Standard Horizon Handheld - not transmitting on ch.80

pvb said:
As PilotWolf has also said, busy doesn't mean that the OP's signal would become faint.
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No, but it would suffer in a way that most operators would describe as a weak signal. Just because the signal isn't weak doesn't mean it's clear.
 
lustyd said:
Not really. Most normal people would say they have a weak signal if they can't distinguish what's being said on the call.
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Earlier in this thread, you advised the OP "Why not just take it into the marina office? Most of the time you can see and hear their set so you don't even need them to participate in the test".

The OP replied "I did a radio check with the marina in the morning - it came through but apparently was faint".

Now, bearing in mind he was doing a radio check with the marina, if there'd been a simultaneous transmission from someone else which had interfered with the OP's transmission, don't you think the marina guy would have realised? And probably asked the OP to repeat the transmission. Or do the marina guys, who work with VHF all day long, also have less experience and understanding than you?
 
pvb said:
Earlier in this thread, you advised the OP "Why not just take it into the marina office? Most of the time you can see and hear their set so you don't even need them to participate in the test".

The OP replied "I did a radio check with the marina in the morning - it came through but apparently was faint".

Now, bearing in mind he was doing a radio check with the marina, if there'd been a simultaneous transmission from someone else which had interfered with the OP's transmission, don't you think the marina guy would have realised? And probably asked the OP to repeat the transmission. Or do the marina guys, who work with VHF all day long, also have less experience and understanding than you?
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When I advised that I didn't know he was in such a high traffic area. If you stand in East Cowes Marina office some time when it's busy you will understand what I mean. You may also pick up some interpersonal skills while out of your house.
 
lustyd said:
The stronger signal doesn't block the weaker though, they interfere with one another which appears to the receiving set as a weak or crackly signal.

There does seem to be a misconception of basic radio theory in this thread.

In a frequency modulated system the stronger of the signals presented to the receiver limiter or discriminator circuit will be demodulated and will be heard. This is called Capture Effect. So the stronger signal will effectively block the weaker signal.

The reason CH 80 was chosen for the marina channel was due to pressure from yachtsman and marine businesses to align with the use of the channel in Europe and other parts of the world. Channel 37(M,M1) that was used at the time as marina channel was not an international marine channel and was not included in the channel plan for equipment sold in other countries.
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seacomm said:
There does seem to be a misconception of basic radio theory in this thread.

In a frequency modulated system the stronger of the signals presented to the receiver limiter or discriminator circuit will be demodulated and will be heard. This is called Capture Effect. So the stronger signal will effectively block the weaker signal.
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Apparently, basic radio theory doesn't apply in the Medina area. ;)
 
seacomm said:
lustyd said:
The stronger signal doesn't block the weaker though, they interfere with one another which appears to the receiving set as a weak or crackly signal.

There does seem to be a misconception of basic radio theory in this thread.

In a frequency modulated system the stronger of the signals presented to the receiver limiter or discriminator circuit will be demodulated and will be heard. This is called Capture Effect. So the stronger signal will effectively block the weaker signal.

The reason CH 80 was chosen for the marina channel was due to pressure from yachtsman and marine businesses to align with the use of the channel in Europe and other parts of the world. Channel 37(M,M1) that was used at the time as marina channel was not an international marine channel and was not included in the channel plan for equipment sold in other countries.
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Thank you Seacomm, much better to see an explanation. So are you saying that even though the two signals are on the same frequency the receiving unit can tell that they are different signals and therefore remove the interference? If that were possible then surely it should also be able to choose to listen to the weaker signal and we could massively increase bandwidth. You could also inform the wifi lot so they could do away with collision detection algorithms on computers! Maybe I have misunderstood but I thought two signals on the same frequency interfered just like all other EM does?
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lustyd said:
Radio technology is not a strongest signal wins solution. All signals will propogate from their originating point and will interfere with any other signal on the same frequency (this works in exactly the same way as throwing two stones into a still pond). Transmission power doesn't really help with this, the stronger signal will go further but that just means it will interfere with even more signals further away (marina comms should always be on low power).
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Nice explanation of an AM system there. Unfortunately marine radio uses FM which utilises the Capture Effect. The Phase Locked Loop locks to the frequency and phase of the main signal. Other signals at the same frequency but at different phases are attenuated. You can here this effect on a car radio at the boundary of two transmitter areas - the radio wil switch back and forth.
 
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st599 said:
Nice explanation of an AM system there. Unfortunately marine radio uses FM which utilises the Capture Effect. The Phase Locked Loop locks to the frequency and phase of the main signal. Other signals at the same frequency but at different phases are attenuated. You can here this effect on a car radio at the boundary of two transmitter areas - the radio wil switch back and forth.
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Thanks for the explanation - this still seems to break down in very busy areas such as the medina though, perhaps because there are too many signals competing.
 
Maybe now given the numerous other replies lustyd may accept that he is NOT correct as I pointed out earlier. I did not bother going into detailed technical explainations as I did not see the point - thank you to secomm and others for doing so.

I would suggest that maybe you try sitting the radio exams above SRC and you might realise that to pass those exams does require a good working knowledge of the subject - possibly why the ROC/GOC course is usually 5 days rather than a day including exam for the SRC?

PW.
 
PilotWolf said:
I would suggest that maybe you try sitting the radio exams above SRC and you might realise that to pass those exams does require a good working knowledge of the subject - possibly why the ROC/GOC course is usually 5 days rather than a day including exam for the SRC?

PW.
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I would suggest that anyone who has 5 days to take a radio exam find something better to do with their time :P
 
Oh and if I am grumpy old man at 43 because I expect accuracy and correct information to be passed on rather than hearsay or what 'you' think is right then I am guilty as charged.

PW.
 
SvenglishTommy said:
I would suggest that anyone who has 5 days to take a radio exam find something better to do with their time :P
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The International Telecommunications Union have received a complaint that RYA obtained SRCs are too easy to obtain. You may get your wish.
 
st599 said:
The International Telecommunications Union have received a complaint that RYA obtained SRCs are too easy to obtain...
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I think I agree with the ITU. I have a background in electronics, and have an Amateur Radio Licence, so the course was a doddle for me. However, it didn't go into nearly enough detail about DSC, preferred channels, and procedure. A couple of the other candidates were clearly having difficulty, but still got their certificates.
 
nigelmercier said:
I think I agree with the ITU. I have a background in electronics, and have an Amateur Radio Licence, so the course was a doddle for me. However, it didn't go into nearly enough detail about DSC, preferred channels, and procedure. A couple of the other candidates were clearly having difficulty, but still got their certificates.
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Yep, from what I have heard it is simply an attendance = pass type course.

But I guess some training is better than none...

PW

PS.
lustyd
...
and from your post it's quite clear that your understanding is less thorough than you think it is.
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I think that this may apply rather more to you than me?
 
PilotWolf said:
Yep, from what I have heard it is simply an attendance = pass type course.

But I guess some training is better than none...

PW

PS.

I think that this may apply rather more to you than me?
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If you can explain what I asked in post 49 then yes, maybe. If not then I guess I'll have to do the course and hope the instructor can explain why radio signals are uniquely immune to EM interference. Perhaps the instructor may have an explanation for the poor reception in busy areas too, which is obviously coincidence rather than interference.
 
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