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Old 07-19-2016, 06:19 PM   #1
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VHF Incompatibility

In our cruising club we are all able to communicate perfectly well with each other except for two specific boats who cannot. He can never hear me although I can always hear him. All other boats hear me and him all the time. The miscommunication happens at distances ranging from a few feet to a quarter of a mile or more. The problem occurs whether we are on 25 watt, high power or low power. Is it possible that two radios operating correctly just won't cooperate with each other for some kind of technical reason?
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Old 07-19-2016, 06:59 PM   #2
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Maybe he's ignoring you.

Seriously, he can't hear you on channel 16?

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Old 07-19-2016, 07:23 PM   #3
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Check that one of the radios is not set to "intl" vs "usa". Frequencies differ a bit. Not sure which channels this affects, would not figure 16.
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Old 07-19-2016, 08:05 PM   #4
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Check that one of the radios is not set to "intl" vs "usa". Frequencies differ a bit. Not sure which channels this affects, would not figure 16.
X2. One of you is set to International or Canadian channels.
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Old 07-19-2016, 10:43 PM   #5
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Check that one of the radios is not set to "intl" vs "usa". Frequencies differ a bit. Not sure which channels this affects, would not figure 16.

That was my thought initially also,but..... Then why would all the others be able to hear everyone!!??

I would suspect bad installation.

Find another member at YC who has your exact radio power connections. Swap radios out from their boat to yours. Then try comms with other boat. (And other boats). If no difference, have other guy swap radios. Use a control. Change out only one radio at a time. See if the problem follows the radio or not. If the problem persists you've got something wrong with antennas or cables.
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Old 07-19-2016, 10:50 PM   #6
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So complicated. ... Call on the cell phone. Aren't VHF channels busy enough?
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Old 07-22-2016, 12:23 PM   #7
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I'll check out the USA vs. International issue. I don't want to call him on 16 to see if he can hear me out of respect for CG rules. Re all the swapping back and forth appraoch, I'm ok with markpierce's reminder that we (boating community) really don't need most of the VHF traffic we hear. Cell phones have moved many of us off landlines, now for off VHF for most comms. What do others think?
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Old 07-22-2016, 12:51 PM   #8
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Cells are NOT a vhf replacement but a useful additional tool.
You guys in high cell coverage areas may, may get away with that thinking but there are still large areas where cells are totally useless.
Vhf covers everyone within range regardless of where or who you are. .
Cells must go to a land base antenna and then be rebroadcast. No tower, no coverage.

Fix the vhf.

If you want to use cell fine but it is not a replacement.

Problems like you describe might need some pro help.
Sounds like his receiver is. faulty. Could be a touch of frequency drift or a poor antenna connection. Poor joins can cause goofy tr6ouble.

Loosened, oxidation of the Pl259 connection. Go through it all carefully and check each connection. Joints should be soldered. Personally I think pressure joints in vhf is just trouble waiting to happen. Helped a few and multiple excess connection were removed and the remaining joints soldered the vhf worked fine .

Two last suggestions,. Get a pro if these checks don,t resolve the issue.
OR
Get a replacement vhf AND antenna as sometimes the antenna is goofy so if the old antenna is kept the new vhf cannot operate properly.
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Old 07-22-2016, 01:21 PM   #9
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Different modes sounds like the most likely explanation. The frequency assigned to a channel is universal regardless of mode, but different countries use different channels. As a result one of you might be using 66 and the other 66A. They transmit on the same frequency, but receive on different frequencies. Which brings up an interesting questions...

How does a channel work where the receive and transmit frequencies are different? Maybe those are simplex channels? Can any HAMs out there shed some light?
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Old 07-22-2016, 01:24 PM   #10
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BTW, if you download any one of the icom VHF manuals they list all the channels in the back along with their frequencies. Try picking a channel that you can both tune to where the send and receive frequencies are the same, then go from there.
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Old 07-22-2016, 02:07 PM   #11
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Some channels have different tx and rx frequencies so there is no need to key the mic. Both parties can talk at the same time. Sometimes referred to as "radiotelephone", but not sure that is the technical term.
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Old 07-22-2016, 03:17 PM   #12
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Quote:
Originally Posted by Clown One View Post
I'll check out the USA vs. International issue. I don't want to call him on 16 to see if he can hear me out of respect for CG rules. Re all the swapping back and forth appraoch, I'm ok with markpierce's reminder that we (boating community) really don't need most of the VHF traffic we hear. Cell phones have moved many of us off landlines, now for off VHF for most comms. What do others think?
VHF 16 is for hailing. You establish contact and them move to a working channel. After establishing contact move to a channel different than what you normally chat on.

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Old 07-22-2016, 03:43 PM   #13
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Some channels have different tx and rx frequencies so there is no need to key the mic. Both parties can talk at the same time. Sometimes referred to as "radiotelephone", but not sure that is the technical term.
That makes sense, but I don't see how both stations can transmit on channel A, and receive on channel B, and hear each other. I could see if one transmitted on A and received on B, and the other transmitted on B and received on A. There must be more to how it works.

Oh, I think I get it. It's strictly for ship to a dedicated shore station. Never fro ship to ship. Ships trans an A and receive on B, and the shore station transmits on B and receives on A. So your VHF can only ever hear what the shore station is transmitting, and never what's coming from other boats.

That sure would explain what the OP is experiencing.
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Old 07-22-2016, 05:11 PM   #14
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Originally Posted by Ski in NC View Post
Some channels have different tx and rx frequencies so there is no need to key the mic. Both parties can talk at the same time. Sometimes referred to as "radiotelephone", but not sure that is the technical term.
It's called Duplex mode, sometime manufactures call it cross channel. The marine Duplex channels are 24 - 28 and 84 - 88. The other US channels are "Simplex Mode" and transmit/receive on the same frequency.

Being in International mode does not effect channel 16 performance.

I'm with the group saying it's either bad install or one radio has technical design/performance issues. VHF Marine radio's sold to the public are generally not built to Mil spec's, they just have to meet minimum FCC requirements. So performance can vary widely.

US Marine channel list:

VHF Marine Radio Channels and Frequencies
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Old 07-22-2016, 06:05 PM   #15
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It's called Duplex mode, sometime manufactures call it cross channel. The marine Duplex channels are 24 - 28 and 84 - 88. The other US channels are "Simplex Mode" and transmit/receive on the same frequency.

Being in International mode does not effect channel 16 performance.

I'm with the group saying it's either bad install or one radio has technical design/performance issues. VHF Marine radio's sold to the public are generally not built to Mil spec's, they just have to meet minimum FCC requirements. So performance can vary widely.

US Marine channel list:

VHF Marine Radio Channels and Frequencies
Based on the Icom sheets, if you are in Canadian or International mode, there are additional channels where xmt and rcv are on different frequencies. Just FYI. I'm no expert on this stuff.
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Old 07-22-2016, 06:44 PM   #16
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Based on the Icom sheets, if you are in Canadian or International mode, there are additional channels where xmt and rcv are on different frequencies. Just FYI. I'm no expert on this stuff.
Good point.

The Canadian duplex channels (based on my last old list) are:
Channels 1, 2, 3, 23, 24, 25, 26, 27, 28, 60, 64, 84, 85, and 86

Also someone else mentioned holding the mike button down without releasing and hearing the other persons reply (like a cell phone). That's called "full duplex."

Since cellphones came on the scene, it's been probably 30 years since I used the Marine Radio Telephone Service. It was still "half duplex" then, you had to say "over" and release the mike button before the other person could talk.

I don't know if they, or your radio, supports "full duplex" yet. Maybe someone else has used it more recently.
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