there is a bounce off the Ionesphere or some such beastie.

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Old 04-27-2015, 04:18 PM   #83
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The guy that used to write the ham books for radio shack had set records for VHF transmissions of hundreds of miles using only LIGHT BULBS for an antenna. Its theory! In practice, the waves bend along the surface of the earth and travel a good 25% or more miles. I've heard boats fishing for stripers 125 miles away at the Chesapeake Bay Bridge Tunnel clear as day and some days have a hard time reaching 5 miles. I routinely talk to a friend in Atlantic City 38 miles away with each of us using a 6db antenna on our center console T-Tops.
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Old 04-27-2015, 04:31 PM   #84
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I know my experience is contrary to conventional wisdom that VHF is line of sight, but I routinely get 50nm loud and clear comms with other boats.....
I think VHF has a lot of funny habits and traits. As I've mentioned, we can be in our slip in Bellingham and hear clear as a bell the radio calls from the BC ferries transiting Active Pass which as the crow flies is 34 miles away with some islands in the way. We talked to one once with no communication clarity problems. We routinely talk to friends from our slip when they are at an island some 16 miles away, again with islands in the way. This is all at 25 watts, of course.

So the theoretical transmission distance of VHF can be altered considerably by other factors.
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Old 04-27-2015, 05:09 PM   #85
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VHF propagation is interesting. There is no doubt that objects such as buildings or mountains can help or hinder communications. As mentioned, the atmosphere also has an effect - specifically something called tropospheric ducting. This is where an inversion layer allows the radio waves to be "bent" and not be diffracted into the atmosphere. I believe the world record for VHF transmission is between Hawaii and California where this effect is known to create "openings" that can stretch over 2000 miles.

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Old 04-28-2015, 11:57 AM   #86
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So what was the OP final solution?
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Old 04-28-2015, 05:34 PM   #87
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So what was the OP final solution?
Nothing final yet. I took the radio (a Uniden, which I think is a "value brand") in for testing. Haven't heard back yet. I did confirm that the connection from the antenna to the radio was good.

I did another test just before yanking the radio out to take it to be bench tested: I tried to talk to the bridge tender at a bridge that's less than a mile from me, with a clear line of sight. I don't know how he heard me, but his replies were very broken up.

I have a feeling I'm going to be buying a new radio - maybe even two (we drive from the flybridge most of the time, but have only a handheld up there now). Standard Horizon and ICOM seem to get pretty good reviews here on TF, right?
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Old 04-28-2015, 06:46 PM   #88
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Standard Horizon and ICOM seem to get pretty good reviews here on TF, right?
Pretty hard to go wrong with either one of them.
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Old 05-11-2015, 07:14 PM   #89
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OP here, with an update: the Uniden radio was bad. Test place said it wouldn't "modulate" (transmit anything intelligible, I guess?). Tossed it in the trash and replaced it with a Standard Horizon - so far, so good. (The bridge tender about a mile from our marina says I'm loud and clear, and he is, too - so that's a start.)

Thanks all, for all the great input - as always!
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Old 05-11-2015, 10:00 PM   #90
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Brian, modulation is the intelligent signal that rides on the carrier wave. If you key your mike and it breaks your friend's squelch but no voice is present on the freq, then the carrier wave worked and it's the modulation that had failed. One needs carrier to get the signal across open space but it's the modulated signal that holds the intelligence we seek in voice comm or navigation signal.
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