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Author Topic: VHF Reception Issue  (Read 1942 times)

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kurt

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VHF Reception Issue
« on: July 26, 2009, 11:05:48 AM »

Hello everyone,

My uniden fixed mount vhf radio appears to not be able to recieve communication on channels 17 through 66 - did not check if transmitting worked on these channels which I will do another day as the thought just hit me.  Channels 67 and above and 16 and below do recieve and transmit based upon previous working history - did check antenna connection at the radio and all looked fine.  Did a quick glance at the manual and didn't see any european configuration settings or things like that being user accessable.

I didn't discover this issue until a race when committee was using 66 2 weeks ago - I suspect the issue has been in place since first install 2.5 years ago.

I suppose antenna, antenna cable, and radio are the only possible suspects here.  I plan to swap out the antenna as that is the least expensive choice of fixes and go from there. 

Any one have any other thoughts re diagnosis or fix?

Thanks,

Kurt
'88 C34 796
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waterdog

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Re: VHF Reception Issue
« Reply #1 on: July 26, 2009, 01:27:12 PM »

Kurt,

In radio terms, you are dealing with a very narrow band of frequencies.   If it works well on some and not on others, it is not very likely to be the antenna or the cable.    Your most likely problem is with the radio itself.   You can have a look at the actual frequencies for the channels here:

http://www.navcen.uscg.gov/marcomms/vhf.htm   

If the channels you are missing are all higher frequencies, you may have some rolloff and a connection or antenna issue.   I would try a different radio before going up the mast to swap an antenna.   See what you can borrow from neighbors and swap out antenna and radio to isolate the problem.   
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Steve Dolling
Former 1988 #804, BlackDragon - Vancouver BC
Now 1999 Manta 40 cat

Jim Hardesty

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Re: VHF Reception Issue
« Reply #2 on: July 26, 2009, 01:57:46 PM »

Kurt,

Try to borrow an RX sensitivity meter.  It won't fix anything but it will tell if the cable/antenna is good or if the radio is bad.  By plugging it in at different places between the radio and the antenna the meter will show where the problem is. 
West Marine has them http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&keyword=6886915&jspStoreDir=wm51&productId=151816&resultCt=1&catalogId=10001&ddkey=SiteSearch 

Jim
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Jim Hardesty
2001 MKII hull #1570 M35BC  "Shamrock"
sailing Lake Erie
from Commodore Perry Yacht Club
Erie, PA

Ron Hill

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Re: VHF Reception Issue
« Reply #3 on: July 26, 2009, 02:38:39 PM »

Kurt : As previously mentioned, I believe that you have a radio/operator problem not receiving the missing frequencies.  The antenna & cabling must be OK or you wouldn't receive channels 16 and above 66 !!

One thing that I found on my boat back in 1989, was that there was a TV connector put in the VHF wiring by the dealer.  That's a NO NO as, TV has 75 rather than the 50 ohms impedance of the VHF wiring.
 
A few thoughts.
« Last Edit: July 28, 2009, 05:38:22 PM by Ron Hill »
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kurt

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Re: VHF Reception Issue
« Reply #4 on: July 27, 2009, 04:14:24 PM »

Thanks everyone for the recommendations.  Fortunately, this turned out to be a user error.  The good folks at West Marine have seen this problem frequently on the Uniden radios - there is a MemUIC button which makes it very easy to toggle between USA Canada and International VHF frequencies.  In my case, it was running on  International VHF band whatever those are which created the disconnect regarding frequencies.  Now if all my boating problems could be so easy to fix.   Thanks again,   Kurt
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