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Old 10-04-2005, 22:13
the_radio_kid
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As i am assisting with an RSL radio station this year - how far roughly would 1 watt go at an aerial height of 10 metres (we have a10watt licence).... just curious to know
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Old 10-04-2005, 22:17
wavester
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Realistically, 10watts, should get you about 3 to 5 miles. A lot depends how high you can mount your aerial.

I'm sure if a 1 watt tx was put on the moon, NASA could pick it up on earth, so it's down to the terrain, and the sensitivity of the receiver as well.

I did actually use to own a 10 watt FM transmitter, never used it in this country obviously (cough), but I (ahem) believe they will go at least 2 miles and probably more.
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Old 10-04-2005, 22:24
Mike West
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Originally Posted by the_radio_kid
As i am assisting with an RSL radio station this year - how far roughly would 1 watt go at an aerial height of 10 metres (we have a10watt licence).... just curious to know
It's mostly goes on terrain and height of antenna, its abit like asking how longs a piece of string, in some circumstances 1 watt is just as effective as 5 watts or even 10 watts. Ideally stick the antenna out of the way of obstructive buildings / trees etc and choose somewhere with the maximised line of sight. I presume you are talking FM, otherwise if it's AM, things get more tricky.

FM - Height is the key, FM strictly works line of sight. Get a decent antenna with some gain to increase effective radiated power too and some decent coax so that the last milliwatt actually makes it to the antenna and radiates. Get a cut to frequency antenna at that and check it with a SWR meter to get mimium deflection, once you done that, take the SWR out of circuit. Plenty of web sites around that will give you step by step help - Good Luck
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Old 10-04-2005, 22:32
the_radio_kid
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Thanks for that guys.
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Old 10-04-2005, 23:08
doubledecks
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Quite a few years ago, a 'Radio Cracker' RSL based on high ground in Malvern used 1w and could be heard clear for about 15miles
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Old 10-04-2005, 23:39
Arthur Grainger
 
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Rule of thumb.

1 watt will comfortably serve a housing estate and, if decently placed, will reach beyond 1 mile for most radios, though it can sometimes cover exceptionally long distances.

10 watts will comfortably cover up to 3 or 4 miles with good line-of-sight to the transmitter. Any obstructions will reduce that. However, with a decent site, 10 watts can go for 10 miles and beyond. E.G. the Northside Radio 2001 RSL in Springburn, Glasgow, was received on people's portable trannies at homes in Paisley.

Another trick. Broadcast in mono. People's radios are much more sensitive for receiving mono signals, due to the lower threshold required to pick up a clean signal. A stereo signal will give listeners lots of hiss beyond 1 mile.
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Old 11-04-2005, 05:01
Spearman
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An excellent explanation was given to me a few weeks ago from a great bloke at the local RSL.

Stick a lightbulb on the top of Big Ben. Go and stand on the other side of the Thames. Can you see it? Maybe. Think of that as your TX, and sympathise with radios! I suppose you could go quite a bit down the road (next to the hospital), and you'd still see it - but the further you get, the less easy it is to see.

Anyway, according to Veronica, as a very sketchy guide:

50mW - 1 to 500 metres
100mW - 1000 metres
1W - 1.5 miles
12W - 7 miles
30W - 11 miles
100W - 30 miles

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Old 11-04-2005, 05:50
rifleman19
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Originally Posted by the_radio_kid
As i am assisting with an RSL radio station this year - how far roughly would 1 watt go at an aerial height of 10 metres (we have a10watt licence).... just curious to know
Im no expert but it does also seem to depend on the frequency in use, Does anyone remember the Susy Radio RSLs over the last few years on 531 from the Redhill area in Sussex? They were supposed to be using just one watt but they put a cracking signal out over a good part of the SE, I could even hear it on a car radio in Essex.
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Old 11-04-2005, 06:35
rifleman19
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Originally Posted by rifleman19
Im no expert but it does also seem to depend on the frequency in use, Does anyone remember the Susy Radio RSLs over the last few years on 531 from the Redhill area in Sussex?
Sorry i meant Surrey not Sussex, I should know where Redhill is My Mother In Law lives there, Then again???
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Old 11-04-2005, 06:49
Spearman
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Originally Posted by rifleman19
Sorry i meant Surrey not Sussex, I should know where Redhill is My Mother In Law lives there, Then again???
I should think you were just blanking out the pain!
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Old 11-04-2005, 06:57
rifleman19
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Originally Posted by Spearman
I should think you were just blanking out the pain!
How right you are, Hang on i had better finish as the wife has just got up.
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Old 11-04-2005, 07:29
Yagi Bare
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You can get a lot further with MW.

I picked up Radio Caroline's 1 Watt MW RSL here in Swansea under night time conditions and last year's RSL from Blaenavon in the South Wales valleys was picked up on the Isle of Skye.
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Old 11-04-2005, 09:51
Geordie_Cy
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Originally Posted by the_radio_kid
As i am assisting with an RSL radio station this year - how far roughly would 1 watt go at an aerial height of 10 metres (we have a10watt licence).... just curious to know

It's frequency dependent, at SW you could get to the USA and Russia or further - at VHF a handful of miles - terrain dependent.
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Old 11-04-2005, 14:29
satman5000
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Originally Posted by Spearman
Anyway, according to Veronica, as a very sketchy guide:

50mW - 1 to 500 metres
100mW - 1000 metres
1W - 1.5 miles
12W - 7 miles
30W - 11 miles
100W - 30 miles

So our local ILR Metro is on 10Kw of power, so how far should that be able to travel if 100W is 30 miles?
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Old 11-04-2005, 15:09
Spearman
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Originally Posted by satman5000
So our local ILR Metro is on 10Kw of power, so how far should that be able to travel if 100W is 30 miles?
Not my figures, Veronica's.

I should imagine the only reason for Kilowatt licenses are for increased field strength in the TSA. 100 Watts might cover the distance, but 10 Kilowatts would give you the decent reception (theoretically, those figures make no sense!).
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Old 11-04-2005, 15:11
Mike West
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Line of sight 10 watts or 10 kwatts, it don't matter, its just that with 10kw you have a stronger 'feild strength' within the line of sight. FM won't travell over or around hills / mountains and large steel framed buildings etc
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Old 11-04-2005, 15:21
getchin
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The key here is that Height = Distance, Power = Penetration.

For example, and I REALLY don't know how this happened, but our 2nd AfanFM RSL was broadcasting on 25W from Mumbles Point (off the coast of Swansea) - now we had a very very clear signal for about 17 miles but the oddest thing happened.

Aberavon RFC, one of our major partners (plus we're the official radio station of the towns main Rugby club) were playing at the Millennium Stadium in Cardiff, we were covering the event, and I get a call from the head coach - "give us a shout out then - we've got you on the stereo outside the Millennium Stadium" - for some perspective, that's about 35 miles

But as our engineer says - it's the height of the aerial that gives you distance, power only gives you penetration

Craig
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Old 11-04-2005, 15:26
Spearman
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You know that's what I meant, you just happen to be much more concise about it.
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Old 11-04-2005, 20:45
efo
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Originally Posted by rifleman19
Im no expert but it does also seem to depend on the frequency in use, Does anyone remember the Susy Radio RSLs over the last few years on 531 from the Redhill area in Sussex? They were supposed to be using just one watt but they put a cracking signal out over a good part of the SE, I could even hear it on a car radio in Essex.
Yup I could hear it down in the new forest when I visited friends, I queried it then and some one on a forum assured me that they were running their licenced 1 watt.

Absolute crap ! I have since spoken to a few of my watery wireless friends involved with that experiment and found out that someone missed 'Kilo' out of the end of the statement. Probably because they were only issued with a 1 watt licence.

From experience 10 - 15 watts on the medium wave will cover 4-6 miles and be receivable on the average tranny. You will pick it up on a car radio a lot further afield. It will all depend on the aerial efficiency and ofcourse whether its a VHF or MF licence. I guess if its 1 watt its MF.
Another feature to look at is the coverage of some of the local hospital MF transmitters. These usually run power of 250mW - 1 watt
Good luck

Henry
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Old 11-04-2005, 21:58
mikeydb
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Assuming listening on an average VHF-FM radio, and the 1W transmitter antenna is 50metres above the surrounding area then expect to receive a listenable signal for about 2 miles. You may find you can receive your signal upto five miles away or a little more if you have excellent line of sight, ie, to nearby hilltops.

It's not just the transmitter power that has an effect, it's the bandwidth of the receiver IF, generally the more narrow the receiver IF then the lower the S/N ratio and the more able it is to receive the weak signal. If you've ever experimented with PMR446 radios then you'll find from a hilltop you can talk to people upto ten miles away or more, despite the maximum power output from a PMR446 radio being set at 500mW.
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Old 11-04-2005, 23:38
Kev_Akas
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We bunged ours on top of a block of flats. It was a massive hit all over the city.
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Old 12-04-2005, 03:33
satboi
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As people have said, it's TOTALLY dependent on local conditions, though making sure you have decent feeder cable and your transmitter is set up properly helps. There is free software out there which will allow you to run a coverage plot to illustrate theoretical coverage, but you won't really know what you'll get until you try it. Do not confuse AM vs FM coverage - FM will never get you as far as AM since as I think somebody mentioned, it's frequency dependent, plus for full FM Stereo, receivers need a higher signal level. Bear in mind that tall buildings or those with a metal infrastructure will interfere with your signal, so careful siting of your Tx site is important. If you're geographically in a dip, it is well worth seeking out a remote site on higher ground overlooking your intended coverage area and linking up to it - UHF links for RSLs can be very effective. 860.6MHz is the most common frequency for temporary stereo linking, but make sure you clear the frequency with JFMG as soon as possible and licence it properly before going ahead.
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Old 12-04-2005, 08:45
smorris
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Originally Posted by efo
Yup I could hear it down in the new forest when I visited friends, I queried it then and some one on a forum assured me that they were running their licenced 1 watt.

Absolute crap ! I have since spoken to a few of my watery wireless friends involved with that experiment and found out that someone missed 'Kilo' out of the end of the statement. Probably because they were only issued with a 1 watt licence.

From experience 10 - 15 watts on the medium wave will cover 4-6 miles and be receivable on the average tranny. You will pick it up on a car radio a lot further afield.
It needn't have been a lot more than 1 watt, though. Spectrum International on 558 runs 1kW and covers a vast area - lamost double the size of Capital Gold (97.5kW) or LBC 1152 (23.5kW). That's because of the low frequency. 1kW on a higher frequency would barely cover half of the capital, hence why Premier (on 1332) using the same power, need multiple relays in the suburbs.

It really would surprise me to discover Susy Radio were using all of 1kW - it certainly couldn't be heard on a normal radio at all up in Warwickshire at the time, whereas Spectrum were quite listenable, although not exactly loud.

A couple of watts on 531 does go a long way, especially if its' anoraks with expensive receivers doing most of the listening, unlike such a power on a typical RSL frequency such as 1503. Not to mention the factor that during the day 531 is dead clear, unlike most of the channels given to low power AM stations.
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Old 12-04-2005, 12:49
Ronan Kerr
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A watt can go a long way - under the right conditions!

Someone once told me that the Radio London RSL was heard in Nova Scotia.
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Old 12-04-2005, 22:28
efo
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Yes, but here on planet earth, and for the every day listener with his or her tranny one watt is for about a mile or two.

Forget us enthusiasts et al with long wires and loop antenna, and midnight DX ing, and when you can hear stations from Canada and the USA on medium wave in the early hours, in real terms its short range local coverage.
Henry
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