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Old 23-04-2013, 12:13   #1
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Radar and Radios

We have a problem that when I use the radar which is about 10 years old a simrad.the UHF radio range is severely compromised. I have been told that the radar uses lot of power and yes it does. We well and truly make enough power to keep the house batteries full running all equipment. I have been told to change the radios on to running off the engine batteries which are all way charged first before we start charging the house batteries.. Has anyone come up with this sort of problem before? If so do you think this is the correct thing to do?
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Old 23-04-2013, 12:19   #2
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Have you actually measured the voltage at the VHF radio while transmitting to see if it is dropping?

Also when you say compromised are you referring to transmitting range or receiver performance?
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Old 23-04-2013, 12:29   #3
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Have you actually measured the voltage at the VHF radio while transmitting to see if it is dropping?

Also when you say compromised are you referring to transmitting range or receiver performance?
It is more receiving range. The marine rescues hear us we cannot hear them and it is not clear. Turn radar off clear as crystal. No I have not measured the voltage.
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Old 23-04-2013, 14:29   #4
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Re: Radar and Radios

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It is more receiving range. The marine rescues hear us we cannot hear them and it is not clear. Turn radar off clear as crystal. No I have not measured the voltage.
Is your VHF antenna in the beam of the radar?
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Old 23-04-2013, 14:42   #5
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It is more receiving range. The marine rescues hear us we cannot hear them and it is not clear. Turn radar off clear as crystal. No I have not measured the voltage.
Well it sounds like the radio is getting enough current when transmitting since you say the rescues can hear you. Has the radio and radar setup been changed recently or has everything been the same then the poor receive problem pop up on its own ?
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Old 24-04-2013, 11:34   #6
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Re: Radar and Radios

The radar is "shouting in the ears" of the UHF radio.

My home's wifi throughput gets compromised by the microwave oven because of the same situation.
Usually it's not a problem, but with a HD streaming program, it freezes every few seconds.

You will probably just have to pick which one is more important at any given time.
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Old 25-04-2013, 15:08   #7
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Well it sounds like the radio is getting enough current when transmitting since you say the rescues can hear you. Has the radio and radar setup been changed recently or has everything been the same then the poor receive problem pop up on its own ?
I don't use the radar that much and on trip from tasmania to Gold Coast I have noticed the problem.
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Old 25-04-2013, 15:09   #8
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Is your VHF antenna in the beam of the radar?
Yes it would cut the aerial in half as it would on a lot of boats
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Old 25-04-2013, 15:33   #9
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Re: Radar and Radios

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Yes it would cut the aerial in half as it would on a lot of boats
Well, there is your problem. The radar is overloading the VHF receiver.

What brand and type is the VHF radio?
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Old 25-04-2013, 17:51   #10
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Well, there is your problem. The radar is overloading the VHF receiver.?
The odds of the emissions from the actual radar array on x or s band desensitizing the receiver of a VHF FM radio are very low. Look at the bridge of most tugs, freighters, and cruise ships and you will see the VHF antennas in the beamwidth of the radar array.

I suspect it maybe a IF or intermittent frequency of the radar unit that is much lower than the primary transmit frequency. Maybe due to loose shielding or bad design but hard to speculate if you can't tell us if its been a long term problem or something that started recently.

One suggestion to see is get a VHF handheld and stand on deck well below the radar (in a safe place) and tune around till you hear a station. Then have someone turn on the radar and see if they get weaker or drop out.
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