VHF Radio Reception on the Thames (Tidal!)

[Chris_d]

Transmitting at high power from a fixed radio to an adjacent portable is never going to give representative results, even if the quality of the transmission is perfect.

The sheer power of the transmission, along with the relatively high power of any spurious signals from the transmitter are going to cause the handheld to distort badly and effectively closes down most of the front end circuits within the receiver.

You need to get the receiver a reasonable distance away.

At the risk of telling you something you know, a radio signal consists of two main components, the basic radio carrier and the audio signal containing the message.

If the report from VTS is correct then:

LOUD = Your carrier signal is fully quietning their receiver
DISTORTED = Your audio (your voice) has a problem.

If, when you have carried out the test to a handheld further away, you get distorted audio on high carrier power, then is still sounds a bit like a DC power problem.

Martin

This is good advice, from what you have said I don't think you have a problem
you were heard and understood which considering the distance, obstructions, height of your aerial etc... is good news. The distorted audio could be many things, your in an open boat was the wind blowing across the mic? was the engine running? do you talk funny? If you still think you have a problem nearly everytime on boat it comes down to poor wiring, check the supply voltage to the radio when transmitting if this is dropping below 12V then you need to check it out, but basicaly it sounds ok to me.

 

[Ramage]

It might be worth trying the radio with the supply leads connected directly to your battery... this would help to determine if you are suffering from voltage drop in your wiring.

 

[bulto]

I can recieve & transmit to London VTS from Laleham.

Suggest that you check all connections. Solder the aeriel connections and not rely on
clamping,test voltage at radio input,run a clean feed from battery,through a fuse.

If all else fails have the radio checked,a lot of the budget ones are not all they are cracked up to be.

Good luck.

 

[Cymrogwyllt]

iirc from my CB days it was quite common for someone to get a distorted TX by holding the mike too close to the mouth or talking too loudly.

Apologies for any offence

 

[No Regrets]

iirc from my CB days it was quite common for someone to get a distorted TX by holding the mike too close to the mouth or talking too loudly.

Apologies for any offence

Sorry, I missed that, could you type it again?

 

[Cymrogwyllt]

Sorry, I missed that, could you type it again?

no Perhaps my fingers were too far from the keyboard

 

[boatone]

I will update and will hopefully with some pictures!

........ and not been heard from since !

What channel should we be listening on ?

 

[Yeoman of England]

VHF Reception on Thames

Boatone

Listen out on Ch14 up to Sea Reach No4, then Ch68, then Ch69.
Simples
As well as Ch16

Yeoman

 

[boatone]

Boatone

Listen out on Ch14 up to Sea Reach No4, then Ch68, then Ch69.
Simples
As well as Ch16

Yeoman

The question was asked in humour and with tongue in cheek ......... you need to read the rest of the thread

 

[Bilgediver]

Hi,

Just a very daft question, my VHF radio receives all annoucements from PLA and even most ferries and sailing boats moving behind Thames Barriers (my boat is moored in Kew) but I do have problem broadcasting from Kew to PLA.

Yesterday, I had to reluctantly ask for Radio check on Channel 14 and PLA operator said the signal is a bit distorted....

Does anyone have similar problem or is it normal not being able to broadcast on a marine VHF radio when I am in Kew? and shall I be closer to PLA in central London?!

Thanks.

You mention that you are on a RIB... What antenna do you have and did you tell the supplier it was for a rib....Some are not! They like a metal mast beneath them

 

[vandy]

Problem Solved!

The issue is with PLA's reception not with my Antenna.

Yesterday I did try contacting PLA again and same message: you are distorted...call again when you are closer to Thames Barriers...

Then called CG on Channel 16! LOUD AND CLEAR!

So now I am going to check the approximate location of their antennas! This should solve a few issues!

 

[teddington_lock]

But why is it just you ?

No one else is received distorted by the PLA.

 

[vandy]

But why is it just you ?

No one else is received distorted by the PLA.

Agree, but some people said they completely loose reception after they have passed hammersmith.

I am at least assured that CG will hear us!

This weekend's plan is to cruise in the evening to Thames Barriers!


Like last week: http://www.youtube.com/watch?v=QXRCZ53MgJc

 

[boatone]

I, and others, have suggested that you seek advice from ICOM about your installation but you seem intent on ignoring our advice.

The vagaries of VHF radio waves can give rise to all sorts of 'normal' transmission and reception experiences and it is quite likely that all is well with your kit. ICOM will be able to advise you on any special issues re antenna type and siting that may be specific to a RIB install.

Your video seems to suggest you were not too intent on observing speed limitations?

 

[Chris_d]

Agree, but some people said they completely loose reception after they have passed hammersmith.

That was me, perhaps I should have qualified that remark but by Hammersmith you definitely cannot hear any of the respondants to London VTS so it will definitely be too far away for an ordinary VHF to transmit sucessfully to VTS however you will hear them loud and clear, I personaly have never tried to speak to London VTS unless I can see the barrier, they always tell you to call back if you call too early.

Just a thought aren't the CG/RNLI at Chiswick pier? in which case you would transmit to them from Kew no problem.

As Boatone says if you think you have a technical issue call Icom they really are very helpful, asking here is like trying to address an audience at a Mental institution

 

[boatone]

......asking here is like trying to address an audience at a Mental institution

Oh come on now, its MUCH worse than that !

 

[Gumpy]

That was me, perhaps I should have qualified that remark but by Hammersmith you definitely cannot hear any of the respondants to London VTS so it will definitely be too far away for an ordinary VHF to transmit sucessfully to VTS however you will hear them loud and clear,

As a boat (due to its size) that has to report to London VTS when we enter or leave the tideway upstream of the barrier all I can say is that london VTS is workable all the way to Teddington. There is nothing special about the system on the barge, just a Midland Neptune VHF and a 5ft long antenna which shouldnt need a groundplane (its the same one as on many Mobo).
Antenna height can be as low as 6ft off the water which is about the same as many Mobo, its really a case of setting the system up corectly.

 

[Yeoman of England]

VHF Reception on the Thames

All
HMCG has different aerial locations to London VTS. Our best spot is Shooters Hill which when we tx blasts out all stations in the vicinity.
London VTS has limited range - this could explain lack of contact.
Yeoman

 

[vandy]

All
HMCG has different aerial locations to London VTS. Our best spot is Shooters Hill which when we tx blasts out all stations in the vicinity.
London VTS has limited range - this could explain lack of contact.
Yeoman

Spot on answer!

To Boatone:

I would have contacted ICOM if I had this problem in the sea, as I was failing to broadcast in an open space environment. Tidal Thames is different, I did expect that buildings etc. block my transmission, but could not understand why CG is hearing me clearly, but VTS isn't!

Now I know why!