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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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6th Dec 2021, 2:41 pm | #121 |
Administrator
Join Date: Dec 2002
Location: Cardiff
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Re: Radio Caroline Power Increase
Nothing here in Cardiff city centre now, unsurprisingly. A weak signal would be lost behind the general background noise and interference on MW here anyway. I'll try again after dark.
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6th Dec 2021, 10:01 pm | #122 |
Triode
Join Date: Nov 2021
Location: Leighton Buzzard, Bedfordshire, UK.
Posts: 32
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Re: Radio Caroline Power Increase
In the *60s I was in Cardiff (on holiday if you can believe!) and remember tuning between Radio Caroline North and Radio Caroline South at similar signal strength.
I lived in London so could only receive Radio Caroline South reliably. *I would guess at 1964 but happy to be corrected.
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7th Dec 2021, 12:10 am | #123 |
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Location: Oxford, UK
Posts: 27,783
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Re: Radio Caroline Power Increase
Given that they're only running 4kw, it seems extremely optimistic to expect a listenable signal in Cardiff using a domestic radio, though a comms receiver may pull something in.
All sorts of odd things can happen after dark of course. |
7th Dec 2021, 12:56 am | #124 |
Nonode
Join Date: Mar 2010
Location: Dukinfield, Cheshire, UK.
Posts: 2,033
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Re: Radio Caroline Power Increase
From the MW Circle (sent to me by a friend):
A fair number of reports mention our audio quality, and this is something we are aware of. We woud like to point out that options for reliable high speed connectivity at our transmission site are somewhat limited, and we are currently using a 64kb/s feed to site, which can tend to limit quality. However, many of the reports also suggest that our audio quality is excellent, so it is very much both a personal taste and a function of the radio you are listening on. Hopefully we can make adjustments to this to everyone's satisfaction in due course. For those with an interest in such matters we are using the same DSPx processor we installed in 2017 and the new transmitter is a Harris DX25U, previously located near Rotterdam and used on 828Khz. We are running an authorised radiated power of 4kw from the omni-directional "reserve" antenna at Orfordness.
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7th Dec 2021, 8:52 am | #125 |
Triode
Join Date: Nov 2021
Location: Leighton Buzzard, Bedfordshire, UK.
Posts: 32
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Re: Radio Caroline Power Increase
Actually this will have been a Perdio mini 66. After dark of course.
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John |
7th Dec 2021, 9:37 am | #126 | |
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Location: Fife, Scotland, UK.
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Re: Radio Caroline Power Increase
Quote:
If they changed to a more efficient antenna, their 4kW radiated licence would require them to reduce power at the transmitter to compensate, and they would get no further range. As the medium wave band has been vacated by many much more powerful transmitters, further power increases for Caroline is an engineering possibility. There may, however, be a policy factor, such as a decision that MW is going to be for local consumption only, acting as the limitation. David
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7th Dec 2021, 12:58 pm | #127 |
Octode
Join Date: Jun 2011
Location: West Midlands, UK.
Posts: 1,571
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Re: Radio Caroline Power Increase
I think the limiting factor is Ofcom and the licence – even if it is a ‘community of interest’ licence rather than a strictly local community licence – Ofcom seem to want to restrict to East Anglia.
My understanding is that Caroline wanted 10kW so they had clearly decided they could afford it. Given that the BBC WS used to run 500kW into a directional aerial pointed at Europe, interference to other users of the channel would hardly seem an issue, especially given the demise of MW since. The other limitation would be finance for an operation that relies mainly on donations. Given the law of diminishing returns, high power transmitters as in the days of old will be out of the question but are a nice pipe dream. However, I remember reading in an official Caroline note that “we feel we have friends at Ofcom” so the relationship would seem more than okay and perhaps advance may be achieved by increments. |
7th Dec 2021, 1:44 pm | #128 | |
Administrator
Join Date: Dec 2002
Location: Cardiff
Posts: 9,059
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Re: Radio Caroline Power Increase
Quote:
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7th Dec 2021, 2:10 pm | #129 |
Pentode
Join Date: Sep 2020
Location: Weymouth, Dorset, UK.
Posts: 134
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Re: Radio Caroline Power Increase
Does anyone know what is the output of the transmitter? Is it 4 Kilowatts I find this reference to EIRP a bit confusing I would like to know the power applied to the areal if that's possible. In the old days when the world made sense medium and shortwave powers were what was fed into the areal. I think ERP is meaningless its real Watts that count
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7th Dec 2021, 2:36 pm | #130 |
Nonode
Join Date: Jun 2013
Location: Surbiton, SW London, UK.
Posts: 2,801
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Re: Radio Caroline Power Increase
An accurate service area map with signal strength in uV/metre would be more useful.
Here is the earlier (2017) service area map; http://static.ofcom.org.uk/static/ra...s/cr101725.pdf |
7th Dec 2021, 4:17 pm | #131 | |
Octode
Join Date: Jun 2011
Location: West Midlands, UK.
Posts: 1,571
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Re: Radio Caroline Power Increase
Quote:
I used to use a power output of 3W SSB on 144MHz but fed this into a 20 element beam and was regularly beating the my pal along the road with 10W into a 5 element. During contacts it was standard practice to state power output and type of antenna as power output alone give little clue to the overall efficiency of the system – though of course some antenna designs with the same number of elements were more efficient than others. And then there is feeder loss to take into account. I think what you would really like to know is how much power is being fed to the antenna from the Tx and then the efficiency of the antenna system. In the case of Caroline, if, for the sake of argument, the umbrella antenna (which will be already more inefficient than a dipole) and the loss in the feeder cables makes the whole system 50% efficient then they would be putting 8kW* into the feeder cable to get the required 4kW into the ether. With the new EMF regulations us hams are now having to do these calculations with regard to risk to the public. Given location factors, etc., my 3W into my 20 ele might be more dangerous to the public (at the same distance from the antenna) than the guy running 25W into a dipole. *Alan Beech at Caroline has done extensive work to the transmitter so it might well be modified to drive at a lower output than factory spec. |
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7th Dec 2021, 4:43 pm | #132 |
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Location: Oxford, UK
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Re: Radio Caroline Power Increase
I suspect there is a school of thought within Ofcom that Caroline represents the thin end of the wedge regarding the establishment of new national and regional AM stations. While many of us here would welcome such developments, they would be counter to stated government policy.
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7th Dec 2021, 6:52 pm | #133 |
Pentode
Join Date: Dec 2011
Location: Camberley, Surrey, UK.
Posts: 145
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Re: Radio Caroline Power Increase
An article here reports that the antenna system efficiency (feeder loss plus antenna loss) is 66% as confirmed by Ofcom.
Previously, to get their 1kW erp output, the Radio Caroline engineers set the earlier transmitter to 1.5kW output. It would therefore seem likely that the new transmitter has to be set to 6kW output to get their 4kW radiated power. Peter |
7th Dec 2021, 11:25 pm | #134 |
Dekatron
Join Date: Sep 2006
Location: Kilmarnock, Ayrshire, UK.
Posts: 5,420
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Re: Radio Caroline Power Increase
Hi.
Here is a video of reception in Kilmarnock on Tuesday evening from 22.04 https://youtu.be/krL540R63W0
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8th Dec 2021, 11:38 am | #135 | |
Octode
Join Date: Jun 2011
Location: West Midlands, UK.
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Re: Radio Caroline Power Increase
Quote:
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8th Dec 2021, 11:42 am | #136 | |
Octode
Join Date: Jun 2011
Location: West Midlands, UK.
Posts: 1,571
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Re: Radio Caroline Power Increase
Quote:
However, I do remember being in Oban in the autumn of 1975 and out of the few stations I could receive with any clarity at night, Caroline was one of the strongest! |
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1st Jan 2022, 10:18 am | #137 |
Heptode
Join Date: Feb 2007
Location: West London, UK.
Posts: 865
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Re: Radio Caroline Power Increase
Taken from the Caroline group,
" Czech CRo Dvojka’s MW transmitter on adjacent channel 639 will closedown. They are switching off a number of their MW transmitters and their only LW transmitter." I do not think this will really affect reception of Radio Caroline, but another loss of MW and LW transmissions making the bands emptier John |
1st Jan 2022, 11:08 am | #138 |
Octode
Join Date: Oct 2011
Location: Wrexham, North Wales, UK.
Posts: 1,457
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Re: Radio Caroline Power Increase
I have very little clue about transmitters other than it creates a radio wave through the air, just to clear that one up.
If a TX supposedly puts out 4kW, does that mean it uses 4 units of electric an hour? I'm curious to know.
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1st Jan 2022, 4:44 pm | #139 |
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Re: Radio Caroline Power Increase
It puts out 4kW, with the unavoidable inefficiency of all things it would need more power in. Brookmans Park in the 1930's had about a 30% efficiency, all analogue and lots of heater power. Modern transmitters get about 90%, mostly digital, transistorized (no heaters) PWM etc., the loss is mainly in the output filter.
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1st Jan 2022, 8:41 pm | #140 |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,675
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Re: Radio Caroline Power Increase
That's right, the power is quoted as ERP Effective Radiated Power and takes account of all the losses (and sometimes gain) of the aerial system.
Contrast that to when I got my amateur licence in 1970, my legal AM power limit in the 1800-2000kHz band was 10W, specified as the "The total direct current power input to (i) the anode circuit of the valve(s) or (ii) any other device energising the aerial" which would have had a closer correlation to the electricity consumed by the tx.
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