VHF range?

[Marin]

Another thing that can affect a radio signal is the proximity of another antenna. When we added a second antenna for our flying bridge radio to replace the selector switch that had been there when we got the boat, the proprietor of the electronics shop we used cautioned us to make sure the new antenna was NOT a specific distance from the other VHF antenna or a multiple of that distance. It's been a long time since we did this so I don't remember the basic distance but seventeen inches comes to mind.

The reason given had to do with the wavelength and the partial signal blocking an antenna at these distances from the transmitting antenna could cause.

Of course if this is a new problem for the OP or for this particular boat, then antenna position would not be a factor since everything was working fine before.

 

[BigJim]

35 year Ham operator here. As you all know VHF is line of sight. If you have a 9 DB antenna then your ERP, effective radiated power is roughly +- nine times your radio output. That is a LOT of power.


VHF is line of sight. If your antenna is up high and in the clear your 9 DB stick should EASILY talk 50 miles if not more.


So you have coax loss, do you have RG58 or RG8? Or maybe you have some crappy 75 Ohm coax. What is it?


You need a good 50 Ohm Coax, RG213 come to mind, unsure of marine grade.


If you have a PL259 connector at the radio make sure it is soldered correctly. No short, continuity to the shield.


I have talked 100+ miles on VHF with a HH and a 3 DB antenna, line of sight, full quieting.


If you are unable to talk 5 miles with a gain antenna you have serious issues.


Look at connectors first, then feedline name and antenna connections.


With 25 watts and a 9DB stick you should be able to talk from Anacortes to any island.

 

[Marin]

With 25 watts and a 9DB stick you should be able to talk from Anacortes to any island.

Yes, we have talked from our slip in Bellingham to boats in the lower half of the Gulf Islands no problem.

 

[Capt.Bill11]

We never bothered to switch the radio from 25 watts (it's normal setting) down to 5. We just left it on 25 watts and there were no problems, no complaints.

Somebody 20 + miles away having to listen to you might not complain directly because they can't reach you on their radio. But that doesn't mean they couldn't hear you and you were not annoying them.

I'm with George. Someone not turning the transmit power down on their VHF when they're talking to some one they can see is one of my pet peeves. It's just lazy and rude. Sort of like having a loud personal conversation on a cell phone while in a public area.

Up where you are it may not happen often. But here, it's constant.

Now I may not always remember to drop the power down on my VHFs all the time but I try to.

 

[Ski in NC]

Corroded connection common cause of poor transmit. Especially if there are connections between radio and ant up in bridge or antenna masts. Usually still receive ok with corroded connections, but transmits poorly.

 

[Marin]

Somebody 20 + miles away having to listen to you might not complain directly because they can't reach you on their radio. But that doesn't mean they couldn't hear you and you were not annoying them.

Up where you are it may not happen often. But here, it's constant.

Now I may not always remember to drop the power down on my VHFs all the time but I try to.

I certainly agree with you when it comes to those folks who blather on and on and on about stuff on the radio. That's annoying at 5 watts or 25. But I and the people I communicate are all "minimalists" on the radio. If we say a partial sentence that's a lot.

I'm more interested in reaching the the person I'm trying to reach when I'm trying to reach them than who else might hear me. And up here, 25 watts does the job every time. Five would not most of the time.

And, as I say, outside of the two tourist months, the radio is silent 95 percent of the time other than the VTS and commercial shipping channels.

 

[ranger58sb]

5 watts?

Our handheld is 5w, or 1w on the low power setting.

Our main radios are 25w or 1w, no 5w choice. There are brands with a 5w choice?

-Chris

 

[Marin]

5 watts?

Our handheld is 5w, or 1w on the low power setting.

Our main radios are 25w or 1w, no 5w choice. There are brands with a 5w choice?

-Chris

You are correct, sorry. Since we never use low power I've confused it with our handheld's power. 25 and 1 is what it is (I'm pretty sure). They're all Icoms and it's been awhile since I installed them and frankly, I've totally forgotten what the low power rating is. Thanks for the correction.

 

[ranger58sb]

Ah. (Well, didn't mean it as a correction anyway, just a question.)

That said, the antenna on our handheld is so puny that 5w on that probably works approx. like 1w on our ICOMs with the 8' antennas mounted 16' off the water.

-Chris

 

[Marin]

When our radio at the lower helm developed a problem and was sent to Icom here in Bellevue for troubleshooting, the owner of the electronics shop we used made us up an adaptor cable that let us plug our VHF handheld (also an Icom) into our 24' antenna. This, he said, would at least extend the radio's range over the little rubber duck antenna it normally uses.

 

[FlyWright]

While power and antenna height both affect signal propagation, antenna height has the greatest effect. Line of sight is the key in VHF comm. Extra power can help some transmissions with slight LOS issues, but you'll see better broadcast and reception performance with a raised antenna. Another significant factor in performance is antenna quality.

 

[River Cruiser]

One of the things that helps clutter up the airwaves is guys transmitting at 25 watts. Completely unnecessary for 99% of coastal cruising.

I typically run on the 1 watt setting and have no problem communicating with the locks and bridges. When I bought the boat on the 25 watt setting to test the VHF I could talk and receive from a lock 27 miles away. While in the slip with the antennas down I have no problem hearing conversation between lock #22 and tows up river 18 miles. I've been told by other boaters the lock guys don't appreciate someone calling from 2 or 3 miles away on hi-power setting, I've at times used my handheld because I can hear better on it using the head set that has the talk to transmit function.

 

[High Wire]

My new Standard Horizon 2200GX has a "safety feature" that I did not expect. When you manually switch to 1 watt on Ch 16 while cruising and then switch to another channel like 9 for a bridge, then go back to 16 using the 16/9 button, it reverts back to 25 watts on its own. I thought I was going crazy. So now I have to look at the power indicator every time I switch. Funny thing is that Ch 9 will stay on 1 watt.

 

[FF]

Folks that run inshore , the AICW or similar should remember that big antenna may have to be laid down for bridges .

At low power with a flat antenna even a great VHF has a hard time going very far.

Solution , second inshore antenna or a hand held VHF to talk to the lock & bridge folks.

 

[Aquabelle]

You could also buy Shakespeare's multi-function test device: it tests Receiver function; Power Output; and Antenna SWR. Available at Defender ( & elsewhere): here's the link to the product page for the ART-3 meter:http://shakespeare-marine.com/sites/brandmarine/files/assets/art-3.pdf

 

[stevensibs]

Assuming good co-ax connections and a properly working VHF radio, with your antenna height of 32' above the water and accounting for earth curvature with no obstructions, you should broadcast and receive to 6.9 miles.

 

[markpierce]

The characteristics and height of the other party's antennae affects the effective range of your radio too.

 

[RCook]

Indeed. Height of 32 feet gives distance to the horizon of 6.12 nm (1.17 x the square root of the height in feet). Calculate for each of the two antennae, and add together. If the receiver's antenna is also at 32 feet, they could be able to converse at a distance of 12+ nm.

Same calculation will tell how far apart someone on a ship can see another ship starting to peek above the horizon.

 

[MYTraveler]

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 (not just ships and USCG) when offshore. Moreover, my AIS (also VHF) is usually receiving active signals from ships more than 100nm distant. -- I am sure the antennas on those ships are a few hundred feet high, but not high enough to explain that range.

 

[psneeld]

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 (not just ships and USCG) when offshore. Moreover, my AIS (also VHF) is usually receiving active signals from ships more than 100nm distant. -- I am sure the antennas on those ships are a few hundred feet high, but not high enough to explain that range.

I too often experience much better range from VHFs than what the theory says.

 

[N4712]

i too often experience much better range from vhfs than what the theory says.

x3!

 

[Manly Q.]

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.

Regards.

David.

 

[High Wire]

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.

 

[Marin]

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.

 

[Britannia]

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.

Richard

 

[Alaskan Sea-Duction]

So what was the OP final solution?

 

[BrianSmith]

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?

 

[Marin]

Standard Horizon and ICOM seem to get pretty good reviews here on TF, right?

Pretty hard to go wrong with either one of them.

 

[BrianSmith]

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!

 

[FlyWright]

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.