What kind of power would any County Radio Be putting out?

[Eoin O]

utt

[dlccr973]

From the wall where I am now,

Maximum Effective Radiated Power (Watts) and Polarsation.

Max. E.R.P. (dBW) Polarisation

10.0 Horizontal
10.0 Vertical

[Leigh Doyle]

Whaaaa?
U been smokin?

[Mike]

It actually varies 5Kw is typical but some run less while Radio Kerry runs 20Kw (ERP) on one of its transmitters

[Eoin O]

20kWatts jesus!! I would have thought about 2 max. Do they generally use omni directional antennas??

[Mike]

usually but not always

[plastic mountains]

FM104 use a 2kW TX.

[ger.c]

thought FM104 was push more in dublin like 4 kw

[plastic mountains]

Nope its a 2kW TX.

[godfrey]

dont forget lads, the difference between 2kW & 4kW is only 3db... ie; virtually nothing

thats why the 'big boys' have to throw lots of money into transmission

g

[Mike]

Isint FM104's ERP listed as 5Kw ?

Of course this could be done with 2Kw into a directional and/or stacked aerial allowing for feeder losses

[mr orban]

can you explain the 2 kw to 4 kw thing when you say 3 db's is that in loubness. I'm New to this end. regards

[Eoin O]

dB just means a ratio of one signal to another. For example if u have a 1kW transmitter giving you 40 miles radius then if u want to get double the range you need not twice the power but roughly about 8 times it. See what i mean. Its a logametric scale not a linear one

[Hissing Sidebands]

Your example is actually exponential, not "logametric" or even logarithmic!
a DB is 10 log(base10) P1/P2,
Rules of thumb:
every doubling of power is plus 3dB , halving is -3dB,
10 x power is +10dB, one tenth power -10dB
Its just a handy way of showing the effevt of perception of changes of power, which apply to any enrgy, be it sound or RF.
It is generally accepted that to be noticable (and affect the signal in a meaningful way), power must change by minimum 3dB
So say you have a 20watt TX, increasing power by 10 watts is not really worth the trouble, you need 3dB = 2x =40watts.
To get the same perceived increase again, you need another 3dB, i.e 80 watts and so on.
so you can see that before long, to get any worthwhile increase, you need to be adding kilowatts.
So for RTE, say who run typically 100 kW erp from their main sites, could save a whopping electricity bill by halving power to 50 kW, and it would barely be noticable! (yes - before anyone points it out, they use 10kW rigs, with 10dB gain antennas to get 100kW, so the saviing wouldn't be that huge)
Get the idea?

[Eoin O]

I didnt mean for it to be a legitimate example just a rough guess to show that doubling you ERP does not double your range. I have been told that power output needs to be roughly multiplied by a factor of ten for twice the range. All maths and formulas aside in practise you need nearly 10 times power to give twice range.

[mr orban]

Thank you both . getting the idea now . Is there any books or websites to gain more info ?